Aeromedical Evacuation Springer New York Berlin Heidelberg Hong Kong London Milan Paris Tokyo William W

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Aeromedical Evacuation Springer New York Berlin Heidelberg Hong Kong London Milan Paris Tokyo William W. Hurd, MD, MS, FACOG Nicholas J. Thompson Professor and Chair, Department of Obstetrics and Gynecology, Wright State University School of Medicine, Dayton, Ohio; Col, USAFR, MC, FS, Commander, 445th Aeromedical Staging Squadron, Wright-Patterson AFB, Dayton, Ohio

John G. Jernigan, MD Brig Gen, USAF, CFS (ret), Formerly Commander, Human Systems Center, Brooks AFB, San Antonio, Texas

Editors Aeromedical Evacuation Management of Acute and Stabilized Patients

Foreword by Paul K. Carlton, Jr., MD Lt Gen, USAF, MC, CFS USAF Surgeon General

With 122 Illustrations

1 3 William W. Hurd, MD, MS John G. Jernigan, MD Nicholas J. Thompson Professor and Chair Brig Gen, USAF, CFS (ret) Department of Obstetrics and Gynecology Formerly Commander Wright State University School of Medicine Human Systems Center Dayton, OH, USA Brooks AFB Col, USAFR, MC, FS San Antonio, TX, USA Commander 445th Aeromedical Staging Squadron Wright-Patterson AFB Dayton, OH, USA

Cover illustration: Litter bearers carry a patient up the ramp of a C-9 Nightingale medical transport aircraft. (US Air Force photo by Staff Sgt. Gary R. Coppage). (Figure 7.4 in text)

Library of Congress Cataloging-in-Publication Data Aeromedical evacuation : management of acute and stabilized patients / [edited by] William W. Hurd, John G. Jernigan. p. ; cm Includes bibliographical references and index. ISBN 0-387-98604-9 (h/c : alk. paper) 1. Airplane ambulances. 2. Emergency medical services. I. Hurd, William W. II. Jernigan, John J. [DNLM: 1. Air Ambulances. 2. Emergency Medical Services. 3. Rescue Work. WX 215 A252 2002] RA996.5 .A325 2002 616.02¢5—dc21 2002021045

ISBN 0-387-98604-9 Printed on acid-free paper. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Departments of the Army, Navy, or Air Force, or the Department of Defense. The use of brand names is for illustrative purposes and does not imply endorsement by the Departments of the Army, Navy, or Air Force, or the Department of Defense. The authors have no finan- cial interest in any commercial device mentioned herein. © 2003 Springer-Verlag New York, Inc. All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. While the advice and information in this book are believed to be true and accurate at the date of going to press, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, expressed or implied with respect to the material contained herein.

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Springer-Verlag New York Berlin Heidelberg A member of BertelsmannSpringer Science+Business Media GmbH Foreword

As Surgeon General of the United States Air Force, it is a real plea- sure to write this foreword for the first modern textbook describing the medical aspects of aeromedical evacuation (AE). This textbook would not only have proven invaluable to me and my colleagues as we served our nation in Europe and Southeast Asia during the 1980s and early 1990s, but today it will provide an absolutely invaluable resource for all medics in the Department of Defense. I would like to say a special thanks to Bill Hurd, whose idea it was to publish this textbook and whose persistence was crucial to making it a reality. As described in chapter 2, AE has always been a vital link in the chain of medical care provided for all our soldiers, sailors, Marines, and airmen. Without AE, neither I nor any of my fellow Surgeons General could guarantee proper “full-spectrum” medical care to our military men and women around the globe. This is our collective responsibility, regardless of where in the world disease or injury occurs. Because of the huge distances involved in moving many of our patients, AE has always been a challenge, but never more so than today. Beginning with Operation Just Cause in Panama (1989), it became apparent that our troops would, at times, suffer injury in a location where only minimal stabilizing medical care is available. In such situations, AE is absolutely critical to assure we can quickly move patients to state-of-the-art trauma centers, even though such centers are hundreds or thousands of miles away. During Operation Desert Shield/Desert Storm (1990 to 1991), the amount of sealift required to move “mobile hospitals,” together with the time required to set them up, mandated that the medical services of all military branches find a new way to deliver medical care to combat troops. My predecessors and I, together with the Surgeons General of the Army and Navy, worked throughout the 1990s to streamline our medical forces. The end result is a truly light, lean, mobile, and capable array of medical forces that can arrive quickly on-scene for medical support of virtually any deployment anywhere in the world. However, such forces are equipped only for stabilization-type procedures and are far less capable than the old fixed facilities we had deployed in Europe during the Cold War. We simply must have the capability to

v vi Foreword move our casualties out of the theater of operations as quickly as possible, and AE is the key to making that happen. In fact, today we can aeromedically evacuate patients who are stabilized but not stable— providing critical care in the air—greatly enhancing the speed and capability of our AE service. Currently, the only people with more than a mere casual understanding of the issues involved in moving patients are those USAF Reserve and Air National Guard forces (mostly nurses and adminis- trators) assigned to AE units, together with a handful of active-duty personnel who have served in one or two AE-related assignments during their careers. This textbook is rich with invaluable information that captures that experience and supplements Air Force guidelines and publications on AE. This textbook will also prove a valuable resource to civilian physicians as they make decisions regarding the medical factors they must consider as they move their patients back to or around the United States. As the world’s economy has become more integrated, American companies are stationing ever more Americans in foreign countries where medical care is often far substandard to expectations. The result is an increasing number of civilian patients who also need AE back to the United States. Further, even within the United States, subspeciality centers such as pediatric cardiothoracic surgery and burn centers often require the movement of patients over thousands of miles. I heartily congratulate the editors and chapter authors of Aeromed- ical Evacuation: Management of Acute and Stabilized Patients.I am conﬁdent it will become a much used resource by the thousands of physicians, nurses, and technicians charged with the responsibility of moving patients over long distances using aircraft. These individuals include members of all branches of the military and the many civilians involved in the commercial AE industry. For them, this book may be, quite literally, a “lifesaver.”

Paul K. Carlton, Jr., MD Lt Gen, USAF, MC, CFS USAF Surgeon General Contents

Foreword, by Paul K. Carlton, Jr...... v Contributors ...... xi

Part 1 The Need

1 Introduction ...... 3 William W. Hurd and John G. Jernigan

2 Aeromedical Evacuation: A Historical Perspective . . . . . 6 Kathleen Vanderburg

3 Indications and Considerations for Emergent Evacuation of the Peacetime Casualty ...... 13 J.D. Polk and William F. Fallon, Jr.

4 Combat and Operational Casualties ...... 27 Robert A. De Lorenzo

Part 2 The Means

5 Military Casualty Evacuation: MEDEVAC ...... 45 Robert A. De Lorenzo

6 Aeromedical Triage Support to Mass-Casualty Events . . 60 Frederick M. Burkle, Jr., Richard Brennan, and Victoria Garshnek

7 Patient Staging for Aeromedical Evacuation ...... 75 William W. Hurd, Anthony M. Rizzo, Eunice K. Taylor, and John M. McNamara

8 Aircraft Considerations for Aeromedical Evacuation . . . 88 John G. Jernigan

vii viii Contents

9 Critical-Care Air Transport: Patient Flight Physiology and Organizational Considerations ...... 111 Thomas E. Grissom

10 Nursing Care In-Flight ...... 136 Susan B. Connor

11 Aeromedical Evacuation of Patients with Contagious Infections ...... 147 Mark R. Withers, George W. Christopher, Steven J. Hatﬁll, and Jose J. Gutierrez-Nunez

12 In-Flight Emergencies: Capabilities and Limitations . . . . 160 R.T. Ross and M. Gage Ochsner, Jr.

Part 3 The Patients

13 General Surgical Casualties: Abdominal Wounds, Urogenital Traumas, and Soft-Tissue Injuries ...... 173 J.D. Polk, Charles J. Yowler, and William F. Fallon, Jr.

14 Air Evacuation of the Neurosurgical Patient ...... 184 Mick J. Perez-Cruet and Rose Leary

15 Otorhinolaryngology Head and Neck Surgery Patients ...... 203 David G. Schall and John R. Bennett

16 Ophthalmic Patients ...... 215 Douglas Joseph Ivan

17 Peripheral Vascular Casualties ...... 225 David L. Dawson

18 Aeromedical Evacuation of Cardiothoracic Casualties . . 241 Kenton E. Stephens, Jr.

19 Patients Requiring Mechanical Ventilation ...... 256 Steven L. Chambers and Thomas G. Ferry

20 Orthopedic Patients ...... 265 Steven L. Oreck

21 Burn Patients ...... 274 David J. Barillo and James E. Craigie

22 Aeromedical Evacuation of Obstetric and Gynecological Patients ...... 287 William W. Hurd, Jeffrey M. Rothenberg, and Robert E. Rogers Contents ix

23 Medical Casualties ...... 313 Thomas J. McLaughlin, J. Christopher Farmer, and Robert A. Klocke

24 Pediatric Casualties ...... 329 Robert J. Wells, Howard S. Heiman, and William W. Hurd

25 Aeromedical Evacuation of Psychiatric Casualties . . . . . 350 Elspeth Cameron Ritchie

Index ...... 359 Contributors

David J. Barillo, MD, FACS Frederick M. Burkle, Jr., MD, MPH, FAAP, Chief, Division of Plastic Surgery FACEP Director, Adult Burn Center Senior Scholar, Scientist, and Visiting Medical University of Professor South Carolina The Center for International Emergency, Charleston, SC, USA Disaster and Refugee Studies LTC, MC, USAR Departments of International Health and Formerly Chief, Clinical Emergency Medicine Division Schools of Public Health and Medicine US Army Burn Center The Johns Hopkins University Medical U.S. Army Institute of Surgical Institutions Research Baltimore, MD, USA Fort Sam Houston, TX, USA Senior Medical and Public Health Advisor Defense Threat Reduction Agency Ft. Belvior, VA, USA CAPT, MC, USNR John R. Bennett, MD Maj, USAF, MC Paul K. Carlton, Jr., MD Department of Otolaryngology-Head and Lt Gen, USAF, MC, CFS Neck Surgery USAF Surgeon General RAF Lakenheath Hospital Bolling AFB, MD, USA Lakenheath, Suffolk, UK

Steven L. Chambers, MD Col, USAF, MC Chief, Department of Medicine Richard Brennan, MBBS, MPH, Director, Medical Intensive Care Unit FACEM Wright-Patterson USAF Medical Center Director, Health Unit Wright-Patterson AFB, Dayton, OH, USA International Rescue Committee New York, NY, USA Assistant Clinical Professor, Division of George W. Christopher, MD Emergency Medicine LtCol, USAF, MC John A. Burns School of Medicine Chief, Infectious Diseases Service University of Hawaii, Honolulu Landstuhl Regional Medical Center Honolulu, HI, USA Landstuhl-Kirchberg, Germany

xi xii Contributors

Susan B. Connor, BS, MSN, CNS J. Christopher Farmer, MD, FACP, FCCP, LtCol, USAF, NC FCCM Chief, Aeromedical Plans and Col, USAF, MC, FS Inspections Chief Medical Ofﬁcer, TRICARE Ofﬁce of the Inspector General Southwest Headquarters, Air Mobility San Antonio, TX, USA Command Associate Professor of Medicine and Scott AFB, IL, USA Surgery Formerly, Commander, Aeromedical Uniformed Services University of the Evacuation Flight Health Sciences Howard AFB, Panama F. Edward Hébert School of Medicine Bethesda, MD, USA

James E. Craigie, MD Chief Resident in Plastic Surgery Thomas G. Ferry Medical University of South Carolina Center for Respiratory Medicine Charleston, SC, USA St Francis Hospital and Health Centers Beech Grove, IN, USA Maj, USAFR, MC David L. Dawson, MD, FACS Wright-Patterson USAF Medical Center LtCol, USAF, MC, FS Wright-Patterson AFB Space Medicine and Health Care Dayton, OH, USA Systems Office NASA Johnson Space Center Houston, TX, USA Associate Professor of Surgery Victoria Garshnek, MS, PhD Uniformed Services University of the Research Scientist Health Sciences Pacific Regional Program Office F. Edward Hébert School of Medicine Center of Excellence in Disaster Bethesda, MD, USA Management & Humanitarian Assistance, Tripler Army Medical Center Robert A. De Lorenzo, MD, FACEP Honolulu, HI, USA LTC, MC, FS, USA Formerly, Research Scientist Brooke Army Medical Center NASA Ames Research Center, CA, Fort Sam Houston, TX, USA USA Associate Adjunct Professor of Military and Emergency Medicine Uniformed Services University of the Thomas E. Grissom, MD, FCCM Health Sciences LtCol, USAF, MC F. Edward Hébert School of Medicine Chairman and Program Director, Bethesda, MD, USA San Antonio Uniformed Services Health Education Consortium Anesthesiology William F. Fallon, Jr., MD, FACS Residency LTC, MC, USAR (ret) Wilford Hall USAF Medical Center Director, Division of Trauma, Critical Care, Lackland AFB, TX, USA Burns and Metro Life Flight Formerly, Director, Critical Care Air Department of Surgery Transport Training Program MetroHealth Medical Center USAF School of Aerospace Medicine Cleveland, OH, USA Brooks AFB, TX, USA Contributors xiii

Jose J. Gutierrez-Nunez, MD Rose Leary, DMD, MD Col, USAF, MC (ret) Maj, USAF, MC Associate Chief of Medicine Department of Neurosurgery Department of Medicine Wilford Hall USAF Medical Center San Juan VA Medical Center Lackland AFB, TX, USA San Juan, PR, USA Thomas J. McLaughlin, DO, FACEP Steven J. Hatﬁll, MD, PhD LtCol, USAF, MC, SFS Virology Division Chairman, Department of Emergency US Army Medical Research Institute of Medicine Infectious Diseases Wilford Hall Medical Center Fort Detrick, MD, USA Lackland AFB, TX, USA Adjunct Assistant Professor of Military and Howard S. Heiman, MD, FAAP Emergency Medicine COL, MC, USA Uniformed Services University of the Chief, Neonatology Service Health Sciences San Antonio Military Pediatric Center F. Edward Hébert School of Medicine Wilford Hall Medical Center Bethesda, MD, USA Lackland AFB, TX, USA John M. McNamara, MD, MS, MPH William W. Hurd, MD, MS, FACOG LtCol, USAF, MC, CFS (ret) Nicholas J. Thompson Professor Ofﬁce Of Occupational Medicine and Chair Occupational Safety and Health Department of Obstetrics and Gynecology Administration Wright State University School of U.S. Department of Labor Medicine Washington, DC Dayton, OH, USA Col, USAFR, MC, FS M. Gage Ochsner, Jr., MD, FACS Commander Chief of Trauma Services and 445th Aeromedical Staging Squadron Surgical/Critical Care Wright-Patterson AFB Department of Surgical Education Dayton, OH, USA Memorial Health University Medical Center Douglas Joseph Ivan, MD, FAsMA Savannah, GA, USA Col, USAF, MC, CFS CAPT, MC, USNR Chief, Ophthalmology Branch Chief of Naval Reserve Surgery Section Clinical Sciences Division Uniformed Services University of the USAF School of Aerospace Medicine Health Sciences Brooks AFB, TX, USA F. Edward Hébert School of Medicine Bethesda, MD, USA John G. Jernigan, MD, FAsMA Brig Gen, USAF, CFS (ret) Steven L. Oreck, MD Formerly Commander, Human Systems Clinical Associate Professor, Orthopedic Center and Plastic Surgery Brooks AFB, San Antonio, TX, USA University of Wisconsin School of Medicine Robert A. Klocke, MD, FACP Madison, WI, USA Professor and Chair CAPT, MC, USNR Department of Medicine Regimental Surgeon State University of New York at Buffalo 23rd Marine Regiment Buffalo, NY, USA 4th Marine Division xiv Contributors

Mick J. Perez-Cruet, MD, MS R.T. Ross, MD Assistant Professor Department of Surgical Education Institute for Spine Care Memorial Health University Medical Rush-Presbyterian St. Lukes Medical Center Center Savannah, Georgia Chicago Institute of Neurosurgery and MAJ, MC, USAR, FS Neuroresearch 429th Evacuation Battalion Chicago, IL, USA Savannah, GA, USA Maj, USAFR, MC Formerly, Deputy Commander Department of Neurosurgery Jeffrey M. Rothenberg, MD, FACOG Director Neuro-spinal Research Associate Professor of Obstetrics and Wilford Hall Medical Center Gynecology Lackland AFB, TX, USA Indiana University School of Medicine Indianapolis, IN, USA

J.D. Polk, DO, FACOEP Major, USAFR, MC, FS David G. Schall, MD, MPH, FACS Expeditionary Flight Surgeon Col, USAF, MC, CFS Wyle Life Sciences/NASA Command Surgeon USAF Academy International Space Station Medical Commander 10th Medical Group Operations USAF Academy, CO, USA Houston, Texas Former Consultant to the Surgeon Critical Care Flight Surgeon General MetroHealth Medical Center Otolaryngology Head and Neck Cleveland, OH, USA Surgery

Kenton E. Stephens, Jr., MD Elspeth Cameron Ritchie, MD Maj, USAFR, MC LTC, MC, USA Formerly, Department of Cardiothoracic Program Director, Mental Health Policy Surgery and Women’s Issues Wilford Hall USAF Medical Center Ofﬁce of the Assistant Secretary of Defense Lackland AFB, TX, USA for Health Affairs Falls Church, VA, USA Eunice K. Taylor, RN, BS, MA, CNA Maj, USAF, NC, CFN Anthony M. Rizzo, MD Chief, Aeromedical Evacuation Col, USAFR, MC, SFS Operations Commander Tanker Airlift Control Center 920th Aeromedical Staging Squadron Scott AFB, IL, USA Patrick AFB, FL, USA

Kathleen Vanderburg, RN, BSN, MS Robert E. Rogers, MD, FACOG Col, USAF, NC (ret) COL, MC, USA (ret) Formerly Chair, Department of Aerospace Emeritus Professor of Obstetrics and Education and Training, and Gynecology Associate Dean, Aerospace Nursing Indiana University School of Medicine USAF School of Aerospace Medicine Indianapolis, IN, USA Brooks AFB, TX, USA Contributors xv

Robert J. Wells, MD Mark R. Withers, MD Professor of Pediatrics MAJ, MC, USA Department of Pediatrics Resident in Aerospace Medicine University of Cincinnati School of USAF School of Aerospace Medicine Medicine Brooks AFB Cincinnati, OH, USA San Antonio, TX, USA Col, USAFR, MC, CFS 445th Aeromedical Squadron Charles J. Yowler, MD, FACS, FCCM Wright-Patterson AFB LTC, MC, USA (ret) Dayton, OH, USA Director, Surgical Critical Care Fellowship MetroHealth Medical Center Assistant Professor of Surgery Case Western Reserve University Cleveland, OH, USA

Abbreviations FCCM: Fellow, American College of Critical Care Medicine AFB: Air Force Base FCCP: Fellow, American College of Chest Brig Gen: Brigadier General Physicians BS: Bachelor of Science FS: Flight Surgeon BSN: Bachelor of Science in Nursing LTC: Lieutenant Colonel (USA) CAPT: Captain (USN) LtCol: Lieutenant Colonel (USAF) Capt: Captain (USAF) Lt Gen: Lieutenant General (USAF) CFN: Chief Flight Nurse MAJ: Major (USA) CFS: Chief Flight Surgeon Maj: Major (USAF) CNA: Certiﬁed, Nursing Administration MBBS: Bachelor of Medicine, Bachelor of CNS: Clinical Nurse Specialist Surgery COL: Colonel (USA) MC: Medical Corps Col: Colonel (USAF) MD: Doctor of Medicine CPT: Captain (USA) MPH: Master of Public Health DMD: Doctor of Dental Medicine MS: Master of Science DO: Doctor of Osteopathic Medicine MSN: Master of Science in Nursing FAAP: Fellow, American Academy of NASA: National Aeronautical and Space Physicians Administration FACEM: Fellow, Australasian College of NC: Nursing Corps Emergency Medicine PhD: Doctor of Philosophy FACEP: Fellow, American College of RAF: Royal Air Force Emergency Physicians SFS: Senior Flight Surgeon FACOG: Fellow, American College of USA: United States Army Obstetrics and Gynecology USAF: United States Air Force FACP: Fellow, American College of Physicians USAFR: United States Air Force Reserve FACS: Fellow, American College of Surgeons USAR: United States Army Reserve FAsMA: Fellow, Aerospace Medical USNR: United States Naval Reserve Association WHO: World Health Organization Part 1 The Need 1 Introduction

William W. Hurd and John G. Jernigan

Aeromedical evacuation (AE) is the long- transport, the patient cannot be definitively distance, usually greater than 300 miles, air treated prior to flight and is often medically transportation of patients after medical treat- unstable. The goal of both is to get the patient ment that is adequate to assure a successful to the closest medical facility that possesses the movement. It is most commonly performed necessary assets to treat the patient’s condition. using specially configured fixed-wing aircraft For urgent AE, a physician with experience with highly trained aeromedical personnel in handling the patient’s medical condition in attendance. AE is inherently different than usually accompanies the patient and medical medical evacuation (MEDEVAC), which refers equipment specific to the patient’s condition to the emergency transportation of patients is also made available if possible. Because to the nearest appropriately equipped medical the appropriate physicians and equipment are facility prior to definitive treatment. When air sometimes difficult to obtain when needed, transportation is required, MEDEVAC is per- the USAF has recently developed the Critical formed almost exclusively using rotary-wing Care Air Transport (CCAT) Team concept for aircraft. these patients. Under ordinary circumstances, the vast A recent revolution in military medical majority of AE is elective. For elective AE, affairs has resulted in the need for a third air transportation is delayed sufficiently long approach to AE that we have referred to in this after definitive therapy so that the rigors of text as contingency. Contingency AE refers air travel are unlikely to result in medical to air transportation of stabilized (rather than decompensation of the patient. The patients are stable) patients as soon as possible after treat- stable and in the convalescent phase of their ment adequate to assure the movement to disease or injury course. Because even the most definitive care without adverse sequelae. At a stable patient may experience difficulty during minimum, a stabilized patient has an assured AE, specially trained flight nurses monitor airway and stabilized fractures, all hemorrhage the patients in-flight. However, most elective is controlled, and fluid resuscitation has begun. AE is accomplished on aircraft that have The reason for development of the contin- limited equipment for dealing with medical gency AE concept is clear. In most potential emergencies. theaters of war in the world, it is impossible A more precarious category of AE is termed to provide adequate fixed or mobile medical urgent. Urgent AE refers to the air transporta- facilities to allow for full patient recovery and tion of a potentially unstable patient to save convalescence in the geographic area where life or limb, primarily because the necessary their injury occurred. The previous doctrine medical facilities or personnel are not available of establishing enough portable hospitals to locally. Urgent AE has many similarities to handle a large number of patients for an ex- MEDEVAC. For both types of aeromedical tended length of time is no longer practical for

3 4 W.W. Hurd and J.G. Jernigan

Figure 1.1. Interior view of a USAF C-17 Globemaster conﬁgured to hold 36 litter and 48 ambulatory patients (USAF photo).

a variety of reasons. Fortunately, technological This results both from the stress of AE advances have resulted in the development of and because decompensation is certainly more an AE system that can transport patients out of common earlier in the course of most disease theater for definitive surgery,recovery,and con- or injury processes, especially in the immediate valescence, thus negating the need for a large postoperative period. Further, the potential in-theater medical capability. early problems that patients may experience Although the concept of contingency AE are often unique to their specific medical has developed as a military model, it has clear condition. civilian applications. Natural or manmade disa- In all cases, the potential stress of AE on sters may also result in more casualties than patients must be carefully considered. Despite can be handled by local facilities. Likewise, an advances in technology, the AE environment is impending military conflict or natural disaster often harsh (Fig. 1.1). A limited number of air may require the movement of recently treated ambulances are available that minimize the patients to a medical facility away from the noise and vibration, maximize lighting, and danger area. limit the hypobaric effects of altitude on the The difference between elective and contin- patient. However, even in peacetime, the gency AE (ie, stable vs stabilized patients) majority of AE is performed using specially has significant medical implications. Whereas reconfigured aircraft that are otherwise used a convalescing stable patient is unlikely to for transportation of personnel or equipment. decompensate, a recently treated, stabilized Military transport aircraft reconfigured for AE patient may be much more likely to do so. are well known for the stresses they put on both 1. Introduction 5 the patients and the aeromedical crew during conditions. In light of the need to perform both prolonged flight. elective and contingency AE when appropriate, Whether elective of contingency, safe and the patients and their conditions are examined successful AE depends on appropriate patient for specific considerations in each type of AE. selection and preparation. Knowledge of the For contingency AE, the patients must be eval- best time to transport patients and the com- uated at the earliest time that safe air trans- plications that may occur, as well as ways to portation is possible. Special emphasis is placed prevent and treat these complications, is an on this preconvalescent period because the imperative. While it may be true that “there patient may be more sensitive to the stresses of is no absolute contraindication to AE,” it is flight and decompensation may be more likely. also true that “there is nothing therapeutic Criteria are given for patients with specific con- about AE.” The injudicious use of AE can ditions that should be fulfilled prior to AE. The result in unnecessary complications for those preparation and equipment required for safe patients who are transported prematurely or transportation and the complications that can those transported without adequate resources be expected are also examined. to handle potentially foreseeable complica- For elective AE, the ideal time for air trans- tions. Selection and medical preparation of portation during the routine course of illness, the patient for AE should be tailored to each injury, or in the postoperative period is ex- patient’s condition. A thorough understanding amined. Certain criteria should be met prior to of both the problems that may occur in-flight AE when there are no limiting factors for con- and the limited medical treatment available valescence prior to AE. The late complications during AE is always required. unique to the condition that can occur when a This book is intended to be a comprehensive patient is exposed to the stresses of AE and summary of the medical needs and considera- methods to prepare for these complications are tions for patients undergoing long-distance AE. delineated. To this end, we have two specific goals. The first We hope that the information in this book is to carefully examine the problems and limi- will serve as a reference for both the military tations of medical care in-flight. This informa- and civilian clinicians who need to prepare tion should increase clinicians’ appreciation of patients for AE. Only by thorough understand- the medical flight environment when considering of the stresses of flight and the risks specific ing AE for their patients. to our patients’ conditions can we provide safe The second goal is to analyze the unique AE long-distance AE for both the stable and stabi- problems and risks for patients with specific lized patient. 2 Aeromedical Evacuation: A Historical Perspective

Kathleen Vanderburg

Aeromedical evacuation (AE) has a long and for the project, proved to be only the beginning fascinating history of trial and error, success of many challenges for this new concept. and failure, and ultimate achievement. The determined progress of AE, which parallels the advances in human flight, has been the World War I Era result of man’s desire to avoid the “ultimate sacrifice” of death while bravely defending World war I will not be remembered for his country’s vital interests. Although early the extent that AE was used, but as a time development of AE progressed slowly, its when air ambulance design made significant many champions steadfastly believed that air progress by trial and error. A French medical transport of the wounded could significantly officer, Eugene Chassaing, first adapted French decrease the morbidity and mortality of those military planes for use as air ambulances.1 Two injured in battle. The story of AE began in the patients were inserted side-by-side into the early part of the 20th century as an important fuselage behind the pilot’s cockpit. Modified facet of military medicine. In the modern era, Dorand II aircraft were used at Flanders in AE has risen to new heights with the imple- April 1918 in what was the first actual AE of mentation of technological advances in both the wounded in airplanes specifically equipped flight and medicine. for patient movement. The United States also used airplanes for evacuating the injured from the battlefield Before World War I in World War I, but found it difficult to use planes not designed for patient airlift.1 The concept of moving the wounded by air Specifically, the fuselages were too small to began almost simultaneously with the concept accommodate stretchers and the open cockpit of fixed-wing aircraft flight. Shortly after the exposed patients to the elements. The USA Wright Brothers successfully flew their first Medical Corps used airplanes primarily to airplane, two United States Pirmy (USA) transport flight surgeons to the site of airplane medical officers, Captain George H. R. Gosman accidents to assist in the ground transportation and Lieutenant A. L. Rhodes, designed an air- of casualties. plane built to transport patients.1 Using their By the end of the War, the USA realized own money, they built and flew the world’s first the need to transport the wounded by air. In air ambulance at Fort Barrancas, Fla, in 1910. 1918, Major Nelson E. Driver and Captain Unfortunately, on its first test flight it only flew William C. Ocker converted a Curtiss JN-4 500yd at an altitude of 100ft before crashing. “Jenny” biplane into an airplane ambulance by This flight, followed by Captain Gosman’s modifying the rear cockpit to accommodate a unsuccessful attempt to obtain official backing standard Army stretcher (Fig. 2.1). This allowed

6 2. Aeromedical Evacuation: A Historical Perspective 7

Figure 2.1. The Curtiss JN-4 Jenny was converted to an air ambulance by removing the rear cockpit seat (USAF photo, 311th Human Systems Wing Archives, Brooks AFB, Tex).

the USA to transport patients by airplane for the USA converted the largest single-engine the first time. airplanes built at the time, the Fokker F-IV,into an air ambulance designated as the A-2. In the same year, a USA physician, Colonel Albert E. Between the World Wars Truby, enumerated the potential uses of the airplane ambulances2: The success of the Curtis JN-4 Jenny Air 1. Transportation of medical officers to the site Ambulances during World War I paved the way of crashes and bringing casualties from the for the further development of AE.1 In 1920, crash back to hospitals. the DeHavilland DH-4 aircraft was modified to 2. Transportation of patients from isolated sta- carry a medical attendant in addition to two tions to larger hospitals where they could side-by-side patients in the fuselage. Shortly receive better treatment. thereafter, the Cox-Klemmin aircraft became 3. In time of war, transportation of seriously the first aircraft built specifically as an air wounded from the front to hospitals in the ambulance. This airplane carried two patients rear. and a medical attendant enclosed within the 4. Transportation of medical supplies in plane. In 1921, the Curtis Eagle aircraft was emergencies. built to transport four patients on litters and six ambulatory patients. Unfortunately, in its first Transportation of patients by air began to year in service a Curtis Eagle crashed during an take on operational importance as well. In electrical storm, killing seven people. 1922, in the Riffian War in Morocco the French Despite this apparent setback, aeromedical Army transported more than 1200 patients by transportation continued to progress. In 1922, air with a fleet of six airplanes.2 In 1928, a Ford 8 K. Vanderburg

Tri-Motor was converted to an air ambulance ties over long distances. The Surgeon for the capable of carrying six litter patients, a crew Army Air Force Combat Command, Major I. B. of two pilots, a flight surgeon, and a medical March, was concerned that field ambulances technician.1 Also in 1928, the US Marines in would not be sufficient to cover the aerial paths Nicaragua developed what we now call “retro- of the Air Forces. In response, the Surgeon grade aeromedical transport.”1 Nonmedical air- of the Third Air Force, Lieutenant Colonel craft that transported supplies into the jungle Malcolm C. Grow, stated that the “chief stum- were used to evacuate sick and wounded bling block in the way of air ambulances has patients to the rear on the return flight. This been the lack of interest on the part of the Army concept continues to be an essential part of Surgeon General....Until he accepts the air- modern AE doctrine. plane as a vehicle for casualty transportation, I In the 1930s a registered nurse and visionary, doubt if very much can be done about it.”2 Lauretta M. Schimmoler, believed that one day The War soon demonstrated the necessity of there would be a need to evacuate the wounded AE.2 Large numbers of casualties needed to be by air and for 15 years was a proponent transported back from distant theaters of war. for establishing the Aerial Nurse Corps of Because designated AE aircraft did not exist, America. However, not everyone supported the Army Air Force made it their policy to this premise. Mary Beard, RN, the Director use the transport planes for AE flights as their of the Red Cross Nursing Service in 1930, secondary mission. Regular transport aircraft stated, “No one of our nursing organizations, were reconfigured for AE using removable no leading school of nursing, nor any other litter supports. In this way, aircraft that had professional group, has taken up this subject transported men and supplies to the theaters of seriously and definitely tried to promote the operation could be utilized as AE aircraft for organization of a group of nurses who under- the return trip. By January 1942, Army Air stand conditions surrounding patients when Force C-47 aircraft had transported more they are traveling by air.” In 1940, the Acting than 10,000 casualties back from Burma, New Superintendent of the Army Nurse Corps Guinea, and Guadalcanal. stated, “The present mobilization plan does not In light of this obvious need, the first Air contemplate the extensive use of aeroplane Surgeon of the Army Air Force, Lieutenant ambulances. For this reason it is believed that a Colonel David N. Grant, strongly supported special corps of nurses with qualifications for AE.2 In 1941, Grant advocated AE as a way to such assignment will not be required.”2 The “lighten and speed the task” of casualty trans- Surgeon General at the time, Major General portation, and pointed out that AE would be C. R. Reynolds, added, “If commercial aviation available when other means of transportation companies require special nurses in any way, were not. The first Medical Air Ambulance which at present I can’t visualize, this is a matter Squadron was established in 1942. which has nothing to do with the Medical As AE evolved, it became clear that specially Department of the Army.2 AE and flight trained personnel were needed to optimize nursing were yet to prove themselves in the casualty care during air transport. Because quest to save lives through air transport. there were not enough physicians to put on every AE flight, Grant proposed establishment of a flight nurse corps.2 Despite opposition from World War II the Army Surgeon General, the designation of “Flight Nurse” was created for specially trained At the beginning of World War II, it was members of the Army Nurse Corps assigned commonly believed that air evacuation of the to the Army Air Forces Evacuation Service. sick and wounded was dangerous, medically In February 1943, the first class of Flight unsound, and militarily impossible.2 The Army Nurses graduated from Bowman Field, Ky, after Medical Department did not believe that the a 4-week course that included aeromedical airplane was a substitute for field ambulances, physiology, aircraft loading procedures, and even when it was necessary to evacuate casual- survival skills. 2. Aeromedical Evacuation: A Historical Perspective 9

Figure 2.2. A US Army Air Force ﬂight nurse attends a wounded soldier being evacuated by air in 1944 (Department of the Army photo).

Soon regular AE routes were established of death during AE had dropped in 1943 to 6 and hospitals were built along airstrips to care of every 100,000 patients.1 By the end of the for the wounded who needed to remain over- War, it was only 1.5 of every 100,000 patients. night along the route.3 In early 1943, AE air- AE was listed along with antibiotics and blood craft began transatlantic flights from Prestwick, products as among the most important medical Scotland, to the United States. By the end of advances in decreasing the mortality rate asso- the same year, the transpacific AE flights trans- ciated with warfare. In 1945, General Dwight ported patients back to the continental United D. Eisenhower stated, “We evacuated almost States via Hawaii. In 1944, a southern Atlantic everyone from our forward hospitals by air, and route to the United States was added, origi- it has unquestionably saved hundreds of lives— nating in North Africa with stopovers in the thousands of lives.”1 Azores and Bermuda (Fig. 2.2). Aircraft used The post-War drawdown changed the face of for AE during the War included the C-54 the US military AE system. By 1946, the system Skymaster, C-46 Commando, C-47 Skytrain, consisted of 12 aircraft at the School of Avia- C-64 Norseman, and C-87 Liberator Express. tion Medicine and one C-47 at each of 12 Bombers and tankers were sometimes used for regional US hospitals. In 1947, the U.S. Air tactical AE to move patients from forward Force (USAF) was established, and in 1949 was battle zones.2 given the official role of providing AE for the The number of patients transported reflects entire US military.3 the importance of AE during World War II.3 This number increased by 500% from 1943 to The Korean War 1945. At its peak, the Army Air Force evacuated the sick and wounded at a rate of almost The unexpected start of the Korean War in 1950 100,000 per month. In 1945, a 1-day AE record caught the AE system as unprepared as the rest was set at 4704 patients.2 of the US military. There was no AE system set The risk of AE to the patient had been a up in Korea and there were few medical facili- concern since the beginning of the War. As the ties located near airstrips anywhere in the aeromedical crews gained experience, the risk Far East. Because of a lack of organizational 10 K. Vanderburg infrastructure and available AE aircraft, the transporting military and civilian patients from Army was required to develop a system of the overseas theaters back to the United States, tactical AE in the Korean theater. Due to a much like today.1 A new aircraft, the Convair critical shortage of combat-ready troops, the C-131A Samaritan, became the first airplane wounded were kept as far forward as possible designed specifically for AE. This first fully so that they could be returned to combat as pressurized twin-engine transport was designed soon as they were physically able. In the early as a “flying hospital ward,” complete with months of the conflict, most patients were air conditioning and oxygen for patients, evacuated by ship from Korea to Japan, even and had the capability to carry bulky medical though empty cargo planes were available.1 equipment, such as the iron lung and chest With the establishment of the Far East Air respirator. The Samaritan accommodated 40 Force, the logistics of establishing an opera- ambulatory or 27 litter patients or a combina- tional AE system was made a top priority.1 tion of both. Without adequate dedicated AE aircraft, the In 1968, the McDonnell Douglas C-9A concept of retrograde aeromedical airlift Nightingale made its debut as the state-of-the- presented the best solution. After offloading art medium-range, swept-wing twin-jet aircraft personnel and cargo near the forward battle used almost exclusively for the AE mission.1 area in central Korea, C-54, C-46, and C-47 air- The Nightingale is a modified version of the craft were used to transport casualties further McDonnell Douglas Aircraft Corp’s DC-9. It south in Korea or to Japan. In the first 6 months is the only aircraft in the present-day USAF of the war, over 30,000 casualties were evacu- inventory specifically designed for the move- ated by air. As the fighting became more ment of litter and ambulatory patients, and can intense, over 10,450 combat casualties were carry 40 ambulatory patients, 40 litter patients, airlifted between January 1 to 24, 1951.1 or a combination of both (Fig. 2.3). By fall 1952, the C-124 Globemaster became the primary air cargo aircraft, almost completely replacing the C-54. When configured Vietnam War for AE, the massive C-124 accommodated 127 litters or 200 ambulatory patients. It also had In 1964, the United States entered the Vietnam the advantage of a shorter enplaning and conflict. Again, the peacetime AE system had deplaning time and required a smaller medical to be built up to meet the wartime needs of the aricrew than the C-54. Unfortunately, because US military. Initially, C-118 and C-130 cargo of its size, the C-124 could not land in Pusan to aircraft were used to evacuate patients within evacuate patients from this area. Instead, the Vietnam and to offshore islands. When the smaller C-46 aircraft, which carried a maximum C-141 Starlifter jet-powered cargo aircraft load of 26 patients was used for intra-theater became available in 1965, it was given the AE AE in Korea and Japan.1 mission in addition to its primary cargo mission. By the conclusion of the Korean War in 1955, By 1967, the Pacific Air Forces Aeromedical the USAF AE system was again capable of Evacuation System had 17 operating locations safely moving a large number of casualties throughout the Pacific. The C-118 became the within the theater and back to the United workhorse for in-theater AE, allowing the States. This system certainly contributed to the C-130 to concentrate on its cargo mission.1 decreased death rate of the wounded during The character of the combat in Vietnam the Korean War, which was 50% less than that made tactical AE especially important. Small seen during World War II.1 transport aircraft, such as the C-123, would arrive at small airstrips carrying cargo. Within a matter of minutes, the aircraft would be Pre-Vietnam War unloaded and reconfigured to carry patients. The number of patients transported by the In the years immediately after the Korean USAF AE system during the Vietnam War was War, the peacetime AE system continued to astounding. During the 1968 Tet Offensive, serve the Department of Defense (DoD) by 688 patients were processed within the Pacific 2. Aeromedical Evacuation: A Historical Perspective 11

Figure 2.3. Early biplane to sophisticated jet: C-9A Nightingale with Curtiss JN-4 Jenny (USAF photo, 311th Human Systems Wing Archives, Brooks AFB, Tex).

Aeromedical Evacuation System on a single Post-Vietnam War day. In May 1968, 12,138 casualties were evacuated from Vietnam on 154 AE missions. By In 1975, responsibility for the DoD AE mission 1969, the Military Airlift Command AE system was shifted to the Military Airlift Command evacuated an average of 11,000 casualties per and remained there for the next 17 years. Four month. An all-time single-day high of 711 active-duty AE squadrons and 28 Reserve and patients were moved out of Vietnam on March Guard units maintained the peacetime AE 7, 1969. In the closing months of 1969, patient system and remained on standby for any world- movements began to decline to less than 7500 wide contingency. Anytime and anywhere there per month.1 was a disaster, bombing, or contingency, the AE During the Vietnam War, many advances system was there. The three primary aircraft were made in AE.1 An important finding was used for AE during this period were the C- that wartime casualties did not do as well if pre- 9A Nightingale, C-141 Starlifter, and C-130 maturely placed on long flights. For this reason, Hercules. patients were stabilized in combat hospitals and The USAF AE system participated in many then transported to offshore islands for defini- noteworthy missions in the next two decades.3 tive treatment. Patients were allowed to conva- In 1975, USAF AE participated in Operation lesce and then either be returned to duty or Babylift out of Saigon. During this operation, a transported back to the United States for pro- C-5A Galaxy crashed due to mechanical prob- longed treatment. The average stay in-theater lems, resulting in the single greatest loss of life prior to long-distance AE was more than during an AE flight. In 1977, active and reserve 1 week.4 Although Saigon fell in 1975, the AE units assisted in the transport of those Pacific AE system stayed relatively unchanged injured in a B-747 collision in the Canary for many years. Islands. In 1983, more than 400 wounded were 12 K. Vanderburg evacuated from Grenada during Operation patient care equipment standardization has Urgent Fury. Several hundred wounded were remained the responsibility of the Air Mobility evacuated from Panama in Operation Just Command. Cause in 1989. In 1990, elements of the US Air In some cases, history almost appears to National Guard and USAF Reserve formed a repeat itself. AE has gone full circle from the provisional Aeromedical Evacuation Squadron days of the Jenny and the Cox-Klemmin, air in Saudi Arabia as part of Operation Desert transporting only two patients in a small plane. Shield. The USAF AE system played a vital Today, many urgent military AE missions role in Somalia in 1992 and 1993 during utilize the C-21, which can hold a maximum of Operation Restore Hope. Routine AE missions two litters and a limited medical crew. This is continued to be flown in the Balkans to support also the case for civilian air ambulances and the military operations there. From the post- helicopters. But, we have come a long way from Vietnam era until today, the AE system the small airplane with an open cockpit to a jet has remained relatively stable in its routes, aircraft with a medical platform that supplies airframes, and missions. oxygen and electrical capabilities and carries a crew trained in critical-care-in-the-air skills. The history of AE continues to be written. The Present With the rapid technological advances in both air travel and medicine, it is only natural that In the last half of the 1990s, AE underwent AE continues to be refined and reengineered further evolution in response to changes in US on almost a daily basis. military doctrine. Modern conflict has resulted in fewer casualties with little lead time. Criti- cally ill patients have had to be evacuated long References distances to the nearest comprehensive medical 1. The Department of the Air Force, Office of the facility because there has often been inade- Surgeon General. A concise history of the USAF quate time to set up a contingency hospital. aeromedical evacuation system. Washington, DC: This has required the movement by the US AE US Government Printing Office; 1976:1–26. system of stabilized in contrast to stable conva- 2. Link ML, Coleman HA. Air evacuation mission. lescing patients. This, in turn, requires the Medical support of the Army Air Forces in World ability to provide intensive care during AE. To War II. Washington, DC: US Government Print- this end, the USAF has developed Critical Care ing Office; 1955:357–412. Air Transport Teams to augment regular AE 3. Mebane R. Timeline events in the history of crews. air evac. Mr Makovec’s aeromedical evacuation The complexity of contingency AE has history index. http://www.ior.com/~jmakovec/ makovec/ae_tmlne.htm. 1999. resulted in administrative changes in the AE 5 4. White MS, Chub RM, Rossing RG, Murphy system as well. The DoD has assigned the role JE. Results of early aeromedical evacuation of setting policy for the flow and care of of Vietnam casualties. Aerosp Med 1971;42: military casualties worldwide to the US Trans- 780–784. portation Command. Overall responsibility 5. Kitfield J. A bigger job for medevac. Air Force for AE training, patient care standards, and Mag 1995; March:52–55. 3 Indications and Considerations for Emergent Evacuation of the Peacetime Casualty

J.D. Polk and William F. Fallon, Jr.

Civilian aeromedical evacuation (AE) has issue merges into the liability issues that are evolved extensively over the past several years. unique to civilian AE. This chapter will update Not long ago, patients were deemed too sick to the civilian and military physician on the dif- be transferred or kept at a community hospital ferent types of civilian air transport and the facility until they were considered “stable.” clinical considerations that must be considered Today, critical patients (such as those on biven- in peacetime AE. tricular assist devices, intra-aortic balloon pumps, etc.) are transferred by aircraft to tertiary centers on a routine basis. Ground Transport vs AE Civilian AE has come a long way from its humble beginnings as a derivative of military There are two principal factors that should be transport. This is primarily because there are taken into account when considering AE: considerable differences between military wartime and treatment. For most patients, such as time transport and civilian peacetime transport. those with multiple trauma, the most important In times of war, the echelons of care are well advantage that AE has over ground trans- defined, the mode of transport is usually portation is the decreased time required for known, and the receiving facility is certain. transport to a trauma center. However, for Peacetime air medical transport is a different other patients continuation of critical care is the story, primarily because of the multiple consid- most important aspect of the transportation. erations involved in the transfer of the critically When a patient in cardiogenic shock is on ill patient. an intra-aortic balloon pump or extracorporal The political and logistic considerations membrane oxygenation (ECMO) device, the involved in transport of a critically injured or ill requirements for medical expertise and careful patient in times of peace often exceed any management are more important than speed. conflicts encountered when moving patients Survival of the patient is the obvious absolute in times of war. Politics are injected into even priority. Sometimes it seems to take an inordi- the simplest patient transfer by third-party nate amount of time to prepare the patient for insurance and other contractual agreements safe transport. However, this preflight prepara- (eg, HMOs, PPOs, out of network, etc.). These tion may be lifesaving in complicated cardiac or agreements often dictate which AE service neonatal cases. must be used and to which hospital the patient In addition to time and treatment, a third can be transferred. Other variables that must factor to consider is the physical environment be considered for civilian AE include the crew that separates the patient from the destination. configuration, the mode of transport (ie, ground In some cases, a 45-minute flight over a moun- vs air, rotary wing vs fixed wing), and which tain range may replace a 3-hour ambulance ride conditions preclude transportation. This last over rough terrain. In other cases, the roads

13 14 J.D. Polk and W.F. Fallon, Jr. may be straight and flat but a 1-hour flight ing a patient to a tertiary care center because can replace a 4-hour ambulance ride in and they can land on or near both medical facili- out of city traffic. Because the length of time ties and accident sites (Fig 3.1). In general, the stabilized patient spends between medical twin-engine helicopters are favored for their facilities increases the risk of medical decom- increased load capacity and added safety (Table pensation, this is not a trivial issue. The physi- 3.1). The larger the aircraft and engine, the cian must weigh all of these factors when more versatile payload capability and the making the decision to transport a patient by greater the range, which can vary from 300 to ground transportation or AE. over 500 statute miles. In places where weather can become a factor, an aircraft equipped to fly by instrument flight rules (IFR:“in the clouds”) Types of Aircraft is preferred over those that can only fly by visual flight rules (VFR: “visual reference with The mission profile of an AE service is estab- the ground”).1 The ability to determine the air- lished by a combination of the type of aircraft craft’s position by global positioning satellite used and the ability of its aeromedical crews. (GPS) is also a desirable feature to help the Aircraft used for AE differ dramatically in their aircraft get to the exact location of a distant safety profile, range, and payload capabilities. medical facility or accident site, even in incle- The medical experience and expertise of aero- ment weather. Another helpful feature, which medical crewmembers can also be widely vari- is not standard in most rotary-wing aircraft, is a able. A firm knowledge of these factors will second pilot. A second set of hands and eyes, help the physician optimize the chances of safe especially at an uncontrolled landing site or in transfer for the patient, even if the patient sud- changing weather conditions, can be an invalu- denly decompensates during flight. able asset. Emergency Medical Service (EMS) crews often wait for the “thumbs-up” from the Rotary-Wing Aircraft pilot to ensure safe approach to the running aircraft. In this respect, the second pilot adds Most community hospitals rely on the local another set of eyes for safety in and around the rotary-wing aeromedical services for transport- operating aircraft (Fig 3.2).

Figure 3.1. Civilian rotary-wing aircraft require a 100- ¥ 100-ft loading area free of debris and obstruction (photo by Frank S. Sallie). 3. Emergent Evacuation of the Peacetime Casualty 15

Table 3.1. Comparison of helicopters commonly used for civilian medical transport. EuroCopter EuroCopter EuroCopter Sikorsky Bell 206 Bell 222 Dauphine BO-105 BK-117 S-76B

Engine conﬁguration Single Twin Twin Twin Twin Twin Range (statute miles) 369 434 578 345 324 403 Maximum cruise speed 127 156 183 149 153 178 Maximum takeoff weight (lb) 4450 8250 9369 5511 7385 11,700 Useful load (lb) 2163 4874 4341 2643 3545 7623 Rotor diameter (ft) 37 42 39 32 43 44 Passenger compartment interior (ft) Length 6.7 9.2 8.0 14.1 9.4 7.9 Width 3.9 4.2 6.3 4.6 4.9 5.5 Height 3.8 4.8 4.5 4.1 4.2 4.5

In our experience, the dual-pilot, IFR-rated hot desert environment in Arizona, where sun- Sikorsky S-76 has proven to be a versatile air- shine predominates. Whereas areas such as craft for transporting several trauma patients or Seattle, Cleveland, or Buffalo may benefit for handling complex equipment needs such as from a larger aircraft with IFR capability, or the dual isolettes, balloon pumps, and ECMO addition of a second pilot, because snow and machines (Fig 3.3). Many hospital-based AE moist climates make for more difficult flying services utilize smaller rotary-wing aircraft such conditions. Budgetary restraints are also having as the BK 117. an impact on which airframe is used. The cost The type of aircraft utilized will depend on of parts, fuel, and refurbishment continue to the mission profile of the aeromedical service. rise. This, in addition to shrinking reimburse- A single-pilot A-Star aircraft with VFR capa- ments for critical care transports have caused bility is probably appropriate for a service in a many hospitals to change their airframes or

Figure 3.2. A secondary pilot gives the “thumbs-up” signal, signifying that it is safe to approach the aircraft (photo by Frank S. Sallie). 16 J.D. Polk and W.F. Fallon, Jr.

Figure 3.3. A medically conﬁgured Sikorsky S-76 helicopter operated by Case Western Reserve Metro- Health Life Flight ﬂies over Cleveland, Ohio (photo by D.S. Resch).

to get out of the business of air transport wing aircraft have been extensively modified altogether. with patient transport in mind. Because high- speed flight limits engineering options, most Fixed-Wing Aircraft civilian fixed-wing aircraft modified for AE (eg, the Lear Jet) are still relatively difficult to load While some helicopters have a range of around litters into. In some aircraft, the doors and cabin 300 to 400 miles, the fixed-wing turbo prop or are so narrow that a litter must be rotated up jet aircraft has a range varying from hundreds to 30 degrees about its long axis to be loaded. to thousands of miles. Fixed-wing aircraft also Unfortunately, some patients or equipment travel at much greater speeds. A rotary-wing may not be able to tolerate these movements. aircraft must rely on its main rotor for both Fortunately, large military aircraft used for AE generating lift and creating forward thrust for (eg, C-9A, C-130, C-141) do not share these flight, thus reaching a practical limit of around problems (see chapter 8). 200 knots. In contrast, modern AE Lear Jets It should be noted that some companies use routinely cruise at 400 knots, decreasing the their fixed-wing aircraft only part time for AE. time taken to travel long distances by more For economic reasons many jet AE operators than half. Fixed-wing aircraft do, however, have use their aircraft to move business people when several drawbacks compared to rotary-wing not moving patients. A certain amount of time aircraft. may be needed to convert their aircraft to a The greatest disadvantage of fixed-wing airmedical configuration and acquire the appro- craft is that they require an airport. This means priate medical crew. In these cases, the referring an additional ground ambulance trip to and physician should assure that the AE service is from the airport on both the referring and in compliance with Federal Aviation Regu- receiving sides of the transport. lation Part 135 for air taxi operation and is A second drawback is that loading and accredited by the Commission on Accreditation unloading of the patient is in general more dif- of Medical Transport Systems. Most large ficult with a fixed-wing aircraft when compared tertiary-care hospitals have fixed-wing AE ser- to a rotary-wing aircraft. Many of the rotary- vices they utilize on a frequent basis, and thus 3. Emergent Evacuation of the Peacetime Casualty 17 will be able to recommend a particular service sequela that may result from either the disease to the referring physician. process or the act of transporting the patient. Military AE during peacetime is arranged The type of mission being flown will determine through Air Mobility Command via the Global the specific makeup of the crew. However, for Patient Movement Requirements Center both logistic and economic reasons, physicians (GPMRC). The GPMRC is a joint service are often not part of the crew of routine AE agency under the US Transportation Command flights. In any case, the diversity of skills found (USTRANSCOM) responsible for coordinat- in mixed crews (nurse–physician, nurse–para- ing military AE between theaters (eg, from medic, and nurse–respiratory therapist) may be Europe to the United States) throughout more advantageous than crews of like training the continental United States (CONUS), and (nurse–nurse, paramedic–paramedic). from nearby offshore locations such as Puerto Rico. It is extremely important to give the Physician–Nurse Crews TRANSCOM officer as much information about the patient and requirements as possible Several AE services that operate from a so that the appropriate decision can be made tertiary-care facility, including our service at whether to utilize USAF or civilian AE aircraft. Metro Life Flight, have a medical crew consist- USTRANSCOM maintains a list of commer- ing of a physician and critical care nurse (Fig cial providers that meet the appropriate pro- 3.4). This crew mix is necessary to care for the fessional standard, which includes the specific types of patients who are routinely transported medical capabilities of each provider. to a level-one trauma and burn center and cardiac surgical referral centers. Advanced training and expertise is required to operate AE Crew Configuration medical devices such as intra-aortic balloon pumps, ECMO devices, and biventricular assist The composition of an aeromedical flight crew devices and care for complex trauma casualties is designed to safely carry out transport of the during flight. The on-board physician adds patient or patients and manage any adverse certain procedural expertise and a broad

Figure 3.4. A MetroHealth Life Flight medical crew consisting of a physician and critical- care nurse are assisted by an emergency medical service (EMS) at the roadside (photo by D.S. Resch). 18 J.D. Polk and W.F. Fallon, Jr. knowledge base that can be particularly useful and expertise that is traditionally lacking in in the complicated patient.2 The presence of a the nursing and physician education. Again, physician also eliminates the need to contact medical control is required as with any crew in base physicians for decision-making authority which a physician is not present. or permission to give certain drugs. If the transport service does not have an on-board physician, the referring physician will carry the bulk Military AE Crews of responsibility and liability for that patient Even during peacetime, routine military AE during transport until the patient is received by aircraft are configured to transport 40 or more the accepting physician. patients, both ambulatory and by litter. The standard AE medical flight crew consists of one Nurse-Only Crews flight nurse and three flight medical technicians for each 10 patients and thus is very flexible. Not all patients need a physician on-board. For unstable patients, the crew is augmented Many services use a crew consisting of two crit- with physicians with the special skills required. ical care flight nurses. This is particularly useful Because of the need to transport critically ill for the rotary-wing service, which provides patients, the USAF has developed Critical Care mostly interhospital ICU to ICU transfers. Air Transport (CCAT) Teams. Each team is Typically, AE flight nurses have at least 3 years made up of a critical care physician, a critical of prior critical care or emergency medicine care nurse, and a respiratory therapist trained experience, and many are EMT or paramedic in AE of critically ill patients. certified. When contracting with GPMRC/USTRANS- Nurse crews require medical control by a COM for fixed-wing AE services, it is important physician. This is ideally achieved using written for the referring physician to give as much infor- protocols that allow the nurse to operate and mation to the transport coordinators as possible perform medical duties under the license of the so that they can assist in tailoring a transport physician medical director. Another important team that will meet the needs of the patient. If aspect of medical control is the ability of the the referring physician believes his patient nurse to directly communicate with a physician requires a physician–nurse team, then he must when needed. make this specific request known to the USTRANSCOM representative. The makeup of the provider team allocated to the flight may Nurse–Paramedic Crews be expressed in terms of aeromedical crew member levels, which gives numerical designa- Many rotary-wing AE services use a relatively tions to crew members based on level of train- practical and cost-effective paramedic–nurse ing (Table 3.2). crew. The paramedic brings valuable and practical prehospital treatment experience to the team that often complements the critical care background of the flight nurse. This crew mix is Types of Patients advantageous when the majority of flights are Requiring Transport accident scene evacuations but is less suited for the transport of critically ill patients, where The predominant diagnoses are remarkably additional physiology and medical knowledge similar in both the peacetime military and is needed. An attempt to remedy this situa- civilian communities, namely, childbirth, heart tion has been made by the development of attacks, strokes, accidents, and infections. Like- the “critical care paramedic.” Unfortunately, a wise, many hospitals in both the military and paramedic with this advanced training cannot civilian communities have specific limitations to be considered an equivalent replacement for a their care based on their diagnostic and thera- critical care nurse or a physician. However, peutic capability and/or the experience level of paramedics do bring considerable expertise in their staff. For this reason, it is often necessary regards to extrication and field care, training in both systems to transfer patients to a higher 3. Emergent Evacuation of the Peacetime Casualty 19

Table 3.2. USAF aeromedical crew member levels. Level Training level Civilian designation

1 Emergency Medical Technician Basic EMT-A or Emergency Medical Technician Intermediate EMT-I 2 Paramedic EMT-P 3 Registered Nurse RN 4 Physician MD, DO level of care offered at a tertiary center (Table The crew should always have ample supply 3.3).3 of the medications needed to support the When the capabilities of your medical facil- patient in case of an unscheduled landing or ity have been exceeded, there are several steps diversion due to aircraft mechanical failure, necessary to effect a safe transfer. First, you weather, or other unforeseen circumstance. A must confirm that the gaining facility has the general rule of thumb is to have three times the capability to meet all of the patient’s require- calculated amount on hand. ments. This is usually accomplished by direct communication with the receiving physician. Cardiac Patients Next, you must identify which AE service is the best qualified to carry out the transfer because Cardiac patients are among the most common their capabilities may be vastly different. The critically ill patients transported by civilian AE. referring physician must be comfortable that The most common scenario is a patient with the patient will fall well within the AE service’s an acute myocardial infarction who has not mission profile, even in the “worst case” responded adequately to thrombolytic therapy medical scenario. at a local medical facility. Because urgent

Table 3.3. Patients requiring air medical transport.

General considerations Burns with associated injuries Optimal scene time or time for interhospital transport Auto crash or pedestrian injury with velocity greater dictated by patient’s illness or injury than 25mph Distances to be covered, local geography, and trafﬁc Intrusion into vehicle by 20in or greater conditions Ejection of patient or rollover Carrier and personnel availability Death of occupant in same crash Weather conditions Penetrating injury to the abdomen, neck, head, or Cost thorax Trauma/scene Fall greater than 15–20ft Trauma center evaluation needed and with ground Age greater than 55 or less than 5 with comorbid transport greater than 15min injuries Mass casualty with local facilities exceeded Known metabolic or cardiac disease with comorbid Mechanism of injury consistent with high-impact injuries trauma Burns requiring burn center evaluation and treatment Rural location Late secondary criteria Trauma/interhospital considerations Sepsis Head injury with Glasgow less than 13, lateralizing Prolonged ventilation with pulmonary rehabilitation signs, or open injury with CSF leak needed; ARDS aggressive tertiary care Spinal cord injury Single- or multiple-system failure Widened mediastinum, major chest wall injury, or blunt Major tissue necrosis or penetrating cardiac injury Medical Patients requiring protracted ventilation Rescue angioplasty or CABG Pelvic ring disruption with shock and evidence of Advanced tertiary care for multisystem failure continuing hemorrhage; open pelvic injury Sepsis Severe facial injury with head injury Acute abdomen in a facility with no surgical support Concomitant head injury and other body system injury Need for tertiary care realized Multiple fractures

Source: Adapted with permission from Blumen and Rodenberg.3 20 J.D. Polk and W.F. Fallon, Jr. rescue angioplasty may be life-saving for this ventricular assist devices and some biventricu- type of patient, they are often candidates for lar devices have mechanical mechanisms that AE to a tertiary center with cardiac catheteri- can be used to maintain patient perfusion in the zation and angioplasty capabilities. Because the event of pump or power failure. Intra-aortic risk of an in-flight cardiac event is high, a qual- balloon pumps, however, will need manual ified critical-care AE team is needed to antici- inflation and deflation of the balloon to avoid pate untoward changes to ensure the patient thrombosis. will survive the flight.3–7 For patients with profound cardiogenic shock, positioning in fixed-wing aircraft is also an important consideration. When possible, the Myocardial Infarction patient’s head should be oriented toward the Myocardial infarction (MI) is a common rear of the aircraft so that the acceleration of malady requiring transport. The usual reasons the aircraft during take-off will force the blood for transport of a patient with an MI is either toward the brain and heart instead of away the need for advanced invasive capabilities, from it. This essentially gives the patient a including emergent angioplasty, coronary momentary boost in preload. artery bypass graft, intra-aortic balloon counterpulsation, or for cardiac intensive care. Prior Dissecting Aortic Aneurysm to flight, a standard MI treatment protocol should be followed, with therapies such as A symptomatic aortic aneurysm, usually aspirin, nitroglycerine, heparin, and throm- related to atherosclerosis or hypertension, is bolytics. The patient should have a functioning another common indication for civilian AE. In- large bore intravenous line because there is a flight leaking or rupture manifests as increased significant risk of postinfarction hypotension or pain and hypotension. The only effective other untoward event occuring in flight. method to sustain the patient long enough to A patient with a recent MI is at high risk for get to the operating room is the liberal use of medical decompensation during AE. This can blood products and isotonic volume expanders. manifest by signs of decompensation such as Although many referring physicians request a hypotension, shock, pulmonary edema, hypox- surgeon accompany their patients in case of ia, florid heart failure, and/or dysrhythmias. rupture, there is no record of a successful tho- For this reason, AE crews must have readily racotomy in flight for this disease process, nor available oxygen, intravenous fluids, advanced is it likely that one could be accomplished. cardiac life support drugs, defibrillator, and pacing capabilities at all times. Advanced Recent Cardiac Arrest assessment of cardiac patients via in-flight echocardiography is now possible and may lend It is sometimes necessary to transport by AE a additional information as to contractility and patient who was recently resuscitated from wall-motion abnormalities in these patients cardiac arrest and who is still moderately hemo- (Fig 3.5). dynamically unstable. The crew must have all necessary equipment to carry out further resus- Cardiogenic Shock citation (eg, defibrillators, airways, oxygen, suction, etc.) in the event the patient arrests in Patients in profound cardiogenic shock may flight. In addition, several antiarrhythmic drugs require AE while undergoing mechanical assis- of differing classes (eg, beta-blockers, calcium tance in the form of an intra-aortic balloon channel blockers, magnesium, amiodarone, pump, ECMO, or ventricular assist device.8 The lidocaine, procainamide, etc.) should be avail- AE crew must have special training in the use able. If there is any question regarding need for of these devices and have plans for contin- cardioversion, it should be done prior to flight. gencies, such as power failure in the aircraft There is no benefit in adopting a “wait and see” (Fig 3.6). Battery back-ups on most of these attitude because of the difficulties attending to machines are limited to 30 minutes. Centrifugal an in-flight cardiac arrest. 3. Emergent Evacuation of the Peacetime Casualty 21

Figure 3.5. A ﬂight surgeon performs an in-ﬂight echo with a sonoheart portable echocardiography machine (photo by Frank S. Sallie).

Figure 3.6. When specialty equipment is used in- special training and expertise for safe transport ﬂight (eg, biventricular assist devices and intra-aortic (photo by Frank S. Sallie). balloon counterpulsation) the AE crew must have 22 J.D. Polk and W.F. Fallon, Jr.

Intracranial Hemorrhage significant changes in oxygenation or ventilation of a patient. Patients with intracranial hemorrhage may need to be transferred by AE so that they can Medical Conditions receive either medical or surgical treatment. Patients with ischemic stroke may need to Patients with pulmonary disease can pose be transported to the tertiary facility within 3 major challenges to the aeromedical transport hours from time of onset to receive appropriate team. The first concern of the crew should be thrombolytic therapy and possible angioplasty. maintenance of the patient’s airway. Patients The aeromedical crew should be prepared with a decreased mental status, heavy secre- to provide an emergency airway should the tions, or labored breathing should be intubated patient’s condition deteriorate. Seizures should prior to transport because their condition will be anticipated and prepared for by having almost certainly worsen at altitude. appropriate amounts of anticonvulsants avail- The most difficult pulmonary cases are those able for use. patients with severe adult respiratory distress Patients with hemorrhagic stroke or intracra- syndrome (ARDS) who are not adequately nial hemorrhage secondary to trauma may be oxygenated despite intubation and positive transferred so that they can receive emergency pressure ventilation. A patient whose oxygen neurosurgical treatment.9,10 The aeromedical saturation is only 90% despite being on a crew should ensure that the patient has a patent ventilator with an FiO2 of 100% and 15cm of airway and an adequate gag reflex, and be pre- positive end-expiratory pressure (PEEP) will pared to provide emergent airway intervention probably not tolerate AE. if the patient deteriorates in-route. A worsening neurological exam during flight is important Pulmonary Trauma information to the surgeon because it may indi- The aeromedical crew should be vigilant in cate the need for expedient surgical interven- monitoring for changing dynamics that may tion. It is for this reason that routine chemical occur in the traumatized patient with chest paralysis should be avoided unless warranted injuries and be prepared to provide the neces- by the patient’s condition. This will help the sary treatments. Placement of a definitive aeromedical crew identify a worsening neuro- airway may be needed in patients with con- logical exam in a more expeditious manner. comitant pulmonary injuries. Complications Patients who have already had neurosurgery that arise from positive pressure ventilation for head trauma are at risk of increased cere- must also be watched for and treated, especially bral edema secondary to changes in atmos- in the traumatized patient. Pneumothorax is an pheric pressure during AE using fixed-wing especially important issue for AE patients aircraft. Ventricular shunts and osmotic diuret- because even a simple 20% pneumothorax at ics may decrease this risk. However, care must sea level will expand at altitude and may lead be taken to keep the cerebral perfusion pres- to total collapse of the lung. A traumatic pneu- sure within a reasonable level by keeping the mothorax of any size requires the placement mean arterial pressure high enough to avoid of a chest tube with a Heimlich valve prior compromise of the cerebral perfusion pressure. to AE. Tension pneumothorax discovered For this reason, it is sometimes necessary to add in-flight should be treated and relieved by dopamine to the patients list of intravenous needle thoracostomy. A significant air leak or a medications. hemopneumothorax that develops in-flight will require placement of a thoracostomy tube if a Pulmonary Patients qualified AE crewmember is available.

There are some important considerations in Neonatal Transportation patients with pulmonary disease, regardless of whether it is of medical or traumatic origin. The Neonates absolutely require specialized teams change in atmospheric pressure, especially and equipment for safe transport. The equip- during fixed-wing AE, can be enough to cause ment and personnel necessary to accomplish 3. Emergent Evacuation of the Peacetime Casualty 23 this mission account for a large part of any flight the patient in active labor who is dilated program’s budget, despite the fact that they may beyond 6cm should not be placed on the air- account for less than 25% of the volume of busi- craft because it is difficult to effectively assist ness. Dedicated AE crews trained solely for the the mother in the small environment of the transport and care of the neonate patient are aircraft. If the patient is in advanced labor, it is ideal. Neonatal nurses and physicians usually far safer to deliver the infant at the referral replace the routine adult or pediatric team institution and then transport the mother and members for these specialized transports. child postdelivery. The heavy and cumbersome equipment In all cases of emergency maternal AE, the needed for neonatal transport (eg, isolette, patient should be transported on a litter and ventilator, and specialized supplies) adds sig- receive nasal oxygen at 4L/minute. If there is nificantly to the overall weight of the aircraft. any sign of maternal or fetal compromise, the Many small rotary-wing aircraft can carry only patient should be supine and in the left Tren- one incubator and thus require either multiple delenburg position. A large-bore intravenous flights or multiple aircraft to transport twins or catheter should be in place to allow the admin- higher-order multiple births. Larger aircraft are istration of fluid or blood in the event the capable of carrying twin isolettes and crews, but patient requires aggressive resuscitation. In- careful consideration of weight and balance on flight portable ultrasound has been used to the part of the pilot(s) is needed. ECMO units make fetal heart rate determinations, as it or high-frequency jet ventilators require addi- offers the advantage of being able to visualize tional qualified personnel as well. the heart rate. Doppler techniques used in Rarely is a neonatal transport a “load and the past are limited due to the noise-filled go” situation. Considerable time is expended at aeromedical environment. External electronic the referral facility to achieve adequate stabi- fetal monitoring can be used. However, the lization and preparation for safe transport of medical utility of this has not been demon- the neonate. Optimization of ventilation, oxy- strated because there is little that can be done genation, and temperature control is critical to in-flight in the event of an ominous tracing.11 successful AE transport of the neonate. Envi- ronmental temperature, altitude, and travel distance are factors that are weighed in the clinical Pediatric Patients decision-making process by the neonatal flight Emergent transport of a child occurs for a crew and greatly impact the amount of time number of reasons, but the majority of emer- spent at the referral facility in preparation for gent evacuations in the pediatric population transport. come about either due to traumatic injury, sepsis, or airway compromise. Obstetric Patients Trauma Obstetric transport requires considerable skill and confidence on the part of the aeromedical After the first year of life, trauma is the leading crew. It is required whenever the referral cause of death in the pediatric population. facility is unable to provide the needed level Burns, smoke inhalation, drowning, blunt trau- of service to either the mother or neonate. matic injury, spinal cord injury, child abuse and Indications for maternal transportation include neglect, falls, and suicide collectively add to the preterm labor, premature rupture of mem- epidemic number of pediatric deaths and dis- branes, eclampsia and preeclampsia, abruptio abilities that occur each year. It is not uncom- placenta, and placenta previa. AE crews who mon for children to engage in dangerous adult perform emergency obstetric transport must be behaviors that put them at significant risk for ready to assist the mother and provide the death and serious injury. Of particular concern initial neonatal resuscitation should a precipi- is the rise in penetrating trauma in the pediatric tous birth occur. population related to gun and knife wounds Certain careful considerations must be made associated with gang activities and drug-related before transporting the obstetric patient. First, violence. 24 J.D. Polk and W.F. Fallon, Jr.

There are specific differences in pediatric precursors to impending respiratory arrest. trauma that are of interest to the aeromedical Should a child with an airway problem begin to crew. First, pediatric trauma patients are much deteriorate, the flight crew must be prepared more likely to sustain head injury than their to obtain an emergency airway. adult counterparts. This is related to the fact The crew must be capable of obtaining an that, in children, the head accounts for a emergent airway in a matter of minutes, most large body surface area and relative weight commonly by endotracheal or nasotracheal in comparison to the remainder of the body. intubation. Transtracheal jet insufflation may Secondary brain injury occurs as a result of be lifesaving in these patients if endotracheal hypoxia, hypercapnea, hypovolemia, seizures, intubation is impossible or impractical. Be- and cerebral edema, all of which can lead cause carbon dioxide begins to accumulate to an increase in intracranial pressure (ICP). immediately, this is a temporary solution and During AE, cerebral perfusion can be opti- retrograde intubation or completion of the mized by intubation and mild to moderate surgical airway is necessary. hyperventilation. The second important difference in children is that they do not show signs of hemodynamic Trauma Patients decompensation until late in the course of the The evacuation of the trauma patient in peace- disease process. Hypotension is a late sign in time usually falls into one of two categories: the pediatric trauma patient, and thus tachy- acute and convalescent. The acute phase cardia should be used in the child to gauge the usually refers to the aeromedical team respond- need for fluid resuscitation. If needed, the ing to the scene of an accident or a smaller com- aeromedical crew should begin fluid resuscita- munity hospital to provide emergent care and tion with repeated boluses of isotonic solution evacuation for the acutely injured patient. The (20cc/kg). If multiple fluid boluses fail to stabi- care provided is consistent with the Advanced lize the pediatric trauma patient, blood prod- Trauma Life Support primary survey and ucts may be required. treatment (see chapter 12). Scene stabilization is usually limited to airway interventions, con- Sepsis tainment of gross hemorrhage, and spinal The toxic-appearing child can have a rapidly immobilization. Chest tubes, intravenous lines, progressive downhill course and thus warrants blood infusion, and other modalities are usually special consideration on the part of the flight initiated and continued in-flight to prevent crew. Emergency in-flight treatment consists of delay in transport of the patient to a trauma bolus intravenous fluid therapy, vasopressors, center. Our program also performs the focused and broad-spectrum intravenous antibiotics. abdominal sonography for trauma (FAST) ultrasound during flight to identify patients with hemoperitoneum to expedite triage at the Airway Compromise trauma center. Thus, the aircraft and crew are The pediatric airway is short and small in an extension of the trauma team, bringing comparison to the adult airway and thus is par- critical-care skills to the patient in the field.12–20 ticularly susceptible to obstructions from con- Airway management is perhaps the single ditions such as asthma, croup, epiglottitis, and most important aspect in the care of a trauma foreign body. One millimeter of tissue edema patient. AE crews must be able to establish decreases the pediatric airway lumen by a and maintain an airway in the most difficult factor of four. Unfortunately, the usual seatbelt patients, even in the vibrating, noisy, poorly lit harness by which we normally ensure safe environment of an aircraft in flight. Medica- transport in a seated position may prevent tions for rapid-sequence intubation are used these patients from assuming a sniffing position frequently by the crews. If an airway cannot be when necessary. Lethargy and bradycardia established by the oral–tracheal route, then the are ominous signs in this population and are crew need to be prepared to rapidly establish 3. Emergent Evacuation of the Peacetime Casualty 25 an airway surgically. Other resuscitation services decreases blunt trauma mortality measures utilized by AE crews, such as chest (see comments). Austr NZ J Surg 1999;69: tube placement, intravenous lines, thoracotomy 697–701. equipment, ultrasound, and blood products, are 3. Blumen I, Rodenberg H, eds. AMPA Handbook. all useless if the patient does not have a patent Salt Lake City; Air Medical Physicians Associa- tion; 1999. airway. 4. Straumann E, Yoon S, Naegeli B, et al. Hospital The second category of trauma patients transfer for primary coronary angioplasty in high requiring aeromedical evacuation is the conva- risk patients with acute myocardial infarction. lescent category. These patients have already Heart 1999;82:415–419. been stabilized and many times have already 5. Castillo C, Lyons T. The transoceanic air evacu- had surgery at the referring institution but ation of unstable angina patients. Aviat Space require either specialized care or perhaps reha- Environ Med 1999;70:103–106. bilitation closer to home. Such patients rarely 6. Werman H, Falcone R, Shaner S, et al. require acute interventions on the part of the Helicopter transport of patients to tertiary care flight crew but may need adjustments in their centers after cardiac arrest. Am J Emerg Med therapy or equipment to ensure safe travel and 1999;17:130–134. 7. Oberg K, Kociszewski C, Dubovsky J, et al. transport. Cardiac patient air transport in the northeast region of the United States. Prehosp Emerg Care 1998;2:297–303. Conclusion 8. Mestres CA, Sanchez-Martos A, Rodriguez- Ribo A, et al. Long distance tranportation of The sickest of patients can be transported patients with a paracorporeal left ventricular assist device. Intl J Artif Organs 1998;21:425– by AE under the right circumstances with the 428. right crew capabilities. The civilian aeromedical 9. Chalea J, Kasner S, Jauch P,Pancioli A. Safety of industry has a wide variety of aircraft, medical air medical tranportation after tissue plasmino- configurations, pilot configurations, and capa- gen activator administration in acute ischemic bilities. It is important, both from a medico- stroke. Stroke 1999;30:2366–2368. legal and patient care standpoint, for any who 10. Conroy M, Rodriguez S, Kimmel S, Kasner S. wish to transport a patient by air to know what Helicopter transfer offers a potential benefit transport capabilities are available in the local to patients with acute stroke. Stroke 1999;30: area. It is also important to know the limita- 2580–2584. tions and contractual agreements of both the 11. Haggerty L. Continuous electronic fetal moni- sending and receiving medical facilities. Prior to toring: Contradictions between practice and research [review]. J Obstet Gynecol Neonat transport, the physician must be aware of the Nurs 1999;28:409–416. preflight preparation based on the patient’s 12. Tso P,Rodriguez A, Cooper C, et al. Sonography condition and disease process, especially in light in blunt abdominal trauma: A preliminary re- of the potential impact that barometric pres- port. J Trauma 1992;33:39. sure changes and exposure to the elements can 13. Rozycki GS, Ochsner MG, Jaffin JH, Champion have on the patient. Safe patient transportation HR. Prospective evaluation of surgeons’ use of by air depends on careful planning and a rea- ultrasound in the evaluation of trauma patients. sonable understanding of the process of AE. J Trauma 1993;34:516. 14. Sustic A, Miletic D, Fuckar Z, et al. Ultrasonog- raphy in the evaluation of hemoperitoneum in References war casualties. Milit Med 1999;164:600. 15. Lichtenstein D, Courret JP. Feasibility of ultra- 1. Wuerz RC, O’Neal R. Role of pilot instrument sound in the helicopter [letter]. Intens Care Med proficiency in the safety of helicopter emergency 1998;24:1119. medical services. Acad Emerg Med 1997;4: 16. Polk JD, Fallon WF. The use of focused assess- 972–975. ment with sonography for trauma (FAST) by a 2. Garner A, Rashford S, Lee A, Bartolacci R. prehospital air medical team in the trauma arrest Addition of physicians to paramedic helicopter patient. Prehosp Emerg Care 2000;4:82–82. 26 J.D. Polk and W.F. Fallon, Jr.

17. Ochsner MG. Future applications of ultra- (FAST): Results from an international consensus sound in the injured patient. Trauma Q 1997;13: conference. J Trauma 1999;46:466. 215. 20. Polk JD, Fallon WF, Kovach B, Mancuso C, 18. Polk JD. The future direction of ultrasound. et al. The “airmedical F.A.S.T.” for trauma Trauma Care Q 2000;10:15–16. patients––The initial report of a novel applica- 19. Scalea TM, Rodriguez A, Chiu WC, et al. tion for sonography. Aviation, Space, & Environ Focused assessment with sonography for trauma Medicine 2001;72:432–436. 4 Combat and Operational Casualties

Robert A. De Lorenzo

Military aeromedical evacuation (AE) must plant extracts, and songs and charms were used necessarily focus on the combat casualty. To to treat hemorrhage.1 this end, it is useful to explore the history The Romans advanced combat casualty care and recent experiences of war. In addition, by establishing a series of Valetudinarian, or the new millennium brings forth a whole casualty care centers, during the 1st and 2nd new array of military contingencies including Centuries AD. The Romans also established a stability support operations, humanitarian mis- medical corps in the legions. Epitaphs record at sions, and reactions to terrorist actions. This least 85 Roman army physicians.2 Following the chapter will provide a brief overview of these fall of the Roman Empire, there is little important historic elements and attempt to recorded evidence of other major advance- shed light on what the immediate future ments in combat casualty care until well over a may hold for AE operations. In addition, a millennium had passed. brief overview of the principles of modern In the late 16th Century during the combat casualty care will be presented to French–Spanish civil and religious wars, highlight the current state of the art in tactical the French physician Ambrose Paré pioneered care. the use of both ligature to achieve hemostasis (instead of cautery) and nutritional care to speed recovery.3 In the early 19th Century, History of Combat Medicine another French physician, Dominique Larrey, pioneered the use of triage to care for wounded 4 Armed Conflict of the Past combatants. He also developed the concept of “far forward care” by putting hospitals and sur- The history of combat medicine is as old as that geons close to the battle lines. of armed combat. The first reliable evidence of In the late 19th Century, anesthesia was combat wounds comes from ancient Egypt introduced and the era of modern care began. around 2000 BC.1 A mass grave of some 60 sol- Unfortunately, death, disability, and disfigure- diers shows evidence of wounds and arrows still ment remained common. For example, during in the body. Later, the Greeks developed a the Crimean War (1853 to 1856) the mortality crude system of caring for casualties of battle, rate from penetrating abdominal wounds was and arranged special barracks or ships 93% for English and 92% for French soldiers.5 (“klisiai”) for their care. During this era, surgi- During the American Civil War, the Union cal care was crude and consisted of removing Army experienced a similarly high mortality arrowheads and barbed spears by either rate of 87% from penetrating abdominal pushing them through or enlarging the hole wounds.6 with a knife. Treatment for pain relief and infec- Other contributions made during the 19th tion prophylaxis was limited to oral or topical Century included the introduction of wound

27 28 R.A. De Lorenzo antisepsis by Lister and nursing care by The combination of disease and nonbattle Florence Nightingale. Despite these advances, injuries (DNBI) represents a tremendous mortality ranged from 14% to 31% for extrem- threat to both the collective mission and the ity gunshot wounds and 26% for amputations.7 individual combatant. Historically, DNBI has By the end of World War (WW) I, the accounted for more combatant deaths than all mortality rate from abdominal wounds had other causes combined. During armed conflicts, declined from 85% to 56%, an improvement US forces have historically sustained only 20% attributed to early surgery.8 Blood transfusion of casualties from battle, with the balance being therapy also began in WW I. Further refine- DNBI.9 In 1942, 55% to 65% of the US Forces ments were brought to combat casualty care planning to attack Guadalcanal contracted during WW II, including better evacuation, filariasis, an invasion of the lymph system by a anesthesia, and surgical technique (Fig 4.1). parasitic roundworm that can cause inflamma- Antibiotic therapy, in particular penicillin, dration, abscesses, and elephantiasis. Also during matically changed the outcomes of many cases WW II the famous unit, Merrill’s Marauders, and brought the first effective treatments to suffered nearly 100% attack rates of diarrhea sepsis and gangrene. Anti-infective agents (eg, while in Burma. The disease was so uncomfort- penicillin, sulfa drug, and quinine) also began to able that it is said an entire platoon cut the seats impact disease, long the biggest killer on the off their pants because the severe diarrhea had battlefield. to be relieved during gun battles.9

Figure 4.1. Casualties aboard a lighter on the island of New Georgia, SW Paciﬁc, 1943 (USA Signal Corps photo by Wendlinger, courtesy of USA Center of Military History). 4. Combat and Operational Casualties 29

Table 4.1. US combatants dying of combat wounds nized by WW I. Data from Vietnam and the during selected wars. 1982 Lebanon War shows that some conflicts War Period % Mortality may generate an exceptional number of combat Mexican 1846–1848 15 stress casualties. By the close of the Vietnam American Civil 1861–1865 14 War, a combat stress casualty rate of 2.5% was Spanish–American 1898 7 reported, equivalent to just under half the WW I 1918 8 wounded-in-action rate.10 Up to one fourth of WW II 1942–1945 4.5 all hospitalized casualties were neuropsychi- Korean 1950–1953 2.5 Vietnam 1965–1972 3.6 atric in nature. During Operation Desert Storm (1991), in contrast, few serious combat stress Source: Adapted from USA data.2 cases resulted despite a long and often tedious buildup phase. This improvement has been Environmental factors, too, have plagued attributed, at least in part, to the avoidance warriors throughout the ages. The brutal of sleep deprivation and dehydration and Russian winter halted the overwhelming the regular use of critical incident stress advances of both Napoleon’s army in the 19th debriefings.10 century and Hitler’s forces a century later. In During both the Korean and Vietnam Wars, contrast, excellent logistics and good preven- mortality from combat wounds continued to tive medicine reduced US heat casualties in the decrease (Table 4.1). This change for the better Saudi desert during Operation Desert Storm. is believed to reflect the combined improve- In future conflicts, DNBI will most likely con- ments in evacuation, resuscitation, and surgical tinue to compromise the largest fraction of and postoperative care.2 During the Vietnam casualties. The AE system must be capable and War, helicopter transport from the point of prepared to handle these problems. injury to hospital was common, as was the Combat stress or psychiatric disease has also administration of intravenous fluids by trained plagued modern forces and was widely recog- enlisted medics (Fig 4.2).

Figure 4.2. During the Vietnam War, the UH-1 southwest of Dak To, 1967, courtesy of USA Center “Huey” helicopter was extensively used to quickly of Military History). evacuate casualties (USA photo taken 20 miles 30 R.A. De Lorenzo

Modern Military Operations the force to be fully capable of managing the types of patients anticipated. In Operation Just The post-Vietnam War era is marked by brief Cause, resuscitation and even some surgery was conflicts, often of high intensity but relatively performed well forward of the traditional zones light in casualty production. It is instructive to of care.14 examine these conflicts, as they are likely to be During Operation Desert Storm in 1991, more similar to future actions than the large- the US military forces sustained only 331 US scale continental wars of the past. Other likely mortalities and 353 wounded in action. Ironi- threats that will face the United States and cally, most of the deaths resulted from non- allied forces in the foreseeable future include combatant injuries and 107 were the result of operations other than war, often referred to allied fire (fratricide).15 Because of the large as “OOTW.” Most often, these will be in the buildups of US forces in the region prior to form of stability support operations, such as the allied invasion, there was a large medi- humanitarian assistance and peacekeeping cal infrastructure available to handle many operations.11 The disease and injury patterns more casualties. It is uncertain, however, if the will most likely be different than those ex- medical assets would have been effective in the periences during armed conflicts of the past face of the large casualty figures initially antic- (Fig 4.3). ipated (as high as 40,000). It is even more The British experience in the Falkland Islands uncertain if the future conflicts will allow the War of 1982 is typical of the modern, brief luxury of a 5-month buildup of combat and conflict. Over 500 casualties were evacuated out medical forces before the outbreak of ground of the theater, including 233 postoperative hostilities. patients who had received only resuscitative The value of far-forward care and rapid evac- surgery.12 During the 1983 invasion of Grenada uation is evidenced in the Soviet–Afghanistan by US forces (Operation Urgent Fury), 18 US War in the 1980s. Afghanistan guerrillas had no soldiers were killed, 116 were wounded, and 28 access to organized battlefield care and instead received nonbattle injuries.13 The US attack in were forced to seek treatment 4 days’ travel Panama in 1989 (Operation Just Cause) resulted time away in Pakistan. The hospital in Pakistan in 25 killed and 323 wounded in action in the that treated many of these casualties reported 6-day operation.14 few wounds of the head, neck, thorax, or These recent conflicts underscore important abdomen, traditionally some of the most com- trends in medical support for regional conflicts. mon types of combat injuries.16 Presumably, The first trend is the need for capable medical casualties with these types of injuries perished assets to accompany the assault force. There because of delays in care.2 may be little or no time to establish traditional More recently, the shift in US operations has field hospitals in these brief conflicts. The shoot- been toward stability support operations such ing may be over before such a large hospital as peacekeeping and humanitarian missions. could be deployed and operating. The second These types of operations tend to be prolonged, trend is the requirement for rapid evacuation involve only sporadic conflicts, and generate off the battlefield, often directly out-of-theater, few combat casualties. Consequently, the need which can require the AE system to handle for a large surgical presence is diminished. casualties who may not have the benefit of com- Disease, nonbattle injuries, and preventable plete stabilization. This was illustrated in health risks (eg, sanitation and vector control) Operation Just Cause, where the majority of the assume a greater importance, and the military 275 serious casualties were evacuated directly medical system must be prepared for these from Howard AFB, Panama, to San Antonio, types of needs.11 Tex. Some casualties arrived in San Antonio Humanitarian missions, in particular, can within 12 hours of their injuries. A third trend present a real challenge for a military medical is the need for the medical assets accompanying system designed for combat trauma. The Cuban 4. Combat and Operational Casualties 31

Figure 4.3. A child is examined at the 86th Combat Support Hospital in El Salvador (USA photo by Spe- cialist Aaron Reed).

and Haitian refugee crises in the mid-1990s is mounting for the US military to achieve generated thousands of patients, many of whom medical care standards resembling those avail- were elderly or children.17 The lack of military able in the continental United States. Whether resources in geriatrics, pediatrics, infectious realistic or not, these expectations will likely disease, gynecology, and primary care proved challenge the military health system as it con- a handicap in this environment. Although tinues to provide support for a wide array of casualties were few in number, the September missions. These expectations have been rein- 11, 2001 terrorist attacks in New York City forced by the rapid treatment and evacuation and Washington, DC underscores the absolute of special forces and other troops wounded need for broad medical capability in military deep within Afganistan during the so-called medicine. The military did respond to these war on terrorism against the Taliban. sites and was fully expected to care for civilian casualties. Essentially no combat wounds and remark- Traditional Combat Casualties ably few disease and nonbattle injuries characterize the Balkan peacekeeping mission, which Bullet and Shrapnel Wounds is still ongoing at the time of this writing. This type of low-casualty operation has also Gunshot (ballistic-type) injuries and shrapnel spawned another phenomenum in the contem- (fragment) injuries remain the largest threat on porary military: increased expectations on the the traditional battleﬁeld. Data from the part of both the troops and the public for a Vietnam War shows that 51% of combat deaths higher standard of care.11 Previous conﬂicts were due to ballistic-type injuries and 47% from have always been marked by a degree of aus- shrapnel. Ballistic-type injuries accounted for terity, remoteness, and hostility that tempered 77% of British casualties during the Falkland expectations regarding the quantity and quality Islands War and 52% of US casualties in of care delivered during the operation. Pressure Operation Desert Storm.12,15 Anatomically, the 32 R.A. De Lorenzo

Table 4.2. Location of combat wounds (%) among several wars and conﬂicts. War Head and neck Thorax Abdomen Extremities

Vietnam 14 4 4 76 Falklands 14 7 11 68 Panama 6 11* 11* 80 Desert Storm 17 4 6 71

* Thoracic and abdominal wounds combined. Source: Adapted from USA data.2,22

extremities are most vulnerable, with the lower was seen in extremity wounds, although room extremity being twice as likely to be wounded as for improvement still exists. It is likely that in the upper extremity (Table 4.2). Although data future conflicts extremity wounds will represent are incomplete at this writing, anecdotal reports the same or greater preponderance because of from the ground war in Afganistan against the improvements in body armor. Taliban reinforce this trend.This is probably due While the treatment of combat trauma shares in part to the larger body mass of the lower many similarities with civilian trauma care, extremities resulting in greater exposure and important differences exist (Table 4.4). The the proximity of the legs to landmines, a main differences between military- and civilian- common cause of shrapnel injuries in modern style care reflect differences of environment, conflicts. Fortunately,extremity wounds are sur- equipment, and on occasion clinical priorities. vivable,in particular if good hemorrhage control However, it cannot be overemphasized that the is achieved immediately after the injury. principles of good patient care do not change, Improvements in both medical care and and any differences in combat casualty care are evacuation have the potential to decrease the overshadowed by the similarities with standard number of combatants who survived the initial trauma care. injury but died subsequently in the medical system. During the Vietnam War, the percent- Blast and Burn Injuries age of casualties dying after entering the medical system varied greatly depending in the Thermal injury is a significant cause of morbid- location of injury (Table 4.3). Over one third of ity in war. Isolated burn injury is uncommon head and thoracic wound deaths occur in the and is usually associated with incendiary medical system. Increased attention to treat- devices. However, thermal injury frequently able problems, such as airway obstruction, accompanies blast and fragment injuries from tension pneumothorax, and shock, may bombs, mortars, shells, and mines. In Operation improve this rate. Although abdominal wounds Desert Storm, 26% of wounded Americans had show a relatively low lethality,early surgery and significant thermal injuries.18 prevention of late deaths from sepsis may Initial management of burns is similar to further improve outcome. The best outcome civilian burn care. Because airway assurance is

Table 4.3. Lethality of combat wounds (%) by location in Vietnam. Outcome Head Neck Thorax Abdomen Extremity

Killed immediately 34 8 41 10 7 Died of wounds 46 8 34 7 5 Survived 17 17 9 6 69

Figures add up to >100% because of overlapping injuries. Source: Adapted from USA data.22 4. Combat and Operational Casualties 33

Table 4.4. Comparison of the characteristics of Severe hollow viscous damage usually mani- combat and civilian trauma. fests by rupture. Tympanic membrane rupture Factor Military Civilian is not life threatening but has considerable bat- Bullet velocity High Low tlefield implications because hearing loss makes Frequency of High Low it difficult for troops to both hear commands shrapnel injury and protect themselves adequately. Anatomic location Extremities Torso Battlefield management of blast injuries is Comorbid disease Low High initially focused on maintenance of ventilation Contamination of High Low wounds and oxygenation. High-flow oxygen can reduce Evacuation time Long (>2h) Short (<30min) the effects of any possible gas emboli that occur. If a large embolus is suspected, placing the patient in the left lateral decubitus position may help prevent the emboli from reaching the brain or other vital organs. Initial management crucial, intubation is a consideration in any of hollow viscera rupture includes fluid resusci- burn patient at serious risk for airway compro- tation and antibiotic coverage. Definitive care mise. Any standard intravenous fluid-dosing will require laparotomy. Tympanic membrane scheme (such as the Brooke or Parkland injury usually requires no specific therapy formula) is effective at replacing the massive because most cases will heal spontaneously. fluid losses associated with burns. Electrocar- diogram monitoring is an important consideration in any severely burned patient owing to Field Treatment significant electrolyte and fluid imbalances. Escharotomy can be lifesaving in selected cases Far-forward battlefield care can be divided into and should be performed when necessary, in three stages of care: (1) care under fire, (2) tac- particular when the patient is embarking on a tical care, and (3) evacuation care.18 Care under long AE journey. Because minimal anesthesia fire is that care rendered when the patient and is needed for this procedure, it should be con- medic are under imminent threat of enemy fire. sidered a far-forward procedure. By necessity, such care is abbreviated, rapid, Blast injuries, like burns, are common accom- and austere. The first priority is protection and paniments of shrapnel wounds from explosive this is accomplished through return fire, cover, devices. It is unusual to encounter an isolated and concealment. The second priority is extrac- blast injury, unless the victim was protected tion of the casualty into a safer zone. The pre- from shrapnel and thermal burns by mechani- ferred method of extraction is self-extraction, cal means. Ironically, protective body armor where the casualty runs or crawls to safety may actually potentiate the effects of blast under his or her own power. However, if the while providing life-saving protection from casualty is seriously wounded assisted extrac- fragments. So-called “blast-effect” munitions tion by drags or carries probably will be may also cause isolated blast injury because required. Medical care while under fire is these devices cause enormous blast waves limited to the control of any significant bleed- but have no casing or shrapnel fragments to ing by tourniquet to prevent exsanguination. expel. All other procedures cannot be justified Air-filled organs suffer the greatest damage because they either take too long or expose the from blast. The three primary organs affected provider to excessive risk. are the lungs, the hollow gastrointestinal Once the casualty is brought under cover or viscera, and the middle ear. Lung damage is concealment, or the enemy has fled or been primarily disruption of the alveoli with resul- suppressed, the next stage of care begins. Tacti- tant pulmonary edema and respiratory distress. cal care is the emergency field care traditionally Arterial gas (air) emboli are a distinct possi- performed by far-forward medical personnel. bility, especially with mechanical ventilation. Airway management, controlling hemor- Pneumothorax is possible but uncommon. rhage, and treating shock are the primary goals 34 R.A. De Lorenzo in tactical care. Manual airway maneuvers a wheeled or helicopter ambulance at the unit and proper positioning, eg, recovery or lateral level and lasts until the casualty reaches either recumbent position, will assure an airway in definitive care in a combat support hospital or most cases. Intubation can be lifesaving in casu- an aeromedical staging facility in preparation alties exhibiting airway obstruction or respira- for evacuation from the theater of military tory failure. In up to 0.4% to 0.6% of all operations. conventional battle casualties, a surgical airway Evacuation care is similar to tactical care may be required.19–20 except the patients and attendants are on the Direct pressure or a tourniquet will control move. Because of the cramped quarters and most external bleeding, but intrathoracic or constant jostling, evacuation care is necessarily intra-abdominal bleeding is much more prob- limited to the essentials. Automatic ventilators, lematic. Overzealous fluid resuscitation may intravenous infusion pumps, and automated actually worsen outcome in these cases. Instead, sphygmomanometers are all in use in civilian maintaining relatively modest hypotension ambulances and have been proposed for evac- (eg, systolic blood pressure 80 to 90mmHg) uation care. However, until they are available may reduce blood loss and promote clot devel- in the field tactical medics will continue to man- opment. A rational approach to the use of ually perform ventilation, IV fluid titration, fluids has been proposed and includes minimal and blood pressure measurements. Because of use of fluids in cases of uncontrolled internal these requirements, a single attendant has a hemorrhage and modest fluid boluses, eg, limited ability to provide complicated lifesaving 1000mL initially, for cases of hemorrhagic procedures while en route. All members of the shock after bleeding has been controlled.18 medical evacuation team must take these limi- When it comes to the choice of fluid for intra- tations into consideration when preparing or venous resuscitation, there is no definitive data receiving casualties. that supports the use of colloid over crystalloid. Normal saline and Ringers lactate are the recommended fluids, based on availability, low Disease and Nonbattle Injuries cost, compatibility, and familiarity. Colloids and blood products may have roles in particu- Disease and nonbattle injuries (ie, DNBI) lar cases. Although synthetic blood products encompass all diseases and injuries sustained and other oxygen-carrying alternatives may during an armed conflict that are not a direct one day redefine the role of fluid resuscita- result of enemy action. Included in this cate- tion, they are not yet available for routine clini- gory are infectious diseases, environmental cal use. Recent reports suggest hypertonic exposure, and injuries such as from falls. saline may be preferable to ordinary crystal- Historically, disease and nonbattle injuries loid. An added benefit is reduced weight of the represent the greatest threat on the battlefield, product. dwarfing the effects of combat wounds in terms Supplemental oxygen is an important adjunct of both morbidity and mortality. The greatest in treating shock. However, for combat casualty causes of disease and nonbattle injuries that care it has been traditionally de-emphasized must concern commanders and medical plan- because of weight, bulk, and resupply con- ners alike are the extremes of heat and cold and straints. The gradually increasing availability both vector-borne and diarrheal illness. of oxygen concentrators and generators in far- Perhaps the best example of the enormous forward units is likely to change this. If avail- impact of disease and nonbattle injuries on able, high-flow oxygen should be administered combat effectiveness and strategic success is to all casualties in shock, with respiratory dis- Napoleon’s invasion of Russia. Of the 600,000 tress, or otherwise seriously compromised. soldiers who started the operation in June The final stage of care is evacuation care, 1812, only 100,000 remained by December. which begins once the casualty enters the While 100,000 died in battle, over 200,000 died formal evacuation chain. This chain begins with of starvation, cold, and disease.21 The balance of 4. Combat and Operational Casualties 35

Napoleon’s troops were captured, deserted, or combat. Today, the term “combat stress” is used were hospitalized. to refer to the spectrum of psychological prob- In WW II, Field Marshal Rommel’s re- lems resulting from acute and chronic exposure nowned “Afrika Corps” suffered severe losses to combat. from disease and nonbattle injuries. For every Data from the Vietnam War illustrate the one of his troops killed in combat, three were potential impact of combat stress on unit effec- lost to disease. Despite his prowess on the bat- tiveness.28 As the War was just getting under- tlefield, it could be argued that Rommel, like way in 1965 to 1966, the casualty rate from Napoleon, ultimately failed because of his igno- combat stress was approximately 12 per 1000 rance of the impact of disease and nonbattle troops. By 1970, the rate had more than injuries.22 doubled. This large fraction of troops hospital- More recent conflicts have avoided the huge ized for combat stress significantly decreased effects of disease and nonbattle injuries in unit combat effectiveness throughout the War. terms of human lives. However, DNBI still represents a significant operational challenge. In US conflicts this century, disease and nonbattle Contemporary Military injuries consistently accounted for 5% of Casualties combat mortalities and considerably greater morbidity.23 A review of more recent conflicts Following the collapse of the Soviet Union in suggests that between 26% and 36% of combat the 1980s, it has become increasingly apparent troops presenting for care have been unable to that future battles and military operations return to duty because of disease and nonbat- will be less likely to resemble wars of the tle injuries.23 During the Gulf War, disease and past. Future engagements are more likely to nonbattle injuries far outnumbered direct be regional conflicts than large-scale wars. combat injuries. Two US Navy hospitals expe- Operations other than war, including humani- rienced a combined disease and nonbattle tarian assistance and peacekeeping operations, injury load of 1820 casualties during a 6-month are growing in frequency. Nontraditional period.24 Burkle et al reported a 6% nontrau- “asymmetrical” threats loom ever larger, and matic casualty rate for allied forces and an 11% include limited nuclear war and chemical and rate for enemy forces treated by allied facili- biologic attacks (Table 4.5). Lastly, there is a ties.25 The majority of the disease and nonbat- subtle but important shift occurring in the tle injury cases were diarrheal and respiratory nature and frequency of combat wounds. Each illnesses, and to a lesser degree orthopedic of these factors separately will require a signif- injuries and dermatologic and psychiatric icant adjustment of the military medical problems.26,27 posture. Together, these factors compel a com- Psychiatric disease has been recognized as an plete medical refocusing for operational care. important cause of nonbattle casualties since This section will explore the contemporary mil- the turn of the century. Both the WW I term itary medical mission and introduce the types “shell shock” and the WW II term “battle of casualties that can be expected in the new fatigue” refer to the psychological effects of millennium.

Table 4.5. Characteristics of nuclear, biologic, and chemical threats. Weapon Likelihood of risk Casualty potential Targetability Portability

Chemical High Moderate Moderate Moderate Biologic Moderate High Low High Nuclear Low High High Low 36 R.A. De Lorenzo

Weapons of Mass Destruction: is often the result of limited nuclear, biologic, Nuclear, Biologic, and or chemical attacks, has allowed the military to Chemical Threats draw up plans for meaningful medical response. The first step in this development is leaving Few catastrophes are as fearsome as the explo- behind the simplistic, common-task approach. sion of a nuclear weapon or the release of Military medical providers must achieve a chemical or biologic agents. In the Cold War greater degree of sophistication in terms of the era, such warfare was contemplated only in the level of care offered. It is no longer enough for context of massive, strategic battles. The possi- the military medical system to focus totally on bility of meaningful medical response with a acute surgical trauma, but now must be equally virtually unlimited number of casualties was, at prepared to treat nuclear, biologic, and chemi- best, severely limited. Consequently, military cal casualties.29 The second step is to prepare to medicine developed a “common-task” ap- deal with new or unusual toxins and pathogens proach to nuclear, biologic, or chemical (ie, because of the rapid evolution of chemical and NBC) attacks, where all soldiers, medical or biologic weapons. The post-September 11, 2001 nonmedical, were expected to provide only the global threat of terrorism only serves to high- most basic care to these casualties. light the potentially disasterous effects of In the post-Cold War era, nuclear, biologic, or weapons of mass destruction. chemical weapons have proliferated. As the The contemporary approach to treating risk of a global nuclear war has decreased, the chemical and biologic agents relies heavily on risk of limited, tactical use of nuclear, biologic, early detection and identification of the offend- or chemical weapons has risen dramatically ing agent. In the absence of a clear etiology, (Table 4.6). This increased risk, coupled with treatment will have to be directed at symptoms. the potentially finite number of casualties that Many chemical and biologic agents cause death through respiratory failure and shock, so airway management, mechanical ventilation, and intravenous fluid therapy remain the cornerstones Table 4.6. Nations known, suspected, seeking, or of empirical therapy.30 capable of producing nuclear, biologic, or chemical Nerve agents perhaps represent the greatest weapons. chemical threat. Successful treatment requires Nation Nuclear Biologic Chemical early and aggressive treatment with the United States ¥¥ ¥injectable antidotes, atropine and pralidoxime. Russia ¥¥ ¥Timing is crucial because only early antidotal ¥ Ukraine therapy will likely improve outcome.31 For this Byelorus ¥ Kazakhstan ¥ reason, soldiers are trained to recognize the China ¥¥ ¥symptoms of nerve gas exposure and use France ¥¥autoinjection devices for both self-care and United Kingdom ¥¥buddy care in the field. Once in the medical ¥¥ ¥ Iraq system, diazepam or other anticonvulsants are North Korea ¥¥ Pakistan ¥ important adjuncts in the prevention and treat- India ¥ ment of nerve-agent-induced seizures. Iran ¥¥Other chemical agents posing significant risk Libya ¥¥include cyanides, pulmonary agents, and vesi- ¥ Algeria cants. The former two classes are less suitable South Africa ¥ Israel ¥¥for battlefield employment because of their dis- Syria ¥ persal and persistence characteristics. Their Egypt ¥ ease of manufacture, however, makes them Taiwan ¥ ideal for terrorist or insurgent use. Vesicants, ¥ Burma because of their high degree of persistence, can Ethiopia ¥ be an effective area denial tool for a tactical Source: Adapted from USA data.32 operation. 4. Combat and Operational Casualties 37

Table 4.7. Characteristics of selected chemical agents. Agent Effect Onset Primary site

Nerve Tabun (GA) Lethal Rapid Lungs, skin Sarin (GB) anticholinesterase Soman (GD) VX (cyanides) Cyanide (AC) Lethal cytochrome Very rapid Lungs

a3 inhibitor Cyanogen (CK) Pulmonary Phosgene Pulmonary irritant Immediate Lungs, eyes Vesicant Mustard (HD, HN) Contact irritant Delayed Skin, eyes Phosgene oxime (CX) Rapid Lewisite (L, HL) Rapid

Source: Adapted from USA data.32

Treatment approaches for each of these therapy are oxygen, bronchodialators, and rest. chemical agent classes is complex and only The key to minimizing vesicant injury is early occasionally adaptable for use by unsupervised (within minutes) decontamination in the field nonmedical personnel. Traditional cyanide to reduce exposure. The characteristics of treatment necessitates a somewhat risky com- selected chemical agents been well described bination of nitrites and thiosulfates. Recently, (Table 4.7).32 experts have argued against such treatments in Biologic weapons are the least understood of cases of inhaled cyanide toxicity, noting the the nuclear, biologic, and chemical threats, but therapy may exacerbate the patient’s condition. because of the incredible potency and trans- The experimental drug hydroxycobalamin missibility of some of these agents they are offers a future hope for an effective antidote potentially devastating.33,34 To complicate mat- without the untoward side effects of current ters, the broad array of potential biologic agents therapy. There is no specific antidote for pul- makes the development of effective counter- monary agents or vesicants, so the mainstays of measures difficult (Table 4.8).35 Biologic toxins

Table 4.8. Characteristics of selected biologic agents. Agent Stability Incubation Effects

Anthrax High 1–6d Shock, death Botulinum High 24–36h Respiratory failure paralysis Brucellosis Moderate 1–4wk Pneumonia, shock Cholera Moderate 1/2h–5d Severe diarrhea Pneumonia plague Low 2–3wk Pneumonia, shock Ricin High <36h Shock and death Staphylococcal High 1–6h Nausea, vomiting, enterotoxin B diarrhea, shock in high doses Trichothecene High Minutes to hours Vesicant like mycotoxin Tularemia Low 2–10d Shock, death

Source: Adapted with permission from Christopher et al.34 38 R.A. De Lorenzo are naturally occurring chemical weapons that have their effect by exposure rather than infection, and include botulinum, ricin, T2 mycotoxin, and staphylococcal enterotoxin B.36 Infectious agents include anthrax, plague, brucellosis, smallpox, and cholera. The anthrax- related terrorism in the US postal system underscores this threat. To be effective, the medical evacuation system must be capable of treating victims of biologic agents. Expertise in resuscitation, airway and ventilatory management, and fluid maintenance will be required. Antibiotic and antitoxin selection and use is important, so physicians, nurses, and ancillary providers must be familiar in prescribing and administering Figure 4.4. Distribution of energy released from a these drugs. The AE system must be capable of typical nuclear bomb (USA photo). maintaining isolation of infectious biologic casualties who pose a communicable threat. For long-distance AE requiring out of the blast, thermal, and nuclear radiation (Fig 4.4). country stopovers, contingency plans must be Blast (mechanical shock wave) accounts for developed in the event that landing permission 50% of the bomb’s energy output.37 Injury is refused for aircraft carrying such patients. occurs by three mechanisms: blast overpres- Nuclear weapons are the most devastating sure, physically throwing the victim, or debris weapons known to man. Even a small bomb acting as missiles. can yield utter destruction to the area at ground Thermal energy is approximately 35% of zero and cause considerable damage many the weapon’s output. First-, second-, or third- thousands of meters away (Table 4.9). As a degree burns are possible and frequently frame of reference, the nuclear weapons present in combination with blast injuries.38 exploded at Hiroshima and Nagasaki would be The unique characteristic of nuclear weapons, considered small by modern standards. The nuclear radiation, occurs both at the time of proliferation of nuclear weapons (Table 4.6) in the blast and subsequently as contaminated the world demonstrates the potential threat dust termed “fallout.”38 The AE system must and the need for medical preparedness for be prepared to handle the potentially delayed nuclear casualties. symptoms of radiation exposure, including Nuclear bombs deliver energy and cause gastrointestinal bleeding, diarrhea resulting in damage through three primary mechanisms: electrolyte imbalance, bone marrow failure, and pancytopenia. Again, the evacuation system must have contingency plans in the event that landing permission is refused for aircraft Table 4.9. Effects of nuclear weapons at various carrying minimally contaminated or radiation- distances (km). exposed nuclear casualties. Size Nuclear radiation* Thermal energy† Blast‡ No discussion of the medical effects of nuclear, biologic, and chemical weapons is com- 1kT 0.71 0.77 0.28 20kT 1.3 1.8 1.0 plete without emphasizing the important role 100kT 1.6 3.2 1.4 of decontamination, the critical first step in 1MT 2.3 4.8 3.8 the medical management of these casualties. 10MT 3.7 14.5 11.7 Ideally, decontamination occurs before the pa- * 1000CGY. tient enters the evacuation chain. However, the † 50% incidence of 2nd-degree burns. inevitable fog of war will most likely result in ‡ 50% incidence of serious injury. missed, incomplete, or inadequate decontami- 4. Combat and Operational Casualties 39 nation. The entire medical and evacuation patients treated by the military medical system system must be fully prepared for this possibil- 52% were female and 49% were less than 13 ity. The AE system will need to be prepared years old.43 During the 1995 siege of Sarajevo to use detection equipment for biologic and Bosnia-Herzegovina, nearly 15,000 wounded chemical agents and take additional decontam- children were treated.44 The age range of war ination steps prior to allowing patients to board injury casualties in one state hospital in aircraft. Sarajevo was from 3 to 88 years.45 In Operation Provide Comfort in northern Iraq, while pro- Operations Other Than War viding relief to as many as 760,000 Kurdish refugees, US and Allied Force medical person- The increased military involvement in opera- nel treated 2971 patients under 12 yeas old.46 tions other than war, in particular humanitarian missions, has great potential to alter the casu- Other Challenges of the 21st Century alty load and patient profile. Despite the recent increase in frequency and duration of these Lasers, masers, particle beam weapons, and types of deployments, the concept of military other so-called directed energy devices are not assistance in disasters is not new. As early as yet tactically deployed but represent potential 1792, Congress sanctioned Army involvement future threats. The little data available on in humanitarian relief efforts. In 1902, over the injury patterns caused by these weapons 10% of the active Army strength participated suggest that focused thermal burns, in parti- in the relief of the San Francisco earthquake.39 cular to the eyes, will be the primary threat. In the aftermath of Hurricane Andrew, 23,000 Particle beam weapons are largely experimen- US troops were deployed for disaster relief.40 tal, but have the interesting characteristic of not Peacemaking, peacekeeping, and similar mis- only transmitting thermal radiation but also sions generate casualty profiles somewhere kinetic energy (as from a bullet or missile). between traditional battles and humanitarian A changing battlefield injury profile may also missions. Depending on such factors as conflict result from changes in tactics and defensive intensity,peace enforcement, and infrastructure equipment in this millennium. Body armor, in of the area, the military medical and evacuation particular, has the potential to convert many system will face variable conditions. A certain lethal missile wounds of the trunk and head degree of traditional combat injuries can be into nonlethal blunt trauma. This potential shift anticipated, together with injuries to non- of injuries among combat casualties will chal- combatants from snipers, mines, and shelling. If lenge a military medical system largely accus- the existing national medical infrastructure tomed to dealing with penetrating trauma. The is damaged, inoperative, or inadequate, large extent of this shift is unknown, but the US mil- numbers of the civilian population may present itary alone is pouring millions of dollars into to military medical facilities for treatment of developing effective protective armor systems significant disease and nonbattle injuries. Mili- for ground troops. In addition, protective body tary medical planners must anticipate this armor may actually potentiate the effects of demand and establish clear guidelines on the primary blast while simultaneously decreasing role of the military medical forces in treating mortality from shrapnel. This may result in an both the civilian population and wounded com- increase in the number of casualties with iso- batants from warring factions. lated blast injury, which historically have been Peacekeeping and peacemaking operations relatively uncommon. can be expected to generate large numbers of general medical, obstetric–gynecological, pediatric, and geriatric-type patients.41,42 Relatively Conclusion few penetrating injuries will be seen. The following examples may give some perspective to The types and numbers of casualties expected the potential problems that can present. During from a given military operation can be as broad the Somalia military relief effort, of those and varied as the types of missions themselves. 40 R.A. De Lorenzo

Traditional combat wounds from missiles, 13. Nolan DL. Airborne tactical medical support in blasts, and burns will continue to figure pro- Grenada. Milit Med 1990;155:104. minently in many conflicts. However, injuries 14. Dice WH. The role of military emergency physi- from nuclear, biologic, and chemical weapons, cians in an assault operation in Panama. Ann as well as disease and nonbattle injuries, are Emerg Med 1991;20:1336. 15. Dunnigan JF,Bay A. From Shield to Storm. New likely to increase in relative importance in York: William Morrow; 1992. future battles. In operations other than war, 16. Bhatnagar MK, Smith GS. Trauma in Afghan such as humanitarian missions, the military guerilla war: Effects of lack of access to care. medical system can expect the whole range of Surgery 1989;105(6):699. human diseases and conditions. Providing ade- 17. Noyes H. Guantanamo, Panama teach medics quate care in the context of a military organi- valuable lessons in humanitarian missions. Army zation can be a challenge. However, careful Med Dept Mercury 1996;23(3):6–7. attention to history and lessons learned can 18. Uhorchak JM, Rodkey WG, Hunt MM, et al. improve planning and ease the burden of Casualty Data Assessment Team Operation meeting the mission. Desert Storm. San Francisco: Letterman Army Institute of Research; 1992. Report 469. References 19. Butler FK, Hagman J, Butler EG. Tactical combat casualty care in special operations. Milit 1. Majno G. The Healing Hand; Man and Wound in Med 1996;161(suppl 1):3–16. the Ancient World. Cambridge, Mass: Harvard 20 Burkle FM, Jr, Newland C, Meister SJ, et al. University Press; 1975. Emergency medicine in the Persian Gulf War— 2. Trunkey DD, Ochsner MG, Jr. Management of part 3: Battlefield casualties. Ann Emerg Med battle casualties. In: Feliciano DV, Moore EE, 1994;23:755–760. Mattox KL, eds. Trauma. 3rd ed. Stamford, 21. Bodart G. Losses of Life in Modern Wars. Conn: Appleton & Lange; 1996. Oxford, UK: Clarendon Press; 1916. 3. Packard FR. Life and Times of Ambrose Pare. 22. Bellamy RF. Combat trauma overview. In: New York: Paul B Hoeber; 1921. Zajtchuk R, Bellamy RF, eds. Anesthesia and 4. Larrey DJ. Memoirs of Military Surgery and Perioperative Care of the Combat Casualty. Campaigns of the French Armies. vol 1. Classics Washington, DC: Department of the Army; 1995. of Surgery Library. Birmingham, Ala: Gryphon 23. Blood CG, Jolly R. Comparisons of disease Editions; 1985. and nonbattle injury incidence across various 5. McGuire H. A system of surgery, theoretical and military operations. Milit Med 1995;160: practical. In: Packard JH, ed. Philadelphia: 258–263. Henry C. Lea’s Son and Co; 1882. 24. Shaw E, Hermansen L, Pugh W, et al. Disease 6. Loria FL. Historical Aspects of Abdominal and Non-Battle Injuries Among Navy and Surgery. Springfield, Ill: Charles C. Thomas; 1968. Marine Corps Personnel During Operation 7. Wangensteen OH, Wangensteen SD. The Rise Desert Shield/Desert Storm. Bethesda, MD: of Surgery from Empiric Craft to Scientific Naval Medical Research and Development Discipline. Minneapolis: University of Min- Command; 1991. Report 91-44. nesota Press; 1978. 25. Burkle FM, Newland C, Orebaugh S, et al. Emer- 8. Cannon WB. Traumatic Shock. New York: gency medicine in the Persian Gulf War—part 2: Appleton & Co; 1923. Triage methodology and lessons learned. Ann 9. Field Manual 21-10 Field Hygiene and Sanita- Emerg Med 1994;23:748–754. tion. Washington, DC: Department of the Army; 26. Riley T. Medical services to the Marine Corps 1983. in Desert Shield and Desert Storm (Bulletin 10. Jones FD. Psychiatric lessons of war. In: 8-92-3/4). Army Med Dept J 1992;March/April: Zajtchuk R, Bellamy RF, eds. War Psychiatry. 42–46. Washington, DC: Department of the Army; 1995. 27. Kussman MJ. Desert Shield/Storm medical 11. De Lorenzo RA. Improving combat casualty issues review and ad hoc working group care and field medicine. Focus on the military (Bulletin 8-92-9/10). Army Med Dept J 1992; medic. Milit Med 1997;162:268–272. Sep/Oct:17–18, 43. 12. Jackson DS, Batty CG, Ryan JM, et al. The 28. Neel S. Vietnam Studies: Medical Support of the Falklands War: Army field surgical experience. US Army in Vietnam, 1965–1970. Washington, Ann Roy Coll Surg Engl 1983;65:281. DC: Department of the Army; 1973. 4. Combat and Operational Casualties 41

29. Blake GH. The area support medical battalion: 39. Sullivan GR. Hurricane Andrew:An after-action A concept validated by Operation Desert Storm/ report. Army 1993;43(1):16–22. Shield. Milit Med 1993;158:722–725. 40 Gunn WA. Humanitarian noncombat role for the 30. Medical Management of Chemical Casualties. military. Prehosp Disast Med 1994;9:s46–s48. 2nd ed. Aberdeen Proving Grounds, MD: US 41. Pierce JR. The role of the United States Army Army Medical Research Institute of Chemical active component pediatricians in Operation Defense; 1995. Desert Shield, Desert Storm, and Operation 31. Zajtchuk R, et al, eds. Medical Aspects of Provide Comfort. Milit Med 1993;158:105– Chemical and Biological Warfare. Washington, 108. DC: Department of the Army; 1997. 42. Burkle FM, Jr, McGrady KAW, Newett SL, et al. 32. Health Services Support in a Nuclear, Biological Complex humanitarian emergencies III: Mea- and Chemical Environment. Washington, DC: sures of effectiveness. Prehosp Disast Med Department of the Army; 1993. Field Manual 1995;10:48–56. 8-10-7. 43. Van Rooyan MJ,Van Rooyan JB, Sloan EP,et al. 33. Holloway HC, et al. The threat of biological Mobile medical relief and military assistance in weapons. JAMA 1997;278:425–428. Somalia. Prehosp Disast Med 1995;10:118–120. 34. Christopher GW, et al. Biological warfare:A his- 44. Pretto EA, Begovic M, Begovic M. Emergency torical perspective. JAMA 1997;278:412–417. medical services during the siege of Sarajevo, 35. Franz DR, et al. Clinical recognition and Bosnia and Herzegovina: A preliminary report. management of patients exposed to biological Prehosp Disast Med 1994;9:s39–s45. warfare agents. JAMA 1997;278:399–411. 45. Vujovic B, Nakas A, Mazlagic D, et al. Epidemi- 36. Medical Management of Biological Casualties. ology and surgical management of abdominal 2nd ed. Ft. Detrick, MD: US Army Research war injuries in Sarajevo; State Hospital of Institute of Infectious Diseases; 1996. Sarajevo experience. Prehosp Disast Med 1994; 37. Zajtchuk R, et al, eds. Medical Consequences of 9:s29–s34. Nuclear Warfare. Washington, DC: Department 46. Bennett BF, Harris L, Loesevit AW, et al. Car- of the Army; 1990. ing for Kurdish refugees: Operation Provide 38. Grace C. Nuclear Weapons: Principles, Effects Comfort. Army Med Dept J 1992;Nov/Dec: and Survivability. London: Brassy’s Ltd; 1995. 37–42. Part 2 The Means 5 Military Casualty Evacuation: MEDEVAC

Robert A. De Lorenzo

Battlefield and tactical medical evacuation the term AE will be used to refer to the long- (MEDEVAC) encompasses all the movement distance air transportation of patients, usually of casualties within the theater of operations.1 for distances greater than 300 miles. This chap- This includes both movement of patients from ter will focus on the most far-forward elements the point of injury or illness to the nearest of MEDEVAC and examine the movement and medical facility (Fig 5.1) and movement of en route care of patients from the point of patients between medical facilities until the injury or illness to the first- or second-level patient is ready for aeromedical evacuation medical facility. (AE) back to the United States. In most theaters, final in-theater destination will be the aeromedical staging facility. History Over the years some ambiguity has developed for the meaning of the term MEDEVAC. MEDEVAC owes its inception to Napoleon’s Originally, it was employed to describe any surgeon-in-chief, Dominique Larrey. He intro- patient movement on the battlefield. With the duced the “Flying Ambulances,” horse-drawn advent of patient transportation by rotary- and carriages that entered the battlefields to fixed-wing aircraft, many people have used the retrieve and care for the wounded soldiers.4 term to refer to several different types of Battlefield evacuation continued to evolve patient movement, including long-distance during the American Civil War, when the first transportation of patients by air. In response, dedicated horse-drawn carts were used to clear some authors have used alternative terms to casualties off the battlefield. Later, when refer to battlefield patient movement, including motorized transport became available, trucks casualty evacuation and tactical evacuation.2 were used to haul the wounded. World War II Throughout this chapter and textbook we will saw the first widespread use of dedicated use the traditional US Army definition of motorized field ambulances to transport casu- MEDEVAC as the ground or air movement of alties from the battlefield to medical facilities casualties from the battlefield to a medical facil- and between medical facilities. Helicopters ity and between medical facilities.1 A related were introduced for tactical evacuation during term, casualty evacuation (CASEVAC), has the Korean War and perfected during the also been used to describe the initial movement Vietnam War.5 The modern inventory now of patients in the tactical environment and includes a large number of specialized ground avoid confusion with the nontactical (strategic) and air ambulances. air transport of patients between medical facil- Throughout the history of MEDEVAC, ities. However, different sources define this important advances have continued to be made term in slightly different fashions, which can be in both the speed and versatility of the vehicles a source of confusion.2,3 Throughout this book, used. This has resulted in dramatic decreases in

45 46 R.A. De Lorenzo

Figure 5.1. Movement of casualties from the battleﬁeld (DoD photo by Petty Ofﬁcer Jeffrey S. Viano, USN).

the time it takes wounded soldiers to receive have provided incremental improvements in treatment, a fact often credited with the the care rendered in the tactical environment. improved casualty survival rates. Unfortu- However, major advances in medical care nately, equivalent advances in transport have during MEDEVAC will only be possible with not been realized at the front lines of the bat- the increased presence of skilled medical tlefield. Wounded soldiers must still be trans- providers and high technology in the forward ported, usually by manual or litter carries, to a environment. vehicle or helicopter waiting a safe distance from the conflict. Carrying an 80-kg soldier with another 20kg of critical gear over rough MEDEVAC Principles terrain remains an exhausting task with few technological advances. MEDEVAC is much more than the simple Likewise, en route care has not improved as movement of casualties from the battlefield. rapidly as evacuation vehicles such as heli- For this reason, six basic principles of battlefield copters. Limited medic training, austere, harsh and tactical MEDEVAC have been identified conditions, and sparse equipment continue to (Table 5.1).6 The key principle is that make it difficult to provide high-quality me- MEDEVAC itself is a medical “intervention” dical care in the back of a field ambulance.6 or procedure subject to physician judgement. However, there is a growing realization among When and where a patient is evacuated, and by military medical leaders that the goal of mili- what means, should always be determined by a tary medicine should not be merely to provide physician, either directly or through delegation austere medical care but rather to provide by protocols and standing operating proce- the highest-quality medical care possible in an dures. In contrast to civilian patient evacuation, austere environment. Important advances in military mission requirements and command techniques for using oxygen and intravenous approval are critical steps in the MEDEVAC fluid therapy, splinting, and bleeding control decision-making process. Ultimately, of course, 5. Military Casualty Evacuation: MEDEVAC 47

Table 5.1. Basic principles of battlefield and tactical medical facility, which is usually (but not MEDEVAC. always) the closest facility.6 The principle of Medical intervention “precedence” refers to the categorization of Speed and effectiveness patients by need for evacuation. Together, Proximity of resources appropriateness and precedence support the Medical care triage concept, whereby casualties are sorted Appropriateness and resources conserved to maximize benefit. Precedence During a mass-casualty situation, medical providers frequently encounter a mismatch of patient needs and evacuation resources and therefore must make difficult triage decisions patient evacuation is a warfighter’s command to assure the limited resources are utilized most decision, but it should be made largely on effectively. Applying the principles of appro- medical recommendation.1 priateness and precedence will help deal with “Speed and effectiveness” of transport is this mismatch. another important principle of MEDEVAC because it reflects the ultimate goal: the rapid transportation of casualties to a medical facil- Echelons of Care ity. The supporting principle of “proximity of resources” is a major challenge because the A basic understanding of the military echelons tactical environment is harsh and chaotic and of care system is needed to fully compre- limits the reach of evacuation assets. In most hend the concept of battlefield and tactical circumstances, the evacuation platform (eg, MEDEVAC. This system describes a hierarchy vehicle or helicopter) will need to be relatively of medical care and facilities designed to close to the anticipated concentration of casu- support the war fighting elements (Table 5.2).7 alties to ensure a rapid response. Although these designations are current at the The principle of “medical care” refers to the time of this writing, both military medical doc- en route patient care provided. This medical trine and nomenclature are changing at a rapid care is what separates merely moving casualties rate. from genuine MEDEVAC. The principle of Echelon I is located closest to the fighting “appropriateness” refers both to utilizing the (forward edge of battle area). Because of the best mode of evacuation (eg, ground or air) and proximity to the battle, echelon I care is austere bringing the casualties to the most appropriate and its elements are light and mobile. It

Table 5.2. Echelons of military medical care. Echelon Military hierarchy Personnel/facility Type of care

I Unit Self/buddy aid First aid Combat lifesaver First aid, beginning emergency treatment Combat medic Emergency medical treatment Battalion aid station Advanced trauma and medical management II Division Medical company Initial resuscitation (clearing station) III Corps Combat support Resuscitative surgery and hospital medical care IV Echelons above Combat support Definitive care Corps hospital V Out-of-theater Fixed medical Restorative and continental US facilities rehabilitative care 48 R.A. De Lorenzo includes four levels of care that become pro- with a broad array of support services. Because gressively more sophisticated. Self-aid and today’s operational requirements call for a buddy-aid is first aid applied by nonmedical more flexible and mobile medical facility, it fighting troops. Combat lifesaver care is more unlikely that a true echelon IV hospital capa- advanced medical aid provided by fighting bility will exist in future warfighting theaters troops with limited medical training. An Army of operation. Instead, an enhanced combat medic, a Navy or Marine Corps corpsman, or an support hospital in the theater, plus direct evac- Air Force medical technician provides “combat uation of “stabilized” patients to the United medic care.” These are the first medically States, will meet this echelon IV requirement. trained providers encountered in the field and Echelon V represents the fixed hospitals provide emergency medical treatment at the located overseas outside the theater of opera- basic life support level, in some cases with intra- tions and in the continental United States. venous fluid therapy. These are primarily military medical facilities, For the US Army and Marines, the battalion augmented within the United States by the aid station is the first medical facility available Veterans Administration, and civilian hospitals to casualties and is staffed by both a physician as part of the National Defense Medical and physician assistant. It is rather austere System. Definitive and rehabilitative care of all and highly mobile, with advanced trauma life types may be found in echelon V facilities. support capabilities, including endotracheal The numeric sequence of these echelons may intubation, tube thoracostomy, intravenous appear to imply a rigid stepwise movement of medication, and other physician-directed patients from echelon I to echelon II and so on. medical care. This may have been true in its earliest concep- Echelon II is a divisional-level “clearing tion but is too inflexible for the modern and station” that is staffed by a medical company dynamic operational environment of modern of physicians, nurses, and medics. Casualties warfare. A strict hierarchy of units and echelons are examined to determine treatment needs is unlikely to exist on the modern battlefield, and evacuation precedence. Emergency medi- where speed, envelopment, penetration, and cal treatment, including initial comprehensive deep attacks blur any sense of a “front line.” resuscitation, is provided and supported by The “rear area,” where echelon III and IV limited radiographic, dental, and laboratory hospitals were by tradition set up, is no longer services with whole blood capacity. It provides static or safe. The impact these changes have patient-holding capability for soldiers expected had on the echelon system is apparent in to return to duty within 3 days, roughly at the the virtual elimination of echelon IV facilities. general ward level under the supervision of a Certainly, this substantial decrease in theater licensed practical nurse. hospital resources increases the charge given Echelon III is the first medical facility a to the strategic AE system, as patients previ- casualty will encounter on the battlefield. At ously hospitalized in the theater will now have present, this will be a combat support hospital to be transported back to the nearest echelon in the US Army system. Echelon III hospitals V facility. provide comprehensive resuscitative surgery Another major change in military medical and medical care. Medical providers include doctrine is the increased forward availability of general surgeons and both surgical and medical medical expertise and technology. “Forward subspecialists with comprehensive anesthesia surgical teams,” whose expertise was previously and nursing support. Patients who are unlikely available only at echelon III facilities, are to return to duty are evacuated as soon as pos- now located in traditional echelon II units. sible after stabilization. The modern addition of surgical capability to Echelon IV was by tradition represented by echelon II units further blurs the distinction comprehensive theater hospitals designated as between echelons. Obviously, the AE system general, field, or station hospitals. These large must evolve in concert with the rapidly chang- and poorly mobile facilities provided definitive ing capabilities of forward medical facilities to medical and surgical care and were equipped ensure that the principle of appropriateness 5. Military Casualty Evacuation: MEDEVAC 49

Table 5.3. Standard US Army precedence categories for MEDEVAC. Priority level Designation Description

I Urgent Evacuated as soon as possible and within 2h to save life, limb, or eyesight or prevent complications of serious illness or permanent disability IA Urgent—surgery Must receive far-forward surgical intervention to save life and stabilize for further evacuation II Priority Requiring evacuation within 4h or his medical conditioncould deteriorate to such a degree that he will become an urgent precedence or will suffer unnecessary pain or disability III Routine Requiring evacuation within 24h, but whose condition is not expected to deteriorate signiﬁcantly IV Convenience Evacuation is a matter of medical convenience rather than necessity

Source: Adapted from USA data.1

continues to be met when matching patient and can tolerate an evacuation delay of 4 hours. needs to medical capabilities. “Routine” patients are unlikely to deteriorate and can tolerate an evacuation delay of 24 hours. “Convenience” patients are being evac- Precedence uated for reasons other than medical necessity, as the name implies. These MEDEVAC prece- A key concept in the care provided to the casu- dence categories should not be confused with alty during evacuation is the MEDEVAC prin- the standard NATO triage designations (ie, ciple of precedence. Correctly choosing which immediate, delayed, minimal, and expectant), casualty goes first and to which medical facility which identify treatment priorities rather than is central to providing good MEDEVAC. Indi- evacuation precedence. vidual precedence decisions made will impact These standard precedence categories are the overall effectiveness of the evacuation necessary to facilitate communication between effort. For this reason, medical commanders the various elements in the evacuation chain. In must ensure that precedence decisions are the US Army MEDEVAC system, a nine-line made by the most qualified medical provider, Medical Evacuation Request form is used and in many cases this may not be the most (Table 5.4). The information is given to a sup- senior or highest-ranking medical officer.8 porting evacuation element, usually by radio, The US Army system uses four standard cat- by reading the nine lines of information in egories to determine MEDEVAC precedence, sequence.1 to which a fifth surgical category has been recently added (Table 5.3).1 “Urgent” patients need immediate evacuation and cannot tolerate Assessment and Care a delay of more than 2 hours without significantly risking death or disability. The “urgent Assessment and care during tactical evacuation surgical” subcategory was created to emphasize is a compromise between the provision of the patient’s need for acute surgical interven- optimal care and the realities of a harsh, tion, thus alerting the evacuation team to trans- austere, often hostile battlefield environment. port the patient to a surgery-capable facility. Assessment is limited by noise, movement, and “Priority” patients are less likely to deteriorate light restrictions. Ongoing medical care is also 50 R.A. De Lorenzo

Table 5.4. US Army “nine-line” medical evacuation include direct visualization of tube placement request. by laryngoscopy,an esophageal detector device, 1. Location of pickup site and observation of respirophasic condensation 2. Radio frequency and call sign on the tube. 3. Number of patients by precedence Pulse and blood pressure are the primary a. Urgent indicators of circulatory status. Electronic phys- b. Urgent surgical iological monitors can reliably measure these c. Priority d. Routine parameters, even in the presence of significant e. Convenience noise and motion. Manually obtained pulse and 4. Special equipment required blood pressure are more difficult to accurately 5. Number of patients by type (litter and ambulatory) obtain in the tactical environment. Capillary 6. Security of pickup site (wartime only) refill, indicative of peripheral vasoconstriction, 7. Method of marking pickup site 8. Patient nationality and status is a reasonable alternative indicator of cir- 9. Nuclear, biologic, or chemical contamination culatory status that can be used in this envi- (wartime only) ronment. Refill time in excess of 3 seconds Terrain description (peacetime) suggests circulatory compromise, and is best Source: Adapted from USA data.1 observed at a central location such as the forehead, neck, chest, or abdomen. Cold exposure can also prolong capillary refill, especially in hindered by equipment shortages, multiple the extremities. casualties, and limited provider skills. Despite Bleeding must always be controlled by what- these limiting factors, effective assessment and ever means necessary. Direct pressure almost care is possible in this environment. always controls external hemorrhage and is the The approach to ongoing care during technique of choice. If direct pressure can be MEDEVAC evacuation is based on the prin- applied and maintained, a tourniquet is almost ciples of good prehospital care (Table 5.5).9 never needed. A tourniquet may be required if The focus is on the airway, breathing, and direct pressure cannot be maintained because circulatory status of the casualty. If available, of high casualty-to-provider ratio, if there is a electronic physiological monitors (eg, sphy- need to move quickly, or under other tactical gmomanometer, pulse oximeter, and capnome- considerations. Once a tourniquet is applied, it ter) should be employed. Because this type of should not be loosened until bleeding can be equipment is frequently unavailable in the chaos of battle, the provider accompanying the casualty will need to rely on traditional inspection, palpation, and auscultation for Table 5.5. Approach to evacuation (ongoing) care. assessment. Airway The adequacy of both the airway and breath- Ensure patency and adequacy of airway ing can be roughly estimated by observing or Breathing palpating chest excursion. The traditional tech- Ensure adequacy of ventilation and oxygenation Circulation nique of breath sound auscultation is often Ensure all bleeding is controlled impossible in the noisy tactical environment. Provide appropriate fluid support Electronic monitoring is extremely useful in Disability and drugs this environment, and pulse oximetry showing Monitor mental status and neurological response peripheral oxygen saturation >95% indicates Recheck splints and dressings Administer appropriate medications satisfactory central oxygenation. In patients Extras receiving supplemental oxygen, pulse oximetry Keep casualty comfortable and warm allows accurate titration of flow rates to keep Provide reassurance and support the saturation >95%, thus conserving scarce Ensure casualty is properly restrained against falls and oxygen supplies.10 In an intubated patient, elec- crashes tronic capnometry is another method to assure Source: Adapted with permission from Butler et al2 and airway patency. Alternative manual methods De Lorenzo and Porter.13 5. Military Casualty Evacuation: MEDEVAC 51 controlled through other means. In general, a is relief of suffering rather than complete relief tourniquet should not be removed until the of pain. This ensures an adequate therapeutic casualty has reached a medical facility capable effect while minimizing the risk of undesirable of initiating and maintaining an adequate resus- side effects such as apnea and hypotension. It citation, even if this means leaving it on for is inhumane and poor medical practice to hours. undertreat pain on the battlefield based on an The approach for administration of intra- excessive fear of inducing respiratory depres- venous fluids to casualties in the field has re- sion or altering the neurological or abdominal cently undergone significant changes. For years, examination. Such patients need appropriate the standard approach for patients suspected of analgesia. having hemorrhagic shock was to administer Antibiotic administration on the battlefield is massive amounts of crystalloid and colloid now recommended for infection prophylaxis fluids in an effort to maintain a normal blood for casualties with penetrating injuries from pressure. Recent trends in the care of pene- bullets and fragments. Early administration trating injuries in the field are moving toward may be most effective, and a typical regimen is administration of just enough crystalloid fluid a single intramuscular or intravenous dose of a to maintain modest hypotension (eg, systolic broad-spectrum cephalosporin (eg, cefazolin or blood pressure of 80 to 90 torr). In contrast, mefoxitan, 1 to 2g). Tetanus prophylaxis with current guidelines for isolated serious head tetanus–diphtheria toxoid is also indicated for injury suggest an avoidance of significant hypo- inadequately immunized casualties, most com- tension. For both conditions, it is now recom- monly civilians and foreign troops. mended that fluid administration be judicious Chemical or biologic attacks bring a new in the initial management of combat-related dimension to the use of lifesaving medications trauma (Table 5.6). Administration of addi- on the battlefield. Many chemical agents have tional fluid may be medically appropriate in antidotes or treatments that are effective if some circumstances, especially when there is a used promptly. Tactical medical providers must delay of >2 to 4 hours between the time of be familiar with atropine, pralidoxime, and injury and definitive medical care. diazepam for nerve agents, nitrites and thiosul- Drugs are playing an increasingly important fate for cyanide, and inhaled bronchodilators role in combat care. Morphine for pain control for pulmonary agents, at an absolute minimum. is one of the few drugs traditionally used on the Repeated dosing of these medications may be battlefield. Sufficient morphine or other potent required throughout the evacuation chain. Bio- analgesics should be administered, preferably logic agents are another potential threat and by the intravenous route, to all casualties who the evacuation chain must be ready to begin are in pain. The appropriate clinical end point drug treatment at the earliest possible time.

Table 5.6. Rational approach to administering intravenous ﬂuid in the tactical setting. Fluid amount (Isotonic Crystalloid) Condition Adult Pediatric

No shock Saline lock Saline lock Compensated shock, hemorrhage controlled 1000mL bolus 20mL/kg bolus Compensated or uncompensated shock with suspected 1000mL bolus 20mL/kg bolus uncontrolled intrathoracic or intraabdominal hemorrhage Uncompensated shock, hemorrhage controlled 1000mL bolus, may 20mL/kg bolus, may repeat up to 3000mL repeat up to 60mL/kg Isolated head injury, no shock Saline lock Saline lock Isolated head injury with shock 1000mL bolus 20mL/kg bolus

Source: Adapted with permission from Butler et al2 and De Lorenzo and Porter.13 52 R.A. De Lorenzo

The last major element in evacuation care is computerized system designed to permit the to ensure the patient is warm, comfortable, and interfacility transfer of patients. It currently safe. Hypothermia is an often-overlooked com- operates at the fixed medical facility level plication of injury and is exacerbated by the but will be extended forward to theater and environmental exposure, fluid resuscitation, tactical levels through modernization. APES and prolonged transport times, all common in supports the USAF AE mission out of the tactical MEDEVAC. Verbal and tactile ges- theater. APES can exchange information with tures of reassurance are also an important DMRIS with the ultimate goal of both being aspect of care and should be provided. improved effectiveness and efficiency throughout evacuation. Transfer of Care Transportation Eventually, the tactical MEDEVAC system interfaces with the medical facility or the thea- The overall goal of MEDEVAC is the safe and ter AE system. The effective transfer of care effective movement of the casualties. Trans- requires good communication between all ele- portation modes might include manual carries, ments, both verbal and written. Neither needs ground vehicles, aircraft, watercraft, or a com- to be lengthy, but should highlight key aspects bination of these depending on the circum- of the casualty’s condition and treatment. stances. All members of the military medical The standard instrument for written docu- team should have a general familiarity with mentation of medical care before and during the common transportation modes used for MEDEVAC is the Field Medical Card (FMC) MEDEVAC. (Fig 5.2). This abbreviated document includes basic demographic data, key physical findings, Manual Carries and treatment rendered. Ideally, the FMC should only take a minute or two to complete. In combat and many military operations other Carbonless copies allow the initiator to keep a than war, the manual carry is the primary record for future accountability. The card itself means of moving casualties from the point is then attached to the casualty in a convenient of injury or illness to a point of safety where fashion. the medical evacuation can begin. Despite Another aspect of the transfer of care is tremendous advances in many other areas of medical regulating. This process for the regula- evacuation, manual carries remain almost un- tion of patient movement is crucial to manage changed over the centuries. While agility and patient flow. The objectives of medical regulat- finesse are essential to executing all manual ing are to (1) ensure an even distribution carries, there remains no substitute for physi- of patient load, (2) provide adequate beds cal strength and endurance. Manual carries and treatment capabilities for current and can be exhausting work and necessarily have a anticipated needs, and (3) ensure that patients range limited to a few hundred or thousand requiring specialized care get to the appropri- meters. ate facility. Historically, medical regulating was Manual carries and drags may aggravate only concerned with theater-level AE. How- fractures and wounds because they offer little ever, as automated systems become more effec- stable support for the casualty’s body. Moving tual, regulating will begin at the level of tactical the casualty along the long axis of the body will MEDEVAC and might one day begin at the minimize further injury to the casualty. Ongo- point of injury. ing care is impossible during a manual carry. If Two systems are in current use in the tactical possible, life-threatening bleeding should be environment for medical regulating: the De- controlled with a tourniquet prior to move- fense Medical Regulating Information System ment. Airway management, ventilation, and (DMRIS) and the Automated Patient Evacua- patient monitoring must be delayed until the tion System (APES).1 DMRIS is an online, casualty reaches a point of safety. 5. Military Casualty Evacuation: MEDEVAC 53

A Figure 5.2. Field Medical Card. Both the front (A) and back (B) of the card are utilized for both MEDEVAC and AE. 54 R.A. De Lorenzo

B Figure 5.2. Continued 5. Military Casualty Evacuation: MEDEVAC 55

Litter Carries Table 5.7. MEDEVAC platforms used by the US Army. Litter transportation offers modest improve- Platform Description Litter capacity ments over manual carries. Some support and comfort is afforded the patient, and spinal M996/M997 Wheeled ambulance, 2–4 immobilization, fracture splinting, oxygen HMMWV chassis M113 Tracked, armored 4 therapy, and other static treatments can often ambulance be maintained during movement. Airway man- AMEV Armored medical 4 agement, ventilation, and other dynamic care evacuation vehicle remains difficult to perform, however. Stryker Wheeled armored 4 Litter carries have the additional advantage medical evacuation vehicle that the work of transporting a patient can be UH-1 Huey Single-engine helicopter 6 shared by two to four persons, markedly UH-60Q Twin-engine helicopter 6 increasing the potential range of transporta- Blackhawk configured for tion. The obvious drawback, however, is that up MEDEVAC to four persons are committed to moving one patient. Litters are lightweight, portable, durable, and readily available on the battlefield. They are also widely used to move patients in and suffers from thin armor, slow speed, and a around medical facilities and on and off evacu- jarring ride. It is organic primarily to the ation vehicles. Therefore, all military medical medical platoon in armor and mechanized providers should be familiar with their use. infantry battalions. The US Army is hoping to replace the aging Ground Vehicles M113 with the armored medical evacuation vehicle (AMEV), which is built on the M2/M3 Ground vehicles are the most common plat- Bradley fighting vehicle chassis. The AMEV form used to move casualties over relatively offers greater armor, speed, range, comfort, and long distances on the battlefield. Current US room than the M113 and has provisions for on- military doctrine places dedicated ambulances board oxygen. In addition, it offers protection in the war-fighting maneuver units such as an against chemical and biologic agents. The high armor or infantry battalion. In most scenarios, price tag, however, will likely delay its deploy- battlefield casualties will be carried or dragged ment for years. The Stryker, a new wheeled several hundred meters to a point of relative armored vehicle for the Army’s medium weight safety (eg, the casualty collection point) where brigade is based on the LAV III already in use a ground ambulance can pick them up. As a by the US Marine Corps. This new vehicle result, ground ambulances can be expected to comes in a variety of configurations including get fairly close to the point of injury in many an ambulance, and offers a combination of pro- cases. tection, moderate weight, maneuverability and There are several ground ambulances in use speed that enhances versatility. today (Table 5.7). The M996/M997 “Humvee” ambulance is built on the highly successful Helicopters high-mobility multipurpose wheeled vehicle (HMMWV) chassis (Fig 5.3). The HMMWV is Helicopter ambulances have been a high- organic to medical platoons of light-infantry visibility element of the MEDEVAC system battalions and most medical companies and can since their introduction for this role during the accommodate up to four litter patients. Korean conflict. By the end of the Vietnam The M113 armored ambulance is little more War, MEDEVAC helicopters offered speed than an ordinary armored personnel carrier and versatility unmatched by ground plat- outfitted to accommodate up to four litters forms.11 They are largely unaffected by terrain (Fig 5.4). It is a pre-Vietnam era design and and can reach remote areas inaccessible to 56 R.A. De Lorenzo

Figure 5.3. M997 wheeled ambulance (photo by Robert A. De Lorenzo).

Figure 5.4. M113 armored ambulance (photo by Robert A. De Lorenzo). 5. Military Casualty Evacuation: MEDEVAC 57

Figure 5.5. UH-1 Huey air ambulance (USA photo). ground vehicles. Disadvantages include the cost Limitations of MEDEVAC and their vulnerability to small-arms fire. This latter factor accounts for the doctrine of MEDEVAC, using either helicopter ambu- keeping helicopter pick-up points a safe dis- lances or their ground counterparts, shares two tance from direct hostile fire. For this reason, significant limitations: availability and limited most casualties will still need to be carried to a patient care en route. Battlefields and disasters point of safety by a combination of manual or are fluid and dynamic situations, making it litter carry and ground vehicle transportation impossible to preposition ambulances where prior to “dustoff.” they will most be needed, even in the unlikely The UH-1 Iroquois (“Huey”) is a Vietnam- event that large numbers were available. Field era airframe that remains on active service medical providers must be capable of impro- some 30 years after its introduction (Fig 5.5). It vising transportation when ambulances are not is a single-turbine, twin-blade rotor aircraft available. Using nonmedical vehicles and per- with a capacity of six litter patients.11 sonnel for casualty evacuation, including trucks, The UH-60 Blackhawk is the current re- buses, and nonmedical helicopters, is a well- placement for the UH-1 (Fig 5.6). It is a recognized part of US Army contingency twin-engine, quad-rotor blade airframe with planning.1 improved range and speed over its predecessor. The second greatest limitation of tactical Like the UH-1, the UH-60 has a capacity of six MEDEVAC is the difficulty involved in pro- litter patients. An improved version of the viding en route or ongoing care. Both ground Blackhawk, the UH-60Q, has been proposed as and air platforms currently in use are cramped, a primary air ambulance. The Q model has noisy, poorly illuminated, and prone to vibra- improved engine power and performance tion, jarring, and sway. Patient access, assess- plus built-in oxygen, suction, lighting, and ment, monitoring, and intervention are difficult, monitoring capability.12 Unfortunately, the high at best. Only in the most modern platforms cost of each aircraft has slowed widespread are there provisions for on-board oxygen and deployment. suction. Airway, breathing, and monitoring 58 R.A. De Lorenzo

Figure 5.6. UH-60 Blackhawk air ambulance (USA photo).

equipment are not built-in and thus must be ment and, if needed, intervention to correct brought on-board separately. urgent problems. Despite these equipment limitations, perhaps the greatest is the limitations of care providers in terms of both numbers and training.5 Most ground and air ambulances have one or two Conclusion attendants assigned for up to six critical patients.12 Obviously, if more than one patient MEDEVAC encompasses all movement of the requires intensive bedside care (eg, active movement of patients: from the point of injury bag–valve–mask ventilation) the single atten- to the nearest medical facility, between medical dant’s capacity to provide care is exceeded. facilities at different echelon levels, and ﬁnally Ironically, it is a common personnel practice to to the site of embarkation out of the theater. assign a junior or inexperienced medical tech- A key component of MEDEVAC is the provi- nician to the job of ambulance attendant. sion of ongoing casualty care. To assure the The rigors of MEDEVAC create two chal- success of what is one of the most important lenges for military medical providers. First, missions of military medicine, all military patients being prepared for tactical evacua- medical providers need to be familiar with the tion must be adequately stabilized for the basic concepts and components of tactical journey. Extra effort should be made to antici- MEDEVAC. pate problems en route. For example, providing critically injured patients with two intravenous lines (in case one fails) before embarking References may prevent the need for restarting a line. 1. Department of the Army. Medical Evacuation in The second challenge occurs at the receiving a Theater of Operations. Washington, DC: US medical facility. Casualties being off-loaded Government Printing Ofﬁce; 1991. Field Manual from ambulances need a thorough reassess- 8-10-6. 5. Military Casualty Evacuation: MEDEVAC 59

2. Butler FK, Hagmann J, Butler EJ. Tactical 8. Swan GS, Swan KG. Triage: The past revisited. combat casualty care in special operations. Milit Milit Med 1996;161:448–452. Med 1996;161(suppl): 3–15. 9. Committee on Trauma. Resources for Optimal 3. Utility and Cargo Helicopter Operations. Care of the Injured Patient: 1999. Chicago: Washington, DC: Department of the Army; 1997. American College of Surgeons; 1998. Field Manual 1-113. 10. Makreth B. Assessing pulse oximetry in the field. 4. Trunkey DD, Ochsner MG, Jr. Management of J Emerg Med Serv 1990;15(6):12–20. battlefield casualties. In: Feliciano DV, Moore 11. Baxt WG, Moody P. The Impact of rotorcraft EE, Mattox KL, eds. Trauma. 3rd ed. Stamford, aeromedical emergency care services on mortal- Conn: Appleton & Lange; 1996. ity. JAMA 1983;249:3047–3051. 5. Hacker LP. Time and its effect on casualties 12. De Lorenzo RA. Military and civilian emer- in WWII and Vietnam. Arch Surg 1969;98:39–40. gency aeromedical services: Common goals and 6. De Lorenzo RA. Improving combat casualty different approaches. Aviat Space Environ Med care and field medicine: Focus on the military 1997;68:56–60. medic. Milit Med 1997;162:268–272. 13. De Lorenzo RA, Porter RS. Tactical Emergency 7. Department of the Army. Health Service Care. Upper Saddle River, NJ: Brady (Prentice Support in a Theater of Operations. Washington, Hall); 1999. DC: US Government Printing Office; 1991. Field Manual 8-10. 6 Aeromedical Triage Support to Mass-Casualty Events

Frederick M. Burkle, Jr., Richard Brennan, and Victoria Garshnek

Triage is a French word meaning to pick out or treatment. In such military triage, treatment sort. It was first introduced into the English lan- and evacuation of the more seriously injured is guage during World War I as a military process an important, but secondary, objective.1 of classifying casualties.1 The modern defini- Sophisticated mass-casualty triage principles tion, according to Gunn, is “the selection and were applied in the Korean War and improved categorization of the casualties of a disaster upon in both the Vietnam and Persian Gulf with the view to appropriate treatment accord- Wars.1,3,4 Mortality rates were reduced from ing to the degree of severity of illness or injury 4.7% in World War 1 to 1% in the Vietnam and the availability of medical and transport War. Rapid triage and stabilization treatment, facilities.”2 Numerous studies and writings together with immediate helicopter evacuation exist that address the methodology of triage. and well-equipped and staffed echelon-level However, there is little attention provided to hospitals, were major factors that contributed triage prior to transport, especially in regard to to the low mortality rate in Vietnam.1 In a aeromedical evacuation (AE). This chapter medical echelon system, such as the military’s, addresses mass-casualty events (civilian or mil- retriage is required at every level in the chain itary) where triage is performed under circum- of evacuation, and thus triage must be a stances in which the number of patients exceeds dynamic process (Fig 6.1). the normal capabilities and resources for a 1 prolonged period of time. Triage becomes a Triage Situations critical aspect of AE in mass-casualty events requiring special skills and considerations. A “triage situation” is any situation where the total patient requirement exceeds available resources, thus requiring temporary prioritiza- Mass-Casualty Triage tion of critical care.1 An example of this most often occurs in rural hospital emergency Mass-casualty care has three principle ele- departments when a limited number of pro- ments: triage, basic field stabilization, and evac- viders are faced with two or more critically uation. The objective of mass-casualty triage is injured patients. A triage situation will exist to accomplish the greatest good for the great- until on-call assistance arrives or casualties are est number in the shortest time, and it is this evacuated to an advanced-care facility. The few type of triage we will discuss in this chapter. studies that address AE triage deal primarily Civilian mass-casualty triage contrasts with with these casualty-limited events in remote that of military triage, where the stark realities or inaccessible areas.5–8 However, these studies of combat require that the first objective is still have some applicability to mass-casualty to determine who can be quickly treated and AE, especially as they relate to recognition of returned to combat immediately following the appropriateness of aeromedical procedures,

60 6. Aeromedical Triage Support to Mass-Casualty Events 61

Figure 6.1. After initial triage and treatment, retriage is required at every level in the chain of evacuation (USAF photo by Staff Sergeant Mark Diamond). the impact of physiological and environmental adequate resources and personnel exist.9,10 factors, and skills required of aircraft and crew, When there are an abundance of resources, as discussed later in this chapter. inclusion criteria prescribe that all necessary resources be utilized first on the “sickest” Triage Criteria patient. This approach to triage methodology and the decision-making process has been Just as there are differences in the types of refined for the different locations at which it triage, ie, mass casualty and military, there may be employed,including the scene of the dis- are different criteria used to determine which aster, the civilian or military hospital emergency patients are moved first. The two most common department entrance, and x-ray and surgical criteria are inclusion and exclusion. suites.1 Unfortunately, the requirements for or influence of AE triage in this process have Inclusion Criteria rarely been addressed. The most common criteria used in the vast Exclusion Criteria majority of civilian mass-casualty events are inclusion criteria. Civilian triage does not utilize Recent experiences during complex humani- the military echelons of care but does utilize tarian emergencies (eg, Somalia, Rwanda, and the same decision-making factors, such as the former Yugoslavia) have been remarkable likelihood of medical success and conservation both for the massive numbers of casualties of scarce resources. In the United States, (primarily civilian) and the extremely limited both military and civilian triage incorporate resources available. In these situations, defini- Advanced Trauma Life Support (ATLS), Ad- tive care is unavailable for most casualties. The vanced Cardiac Life Support (ACLS), and result is that triage occurs at only one level, ie, Advanced Pediatric Life Support (APLS) the besieged hospital, where further evacuation standards of care. These have also become the (ground and air) is often impossible (Fig 6.2).9 inclusion criteria expected for triage manage- Mass-casualty events during complex emergen- ment in most developed countries where cies often require triage officers to make exclu- 62 F.M. Burkle, Jr., R. Brennan, and V. Garshnek

Figure 6.2. Hurricane casualties in Honduras awaiting medical evaluation and treatment (USA photo by Staff Sergeant. Jeff Troth, 49th Public Affairs Detachment, Airborne). sion criteria decisions that reflect the relative zations. It was also used in Rwandan refugee scarcity of multiple basic medical provisions, camps, such as Goma, where the intravenous including resuscitation equipment, surgical (IV) fluids available for rehydration during expertise, blood supplies, electricity, clean cholera epidemics were extremely limited.12 water, and security for both patients and Decisions using exclusion criteria become even medical personnel, as required by international more critical if evacuation options are unavail- humanitarian law and the Geneva Conven- able, limited, or threatened. The potential tions.9,11 When a medical system is over- remains high for triage officers to deploy to whelmed, this is the only possible way to keep locations where they may face these difficult scarce resources available for patients with a decisions during a mass-casualty event or reasonable chance for survival. armed conflict. Guidelines for applying exclusion criteria must be determined as early as possible when Triage Considerations in Large-Scale triage is required for this type of complex mass- Weapons of Mass Destruction casualty event. As soon as the relative scarcity (WMD) Events of medical provisions has been determined, triage personnel must agree on which casualties WMD may occur as a result of a terrorist have little hope for survival without using a induced biological, chemical, nuclear, or mixed large amount of resources (eg, patients requir- event. Also, an explosive device may be pur- ing cardiac resuscitation, immediate surgery, or posefully contaminated with a bioagent or substantial blood transfusion). These patients chemical resulting in a confusing, early or de- will be treated only with comfort measures. This layed, clinical presentation of an otherwise use of seemingly harsh exclusion criteria for physically traumatized victim. In a large-scale aggressive treatment were required in Kigali, WMD event (PICE stages I–III), triage will be Rwanda, where over 20,000 trauma casualties practiced in a resource-constrained environ- were triaged by underresourced relief organi- ment. Exclusion criteria will be utilized, and 6. Aeromedical Triage Support to Mass-Casualty Events 63

Table 6.1. Triage considerations. Nuclear Bioterrorism A B C PICE Stage The contraindications of triaged victims are less Static Controlled Local 0 critical to individual victims unless the AE is Dynamic Disruptive Regional I entering a contaminated area. As with any Dynamic Paralytic National II large-scale WMD event, the decision-makers Dynamic Paralytic International III must, early in the triage process, determine how Source: From Koenig KL, Dinerman N, Kuehl AE: Dis- AE assests will, if ever, be used and under what aster nomenclature––A functional impact approach: The circumstances and operational protocols. PICE system. Acad Emerg Med 3:723–727, 1996.

Mixed Agent Terrorism All triage personnel must consider the possi- as such, AE capability and capacity may be bility that victims in a terrorist event, especially severely compromised. In Table 6.1, column A those experiencing an explosive device, have describes the potential for additional casualties. suffered additional exposure to a biological (eg, Column B describes whether resources are botulism toxin) or chemical agent (eg, nerve overwhelmed and, if so, whether they must gas). Nerve gas may cause spasms in exposed be augmented (disruptive) or ﬁrst need to be voluntary muscles observed during the triage reconstituted (paralytic). Column C describes process, requiring immediate decontamination the extent of geographic involvement. The before AE and surgery. PICE stage refers to the likelihood that outside medical assistance will be needed.

Biological Terrorism Aeromedical Triage A primary objective of current education and Aeromedical triage is extremely complex and training of healthcare providers in the clinical requires knowledge of multiple factors. It can recognition and management of biological be defined as the triage support that prioritizes agents, and in the use of detection technologies, and prepares patients for AE, including appro- is to determine, as early as possible, whether the priate specialized care during transport. Aero- bioagent is contagious. In a non-contagious medical triage requires attention to unique bioagent environment (eg, anthrax), standard physiological and air transport environmental patient precautions will be followed. There will factors that may directly affect: (1) the decision be few contraindications to AE. With a conta- to transport, (2) pre-existing triage and evacu- gious bioagent (eg, smallpox) triage must con- ation priorities (3) treatment and resource allo- sider the vulnerability of AE personnel, their cation, and (4) risk analysis decisions. equipment and aircraft. In general, contagious In both battlefield and true mass-casualty victims will not receive AE unless containment events, there is often no reasonable alternative equipment and personnel protections (ie, to AE.1,4,5 Therefore, aeromedical triage must portable isolation units, protective gear, vacci- ensure that appropriate triage methods are nation coverage, etc.) are guaranteed. utilized to prevent the misuse of limited aircraft and still move patients efficiently. Lack of pro- Chemical Terrorism per triage has been shown to limit patient trans- AE triage criteria will vary depending on the fer and the efficiency of long-distance AE.5,13 chemical used and whether the victims have Triage officers, both military and civilian, been appropriately decontaminated before responsible for mass-casualty care are required flight. As was the case in preparations for the to incorporate and communicate critical Persian Gulf War, decontamination equipment aeromedical factors into the management must be available for AE aircraft and equip- process. ment. If not, AE becomes exclusionary in the The triage officer requires a myriad of criti- triage and management process. cal information to make AE triage decisions. 64 F.M. Burkle, Jr., R. Brennan, and V. Garshnek

Triage teams must maintain an umbrella view not deteriorate more during AE than would of the larger triage and evacuation system with have occurred on the ground.14 its capabilities, responsibilities, and limitations, 6. Triage officers must have advanced me- as well as exercising the flexibility needed dical knowledge of triage and evacuation to work within this complex system. With priorities, modes of transportation, transport numerous advances in AE being made daily management, and hospital destination to mini- (eg, telecommunications, training of personnel, mize triage-related errors, eliminate medical capability of aircraft), triage officers must stay bottlenecks, and afford early and appropriate current so that they may incorporate their definitive care to those most in need.1,14,15 knowledge of aeromedical factors into their 7. Guidelines must be in place to minimize triage decisions. unnecessary casualty transfers resulting from Patient triage is one of the basic require- either undertriage or overtriage as described ments that all AE systems must meet in addi- below.16 tion to medical crew training, in-flight patient 8. The triage officers must be mindful that monitoring and treatment, and access to appro- crisis intervention begins at the scene, both priate target medical facilities. In turn, each during and after evacuation, for casualties, rel- aeromedical triage system should meet certain atives, rescuers, and health workers.15 minimal requirements. If triage is done properly by the triage officer, the patients will receive care in a continuum throughout evacu- Factors Influencing ation, not just a simple flight in an aircraft. Triage Decisions

AE Triage Minimal Requirements In any mass-casualty situation, the possibility of 1. The triage officer and escorting providers either overtriage or undertriage always exists, should be aware of the differences between and it is the purpose of aeromedical triage working in the airborne environment and support to minimize this waste. In overtriage, working in the static ground-based facility of relatively minor injuries are either sent to the field environment. trauma centers with far more capability than 2. All patients must receive a primary survey required or are transported more quickly designed to identify indicators of impending or than their condition requires. In undertriage, existing respiratory failure or shock. This patients with life-threatening injuries are either survey should include an assessment of how transported too slowly or to facilities incapable aeromedical physiological and environmental of treating them. In day-to-day civilian practice, factors might contribute to respiratory failure an acceptable overtriage rate is 50%, primarily 1,16 or shock. At a minimum, this should include a because capability far exceeds requirement. systematic evaluation of the airway, breathing, However, in a mass-casualty situation a waste circulation, and immobilization. of either transportation or treatment assets 3. Triage officers should conduct frequent is unacceptable. There are a number of key repeat triage using clear guidelines to ensure factors that can be used to influence the optimal and rapid modification of medical care best possible triage decisions described below during transport. (Table 6.2). 4. Triage officers should use clinical protocols for specific injuries and illnesses, based on Triage and Evacuation Priorities mechanism of injury, physiological status of the patient, and predicted transport times, to Mass-casualty field triage refers to the sorting improve outcomes and significantly reduce the and classification of patients, assessing patients interval between injury and patient arrival at an to determine the most appropriate receiving appropriate medical facility. facility, and specifically deciding whether to 5. Medical care must be of high enough bypass the closest hospital in favor of another. quality that the condition of mass casualties will The goal is to ensure that all seriously injured 6. Aeromedical Triage Support to Mass-Casualty Events 65

Table 6.2. Aeromedical factors that influence triage Priority 2: Delayed. Casualties can wait for decisions. care or air/ground transport. Basic first aid, Triage and evacuation priorities retriage, and monitoring are provided. Tri- Triage categories age officer determines both priority and Number of casualties sequence of air transport, accelerating the Types of casualties transport if condition deteriorates, a trans- Quantitative scoring systems port opportunity hastens care and recovery, Transport management Procedures or space allows. Equipment Priority 3: Minimal. No impairment of function, Crew skills can either treat self or be treated by a non- Physiological factors professional. Appropriate for ground trans- Cost–benefit analysis portation. Should not reenter air transport Mode of transportation Type triage process. Distance/speed Priority 4: Expectant. Extremely critical or Crew composition moribund casualties with little hope of Environmental hazards survival under the best of circumstances Evacuation destination of medical care. Will not benefit from air Level of designation Operating theaters evacuation. Specialty availability Quantitative Scoring Methods Although experienced triage officers rely on patients are brought to a trauma or specialty their best clinical judgement, no triage guide- referral center while maximally utilizing scarce lines perfectly predict which patients are truly resources. Flight crew expertise and ability to emergencies. Quantitative methods that assign monitor, resuscitate, and provide critical proce- an objective score to a casualty’s clinical status dures during air transport are critical to the can assist assessment and triage, especially in overall triage process. identifying those casualties most suitable for evacuation to trauma facilities. A study has Triage Categories shown that the instinctive or “gut feeling” was unreliable alone, but when used in conjunction Both qualitative and quantitative methods with a mechanism of injury scoring system it of triage are used to classify patients into tri- enhanced the identification of major trauma age categories. Qualitative methods classify casualties.17 Complicated scoring systems or patients subjectively into a group of categories, time-consuming evaluations are to be avoided usually two to five in number. Quantitative due to risk of delay in transport, but such quan- methods use various types of numeric scales to titative systems do have value. place an “exact” value on the patient’s need to Multiple quantitative scoring systems have move. In mass-casualty events, triage categories been developed to predict survival outcomes. must be kept simple and functional and These systems are based on a number of complement the unique requirements of the different criteria including anatomy, injury aeromedical environment. For this reason, the severity, physiological measurements, and me- authors have developed a modified four-tiered chanism of injury.16 An example of the effec- qualitative sorting system that communicates tiveness of one such system is a trend toward aeromedical factors critical to transport and increased survival observed among patients treatment1: transported by helicopter with higher injury Priority 1: Immediate. Seriously injured with severity scores.18 In general, anatomic and phys- reasonable chance of survival if transported iological criteria as measured by the Trauma by air to a proper facility. Expectations are Score provide the triage officer a means to that advanced care will continue or be predict survival outcomes and audit the system enhanced during transport. more accurately with information about the 66 F.M. Burkle, Jr., R. Brennan, and V. Garshnek severity of a patient’s injuries or condition than these patients to trauma centers for definitive criteria based on mechanism of injury alone.16 care may be more critical than the timing of the To be useful, the anatomic and physiological transfer.14 criteria must be clear, concise, and readily A deadly combination is blunt injury fol- determined by field personnel. Incident criteria lowed by cardiac arrest, and physician inter- such as the anatomic factor and mechanisms of vention at the scene is not likely to improve injury scoring tend to result in excessive over- mortality in these cases.23 Thus, it is appropriate triage but are valuable in raising suspicion of to triage casualties who have both blunt injury serious injury.3 The Revised Trauma Score for and cardiac arrest into the “expectant”category. Field Triage is a quantitative system that has been used to predict survival outcomes and Head Injury therefore, indirectly, the feasibility of air trans- Appropriate AE triage of closed-head injury port and aircraft suitability.19 patients is crucial and requires considerable judgement and expertise. In one study, a 9% Number of Casualties reduction in head injury-related mortality has By definition, mass-casualty situations involve been attributed to AE.24 These casualties can be the movement of large numbers of casualties. divided into groups based on their risk of Effective measures must be utilized to accu- significant head injury. The high-risk groups rately assess the effectiveness of each mass- appropriate for immediate AE are those casu- casualty triage effort.20 One measure of alties who have one or more of the following: effectiveness for triage is associated with how 1. Depressed levels of consciousness indicated well patients were transported to the medical by a Glascow Coma Scale (GCS) of 13 or facility that could meet their need on the first less, focal neurological signs. transport. This measure is the ratio between 2. Decreasing levels of consciousness. interhospital transfer due to triage errors 3. Penetrating skull injuries. and the total casualty population who needed 4. Those with evidence of a depressed or 21 transfer. basilar skull fracture.

Types of Casualties The moderate-risk group of casualties are those who had a brief history of loss of Virtually all mass-casualty events will generate consciousness, change in consciousness, pro- a significant number of trauma casualties who gressive headache, vomiting, or posttraumatic will present with a wide variety of injury pat- amnesia.25 These casualties create the most dif- terns. When considering the most common ficult triage decisions. In the primary survey, the types of injuries, two important factors should triage officer must evaluate and monitor the always be kept in mind. First, the chief causes level of consciousness (LOC) by the awake, of death are hemorrhage, sepsis, and respiratory verbal, pain, and unresponsive (AVPU) scale, failure (eg, adult respiratory distress syndrome and re-evaluate this every 15 minutes.24,25 Any [ARDS]).1 Second, hypovolemic shock will be casualty experiencing variations in LOC is re- overlooked by trained medical personnel in assigned to the high-risk group and requires many casualties.1 immediate evacuation. The lowest-risk group is made up of casual- Blunt/Crush Injury ties who have remained alert and have a normal neurological examination. Their AE can be To make appropriate triage decisions for casu- delayed because they have less than 1 in 1000 alties with blunt or crush injuries, a number of chance of having a significant head injury.24,25 important factors must be considered. AE can reduce predicted mortality for casualties with Burn Injuries blunt injuries by more than 50%.22 However, these types of injuries are missed more often Appropriate triage of burn and inhalation than penetrating injuries. Appropriate triage of injuries is crucial because this category 6. Aeromedical Triage Support to Mass-Casualty Events 67 predominates in many mass-casualty events, casualties are also at risk for compartment such as hotel fires and airshow accidents.26 syndrome and acute renal failure (see Blunt/ Immediate evacuation is indicated for casual- Crush Injury). Stable orthopedic patients ties with second-degree burns involving 10% or triaged as “delayed” should be immobilized more of body surface area (BSA), third-degree while awaiting transport. The triage officer burns of 5% BSA, burns involving face, eyes, must assure that weights are removed from any ears, hands, feet, or perineum, or any burn asso- traction devices prior to flight and ensure that ciated with a fracture. Immediate evacuation is patients with air splints are properly managed also indicated for casualties with circumferen- during flight.30 tial burns of extremities or digits because they may require an escarotomy.26 Chemical Contaminated/Mixed Burn patients are among the most difficult to Contaminated–Surgical Trauma Casualty move, and excellent triage decisions are crucial These casualties should be suspected whenever to successfully move them. Because of airway large numbers of casualties occur and chemical burns and inhalation injury, some patients may contamination from an industrial accident or be too unstable for flight without preflight terrorism cannot be ruled out. Fasciculation of treatment. Common procedures that may be muscle groups and in muscles of an exposed required to make a patient stable enough wound or traumatic amputation should alert for evacuation include insertion of catheters, the triage team to possible nerve gas expo- immediate pulmonary care, escharotomy, and sure.31 Even in the presence of contamination, adjustments of IV fluids.27 Triage officers should triage decisions must still be based on the remind the aeromedicat crew of the risk for patients’ total medical condition, including unsuspected pneumothoraces28 during flight ambulatory status, respiratory status, and addi- and specifically request the in-flight availability tional injuries. of pulse oximeters, needle aspiration equip- Decontamination before transfer is critical, ment, and supplemental oxygen for these because contaminated patients may get worse patients. in the closed environment of an ambulance or aircraft and further place aircraft crew at risk. ARDS/Chest Trauma Iran–Iraq War nerve gas casualties, thought Immediate evacuation to appropriate ICU to be decontaminated days before, were sent facilities is indicated for any casualty with without any precautions to France on a com- ARDS. This potentially life-threatening commercial flight for specialized treatment, only to plication can develop in any seriously injured contaminate unsuspecting flight attendants and trauma casualty, especially one who has had crew.32 In the Tokyo sarin attack, casualties blunt or blast injuries. The triage officer must triaged as minimal were not decontaminated at take into account the risk of altitude-related the scene, worsened during evacuation, and hypoxemia, which can be partially compen- contaminated both transport and hospital- sated for by breathing supplementary oxygen, based health providers. Before the Persian Gulf as long as cardiac output and hematocrit War, plans were developed to use helicopters in are adequate.29 Casualties with severe ARDS the decontamination process, but this required should be transported in helicopters flying at extensive aircraft washing facilities unlikely to low altitudes or pressurized fixed-wing aircraft be available during peacetime.3 The triage with supplementary oxygen and pulse oximetry. officer should make certain that the proposed destination medical facility has the capacity to Orthopedic Injuries offer further decontamination antidotes, and ventilation support. Orthopedic injuries are common and frequently missed injuries associated with Pediatric mass-casualty events such as earthquakes and building collapse.1 If orthopedic injuries are Critically injured or ill pediatric patients are associated with prolonged extrication, the extremely vulnerable during AE. One of the 68 F.M. Burkle, Jr., R. Brennan, and V. Garshnek most common reasons for AE of pediatric commonly performed by aeromedical crews patients in a mass-casualty situation is head include5,8,14,20,26,28–30,34: injury due to the relatively large size of the • nasogastric tube insertion head in relationship to the rest of the body.24 • endotracheal intubation Brain complications can be compounded by • cardiopulmonary resuscitation AE because altitude-related hypoxia is the • IV lines most common complication of pediatric air • central venous access transport. It is the triage officer’s responsibility • extrication and splinting to make sure that the medical aircrew is pre- • bladder catheterization pared to take steps to minimize this risk. • venous cutdown • tube thoracostomy Combative/Violent Patient • cricothyrotomy In the overall evacuation process, from patient • pericardiocentesis identification to successful outcome at destina- • MAST garment application tion, many overlapping agencies and organiza- These procedures are best performed prior tions are involved in the triage process. The to flight. The triage officer must first consider potential for confusion and miscommunication the pertinent physiological and aeromedical are probably the greatest for combative or constraints that may affect the procedure. violent patients. The responsibility of the triage He must also assure that limited supplies and officer when confronted with neuropsychiatric equipment are not used on expectant patients. patients is often incompletely understood.33 For A common consideration is the timing of mass-casualty triage purposes, bizzare behavior endotracheal intubation. If performing this should be assumed to be the result of head procedure on the ground will delay evacuation, injury, hypoxia, or toxin exposure until proven experienced aeromedical crew members can otherwise.1,3 Unless the patient is known to intubate both adults and children in-flight, even have a preexisting neuropsychiatric condition, if neuromuscular blockade paralysis is required it is critical to search for such acute causes and for intubation.35 begin appropriate treatment. The triage officer A casualty with multiple trauma will often should advise the AE crew if there is a need for require placement of a chest tube or needle attendants, sedation, or restraints.33 aspiration. Patients who undergo emergent tube thoracostomy in the field are at increased Transportation Management risk for complications, in particular from a mal- functioning or malpositioned chest tube that Once the decision is made to move a patient may require repositioning in-flight. Alterna- through the AE system, a number of factors tively, needle catheter aspiration is a rapid must be considered to properly manage the intervention for the treatment of suspected transportation. Among these factors are the tension pneumothorax, which has been shown procedures that AE crews can reasonably to be relatively safe and effective and have low 36 perform in the air, the equipment available, the morbidity. skills of the crew, and the physiological effects The triage officer should make special of flight. arrangements for cardiac patients with temporary pacemakers and automatic defibrillators. Procedures Performed by These devices must be set to a mode where the Flight Crews vibrations of flight will not trigger any inappropriate firings. If the preflight setting and equip- The AE crew can be expected to accomplish a ment allows, permanent pacemakers should limited number of medical procedures for a be programmed to nonatrial sensitivity or asyn- variety of reasons, including noise, poor light- chronous mode before the patient is on-board ing, constant vibration with intermittent severe the aircraft.37 The triage officer should ensure turbulence, and limited space. Procedures that this type of cardiac-related electrical 6. Aeromedical Triage Support to Mass-Casualty Events 69 equipment is compatible with the aviation envi- pneumothorax, gas gangrene, or air trapped ronment, both in fixed-wing and rotary-wing in the cranium or abdomen.42 Diminished aircraft.38 ambient air pressure causes gases in closed spaces and tissues to expand rapidly. Fortu- Physiological Factors nately, gas expansion will in general not be a problem when flying below 5000ft (1500m).42 A number of physiological factors must be con- Penetrating eye injuries may also worsen with sidered in the decision to send patients in the altitude. The triage officer should alert the AE AE system, but none are more important than crew if there are any patients who may be at respiratory factors. Adequate patient ventila- risk for gas expansion, and a decision must be tion is the cornerstone of safe, successful AE. made whether or not to establish an altitude Common effects of AE that may hamper restriction. patient ventilation include altitude-related hypoxia, gas expansion, and even acceleration forces.28,39–41 Triage officers must have a solid Mode of Transportation grasp of the inherent limits of the aeromedical There is risk in mass-casualty events that AE environment and a well-developed understand- will be used inappropriately. In one wartime ing of altitude-related pressure effects on pul- study, only 22% of patients were found to have monary physiology, procedures, and medical benefited from AE as compared to calcul- devices used during flight.39,41 ated road ambulance evacuation. This resulted despite a high percentage of trauma patients, Altitude Hypoxia rural setting, and poor road conditions and In a mass-casualty event, oxygen therapy emphasizes the need to devise a system that can 43 during flight may not always be available. If screen out unnecessary flights. Crew safety patients at risk for hypoxia are being trans- and the high costs of flying are two important 42 ported without supplemental oxygen, both considerations in the triage process. Casualty- the aircrew and aeromedical crew should be limited events, such as a two-casualties auto- advised that altitude restrictions may be mobile accident, are especially prone to the required. It must be remembered that pressur- overuse of helicopter evacuation for casualties ized cabins provide only partial atmospheric with low severity scores, which has been pressure, with minimum pressures usually reported to be as high as 85% of flights in some 44 equivalent to an altitude of 8000ft.28 Pulse studies. Decisions to use helicopters for oximetry is a useful way to determine which trauma patients are more often based on physi- patients are desaturating in-flight. Unfortu- cian attitudes about air transport than triage 45 nately, if oxygen is in short supply these devices guidelines, making a trained triage officer role will almost certainly be as well. invaluable in these situations. The decision to use aircraft should not be made lightly even in mass-casualty events. One Accelerative Forces of the major responsibilities of the triage officer Gravitational forces are important factors in is to assist in the determination of the need to the AE environment, but should rarely affect use aircraft, what type of aircraft to use, and for triage decisions. However, triage officers should what purpose is an aircraft required. Indica- be aware that certain patients, eg, head trauma, tions for AE include the need to circumvent should have their litter positioned so their geographic impediments, cover large distances heads are toward the rear of the aircraft to in a short time, access isolated areas, and, most maintain their cerebral circulation. critically, get the casualties quickly to specialized medical care. In a mass-casualty situation, Gas Expansion the triage officer may not have any control over the type of aircraft that arrives, but once air- Changes in altitude associated with AE can craft are available they should be used to have serious effects for patients with untreated benefit the most patients possible. 70 F.M. Burkle, Jr., R. Brennan, and V. Garshnek

Use of aircraft in urban mass-casualty events flight planning time, but are less hampered is rarely indicated. However, aircraft may be by weather. With proper triage and in-flight required to transport patients from local medical care, casualties can be transported medical facilities to Level I trauma centers or 800 miles or more without increasing trans- specialized care facilities (eg, burn centers). port-related mortality. These long-range move- These moves should occur after initial stabi- ments are almost always accomplished to lization at the local hospital. In addition, the use provide access to a major trauma center or burn of aircraft to rapidly transport qualified per- center. Compared to a helicopter, cabin spaces sonnel to the scene or to a nearby treatment are much larger and usually pressurized. facility may be an expedient triage decision. Because of the decreased cabin pressure at usual cruise altitude, oxygen supplementation is routine for all at-risk patients at altitude. Triage Rotary-Wing vs Fixed-Wing Aircraft officers must assure that aircraft have enough In the civilian AE setting, helicopter missions oxygen to meet all patient needs before the outnumber fixed-wing missions in a ratio of aircraft departs. 7:1.46 In mass-casualty events in field conditions, immediate air evacuations are almost Crew Safety, Skills, and Composition exclusively by helicopter because of their unique capabilities. Helicopters deploy rapidly, Optimal aeromedical triage is dependent on require shorter preflight planning, do not the medical input and guidance by trained and require an airfield for landing, and provide experienced triage officers. Their roles include more rapid turnaround times critical for protocol development, training, and continuing mass-casualty evacuations.46 Vertical take-off education in mass-casualty care as well as avoids complications caused by horizontal coordination of lessons learned in aeromedical accelerative/decelerative forces. A helicopter’s triage and evacuation. The most important normal flying altitude is less than 2000ft qualifications for a mass-casualty triage officer (600m) above ground level, so hypoxia is rarely include good judgement, broad-based knowl- a problem.47 These advantages of helicopters edge of aeromedical factors, and solid leader- may be offset in some circumstances by their ship and management skills. It is crucial that the disadvantages compared to fixed-wing aircraft. on-site individual with the greatest skills serve These disadvantages include short range, as triage officer regardless of professional train- small passenger/patient load, vibration, noise, ing (ie, doctor, nurse, paramedic). no pressurization, weather limitation, and It is critical for on-scene triage officers to increased risk of motion sickness.47 know the composition and skills of available Studies suggest that improved clinical out- AE crews and match casualties with both air- comes are associated with helicopters that are craft and crews. This is often made difficult by faster and provide more cabin space. Most the unpredictable mix of airframes, crew com- cabins provide for one belted crew member at position, and skills that are available during a the patient’s head and one on the side to mass-casualty event. An abiding principle is monitor vital signs and perform necessary non- that no mission should be flown if it cannot be airway–related procedures. Helicopters with a accomplished safely. two-patient capacity greatly increase demands The types of aircraft and crews available will on the flight crew and diminish access and differ greatly depending on whether they are care to both patients.20 Triage officers must civilian or military. Civilian programs utilize communicate with the aircrew to ensure an small to midsized aircraft (most commonly heli- appropriate provider-to-patient ratio, as well as copters), often with a single pilot (see chapter compliance with maximum take-off weights. 3). The AE crew usually consists of two highly This final point is crucial because take-off trained medical crewmembers, usually a weights can easily be exceeded due to the combination of technicians, paramedics, nurses, weight of certain medical equipment.48 or physicians. They are in general always Fixed-wing aircraft have the disadvantage equipped with state-of-the-art medical equip- of requiring an airfield and needing more pre- ment.42 The USAF uses a variety of transport 6. Aeromedical Triage Support to Mass-Casualty Events 71 aircraft in the AE role (see chapter 8), all of to send these doctors and nurses with a flight or which have at least two pilots and an aeromed- keep them at the staging facility. ical crew structured to meet the needs of the patient load. By tradition, military programs Weather and Environmental operate larger aircraft and utilize two pilots per Conditions aircraft. Safety is a high priority, with emphasis on crashworthiness and protective gear. And, Triage officers must have a working knowledge finally, because the historical mission is one of of the effects rain, fog, haze, clouds, airframe evacuation of multiple stable casualties in icing, turbulence, and wind shear have on the wartime, military aircraft by tradition utilize decision to fly. Conventional disaster managers aeromedical crewmembers with limited train- do not necessarily understand the nuances of ing in critical care and limited equipment.43 The visual meteorological conditions (VMCs) and current development of the Critical Care Air instrument flight rules (IFRs). So, the triage Transport (CCAT) Team concept will change officer is responsible for interpreting these find- this crew factor. ings to site managers whenever conditions To comply with legal and operational might prohibit or alter triage and evacuation requirements, it is important that the skill options.14 level of the AE crew be of the highest quality 42 possible, even during mass-casualty events. Evacuation Destination Because the skills of AE crews can vary greatly, the triage officer may have to arrange for aug- Prior to AE, the triage officer must consider mentation of the crews with trained medical both the specialization and intensity of care and providers. services available at the destination site. The Studies on how varying compositions of availability of operating rooms and qualifica- AE crews effects patient outcomes have been tions of medical personnel (not merely avail- mixed. No objective differences in outcome able hospital beds) are determining factors for of severity-paired patients were found between triage-to-destination decisions.51 In short, if the paramedic–nurse and nurse–nurse teams. Use casualties require a full trauma center then the of paralytic drugs by paramedics is becom- transportation plan must assure that they arrive ing standard care in many out-of-hospital at such a center. systems, and nurses providing ATLS during flight perform equally when compared with 49 Telemedicine as an Aeromedical physicians. However, a 35% improvement Triage Tool in outcome for blunt trauma patients was associated with using flight nurse–flight phy- Advances in telemedicine and telecommunica- sician teams over nurse–paramedic-staffed tions, as a resource tool, have the potential to helicopters.50 positively influence triage decisions in the field The addition of a flight surgeon to AE crews and then remotely care for the victim in-flight. during military actions has been shown to For more than a decade, commercial airlines provide the flexibility to transport and resusci- have been utilizing telemedicine services to tate critically ill patients during flight.51 Dedi- assist in-flight passenger medical emergencies.53 cated MEDEVAC flight surgeons fill a unique Specifically,telemedicine has been used for spe- and valuable role in some circumstances. Nor- cialty consultation, access to medical informa- wegian experience has shown benefit in having tion, and biomedical monitoring/forwarding a designated physician specially trained in aero- of patient parameters via special flight-worthy space medicine and acute medicine/surgery as monitoring systems and equipment. A survey a permanent crewmember.52 conducted by the FAA reported that flight Crew composition is not usually a peacetime crews complied with medical advice in 97% of triage factor, but could easily become a part of cases, and diversions of aircraft resulted in the triage decision in wartime. The limited hospital admissions 86% of the time.54 Tele- supply of intensive-care physicians and nurses medicine services provide a 24-hour medical could easily force a decision regarding whether emergency hotline (via radio, telephone, and 72 F.M. Burkle, Jr., R. Brennan, and V. Garshnek satellite) for direct and immediate consultation management. Advanced technologies such with board-certified emergency physicians as telemedicine/telecommunications have the qualified in remote diagnosis and trained to deal potential of augmenting aeromedical triage with illness and injury at altitude, and provides decision making from great distances. physicians immediate access to specialists in more than 45 fields of medicine.55 References In addition, special equipment has been 1. Burkle FM. Triage. In: Burkle FM, Sanner PH, adapted for in-flight utility. Tests have shown Wolcott BW, eds. Disaster Medicine. New Hyde that useful vital sign information (ECG, blood Park, NY: Excerpta Medica Publications/Else- pressure, transcutaneous pulse oximetry, and vier Press; 1984:145. respiratory parameters) can be transmitted 2. Gunn SWA. Multilingual Dictionary of Disaster from an isolated location to a distant triage Medicine and International Retief. Dordrecht, officer even at communications speeds as low The Netherlands: Kluwer Academic Publishers; as 2400 baud.56 These devices can be operated 1990:87. under remote guidance and utilize a portable 3. Burkle FM, Newland C, Orebaugh S. Emergency lightweight computer unit connected directly medicine in the Persian Gulf War, part 2: Triage methodology and lessons learned. Ann Emerg with any available communications, including Med 1994;23:748–754. cellular phones. Units are adapted to Inmarsat 4. Howard JM, DeBakey M. The Cost of Delayed (utilizing two Inmarsat mini-M terminals, one Medical Care. Fort Sam Houston, Tex: Sympo- for voice and one for data) so that data can be sium on Management of Mass Casualties, transmitted over large bodies of water, allow- Medical Field Service School; 1962. ing triage support from anywhere in the 5. Martin TE. Resolving the casualty evacuation world.56 conflict. Injury 1993;24:514–516. The Telemedicine Instrument Pack (TIP) 6. Lindbeck GH. Reimbursement patterns in a was successfully tested onboard a US Space hospital-based fixed-wing aeromedical service. Shuttle flight (STS-89) in 1998 and has proved Am J Emerg Med 1993;11:586–589. to be equally operational on air ambulances.57 7. Mabry EW, Munson RA, Richardson LA. The wartime need for aeromedical evacuation physi- The DoD has developed a Life Support for cians: The U.S. Air Force experience during Trauma and Transport (LSTAT) or “Smart Operation Desert Storm. Aviat Space Environ Stretcher” that functions as an entire ICU uti- Med 1993;64:941–946. lizing embedded microminiaturized devices 8. Wilden JN. Effects of helicopter service on sur- to monitor vital signs and the regulation of vival after trauma. Helicopters do not care for various fluid and medication administration by patients. Br Med J 1995;311:217–222. remote physicians.58,59 The civilian counterpart 9. Coupland RM. Epidemiological approach to Mobile Intensive Care Rescue Facility (MIRF) surgical management of the casualties of war. Br allows for stand-alone intensive-care manage- Med J 1994;308:1693–1697. ment (multifunction monitor, ventilator, infu- 10. Burkle FM. Triage in Complex Emergencies. sion pump, syringe pump, and defibrillator) and Honolulu: COE/DMHA; 1999. CHART course. 11. Burkle FM. Lessons learnt and future expecta- fits into a large range of aircraft for transport 60 tions of complex emergencies. Br Med J 1999; of the critically triaged. 319:422–426. 12. Medecins sans Frontieres. Refugee Health: An Conclusion Approach to Emergency Situations. London: Macmillan; 1997. Triage officers have an opportunity to con- 13. Kearney PA, Terry L, Burney RE. Outcome of patients with blunt trauma transferred after tribute greatly to the effective management diagnostic or treatment procedures or four-hour of mass-casualty events, transforming the delay. Ann Emerg Med 1991;20:882–886. casualties to patients as they move from the 14. Mulrooney P.Aeromedical patient transfer. Br J disaster to a hospital bed. The factors unique Hosp Med 1991;45:209–212. to aeromedical triage support are critical to 15. Anantharaman V. Burns mass-casualty disasters: overall mass-casualty triage, evacuation, and Aetiology, predisposing situations and initial 6. Aeromedical Triage Support to Mass-Casualty Events 73

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William W. Hurd, Anthony M. Rizzo, Eunice K. Taylor, and John M. McNamara

Staging is a general military term that refers to Medical Clearance for AE the careful preparation and organization of personnel and equipment prior to deployment. In all cases, the patient must be determined to For aeromedical evacuation (AE), patient be healthy enough to withstand the rigors of staging includes the preparation of the patient, AE. At the same time, any special patient needs personnel, and equipment prior to the AE must be identified. In the military AE system, flight. Although the term is infrequently used in specific peacetime protocols have been de- the civilian world, every patient must be effec- veloped for preflight medical clearance. In a tively staged prior to any AE flight regardless contingency situation, the greatly increased of the venue. number of patients who must be moved quickly From a medical perspective, patient staging is may complicate medical clearance. Although of the utmost importance. Once in the air, the the specific personnel involved may be differ- medical care available to the patient is entirely ent for civilian AE, the medical considerations dependent on the thoroughness with which pre- remain the same. flight preparations have been made. Complica- The importance of preflight screening for AE tions or emergencies can be effectively treated is related to the difficulty in both detecting and only if the appropriate equipment, medical sup- treating patient decompensation during flight. plies, and trained medical personnel are avail- Detecting in-flight medical decompensation is able. Unanticipated in-flight emergencies may made difficult by two factors common during receive only the most rudimentary emergency military AE. First, the noisy and dark environ- care because the medical supplies, medica- ment of many of the airframes used for AE tions, and medical expertise available during a hinders the ability to detect small changes in routine AE flight are relatively limited. Subse- the patients’ conditions. Although the interior quent care for unexpected complications is of the C-9 Nightingale (the aircraft most com- usually delayed until emergency diversion to a monly used for AE during peacetime) is well lit, medical treatment facility is accomplished. Any it has approximately the same ambient noise lack of planning not only increases discomfort level of a commercial aircraft. During a contin- for the patient but also may adversely affect the gency operation, only a minority of military patient’s health. patients will be transported on these aircraft. In light of the inherent limitations of AE, The aircraft commonly used for tactical and patient staging has three main medical pur- strategic AE (eg, C-141, C-130) are noisy and poses: first, to appropriately select patients for dark, with significant amounts of vibration AE; second, to arrange for the appropriate and potentially extreme swings in temperature in-flight equipment and personnel; third, to from hot to cold. All of these factors hinder prepare the patient both medically and psy- the ability to detect changes in the patients’ chologically for flight. conditions.

75 76 W.W. Hurd et al.

Another factor that makes detecting changes above. Lack of space is a second critical factor. in the patients’ conditions difficult is the high When a C-141 is used to transport multiple patient-to-provider ratio that occurs in mass- litter patients, as many as 100 litters are casualty situations. A military AE medical “stacked” in tiers of 4 patients, with only 21in flight crew consists of 1 flight nurse and 3 of clearance between litters (Fig 7.1). This con- flight medical technicians for each 10 patients. figuration results in the top stretcher being Because a fully loaded C-141 can carry over 100 located more than 5ft above the deck. Little litter patients, the number of patients per meaningful patient care can be done at this provider may be higher in a contingency situa- level without removing the litter from its tier tion. The decompensation of a single patient and placing it on the cabin floor. further draws attention away from the other A final factor that makes treatment more dif- patients. As a result, many changes in condition ficult is a lack of specialized equipment and that would be noticed in a quiet, brightly lit hos- training. While all flight nurses, technicians, and pital environment might go unnoticed for hours physicians are trained in basic emergency treat- during a difficult AE flight. ment, routine AE flights are equipped only with The treatment of patients who become un- standard emergency equipment and drugs. If stable during flight is likewise more difficult the risk of patient decompensation is signifi- during AE because of several factors. The first cant, special arrangements must be made for is the noisy and dark environment as discussed extra personnel and equipment to assure that

Figure 7.1. A flight nurse checks on patients in a USAF C-141 Starlifter configured to hold litter patients during an AE exercise (USAF photo by Airman 1st Class Angela Furry). 7. Patient Staging for Aeromedical Evacuation 77 the patient receives optimal care during AE. important of which is the lack of comprehen- This is a key function of staging because failure sive medical care locally.1 For the purposes of to make appropriate special arrangements this textbook, contingency AE is defined as AE prior to AE may make it difficult or impossible of casualties as soon as possible after stabiliz- to effectively treat unexpected changes in ing treatment, for logistic reasons. patient condition during flight. Peacetime AE Peacetime vs Contingency AE For AE during peacetime, the referring physician performs medical screening and primary There are considerable differences between preparation (Fig 7.2A). This is done in con- peacetime and contingency AE during armed junction with a flight surgeon familiar with AE conflict or a natural disaster. During peacetime, to make sure that altitude, personnel, and the vast majority of military AE is elective and, equipment-related limitations are considered. in most cases, the timing of such AE is based on Prior to AE, the transfer must be coordinated medical considerations. This is in contrast to with an accepting physician at the receiving AE during a contingency, where patients may medical treatment facility. In the military need to be moved at the first available op- system, final AE clearance is given after review portunity for logistic considerations, the most of each patient’s diagnosis, condition, and

Figure 7.2. Graphic representation of the differences between peacetime and contingency AE as performed by the USAF AE system. During peacetime (A), the transfer is primarily between USAF medical treatment facilities, with ASF personnel playing a relatively minor role in their medical care. During contingency AE (B), ASF personnel will play a much greater role in the medical care of stabilized patients en route. Note that neither physician-to- physician coordination nor individual medical clearance for AE may be possible during contingency AE, making the role of the ASF critical for successful AE. 78 W.W. Hurd et al. special needs by an experienced flight nurse AE Movement Precedence (patient movement clinical coordinator) at the Global Patient Movement Requirements Movement precedence categories have been Center (GPMRC). As the patient passes developed to assist the GPMRC during peace- through the aeromedical staging facility (ASF), time in assuring that patients are moved in an medical personnel verify that the patient is appropriately timely fashion with the appropri- stable and has the necessary supplies and med- ate personnel and equipment. They can also be ications for the flight (see later in this chapter). applied to casualties during contingency AE if the number of casualties exceeds the AE Contingency AE capability. These categories reflect the patients’ conditions but not necessarily their medical A sudden increase in the number and severity stability (Table 7.1).3 of patients requiring military AE will necessarily alter the way patients are medically cleared. During contingencies, such as armed conflict or Routine AE natural disaster, a much smaller percentage Stable patients who need little medical moni- of the treating physicians will have the back- toring or care in-flight are classified as routine. ground or time to clear the patients for AE. In These patients may be in the convalescent addition, flight surgeons are unlikely to be phase of their illness or injury or may have a readily available in a non-USAF medical facil- stable condition that makes them unlikely to ity, During an armed conflict, the majority of experience medical decompensation. They are patients will originate in Army medical facili- most often ambulatory, although some may ties, where physicians expert in the treatment of require transportation by litter because of their battlefield trauma are less likely to have the conditions. expertise to clear patients for AE. Further, mass casualties may overwhelm the GPMRC system and will almost certainly make it impossible to Urgent AE individually coordinate patients with the referral physicians at the accepting medical facility. In peacetime, a certain percentage of patients For these reasons, the responsibility for will require quicker transportation than can be medically clearing and preparing patients for afforded by routine AE. The most drastic of military AE will often shift to ASF medical per- these are patients designated for urgent AE. sonnel during a contingency operation (Fig This is defined as patients who require emer- 7.2B). The ASF will serve as the point of gency AE to save life, limb, or eyesight or medical clearance for most patients requiring prevent serious complications of injury or exist- AE and may be the point of origin for some ing medical conditions. In almost all cases of patients. Undoubtedly, there will be less time urgent AE, the driving factor is that the medical and personnel to manage a greater number of expertise or equipment is not available to treat patients. the patient in a local medical facility. Because At the same time, the types of patients trans- these patients are often unstable, they may also ported by contingency AE make appropriate require special expertise or equipment and medical clearance even more critical. During a thus may also be classified as special AE (see contingency operation, most patients will not later in this chapter). be in the stable convalescence phase of their recovery. Patients who have only recently been Priority AE treated and stabilized in a medical facility will be at increased risk of medical decompensation These are patients who must be transported by before or during the AE flight. Experience AE within 24 hours, usually because appropri- teaches that transportation of patients before ate care is not available locally. In some cases, they are reasonably stabilized can have tragic the patient may be medically stable and require results.2 minimal in-flight monitoring or care. More 7. Patient Staging for Aeromedical Evacuation 79

Table 7.1. AE triage categories. Category Requirement

Peacetime AE Routine* Standard equipment and personnel at the next scheduled ﬂight Priority† AE within 24h Urgent† AE as soon as possible to save life or limb Special‡ Augmented Limited special equipment and personnel readily available in-theater CCAT Special team with critical-care equipment and expertise Contingency AE Routine‡ Standard AE equipment and personnel Augmented‡ Requires limited special equipment and personnel readily available in-theater CCAT‡ Special team with critical-care equipment and expertise

* Implies both capability and timing. † Implies only timing. ‡ Implies only capability. commonly, the patient may be relatively unsta- the appropriate supplies and medications are ble and require the special expertise or equip- sent with the patient. They also serve as a ment of special AE. double check for medical clearance for AE by verifying that patients are in the same condition Special AE as when they left the medical facility. The role of the ASF dramatically expands This refers to any patient who requires special during a contingency or mass-casualty opera- expertise, equipment, or in-flight care not nor- tion. The ASF medical personnel may be the mally offered by the AE system. Many patients first caregivers experienced in AE medicine to classified as urgent or priority AE will be rela- evaluate the patient and thus may be responsi- tively unstable and require special care during ble for medical clearance of AE. In addition, AE. These patients must be accompanied by the rapidly increased demands placed on the physicians, nurses, and/or other providers who medical system during these types of opera- are expert in the management of their critical tions may require the ASF to provide a wide problems. In the military system, these aug- variety of care, including medical–surgical ward menting personnel usually originate from the care, intensive care, and emergency care. referring medical facility. However, with the development of the Critical Care Air Transport Peacetime Roles of the ASF (CCAT) Teams program, a team of specially trained medical personnel may be brought During peacetime, the majority of AE patients from a different medical facility specifically for will be categorized as routine and the majority this transportation. of these will be ambulatory. The primary ASF role is to coordinate the safe transition of these patients from the medical facility to the AE Aeromedical Staging Facility system. This mission can be categorized into several specific tasks. For military AE, the ASF serves as an entryway Medical Care and Preparation for AE to the AE system. During peacetime, the ASF accomplishes this through many important Medical preparation is critical to the safety of functions, including patient preparation, final patients during AE and is probably the most medical clearance, and transportation to and specialized role of the ASF. To this end, the from the flight line. ASF personnel confirm that patients’ medical stability for AE must first 80 W.W. Hurd et al. be confirmed. For inpatients, vital signs must and their personal assets for dangerous items. be monitored during the several hours they Antihijacking precautions, in the form of metal are in the ASF. These patients must receive detection devices, x-ray machines, and other appropriate fluids and medications, as ordered strategies, are imperative for both civilian and by the referring physician. Sudden changes military AE operations. in these patients’ conditions are uncommon because these are usually stable convalescing Patient Transportation patients. However,ASF medical personnel must A relatively unique role of the ASF is to have the knowledge and equipment to perform provide safe transportation for patients under emergency resuscitation because sudden de- challenging conditions (Fig 7.3). This involves compensation remains a risk for all patients. transporting ambulatory and litter patients Verification that the patient has an appropri- from the ASF to the aircraft via ground trans- ate supply of medications and other patient portation (van, ambulance bus, or ambulance). needs is another important aspect of prepara- Although the primary goal is to avoid pa- tion for AE. This is critical, especially when a tient injury, avoiding aircraft damage is also large number of patients are being transported, extremely important. The manner in which because a limited amount of extra supplies are they are transported will be determined by a available on the aircraft. Unexpected delays en flight surgeon prior to transportation (Table route may occur due to changes in the medical 7.2).5 condition of other patients on the flight or Litter patients must be carefully moved from changes in itinerary, weather conditions, or the ASF onto the bus or ambulance and then operational limitations of the aircraft or flight onto the AE aircraft (Fig 7.4). The demands of crew. This may result in the need for a much this role make it potentially one of the most greater amount of supplies or medications than dangerous duties carried out by ASF personnel was originally planned. Further, specialized during peacetime. The patients are at risk of medications are in particular difficult to obtain injury during transportation, as is obvious to in smaller or foreign medical facilities located anyone who has ever carried a litter. The ASF near sites where an AE flight is likely to be personnel are at risk of musculoskeletal injury delayed. Because of this, the ASF attempts to when moving heavy patients to the awkward provide the patient with several days’ supply of places found in both ground vehicles and air- all required medications, even if the planned craft. The task is complicated by the variation AE flight is only a matter of hours. For military in AE aircraft configuration, as shown in AE, the standard is 3 days’ supply for intrathe- chapter 8. In addition, the hardware necessary ater AE and 5 days’ supply for intertheater AE.4 to secure patient litters may cause injury to the During peacetime, special AE patients often litter carrier’s fingers and hands. To minimize do not spend time in the ASF because of the these risks, ASF personnel must be extensively acuity of their medical condition. Rather, they trained in patient movement techniques so that are transported directly from the referring they are familiar with challenges posed by the medical facility to the flight line, and at the con- configuration of the various ground vehicles clusions of their flight they are transported and aircraft. directly to the accepting medical facility. The medical care of these patients is primarily Patient Sustenance and Comfort under the control of the augmenting medical personnel. However, the coordination and Another extremely important role of the ASF transportation for AE remains the responsibil- is the sustenance and comfort of patients await- ity of the ASF personnel. ing AE because it is not uncommon for patients to remain in the ASF for several days. ASF personnel must assure comfortable lodging for Security both ambulatory and litter patients and their The ultimate safety of an AE flight depends on nonmedical attendants. The patient arrange- careful preflight screening of the passengers ments must take into consideration the types 7. Patient Staging for Aeromedical Evacuation 81

Figure 7.3. C-17 Globemaster conﬁgured to trans- to shoulder level requires both strength and skill to port 36 littered patients and 48 ambulatory patients avoid injury to the patient or litter bearers or using a three-tier litter system. Lifting heavy patients damage to the aircraft (USAF photo).

and severities of their illnesses. ASF staffing whenever possible during peacetime. In the provisions must accommodate all types and military system, the referring physician deter- severities of illness and injury 24 hours per day, mines the need for a nonmedical attendant. 7 days per week. Another important mission of the ASF is to make sure that patients receive appropriate Roles of the ASF for Contingency AE meals on the ground and in the air. Each ASF Implications of Stable Rather Than has nutrition technicians on-staff to make sure Stabilized Patients that regular and special dietary needs of patients are met, as determined by referring When a large number of patients must be trans- physicians. ported out of theater during an armed conflict Psychological support of patients is essential or a mass-casualty operation, the role of the to AE. Many patients are experiencing serious ASF dramatically increases in scope. During injuries or illnesses for the first time in their contingency AE, patients are moved as soon lives, and most are about to undertake their first as possible after initial stabilization. From a AE flight. If unprepared, the stress and isola- medical perspective, these “stabilized” patients tion of the AE environment may further are markedly different from the “stable” con- increase their apprehension and delay their valescing patients transported by AE during healing and recovery. For this reason, a non- peacetime.6 In the past, patients were allowed medical attendant (usually a family member) to convalesce prior to AE, as shown in the should be allowed to accompany the patient Vietnam War, where the average length of 82 W.W. Hurd et al.

Table 7.2. AE categories used by the US Military.

Inpatient Category 1: Psychiatric Litter 1A Severe: Requiring restraints, sedation, and close observation 1B Intermediate severity: Potentially dangerous, but not presently disturbed, who require sedation; restraints should be available Ambulatory 1C Moderately severe: Cooperative and reliable under observation Categories 2 and 3: Medical/surgical Litter 2A Immobile litter patient: Unable to move unassisted 2B Mobile litter patient: Able to move unassisted under emergency circumstances Ambulatory 3A Patients going for treatment or evaluation: All medical and surgical conditions excluding drug or alcohol abuse 3B Recovered patients returning to station 3C Patients with drug or alcohol abuse going for treatment Category 4: Infants and children <3y old Ambulatory 4A Infant or child going for treatment traveling in an aircraft seat 4B Infant or child returning from treatment traveling in an aircraft seat Litter 4C Infant requiring an incubator 4D Infant or child going for treatment traveling by litter Ambulatory outpatients 4E Infant or child, ambulatory outpatient Outpatient Category 5: Outpatient adults and children >3y old Ambulatory 5A Patient going for treatment or evaluation: All medical and surgical conditions excluding drug or alcohol abuse 5B Patient with drug or alcohol abuse going for treatment 5C Psychiatric patient going for treatment Litter 5D Patient going on litter for comfort for treatment or evaluation: All medical and surgical conditions excluding drug or alcohol abuse 5E Patient returning from treatment going on litter for comfort Ambulatory 5C Patient returning from treatment Nonpatient Category 6: Attendant 6A Medical attendant 6B Nonmedical attendant

Source: Adapted from Department of the Air Force.8

convalescence prior to AE from the theater was his or her diagnosis and present condition. This 7 days from the time of injury.2 However, in a is one of the critical issues that will be covered contemporary contingency operation it may in the clinical chapters in this book. Premature not be possible to keep patients in-theater for AE may result in potentially avoidable medical even a matter of days after deﬁnitive medical complications, morbidity, and, in the worst treatment. case, mortality.2 Depending on the availability The medical implications of contingency AE of specially trained transport teams and equip- are two-fold. First, the earliest time for safe AE ment, there are certainly absolute contraindi- must be determined for each patient based on cations to AE.7 7. Patient Staging for Aeromedical Evacuation 83

Figure 7.4. Litter bearers carry a patient up the ramp of a C-9 Nightingale medical transport aircraft (USAF photo by Staff Sergeant Gary R. Coppage).

The second medical implication of contin- ing of stabilized patients for contingency AE. gency AE is that patients will be at increased Ideally,all patients who reach the ASF will have risk for early complications and medical already been cleared for AE.8 In reality, this decompensation because they are relatively may not always be the case in a contingency sit- early in the course of their diseases or injuries.2 uation,9 as noted by J.M. McNamara (written These possibilities must be anticipated because communication, October 1993). Many medical lack of preparedness will make it impossible to personnel treating patients outside of the ASF effectively treat them in fight. may have little AE experience and thus will be unable to adequately evaluate the patients’ Medical Care and Preparation for AE ability to undergo AE. During military operations, approximately 98% of the casualties are During a contingency, patients early in the Army and Marine personnel, and medical per- recovery phase of their injuries or illnesses are sonnel organic to the respective service branch certainly more likely to have acute changes in (with limited AE experience) will treat the their medical conditions, potentially requiring majority.2,10 Experience from recent contin- emergency resuscitation while they are in the gency operations indicates that medical clear- ASF awaiting AE. Therefore, early recognition ance for AE will be the responsibility of the and prompt treatment will require a highly flight surgeons assigned to the ASF, as noted skilled and trained medical and nursing staff. by J.M. McNamara (written communication, All of the peacetime medical roles of the ASF October 1993). discussed above are even more important. Another different aspect of AE during a contingency operation with a large number of Medical Clearance for AE casualties is the lack of direct communication A relatively unique role of the ASF during a between the referring and receiving physicians contingency operation will be medical screen- that occurs during peacetime. Communication 84 W.W. Hurd et al. between the theater and receiving medical load. In a contingency operation, the number facilities may be limited to the number, diag- of casualties may be significantly greater than noses, and severity of the patients. In most the AE capacity. As a result, prioritization of cases, the ASF will act as the interface between patients for transportation at the ASF level the sending and receiving medical facility. Prior may become a major issue. The following con- to AE, updated patient information will be for- siderations must be taken into account for this warded to the GPMRC for worldwide patient purpose. tracking by a new automated system known as the TRANSCOM Regulating and Command & Availability of Transportation Control Evacuation System (TRAC2ES). The most obvious potential limitation will be the availability of ground and air transpor- Patient Transportation tation. Each AE flight will be configured Patient transportation is also dramatically dif- for a certain number of ambulatory and litter ferent in a contingency situation because both patients. This configuration can be varied the number of patients and the number of per- depending on the number and types of casual- sonnel required to move them will markedly ties, equipment, and supplies required and the increase. The transportation teams will be number of medical personnel available. In the under significant stress related to transporting military setting, close coordination between the a large number of patients with traumatic ASF, the Theater Patient Movement Require- injury, as well as the long hours that may be ments Center (TPMRC), and the GPMRC will required. Other factors that may affect trans- be mandatory to optimize AE efficiency. If the portation are challenging weather and road number of patients for each category exceeds conditions, plus an overtaxed flight line. the AE capacity, other prioritization criteria Further, in a wartime scenario patient trans- will be required. portation may have to be carried out in chemical ground ensemble. Despite the absense of Intensive-Care Support these factors in routine operations, the focus of peacetime training must be to prepare for and In a large contingency operation, another lim- minimize these effects. iting factor will be the amount of intensive-care support available, both in the ASF and in-flight. With the advent of CCAT teams, trained Patient Subsistence and Comfort intensive-care personnel and specialized equip- Patient subsistence and comfort remains a high ment for AE will be more readily available. priority during a contingency operation. It is However, the number of critical patients may especially important to appreciate the psy- be greater than the number of CCAT teams. chological stress associated with unexpected Every AE flight must be staffed with appropri- injuries resulting from combat or natural disas- ate medical personnel, equipment, and supplies ter. Nursing and medical staff will need to to care for both the critically ill and less acutely ensure that the psychological and emotional ill patients aboard. status of all patients is assessed as part of the preflight screening. All ASFs have a psychologi- Medical Urgency of Continued Care cal care team on-staff specifically for this purpose. The final consideration in a contingency situation is the medical urgency of continued care. Although contingency AE will result in the Prioritization of Patients for AE movement of all patients as quickly as possible, Prioritizing patients for AE is a standard part those patients who are urgent or priority must of patient staging. During peacetime, this is be recognized and moved at the earliest time done at the GPMRC level because the patient that appropriate personnel and equipment are capacity of AE is much greater than the patient available. 7. Patient Staging for Aeromedical Evacuation 85

Hospital Ward Care Patient Organization in a During a large contingency operation, the ASF Contingency ASF role in hospital ward care may be unexpectedly expanded. Hospital ward care is only a minor Multiple problems are inherent in taking care part of the peacetime ASF role because most of a large number of patients in a contingency of the patients are ambulatory and the litter ASF. Military planners have envisioned the patients are usually in the convalescent, out- need for ASFs large enough to care for up to patient phase of their illnesses. Most seriously 250 casualties. This large group of patients with ill special AE patients are transported directly variable medical problems must be carefully from the medical facility to the flight line. organized both to optimize medical care with During a contingency, military plans direct that limited personnel and allow appropriate prior- patient time in the ASF will be limited, as there itization for AE. will be limited medical support and supplies. However, with a large number of casualties Organization by Diagnosis both the theater medical system and the AE system may both be overloaded. There may be Diagnosis is the most obvious basis for organiz- rearward pressure in theater medical facilities ing patients. Patients with severe injuries to transfer patients to ASFs to make room for or illnesses should be grouped together to incoming casualties. AE delays related to lack optimize nursing and medical care. The best of aircraft, weather, or crew limitations may example is severely burned patients,who should result in patients remaining in the ASF longer be grouped because they will require special- than planned. Finally, overtaxed ground trans- ized and intensive nursing care in terms of fluid portation may make it difficult to send ASF replacement and pain relief. Postoperative and patients back to the medical facility in the event posttraumatic patients can also be grouped of AE delays. As a result of the inevitable “fog because they need both pain relief and careful of war” associated with contingency operations, observation for signs of hemodynamic instabil- the ASF should be prepared to provide some ity or other complications. degree of medical and surgical ward care. Infectious Disease Considerations Second-Echelon Response During the planning stage, a contingency ASF A final contingency role that may be required should design an infectious disease isolation of an ASF is a mass-casualty situation where area because with large numbers of patients the second-echelon “emergency room” care is infectious disease considerations are important. required, especially for any ASF that is not In a wartime scenario, more than one half of the colocated with a theater medical facility. In a casualties will result from disease, and many of contingency, the ASF may be the closest these patients may be infectious.11 A more medical facility to the battlefield or site of recent threat is biologic weapons. Both residual injury, as noted by J.M. McNamara (written contamination and communicable disease may communication, October 1993). With a full present risks to both medical personnel and cadre of highly trained physicians and nurses, it other casualties. will be important to have an area set up with the necessary equipment and supplies to care Psychiatric Patients for such casualties. This area can be the same “acute care area” used for resuscitation of Another group of patients requiring special decompensated ASF patients. Plans should be consideration is those with psychiatric diag- made for triage, emergency decontamination, noses. These are patients who might exhibit dis- resuscitation, medical stabilization, and emer- ruptive behaviors, including combativeness or gency transportation to the nearest medical disorderliness. The sight of severely injured facility for definitive care. patients may agitate them as well. At the same 86 W.W. Hurd et al. time, some of these patients may need close while he stabilized his wife at the US Embassy. observation. For these reasons, an isolated Military AE was not available because the observation area should be set up for psychi- United States had no landing rights in this atric patients. country. For this reason, arrangements were made to transport both patients on a civilian Medical Stability airliner to a Middle Eastern country. The wife was transported by stretcher in a semiconscious For purposes of ASF organization, patient can state without medical support and the author be roughly divided into three levels of stability: accompanied her as an ambulatory patient. The stable, stabilized, and unstable. Stable patients only medical personnel and supplies available are those unlikely to medically decompensate during the flight was the author and the limited and require minimal medical care and moni- supplies he could carry (eg, bandages, intra- toring. These patients would be outpatients venous fluids). under normal circumstances. Many of these Upon arrival in the Middle Eastern country, patients will be ambulatory, and those with less the author’s wife was taken to a foreign mili- serious injuries can be kept separate from the tary hospital, where local physicians did not more seriously ill patients. expect her to live and thus offered only pallia- Stabilized patients are those who have been tive care. Two American expatriot nurses were treated but, because they are relatively early in allowed to care for her throughout the night the convalescent phase of their illness, are at and treat her with intravenous fluids, anti- higher risk for medical decompensation. These biotics, and blood transfusions. The following patients will need a higher level of medical day, the critically ill patient and her less monitoring similar to inpatient medical facility seriously injured husband were transported by care. US military AE aboard a C-9 Nightingale. Unstable patients are those who have de- After a change of aircraft in Athens, they compensated, either en route or since arriving landed in Frankfurt and arrived at Wiesbaden at the ASF.When patients are transported early USAF Medical Center approximately 48 hours in the course of their recovery, “resuscitation is after the initial injury. a frequent requirement.”11 For this reason, a At the Medical Center, she received three special acute care area should be set up for surgical procedures over a 3-day period and resuscitation and equipped with a full array of was placed in a body cast. On the fourth day resuscitation equipment. Once resuscitated, (approximately 6 days after the injury), she was these patients will require the equivalent determined to be stable enough for elective AE of intensive care until they can be returned to and placed on a fully loaded C-141 bound for the medical facility or are stable enough for the Continental United States, with her injured AE. husband as her nonmedical attendant. Because the body cast did not fit between the tiered stretchers in a supine position, she was wedged Importance of AE Staging: between the first- and second-tier litter posi- A Case Report tions at a 45-degree angle. The flight was originally scheduled to last 7 One of the authors (A.M.R.) and his wife were hours. However, a pregnant patient with a diag- victims of a terrorist attack while stationed in nosis of premature labor delivered unexpect- an African country. The author sustained a flail edly in-flight, and the flight was thus diverted to chest and lacerations but was ambulatory, England. The plane was delayed on the ground whereas his wife was injured critically. Her for several hours for an equipment malfunc- injuries included blunt head trauma associated tion. Once airborne, the remainder of the flight with concussion, severe injury of the right arm was uneventful. However, the noise, cold, vibra- with soft-tissue avulsion and multiple fractures, tions, and inability to change positions, com- and fractures of the right leg and pelvis. The bined with the isolation and fear, were almost author received first aid from a US Marine intolerable for the wife. 7. Patient Staging for Aeromedical Evacuation 87

During the flight, she required hand-feeding, References intravenous fluids, Foley catheter care, and medications. Because of demands on the nurses 1. Batty CG. Changes in the care of the battle casualty: Lessons learned from the Falkland cam- by other patients, these tasks were performed paign. Milit Med 1999;164:336–340. principally by her injured husband. The ability 2. White MS, Chub RM, Rossing RG, Murphy JE. of a nonmedical attendant with medical training Results of early aeromedical evacuation of to carry out the required care during flight was Vietnam casualties. Aerosp Med 1971;42: crucial to successfully completing this mission. 780–784. Approximately 12 hours after leaving 3. Department of the Air Force. Aeromedical Germany, the AE flight arrived in the United Evacuation Patient Considerations and Stan- States. However, she did not reach a medical dards of Care. Washington, DC: US Government facility for an additional 2 hours because of dif- Printing Office; 1997. AFI 41-307. ficulties in unloading the C-141. Her first exami- 4. Department of the Air Force. Administering nation revealed a decubitus ulcer due to the long Aeromedical Staging Facilities. Washington, DC: US Government Printing Office; 1997. AFI 41- period of absolute immobility during flight, 305. which subsequently required skin grafting. 5. Department of the Army. Medical Evacuation in After a 31-day hospitalization and two addi- a Theater of Operations: Tactics, Techniques, and tional surgical procedures, she subsequently Procedures. Washington, DC: US Government made a full recovery. However, the memory of Printing Office; 1991. Field Manual 8-10-6. this AE flight from Germany to the United 6. Lyons TJ, Connor SB. Commentary: Increased States will always remain with this patient as a flight surgeons role in military aeromedical evac- frightening memory of the most difficult aspect uation. Aviat Space Environ Med 1995;66: of her medical care. This case is a graphic 927–929. example of the stresses associated with AE and 7. Strickland BA, Jr, Rafferty JA. Effects of air the critical role of adequate preflight prepara- transportation on clinical conditions. JAMA 1951;145:129–133. tion and in-flight care. 8. Department of the Air Force. Physicians’ Roles and Responsibilities in Aeromedical Evacua- tion. Washington, DC: US Government Printing Conclusion Office; 1999. AFI 41-306. 9. Mabry EW, Munson RA, Richardson LA. The In peacetime, the ASF serves as a hybrid wartime need for aeromedical evacuation physi- between a hospital ward and an air terminal. cians: The U.S. Air Force experience during When a patient suddenly decompensates, the Operation Desert Storm. Aviat Space Environ ability of medical personnel to effectively Med 1993;63:941–946. respond can be lifesaving. In a contingency sit- 10. Walker GJ, Blood CG. The patient flow of wounded marines within a multi-echelon system uation, the ASF plays an expanded and more of care. Milit Med 1999;164:423–427. critical role in the AE system. Our ability to 11. White MS. Medical aspects of air evacuation of effectively plan for a contingency will ulti- casualties from Southeast Asia. Aerosp Med mately determine our ability to “bring them 1968;39:1338–1341. home safely.” 8 Aircraft Considerations for Aeromedical Evacuation

John G. Jernigan

Any aircraft that can carry passengers can con- around the world than any other organization, ceivably be used for aeromedical evacuation including large numbers of civilians. In addition (AE), depending on the situation. In response to aircraft specifics, this chapter will describe to the special needs of AE, multiple aircraft the capability of the USAF AE system. have been specifically designed for AE. Unfor- tunately,it is impossible to discuss every aircraft used for AE throughout the world. Instead, this Aircraft Selection for AE chapter will deal with the most important factors that must be considered in choosing To select the best possible aircraft for any the correct aircraft for the patient or patients’ AE mission, both logistic and patient-related needs, including alternative methods of moving factors must be considered. Although patient- patients. To illustrate these important factors, related factors are paramount, logistic factors this chapter includes a detailed discussion of may often determine the type of aircraft the aircraft presently used by the USAF for needed. These logistic factors include the num- AE, together with a civilian jet representative ber of patients, the distance required for the of the many aircraft used by the commercial air particular AE mission, and the runway length ambulance industry. at the AE sites of origin and destination. It is obvious why military medical personnel Patient-related factors include the need for should be familiar with USAF aircraft used for pressurization, the amount and type of special AE. However, it is important for civilian AE equipment needed, and the aspects of medical personnel to be aware of USAF air- aircraft configuration that affect patient care. craft as well because in a disaster situation AE Depending on the situation, each of these assistance can be requested through the DoD. factors can be critically important in making the As the events of September 11, 2001, clearly ultimate decision on which airframe or combi- showed, a requirement to move large numbers nation of airframes best meets the particular of casualties may arise suddenly, and the USAF requirements. The following is a detailed dis- AE system could prove crucial to meeting the cussion of each factor. patients’ needs. The USAF AE system is a national treasure that has been called upon for over 50 years to move casualties resulting from Logistic Considerations military operations (both armed conflicts and Number of Patients operations other than war) and civilian disasters beyond the local capability to respond. The total number and complexity of patients is Although the DoD does not exist to compete often the determining factor regarding which with civilian air evacuation companies, the aircraft is used. If only one or two patients need USAF AE system has moved more patients movement, then virtually any aircraft is capable

88 8. Aircraft Considerations for Aeromedical Evacuation 89 of meeting this need. When large numbers of Aircraft Range patients need to be moved from the same place, Range is another crucial determinate because the solution becomes more complex. Adding all aircraft have a finite distance they can fly to the complexity of large patient movements with a full load and still arrive safely at the des- is the fact that tragedy is frequently associated, tination. The range for all USAF AE aircraft is eg, the Oklahoma City bombing. In such in- measured in thousands of miles, but may be stances, the airfield serving one’s patients will shorter for some civilian aircraft. In-flight aerial also be involved with a dramatic increase in air refueling can extend the range of certain USAF traffic, which will limit the departure or arrival aircraft (eg, the C-141) if the needs of the “slots” for AE missions. As a result, using mul- patients are critical. This is most frequently tiple aircraft may not be a viable option and a accomplished when moving severely injured large aircraft, eg, the C-141, may become the patients from Japan or Korea to the United only solution to move large numbers of seri- States. However, because of the difficulty, ously wounded patients. expense, and potential danger, in-flight refueling is rarely used for routine AE. Related to Distance range is the cruise speed of the aircraft. Al- The distance required to move the patient from though the C-130 has a long range, its cruise origin to destination will determine whether speed is slow enough that the flight time differ- AE is the appropriate means and will also limit ential between the C-130 and a jet aircraft over the choices of aircraft once that decision is long distances makes the choice of a jet much made. In general, AE should not be considered more likely. unless the distance is too great to be accomplished by more readily available means of transport, eg, ground ambulance or medical En Route Stops helicopter. Rarely is there a reason to consider AE for distances shorter than 300 miles. The effective range for aircraft commonly used Once the decision is made that AE is for AE varies from 1250 to over 5000 miles required, the type of aircraft capable of meeting (Table 8.1), but this range can be extended the requirement becomes more limited (Table almost indefinitely by the judicious use of en 8.1). This is especially true for the USAF, which route stops. Assuming each leg is within their is often asked to accomplish missions that seem range, en route stops allow any aircraft to impossible at first glance. An example is the move patients over long distances. This method movement of critical burn patients thousands has been extremely important for the USAF of miles without stops, eg, from Japan to San in moving patients from the Western Pacific Antonio. On the other hand, if the distance region to medical facilities in Hawaii during the were short enough, eg, less than 1000 miles, then 1990s. The use of en route stops may become virtually any of the aircraft used for AE, includ- even more important for military AE in the ing all those discussed in this chapter, would future as the premier long-distance transport, suffice. the C-141, becomes less available.

Table 8.1. Characteristics of aircraft used for AE by the USAF. Characteristic C-9A C-141 C-130 C-21

Range (nautical mi) 2500 5000 3000 1250 In-ﬂight refueling capability No Yes Yes No Maximum patients (total) 40 128 80 6 Ambulatory 40 90 46 6 Litter 40 103 74 2 90 J.G. Jernigan

Available Medical Care at the En Route Stop environment is frequently a problem for the USAF as it meets the needs of the DoD around The availability of medical care at the en route the world, and often is the constraining factor stop becomes extremely important for long- that mandates the use of a speciﬁc aircraft, eg, distance AE. This consideration is crucial the C-130, when another aircraft would have because aircraft frequently experience me- been preferred. This factor is rarely a problem chanical problems or weather constraints that for civilian moves from one large metropolitan prevent take-off from the en route location. area to another because the runways at the air- Therefore, a planned delay of 2 hours for ports serving such cities are almost always long refueling can easily turn into a delay of several enough to meet the requirements of any of the days, so a plan for providing care to one’s aircraft described in this chapter. patients becomes critical.

Landing Limitations Patient-Related Another potentially life-threatening danger to Pressurization the flight and medical crew exists when problems arise at an en route stop and alternate air- One of the unique aspects of AE, when com- fields are unavailable. This factor alone would pared to ground and sea casualty transporta- have forced the USAF to drop consideration tion, is the issue of cabin pressure. Although of using en route stops to move patients out of most medical conditions are unaffected by the Western Pacific, ie, the risk of running out decreased pressure, there are several medical of gas trying to find the small islands used as conditions (eg, decompression sickness) that en route stops would have been too great a risk are adversely affected by cabin pressures lower to plan such a mission. Fortunately, recent than those found at sea level. It is extremely improvements in navigation using global posi- important that the flight crew, ie, pilots, be tioning satellites (GPSs) have minimized this made aware of any altitude restrictions that danger. are required for medical indications during AE. Lavatory and Feeding Station All modern aircraft used for AE are pressurized such that the cabin pressure never drops The ability to feed patients and provide them below a pressure equivalent altitude of 9700 with adequate lavatory facilities must be con- feet (unless an unplanned decompression sidered for all missions. This is not an absolute occurs). If patients require altitude restrictions requirement for all patient moves, but is crucial on this basis, an aircraft that is more efficiently for long nonstop missions. The C-9A was pressurized (such as the C-9A) should be used designed with basically the same capability as whenever possible. the airline DC-9s, so it can be considered the Within the limitations of the patients’ top of the line. Many civilian aircraft used by medical condition, it is important to keep cabin AE companies have comparable capability, altitude restrictions to a minimum (ie, allow a although few are as robust as the C-9A. The C- cruising altitude as high as possible). The rea- 141 relies on a large removable module called son for this is that the aircraft pays a huge price the “comfort pallet” to meet this requirement. in terms of both speed and fuel to accomplish The C-130 has minimal capability but its usual an altitude restriction. For example, the C-9A short-duration missions do not in general aircraft has a range of 2500 miles at a cruising require it. altitude of 35,000ft but only a range of 2000 miles at 18,000ft, the altitude required to main- Runway Length for Landing/Take-off tain cabin altitudes near sea level. Further, Medical planners do not routinely consider ground speed is in general less at the lower alti- runways and runway environments in their tude. The net result is that the mission takes analyses, but runways can easily become the longer and may require more en route stops, limiting factor in completing a mission. Runway both of which can adversely affect the patients. 8. Aircraft Considerations for Aeromedical Evacuation 91

Special AE Equipment Suction The range of capability provided by special Suction is also an integral element of medical equipment used to move patients has dramati- care for the seriously injured patient. The C-9A cally increased over the past several years. and most commercial AE aircraft have suction Types of equipment include electrical equip- available at all litter stations. On military trans- ment, oxygen and ventilatory equipment, port aircraft, such as the C-141, movable suction suction devices, and multiple other types of devices are placed near those patients requir- special equipment. These pieces of equipment ing it, and the capability of such suction devices are challenging to use in the AE environment is “low-tech” at best. for several reasons. Aircraft Characteristics Electrical Requirements Aircraft Entry Doors Use of electrical equipment is taken for granted on hospital wards but cannot be assumed on A crucial limiting factor in transporting litter any AE mission, even those using well-designed patients by AE is the difficulty involved in AE aircraft. Although most equipment used in loading litters into the aircraft. Civilian and patient transport today is battery capable, the military aircraft specifically designed for AE length of many AE missions exceeds even the do not present a problem in this regard. The longest battery capability. Most civilian aircraft C-9A was designed with a retractable ramp that used for AE, and the USAF’s C-9A, have exist- allows crew members to easily meet this ing electrical plug-in capability with the correct requirement. The size of the rear entry of the voltage/frequency used by medical equipment. C-141 and C-130 are also more than adequate. However, even in these aircraft the total patient Unfortunately, the C-21 form of the Lear Jet need may exceed capability. was not designed to carry litters, and placing USAF transport aircraft that can be modified them on-board is relatively difficult. for AE (eg, C-141, C-130) are not set up to use modern AE medical equipment on-board. The Cabin Space current solution is a bulky transformer that The cabin area must have adequate room for converts the aircraft-generated electricity to a the medical crew to meet the needs of all usable voltage and frequency. It is known affec- patients. In general, this is not a problem with tionately as “Big Bertha” because it weighs either the civilian or military aircraft used approximately 130 pounds, with a size of 11 ¥ routinely for AE. However, the routine litter 14 ¥ 36in. The size and weight of this trans- spacing for most military AE configurations is former becomes a constraint in itself because it 21in, so meaningful procedures often require cannot be carried as a routine piece of equip- removing patients from their litter tiers. Also, ment in all C-141s. small jets like the Lear Jet provide little crew Medical Oxygen space. Because the effective cabin altitude of most air- Climate Control craft used for AE is between 6000 to 8000ft, consideration of medical oxygen should occur Maintaining a comfortable temperature is for all but the most stable patients. The C-9A important when transporting patients for long serves as the model, with humidified oxygen distances, as sick and injured patients may have available at all litter stations. Again, USAF difficulty regulating their core temperatures. transport aircraft modified for AE (eg, C-141, Although commercial airliners sometimes have C-130) are not set up to administer medical a difficult time trying to maintain the “ideal” oxygen to a large number of patients. Individ- temperature in all parts of the aircraft cabin, ual patients can be given supplemental oxygen differences in various parts of these aircraft are from either a portable oxygen canister or con- negligible. Both the C-9A and commercial AE nectors to existing aircraft oxygen sources. aircraft accomplish uniform comfort reason- 92 J.G. Jernigan ably well, but having a large supply of blankets together with its large capacity,make it ideal for is still crucial for all missions. moving large numbers of patients from remote However, the problem of temperature locations. Although there are some limitations control is highly significant in the huge cabins that will be discussed in this section, it is safe of military transport aircraft. It is not unusual to state that the USAF could not execute its during AE in these aircraft for some patients worldwide mission without the C-130. to require several blankets while others are Since its introduction to the USAF inventory shedding clothes to remain cool! Sensitivity of in the 1950s, the C-130 has arguably become the the medical flight crew to this problem can be most versatile aircraft ever developed (Fig 8.1). vitally important. Its roles are extremely diverse, extending far beyond the primary role of airlifting small loads Cabin Noise Levels of supplies and equipment to remote locations, a role it has executed in countless conflicts and The noise level during flight varies significantly civilian emergencies. It also flies into hurricanes for different aircraft. For the C-130 and C-141, to track motion and access strength. It serves the noise level is approximately 95 to 100dB as a flying gunship, a role vital to Operation during flight and thus ear plugs are required for Just Cause in Panama and the recent war in all passengers and crew. For the C-9A and Afghanistan. Finally, it has a role germane to commercial AE aircraft, noise is considerably this text, ie, serving as the primary AE platform less (approximately 70 to 80dB), but it is still a to reach patients in remote locations. The capa- factor that needs consideration. Auscultation is bility to land on virtually any cleared, semi- almost impossible during AE, even with stetho- improved surface has made the C-130 a vital scopes specifically developed for this purpose. part of the USAF’s ability to move any patient For this reason, alternative means of monitor- from any place at any time. An example of this ing the patient have been developed, such as was shown during the Gulf War when the C-130 digital readout of blood pressure cuffs and flew missions (fortunately few) into southern pulse oximeters. Iraq to move patients from the Army units attacking the enemy in that part of the desert. Cabin Lighting These missions required landing on a crude Lighting levels in aircraft cabins vary dramati- road, and could not be accomplished with any cally. The C-9A represents the benchmark for other aircraft. lighting, while the C-130 is poorly lit. AE crews must be aware of the lighting levels of the air- General Characteristics craft in which they will be flying so they can bring supplemental lighting on-board for those The C-130 is a four-engine turboprop aircraft aircraft that require it. with a cruise speed of approximately 380mph. It has a fuel capacity that allows it to cruise for approximately 10 hours, giving it a range poten- Specific Aircraft tial of approximately 3500 miles. However, for the reasons described under weaknesses, the C- This section will describe the general char- 130 would only be used as a last resort to move acteristics, strengths, and weaknesses of the patients over such a long distance. Its high wing USAF aircraft and a representative civilian air- configuration prevents debris from ruining the craft most commonly used for AE. In addition, engines while operating in poorly improved ways to use other aircraft for AE in emergency airstrips. It has a short take-off (4700ft) and situations are described. landing (2900ft) capability unmatched by any other large aircraft. Its maximum litter capac- C-130 Hercules ity is 74, and the litter stanchions (the supports into which the litters are placed) used in this The C-130 has a truly unique role in the world role are kept on-board at all times. This factor of AE. Its versatility in take-off and landing, adds incredible flexibility to the fleet of C-130s 8. Aircraft Considerations for Aeromedical Evacuation 93

Figure 8.1. C-130 Hercules (USAF photo).

as they operate in a variety of missions around years to come. Medical planners simply would the world. Using web seats along the sides not have been able to develop a viable plan to of the cabin, a maximum of 92 ambulatory move the projected casualties during the Gulf patients could be moved. However, the discom- War without this capability. This same capabil- fort and potential damage to patients would ity makes virtually any en route stop a viable make such a configuration reasonable only for option, so medical planners can use the C-130 a short mission when no other alternative was for missions of extremely long distances. available. In military situations such as an air- However, the weaknesses described later make field under fire, the C-130 can also be floor- such planning a last resort. loaded safely with 15 litter and approximately The patient movement capacity, ie, potential 30 ambulatory patients. The usual configura- for 74 litter or 92 ambulatory, makes the C-130 tions for moving combinations of litter and an ideal aircraft for medical planners as they ambulatory patients will be described at the attempt to minimize the number of far-forward end of this section. AE missions required to support front-line troops in wartime. Although potential range (approximately 3500 miles) is a strength, the Strengths lack of comfort for the patient would make By far the greatest strength of the C-130 is its such a mission unlikely. The final strength of ability to land on short, minimally improved this aircraft is the ease of loading through the surfaces. Obviously,helicopters can also be used rear “clamshell” door. This wide open space to pick up patients in similar situations, even allows crews to load large numbers of patients with the total absence of any airstrip. However, in approximately 20 minutes, including engine- the limitation of helicopters is the small number running onloads (EROs). Such EROs would of patients that can be moved by each aircraft. only be accomplished at airfields under fire So it is this one crucial strength that will keep from the enemy or when ground time had to be the C-130 a vital member of the AE team for minimized for another compelling reason. 94 J.G. Jernigan

Weaknesses curtain. There is no food service available, so boxed lunches are the only means of feeding Noise is a major problem in the C-130 cabin, patients. Climate control is poor, with cabin often making it necessary to shout within 18in temperature rarely in the comfortable range. of the “listener” to be heard. As a result, verbal Neither patient oxygen nor suction is available, communication between crew members is so both of these must be brought onto the air- difficult and communication between medical craft for all missions requiring them. Finally, the crew and their patients is often impossible. C-130 cannot pressurize to sea level. Obviously, procedures requiring auscultation are impossible. Lighting is also extremely poor Configurations throughout the cabin, so medical crews must have a plan for providing lighting adequate The USAF uses four different configurations enough for patient evaluation. Electrical con- for the C-130 in its AE role.1 The first provides nections are available for attaching transform- 30 litter spaces with 46web seats for ambula- ers, eg, the Big Bertha described earlier, but tory patients and AE crew (Fig 8.2). This even with the transformer electrical equipment configuration provides the most space for the support is extremely limited. The combination ambulatory patients, so it would be used when of limited space between litter stanchions and “stretching room” for ambulatory patients was the effect of moderate turbulence, present on important. The second configuration provides virtually every mission, makes care for patients 70, 73, or 74 litter spaces with 6 seats for AE extremely difficult. Simple care such as feeding crews (Fig 8.3A). This configuration would only and taking vital signs are easy, but more be used when a specific large load of litter complex procedures are difficult. The only lava- patients was required. A third configuration tory facilities available are a funnel that leads provides 20 litter spaces with 44 sidewall seats, to the exterior of the aircraft, with a curtain for and this configuration would be used when privacy,and a small chemical seat with a privacy space for medical equipment or cargo in the

Figure 8.2. Interior of C-130 Hercules conﬁgured for tactical AE. 8. Aircraft Considerations for Aeromedical Evacuation 95

Figure 8.3. C-130 Hercules configured for (A) maximum litter patients and (B) tactical AE. forward central portion of the cabin floor was load only four patients per upright station, thus required. The final configuration provides 50 giving more comfort to the litter patients and litter spaces and 30 sidewall seats (Fig 8.3B). making nursing care more practical. Such a This configuration is the one most commonly decision would only be made if all patients used in contingency or wartime operations could be moved. because virtually any patient loads at the locations supported by the C-130 would include a Summary combination of litter and ambulatory, with the From the strengths and weaknesses it is obvious majority being litter. that the niche for the C-130 is moving patients A unique feature of the C-130 is that all litter out of “harm’s way” from far-forward positions. stanchion equipment needed to configure for Every effort will be made to minimize the AE is carried with each of the many (several length of these missions so the patients can be hundred) C-130s deployed worldwide at any delivered to greater medical capability as soon time. The total number of litter patients as possible. Later transfer to another aircraft described in the configurations above depends will be done if further movement is required. on stacking 5 patients in each litter tier This aircraft will remain a vital part of the with approximately 21in of spacing between USAF inventory as long as this requirement patients. Although the USAF practices this exists and other aircraft cannot meet the need. method of loading, the highest of the five patients is both difficult to load and virtually C-9A Nightingale completely inaccessible for crew members to treat. Therefore, depending on circumstances, The C-9A is truly the “Cadillac” of the AE fleet the medical crew director might well decide to (Fig 8.4). The patient care amenities that are 96 J.G. Jernigan

Figure 8.4. C-9A Nightingale (USAF photo). built into the cabin area, together with the tiple patients in the Western Pacific and capabilities of the aircraft itself, make it ideal Europe. This role was necessitated by the for a number of roles. It is used primarily for frequent lack of availability of the C-141, the midrange missions into improved runways, but premier long-range AE asset. The C-141 fleet is can also be used in a strategic, ie, long-distance, rapidly drawing down (it has decreased by role if there are adequate en route stops. about 50% from 1995 to 2000), and it is com- By the mid-1960s it had become apparent to mitted to more worldwide airlift missions than the entire military establishment, including ever before. Therefore, this “bridging role” for then US President Lyndon B. Johnson, that the the C-9A is likely to continue and may even fleet of aircraft being used for AE in the increase. It is fortunate that navigational aides Vietnam War were entirely inadequate. To have improved enough that the C-9A can reli- address this problem, a team of flight surgeons, ably locate the small islands in the Pacific flight nurses, and enlisted AE technicians was needed for en route stops. Without this relia- formed to work with McDonnell Douglas Corp bility the C-9A could not possibly take over this on a modification to the DC-9 for the sole pur- mission, even for a short time. pose of performing AE missions. The result is Although the C-9A has rarely been used for the C-9A that has served the DoD as its only actual wartime missions, the concept of using it dedicated AE asset for over 30 years. Given the for that role was proven in a military exercise relatively low number of average flying hours called Reforger during the late 1980s. Depend- per aircraft, it should be capable of continuing ing on the timing of actual casualties, the C-9A in that role for many more years. There are a could easily become the only available asset to total of 19 C-9As deployed around the world. move patients in the early days of a conflict. The Usually, 10 aircraft are located at Scott AFB in other airframes, ie, the C-141, C-130, and C-17, Illinois, 5 are in Europe, and 4 are in Japan, but would likely be totally committed to the role of the airframes are moved to whichever theater getting “shooters” and their materiel into the has the greatest need. war zone. Further, the historical doctrine of Although the majority of C-9 missions over reconfiguring (ie, changing from transport to the past 30 years have been flown in the AE) these aircraft for a return AE mission continental United States, it has proven its flex- might not be followed in future conflicts. This ibility by serving as an urgent AE asset for mul- change in doctrine is due to the fact that recon- 8. Aircraft Considerations for Aeromedical Evacuation 97

figuration takes too long to be practical in a considered a quiet aircraft, it is quiet on a rela- constrained lift environment. The advantage of tive scale when compared with other USAF the C-9A is that it could land already config- aircraft used in the AE role. Communication ured for the exact patient requirement, load between crew members is not difficult, nor is it quickly, and then leave without clogging the difficult to communicate with patients who can airfield. talk above a whisper. However, use of a stethoscope is limited to a special type that was General Characteristics developed specifically for use on this aircraft. Lighting is excellent in virtually all parts of the The C-9A is a modified version of the cabin so assessment of patients is as close to McDonnell Douglas DC-9 commercial airliner. optimum as possible in the AE environment. Multiple interior modifications for the AE role Appropriate electrical outlets are available at will be described in the section on strengths. every patient position so supporting equipment The most dramatic exterior modification is is possible for all patients without carrying the large rectangular hole cut into the left side transformers. of the fuselage with a retractable ramp fitting The retractable ramp makes loading of litter into that hole. This modification gives the air- patients easy at every stop. This ramp is covered craft the capability to immediately begin with a nonslip surface that has proven reliable loading litter patients wherever it lands. The moving patients in every possible weather C-9A is a twin-engine jet (engines mounted condition. Ambulatory patients can be loaded on the tail section) with a cruise speed of through stairs at the front and rear of the approximately 500mph. Its fuel capacity gives aircraft, just as they are with the commercial it a range of about 2400 miles, thus making it an models of this aircraft. The cabin space is excel- intermediates-range AE aircraft. As described lent for providing access to each patient under earlier, this range, coupled with appropriate virtually all conditions. In the 40-litter confi- intermediate stops, makes it an acceptable long- guration, the ability to care for the patients range aircraft if needed in that role. The length located on the top litter position would be of runway required for landing (2700ft) and limited, but there is still adequate room to take-off (5000ft) limits the number of airfields easily move such patients to the cabin floor the C-9A can utilize, but this is not in general a while delivering intensive care. Lavatory and “showstopper” in accomplishing a mission. food services are excellent because they are During the Gulf War, the USAF decided to essentially unchanged from those found in the severely limit the planned use of the C-9A in commercial version of this aircraft. As a result, the Southwest Asia theater. This decision was feeding and providing “creature comforts” to primarily based on concern over the poor patients is better in the C-9A than in any other quality of the runway environment in that AE aircraft. theater, which could have easily destroyed Medical oxygen and suction are available an engine, resulting in a “broken” aircraft and at 11 positions in the cabin, 3 in the forward clogged airfield. In summary, the use of the special care area, and 8 in the remainder of C-9A is flexible but not unlimited. the cabin. They are located so that each potential litter tier will have access to both. Climate Strengths control is excellent when compared to other Because the C-9A was designed specifically for AE aircraft but is still not perfect, and will the AE role, its strengths far outnumber its likely become worse as the aircraft ages. This weaknesses, its first strength is flexibility to is easily overcome by providing blankets to accomplish long-distance (strategic) as well as those who need them. The C-9A is capable intermediate-length missions. While en route of pressurizing to sea-level atmospheric pres- stops are a potential constraint, appropriate sure so it can move all patients, including stops can almost always be found to stretch those with decompression sickness. However, the C-9A from an intermediate AE aircraft into the cruise altitude required to pressurize is so a long-range aircraft. While the C-9A is not low (usually around 18,000ft) that the range 98 J.G. Jernigan of an altitude-restricted mission becomes a real area contains the equipment necessary to challenge. change the mix of seats and litters, a capability that proves crucial when the requirement changes at one of the mission’s en route stops. Weaknesses During peacetime, the C-9 most frequently flies Because the C-9A was designed specifically for with a configuration using 3 litter tiers and 30 the AE role, its weaknesses are limited. While or 34 seats (Fig 8.5A). In general, four seats are its landing and take-off length is excellent for given up for each litter tier, but as these two most uses in the continental United States, its configurations show, the exact locations of the ability to meet the DoD requirements around tiers can change this ratio. The most litters pos- the world is limited. Despite this relative weak- sible is 40, and such a configuration would only ness, the C-9A remains the one asset within be used in wartime (Fig 8.5B). Even then, it is the USAF that cannot be diverted to other difficult to envision the exact patient require- missions. ment that would make the C-9A the most effi- Although limited cabin noise is a relative cient means of meeting that requirement strength, budgetary constraints in the late 1990s (Fig 8.6). required the USAF to cancel plans to place new engines on the C-9A fleet. These engines are Summary required to meet current civilian airport external noise restrictions. Although this could theo- The C-9A is a wonderful asset for the entire retically become a problem in wartime, it is country and it stands ready for a wide variety hard to imagine that the FAA would deny of disasters, whether military or civilian. As landing rights to the C-9A if no other means mentioned previously, the AE system could were available for moving casualties. In peace- be made available in disaster through the joint time, there are multiple ways to move patients military command called US Transportation who require access to noise-restricted airfields. Command. Even though the C-9A has been The patient capacity of 40 is a relative weakness used to move peacetime DoD patients around vis-à-vis the C-130 and C-141, but as a result the the United States during most of its life, it comfort of patients and accessibility by the is a proven asset that provides flexibility medical crew is maximized. for medical planners in a wide variety of missions. Configurations C-141 Starlifter The USAF utilizes 13 different configurations that are combinations of litter and ambulatory The C-141 has been the premier strategic (long- seats, ranging from 1 tier of litters in the special range) AE airframe for the USAF from the care area and 40 seats to 10 tiers of litters and time it first became operational. It has great no seats. The patient seats are rear-facing, air- strengths, eg, virtually unlimited range with line first-class sized, with two seats on each side aerial refueling, but also has weaknesses, such of a center aisle. In all configurations there are as limited numbers of airfields from which it seats built in for the medical crew,with a nurse’s can operate. It has accomplished this strategic station just aft of the special care unit on the mission so well that the USAF faces a great right side of the cabin. A large storage area challenge in replacing this capability with for special equipment, blankets, and patient- another aircraft. specific items is located opposite the nurses’ The C-141’s primary role for the military is station. There is also a sink and refrigerator long-range airlift of cargo, passengers (although opposite the special care area. All of these this role is mostly accomplished with contracts features remain regardless of the exact combi- today), and patients. The C-141 has been the nation of litters and seats. workhorse of the DoD for moving large The C-9A has a large storage area in the belly numbers of patients over long distances for of the aircraft below the cabin. This storage almost four decades (Fig 8.7). It has been an 8. Aircraft Considerations for Aeromedical Evacuation 99

Figure 8.5. C-9A Nightingale conﬁgured for (A) peacetime AE and (B) maximum litter patients.

Figure 8.6. Interior of a C-9A Nightingale conﬁgured for maximum litter patients. 100 J.G. Jernigan

Figure 8.7. C-141 Starlifter (USAF photo). absolutely vital link for the thousands of active- Strengths duty members and their families deployed One of the greatest strengths of the C-141 is its around the world. However, it is currently ability to accomplish air-to-air refueling from reaching the end of its useful life, and each USAF tankers. This eliminates the need for any month more C-141s are taken out of the consideration of en route stops, regardless of actively flying inventory and retired to the mission length, and therefore negates the prob- aircraft “bone yard” in Arizona. Because the lems caused by these stops. Because there is requirement to move cargo in support of mul- a slight risk to the patients and medical crew tiple contingencies has increased markedly in from increased turbulence during contact with the 1990s, the availability of this aircraft for the the tanker aircraft, missions are not routinely AE role has diminished, in particular in the planned using this procedure. An example of Western Pacific. how this capability has proven tremendously beneficial is moving severely burned patients from Korea to San Antonio, where the Brooke General Characteristics Army Burn Center is located. Appropriate The C-141 is a multiple-purpose aircraft timing of each burn move and minimizing the designed to transport passengers, cargo, and total length of time required for transfer patients. Its cruise speed is 550mph with a between hospitals is directly correlated to maximum range (unrefueled) of over 5000 better outcomes, so this capability is vital for miles, making it a high-speed, high-altitude, military operations. It is by far the largest- long-range airlifter. Its take-off and landing capacity AE aircraft, having the capability to distances are dependent on exact weight, but move a combination of 128 litter and ambula- in all cases are long (over 6000ft). All planned tory patients in one configuration and 103 litter- AE missions are equipped with a comfort pallet only patients in another. As described earlier, that provides cooking capability and lavatory its range is a tremendous asset, limited only by facilities. the crew rest requirements for the pilots. The 8. Aircraft Considerations for Aeromedical Evacuation 101 rear clamshell doors, which provide a gently imagination are the only way to overcome this sloping ramp to the flight line, make loading of problem. patients extremely easy. Cabin space is large and, with the exception of those litter patients Configurations positioned at the top of each tier of litters, The USAF uses five different configurations for patient accessibility is good. With the comfort AE missions. In four of these configurations, a pallet in place, feeding and lavatory facilities comfort pallet is located at the front of the are certainly adequate. The C-141 does have cabin. The maximum litter configuration, 103 the capability to pressurize to sea level, but litter capacity (Fig 8.8A), uses only portable doing so negates many of the previously men- lavatories and urinals and is therefore limited tioned strengths. to a maximum of 12 hours’ duration for each mission. The most commonly used configuration utilizes rear-facing airline-type seats with Weaknesses 42-in spacing, which achieves a total load of 23 to 46 litter and 60 to 90 ambulatory patients When the C-141 is fully loaded with patients (Fig 8.8B). Another configuration that uses and the fuel required for its maximum range, web troop seats on the side of the cabin for runway length for take-off becomes long. the ambulatory patients maximizes total pa- As a result, planning to use this aircraft in both tients (48 litter and 80 ambulatory) (Fig. 8.9). peacetime and war is limited to a few However, because the role of the C-141 is long- “strategic”airfields in all theaters. Noise is a real distance and long-duration missions, this con- problem in the cabin, ranking somewhere figuration is rarely used because of discomfort between the C-130 and the C-9A. As a result, for ambulatory patients. communication is extremely difficult. Light is extremely poor throughout the cabin and the Summary medical crew must have a plan for providing adequate light to assess their patients. Electri- The C-141 brings a unique long-range, high- cal support is severely limited. There is only one volume capability to the world of AE, a capa- outlet in each latrine that can supply 115-V/ bility unmatched by any other aircraft, military 60-cycle AC, but these outlets are used solely or civilian. As the total number of C-141s for electric shavers. There are several elec- remaining in the active USAF inventory trical outlets in the cabin, but the previously decreases, the difficulty in filling the void it described transformers must be used to supply leaves becomes more apparent each passing appropriate electricity to medical equipment. month. Obviously, this requirement complicates AE planning because there are a limited number of C-17 Globemaster transformers in the USAF inventory. Assuring The C-17 is the newest transport jet in the USAF that the transformers are in the right place at inventory and, among its other missions, it has the right time can become a major problem. the capability to perform the AE role. It has Although therapeutic oxygen is available in the multiple strengths that would make it ideal cabin, it is supplied at high pressure (300psi) for this role. However, the total number of air- through seven outlets located on two separate craft currently planned for purchase is so small panels. These outlets must be attached to (80) that its availability for AE is question- devices called therapeutic oxygen manifold able. Because the C-17 is so new to the USAF systems (TOMSs), each of which can supply fleet, it does not have a track record as an AE three litter patients. Climate control is poor at aircraft. best. It is not uncommon for litter patients located on the top tier position to complain General Characteristics of excessive heat while ambulatory patients near the sides of the cabin are complaining The C-17’s incredible capabilities were first de- about “freezing” feet! Again, blankets and monstrated during the initial deployment of 102 J.G. Jernigan

Figure 8.8. C-141 Starlifter conﬁgured for (A) maximum litter patients and (B) a combination of litter and ambulatory patients.

Figure 8.9. Interior of C-141 Starlifter conﬁgured for a combination of litter and ambulatory patients. 8. Aircraft Considerations for Aeromedical Evacuation 103

Figure 8.10. C-17 Globemaster (USAF photo by 1st Lieutenant Laurel Scherer).

troops to Bosnia in late 1995 (Fig 8.10). Its C-17. Perhaps its greatest strength is its unlim- primary mission is flying large loads, especially ited range with aerial refueling. A close second oversized loads, directly to minimally improved is the ability to land on almost any semi- short runways. It is also designed to accom- improved airfield. This combination makes it plish other missions, including AE and support ideal for moving patients from almost any of Army airborne units. However, the total location directly back to the United States number of aircraft currently planned for pur- without en route stops. Its litter stanchions chase, ie, only 80, will probably limit the number will accommodate 36 litter patients and a of times this aircraft is used in AE. Neverthe- variable number of ambulatory patients de- less, kits have been designed and manufactured pending upon the types of seats used (Fig 8.11). that will allow the C-17 to accomplish the AE Noise and lighting are almost as good as mission. As with any new system, multiple pro- the C-9A and are certainly better than the blems were discovered in the initial tests of the C-130 or C-141. The large clamshell doors make AE configuration, but none of the required loading extremely easy. Cabin space is huge “fixes” for these problems were complicated and the litter support structure gives excellent and the solutions are occurring at the time of access to each patient. Comfort pallets are used this writing. to provide feeding and lavatory facilities, as with the C-141. Climate control is better than either the C-130 or C-141 but not as good as Strengths smaller cabins (eg, the C-21). Pressurizing to Virtually every previously described character- sea level is possible with the usual mission istic of an AE aircraft is a strength for the constraints. 104 J.G. Jernigan

Figure 8.11. Interior of C-17 Globemaster conﬁgured for tactical AE (USAF photo).

Weaknesses experience will show which of these configurations works best. One obvious advantage of Because the C-17 was not built primarily for using the existing peripheral seats is that all C- AE, there is neither built-in oxygen nor suction. 17s can be configured this way without having Like other large aircraft, climate control seats available. requires plenty of blankets to make sure all patients are warm enough. Undoubtedly the Summary greatest weakness of the C-17 is the fact that few airframes are likely to be made available In summary, the C-17 is a superlative aircraft for the AE role. for accomplishing the AE mission for all the reasons listed under strengths, especially its Configurations speed, range, and short landing capabilities. At Recently, two configurations of the C-17 have this time the small number of aircraft planned been approved for AE. In one, there are only 3 for the USAF force will almost certainly be litter tiers utilized, giving the capability to move fully employed in other missions, so it remains 9 litter patients and 54 ambulatory seats on the to be seen how much AE this aircraft will see. periphery of the cabin. In the second configuration, there are 12 litter tiers, giving a total C-21 Lear Jet capacity of 36 litter and 54 ambulatory patients. In both configurations, up to 48 centerline seats While the C-21 was not originally acquired for can be added, but doing so makes the periph- the AE role, it has proven itself highly effec- eral seats outboard of the litter stanchions tive in moving the right type of patient. Mov- unavailable. As the C-17 is used in the AE role, ing neonates to the limited number of DoD 8. Aircraft Considerations for Aeromedical Evacuation 105 neonatal units has become the AE mission for also excellent. A final strength is the ability to which it is best known. pressurize to sea level.

General Characteristics Weaknesses The C-21 is a small twin-engine jet with a cabin Patient capacity is the greatest weakness, but large enough for six people or one litter plus that is in general not a problem because its two attendants (Fig 8.12). The USAF procured mission is almost always picking up only one it in the early 1980s with a primary role of patient. It does not have equipment support, moving high-ranking DoD personnel in peace- but batteries are adequate for its mission be- time and moving critical parts and people in cause flight times rarely exceed battery capa- war. In the late 1980s, AE was added to its mis- bility. Entry is a problem for adult litter patients sions. Several civilian air ambulance services because of a built-in closet near the door. Cabin use versions of the same Lear Jet, but all of space is extremely limited, and unlike all other these have been specifically designed for the USAF AE aircraft the crew cannot stand up in AE role. the cabin. The only lavatory is a chemical seat not readily available, and there are no feeding Strengths facilities. Finally, there is no oxygen or suction capability. The C-21 requires little runway for take-off or landing and can therefore move patients into or Configuration out of most locations. The range is about 2000 miles at a cruise speed of about 500mph. This If only ambulatory patients are being moved, combination provides a capability to move the C-21 does not require any modification. It patients throughout the United States. Noise simply uses its existing four individual seats is minimal and lighting is excellent. Because of and two-person bench-type seat to move the the small size, climate control in the cabin is patients and crew. If a litter or neonatal isolette

Figure 8.12. C-21 Lear Jet (photo by Lieutenant Colonel John M. McNamara). 106 J.G. Jernigan is used, two seats on the same side are removed 1980s indicated a need to use the CRAF to and the litter or isolette is installed. meet the AE requirement, and the Boeing 767 was selected for this role. Summary The C-21 is an excellent AE aircraft for specific patients. Its niche is newborns and ambulatory General Characteristics patients for whom quick transportation is most The Boeing 767 is a twin-engine jet used by the important, eg certain organ recipients. Its small airlines for transcontinental or transoceanic entryway, relatively short range, and lack of routes, thus making it ideal for strategic AE room to fully utilize equipment for some (Fig 8.13). To make the 767 AE capable, the patients will always limit its use. USAF purchased a number of conversion kits that are used to transform the interior of the Boeing 767 767 into a premier AE aircraft much like the C-9A. The kits used for this conversion are A brief description of the Civil Reserve Air comprised of a number of different parts. First, Fleet (CRAF) is necessary to understand why litter support structures were developed to con- the Boeing 767 is part of an AE textbook. nect with the fittings that remain on the cabin Under the CRAF program, all US airlines floor after the commercial passenger seats have are given the opportunity to sign contracts in been removed. The second component is an which they agree to release specific numbers oxygen delivery system that utilizes oxygen of aircraft for use by the USAF in crisis situa- storage containers in the cargo belly of the air- tions. The benefit of the CRAF program for the craft, together with tubing to bring the oxygen USAF is that airframes are leased for a specific to each litter station. price only when absolutely needed in a contin- Electrical fittings were added to assure an gency. This program saves the USAF millions electrical system that will deliver 110-V, 60- of dollars by preventing the purchase and oper- cycle electrical current to each litter station. ation and maintenance costs of owning the air- Finally, nursing workstations were developed craft. Analysis by medical planners in the early that attach into remaining floor fittings.

Figure 8.13. Boeing 767. 8. Aircraft Considerations for Aeromedical Evacuation 107

Figure 8.14. Interior of Boeing 767 conﬁgured for AE.

Strengths the conversion kit. It cannot pressurize to sea level and so cannot move decompression sick- The long range of the 767 makes it ideal for ness patients. Finally, like the C-141, there the strategic AE mission, allowing it to accom- are a limited number of airfields that meet its plish all missions except those requiring aerial landing or take-off requirements. This should refueling. It has tremendous capacity to move not be a constraint because of the locations at patients. The exact number of patients moved which it is planned to serve. will depend on the mix and severity of patients’ injuries, but will be around 100 in any possible configuration. Noise is not a problem because Configurations the cabin is quieter than even the C-9A. Light- ing is excellent throughout the cabin. Oxygen As described above, there are multiple possible and electrical equipment are both supportable configurations using the conversion kits. At by the conversion kit. Cabin space is excellent, the time of this writing, the responsible organi- providing excellent access to every patient (Fig zation, Air Mobility Command, has not pub- 8.14). The lavatory and feeding capability is lished a configuration so none is shown here. unmatched because this is an airliner. Climate Basically, all configurations will allow approxi- control is first class, again because this is an mately 100 patients to be moved. airliner. Summary Weaknesses The Boeing 767 has proved itself in tests with The greatest weakness is the difficulty in mock patients, but thankfully it has never loading patients onto the 767. Although a new been required in a full contingency role moving ramp with the same pitch as the C-9A ramp has “real” casualties. Since it is such a ubiquitous made loading easier, it still takes up to 2 hours commercial aircraft there should always be to load. There is no suction capability built into adequate numbers available if they are ever 108 J.G. Jernigan

Figure 8.15. Challenger 601.

required for fitting with the existing patient aviation AE role today. With a cabin width of conversion kits. 8ft, 2in, it is capable of seating ambulatory patients three or four abreast (Fig 8.16). The cabin height of 6ft, 1in, allows for comfortable Civilian Airframes movement of patients and medical crew but is significantly shorter than any of the USAF air- Challenger 601-3R craft previously described except the C-21. It has a cruise speed exceeding 500mph and a This aircraft is reflective of the wide variety of range of 3400 nautical miles. aircraft used to move patients in the civilian air ambulance industry (Fig 8.15). It is highly Strengths capable as shown in the following discussion. The greatest strength of this airframe, as well as others used by the civilian air ambulance indus- General Characteristics try, is the robust list of equipment available This twin-engine jet is among the most capable for each mission and the outstanding crew-to- jets serving the civilian AE mission, and is the patient ratio. This ratio is possible because of only true wide-body aircraft used in the general the limited number of patients carried in most

Figure 8.16. Challenger 601 conﬁgured for both litter and ambulatory patients. 8. Aircraft Considerations for Aeromedical Evacuation 109

Table 8.2. Equipment commonly used by commer- Summary cial AE companies. The Challenger 601 is a highly capable AE air- Deﬁbrillator with pacing capability frame and is representative of the highest level One ventilator End-tidal carbon dioxide monitor of AE capability available in the general avia- Oxygen monitor tion environment. There are multiple other jet Two IV pumps capable of supporting three lines per aircraft used in the commercial AE mission, pump including the Lockheed 731, the Hawker 3A, Two oxygen outlets and the Falcon 50, all of which have essentially Two suction canisters Six electrical outlets with 115-V/60-cycle current the same strengths and weaknesses described above.

missions. All reputable civilian air ambulance Alternative AE Capabilities systems have access to exactly the mix of doctors, nurses, and technicians needed to meet Even with the best possible planning, occa- any patient’s needs. A list of typical equipment sions will arise when none of the previously immediately available in the stretcher/ICU described airframes are available. To address position includes the items shown in Table 8.2. such situations, other alternatives should be Noise within the cabin is less than the C-9 and considered including the following. lighting is excellent. The cabin environment is easily temperature controlled, primarily due to Palletized Patients its relative small size. An exciting concept developed at Charleston Weaknesses AFB is the concept of preloading patients onto standard USAF pallets. These pallets are Although the Challenger 601 has a longer square wooden structures that are used to range than the C-9A, it is still not long enough move military supplies and equipment around for transoceanic missions without en route the world. Their advantage is that they can be stops. Therefore, the same considerations de- immediately loaded onto USAF aircraft, much scribed in using the C-9A for a transoceanic like the containers used in worldwide airlift. role apply to this aircraft. This airframe can Patients are loaded onto these pallets prior to move relatively few patients. The maximum the aircraft arrival, and this cuts load time to an capacity is two litters and up to nine ambula- absolute minimum. In this concept, patients are tory patients, as long as none require extensive secured to standard pallets using field-style nursing care. Cabin space is adequate for crew mobile litters tied down with standard straps. movement but less than any of the USAF air- All supporting equipment is also secured using frames described previously. Loading of litter standard USAF straps. As a result, small num- patients is possible without undue tilting of the bers of litter patients can be completely ready litter but is still more difficult than loading any for loading at those far-forward airfields where of USAF aircraft. turnaround time for transport is critical. Using this technique, patients can be loaded onto Configuration transports in less than 5 minutes immediately The configuration remains as shown in Figure after they have unloaded their inbound cargo. 8.14 for virtually all missions, although both These patients are completely ready for the litter positions in the intensive-care part of the mission, including all required support equip- cabin are not used in all missions. The seats ment. Reconfiguring the same aircraft for an shown in the diagram can be used for either outbound AE mission would take at least 30 ambulatory patients or medical crew members minutes and potentially as much as 2 hours. depending on the requirements of the patients. This difference might be vital in convincing the 110 J.G. Jernigan appropriate command authority to release an line service, thus making such moves practical aircraft for an AE role. The feasibility of this with little delay. Using this technique, one can concept has been proven using mock patients safely move a patient for $2000 to 3000 when in the C-17 at Charleston, but has not pro- commercial AE service might cost as much as gressed to a fully implemented plan at this time. $50,000.

Commercial Airline Seats Conclusions For certain patients, the urgency to move may In summary, the USAF possesses a wide variety preclude waiting for a properly equipped and of aircraft with a proven capability of moving staffed AE airframe. In most cases commer- large numbers of patients. Each aircraft used in cial airline service is available to meet such the AE role has specific strengths and weak- patient’s needs, with the obvious exception nesses as described. While the civil air ambu- being those requiring a flying intensive-care lance industry is highly capable of moving small unit. Usually, such moves should be accom- numbers of patients, their experience with large plished by purchasing two side-by-side first- numbers is limited. Therefore, in the event of a class seats. This allows the patient to rest sudden disaster requiring AE of large numbers appropriately on long flights and provides of patients, the expertise and capability of the the medical attendant immediate access to USAF (through US Transportation Command) the patient. This method is often used by will be required. commercial AE companies in the Western Pacific region, where multinational companies have small numbers of US citizens working Reference in many nations separated by thousands of 1. Department of the Air Force. C-130 Configura- miles of ocean. Most of these countries lack tion and Mission Planning. Washington, DC: US western-quality medical service but have air- Government Printing Office; 1997. MCI 11-258. 9 Critical-Care Air Transport: Patient Flight Physiology and Organizational Considerations

Thomas E. Grissom

The air transport of patients encompasses a The second section covers organizational issues, range of missions from long-distance, fixed- such as manpower, equipment, and training wing aeromedical evacuation (AE) movements considerations, in the establishment and main- to short-distance, rotary-wing “scene” pickups. tenance of a critical-care air transport service While certain aspects of the transport receive for AE. Integration of these areas with a different emphasis dependent on distance, solid clinical background will allow most pro- mode of transport, and patient condition, the viders to accommodate to the flying environ- overall goals remain the same (Table 9.1). In ment where they can deliver “critical care in attempting to meet these goals, a number of the air.” questions will arise regarding the approach. Are there any special considerations for the movement of critically ill or injured patients by Patient Flight Physiology air transport? Who is best qualified to provide en route care? What types of equipment are Aviation medicine has long been concerned safe for use in the flying environment? What is with the effects of altitude and flight stresses the best means of monitoring the patient in- on the performance of the aircrew. Less is flight? What are the basic skill levels required known about the influence these factors have to be a part of the team? on the care and outcome of critically ill patients While the specifics of care provided on the moved within an AE system, in particular ground and in the air should not change signif- during long flights. It is not difficult to antici- icantly, there are a number of considerations pate that the environmental stresses associated and limitations that the transport team must be with flight have the potential to disrupt the aware of when moving the critically ill patient. delivery of care provided to the patient during Some of these areas are covered in other transport. These stresses impact not only the chapters discussing preflight triage, aeromedical patient but those managing care as well. staging, airframe capabilities, and in-flight Beyond a straight assessment of the environ- treatment options. Additional chapters detail- mental factors, the platform being used to ing specific conditions, such as trauma, burn, transport the patient may ameliorate or mag- and psychiatric injuries, highlight relevant con- nify the potential problems. As discussed in siderations for those diagnoses. In this chapter, chapter 8, most fixed-wing military aircraft used the first section examines the general impact of for AE do not protect medical personnel or the classic flight stressors on patient physiology patients from the stresses of flight to the same and care delivery. The role that decreased baro- degree that commercial airliners protect their metric pressure, temperature, noise, vibration, passengers. Patients moved on rotary-wing decreased humidity, acceleration, and fatigue transports experience more vibration and noise play in patient movements by air is not trivial. than those on fixed-wing missions. Duration of

111 112 T.E. Grissom

Table 9.1. Goals of air transport. Gas Laws Proper preparation of the patient Most of the physiological results of ascent and Appropriate utilization of available resources descent within the Earth’s atmosphere can be Prevention of delays during transports Provision of a safe transport environment for patient and explained by several elementary principles of staff gas behavior. Accurate en route monitoring of the patient for status changes Boyle’s Law. When the temperature remains Safe delivery to the appropriate level of care constant, as in the human body, a volume of Rapid effective response to changes in patient condition gas is inversely proportional to the pressure surrounding it. This principle explains why a balloon expands as it ascends and also why a volume of trapped air expands in a body exposure to these stressors will also play a role cavity when the pressure around it is reduced. in their impact on the patient. The response to A given volume can expect to be doubled at a short scene mission in a helicopter will most 18,000ft (5500m). The formula for Boyle’s likely be different than that seen with a 12-hour Law is transatlantic flight. PP= VV, In this chapter, we will review the general 12 21 impact of the classic flight stressors on patient where temperature is constant and P1 = initial physiology and care delivery. In subsequent pressure, V1 = initial volume, P2 = final pressure, chapters, the role, decreased barometric pres- and V2 = final volume. sure, temperature, noise, vibration, decreased humidity, acceleration, and fatigue have on Henry’s Law. The amount of gas in a solution patient care will be related to specific dis- varies directly with the partial pressure of that ease or injury conditions. An understanding of gas over the solution. Therefore, if pressure is altitude physiology combined with disease- or reduced above the solution some gas will come injury-specific considerations will better pre- out of solution. This principle explains why pare you to not only ready the patient for carbon dioxide bubbles are released when a aeromedical transport but also allow you to carbonated beverage container is opened and anticipate and respond to potential problems. why nitrogen bubbles may come out of solution in body tissues during ascent. The nitrogen bubbles can lead to altitude-induced decom- Stresses of Flight pression sickness. The formula for Henry’s Barometric Pressure Changes Law is = The most prominent environmental considera- PP12 AA 1 2, tion in AE operations is the impact of changes where P1 = initial partial pressure of a given gas, in barometric pressure on oxygen delivery and P2 = final partial pressure of a given gas, A1 = gas expansion. The acceptable altitude range in initial amount of gas dissolved in a given solu- which physiological functions are minimally tion, and A2 = final amount of gas dissolved in impaired is limited to a fraction of the Earth’s the same solution. atmosphere. From sea level to 12,000ft, most normal individuals can move with no or Dalton’s Law. The total pressure of a mixture minimal impairment.1 Above this level, nor- of gases is equal to the sum of the partial pres- mal function is progressively impaired unless sures of each gas in the mixture. The pressure appropriate environmental interventions are exerted by each gas in a mixture is independent made. Movement of patients through this of other gases in the mixture. Remember, the environment requires an understanding of the atmospheric pressure at sea level is 760mmHg. classic gas laws and an application of their prin- This total pressure equals the partial pres- ciples as they apply to normal and abnormal sures of nitrogen (78%), oxygen (21%), and physiology. trace gases (1%) making up the atmosphere. 9. Critical-Care Air Transport: Physiology and Organizational Considerations 113

The formula for Dalton’s Law is cal patients developed a PaO2 of less than 60mmHg when flying at cabin altitudes = + + + Pt P1 P2 P3 ... Pn, between 3000 to 7500ft.3 where Pt = total pressure of the mixture, P1, P2, Four Classic Physiological Categories of P3, ... = partial pressures of the individual gases, and n = total number of gases present. Hypoxia. Hypoxic hypoxia occurs as a result of Dalton’s Law explains how exposure to a a decrease in the partial pressure of oxygen in high ambient altitude reduces the available the lungs or of other conditions that reduce the oxygen. As ambient altitude increases, the par- diffusion of oxygen across the alveolar–pul- tial pressure of oxygen decreases even though monary capillary membrane. This is the most the percentage of oxygen remains the same. For common type reported in flying personnel example, at sea level the partial pressure of exposed to a lowered partial pressure of oxygen at high altitude. Additional causes include ven- oxygen (PO2) is 21% of 760mmHg or 160mm Hg. Correspondingly, with a reduction of total tilation perfusion defects, airway obstruction, pressure the partial pressure of each gas will and apnea. Partial compensation through an decrease proportionately. At 18,000ft (5500m), increase in tidal volume and respiratory rate can be seen starting at 5000ft (1500m) with a PO2 is 21% of 380mmHg or 80mmHg. resulting drop in PaCO2 (Fig 9.1). Additional Charles’ Law. When volume is constant, the compensation occurs through increases in heart pressure of a gas increases or decreases pro- rate and cardiac output resulting in a decrease portionally to an increase or decrease in its in the arteriovenous oxygen difference with an temperature. Evidence of this law can be seen elevation in mean capillary oxygen tension.2 in the small decrease in pressure recorded from Pressurized aircraft, including commercial an oxygen cylinder taken from ground level on airliners, rarely exceed a cabin pressure altitude 4 a hot day to an unpressurized aircraft altitude of 10,000ft (3000m). Because PaO2 at that alti- of 10,000ft (3056m). Consequently, the cooler tude is approximately 60mmHg (O2 saturation temperature at this altitude leads to a decrease 90%), the majority of patients and normal pas- in the pressure within the oxygen cylinder. The sengers would be minimally affected at that formula for Charles’ Law is cabin pressure. In a small study looking at 29 patients with known or suspected ischemic = PP12 TT 12, heart disease requiring AE, Bendrick et al demonstrated that 5 (17%) of these patients where volume is constant and P1 = initial dropped their oxygen saturation to less than pressure, T1 = initial temperature, P2 = final 90%.5 The average cabin altitude during the pressure, and T2 = final temperature. flights was 6900ft (2108m) in a C-9A aircraft, representing the usual flight profile for this Hypoxia type of AE mission. In all cases, the addition One of the principle areas of interest to indi- of 4L/min of oxygen corrected the level of viduals involved in AE is hypoxia, its effects on desaturation. patients and medical personnel, and the equip- Hypemic hypoxia occurs when there is a ment used to prevent it. Patients requiring reduction in the capacity of blood to carry a suf- AE frequently have a number of factors ficient amount of oxygen. This includes blood that already predispose them to developing loss (anemic hypoxia), dyshemoglobinemias, hypoxia, defined as oxygen “deficiency” suffi- excessive smoking, and carbon monoxide poi- cient to cause impairment of function.2 A soning. For medical personnel and patients decrease in barometric pressure with a reduc- who smoke tobacco products, the formation of tion in the inspired partial pressure of oxygen carboxyhemoglobin through the inhalation of may be enough to push the “stabilized” patient carbon monoxide will make the individual over the edge. In a classic 1969 study looking at more susceptible to this type of hypoxia. Typi- casualties being transferred from Vietnam to cally, military aircrew members who donate other locations, 95 of 201 postoperative surgi- blood are grounded for 72 hours following 114 T.E. Grissom

Figure 9.1. Partial pressure of

alveolar PaO2 and PaCO2 during exposure to altitude (adapted with permission from Shefﬁeld and Heimbach2).

blood donation due to the reduced hemoglobin such as congestive heart failure, shock, and pos- level.6 itive pressure ventilation. This concept can be To illustrate the contribution of anemia to extended to specific organ systems such as the the development of hypoxia at reduced baro- development of cerebral vasoconstriction and metric pressure, it is necessary to examine reduced blood flow that occurs with hyperven- the impact of the reduced partial pressure tilation. The use of supplemental oxygen will of oxygen on the oxygen-carrying capacity of often be necessary in patients with stagnant blood. Oxygen-carrying capacity is defined as hypoxia, in particular when any of the other contributing factors such as altitude (hypoxic) CaO() mL O 100 mL blood 22 or reduced carrying capacity (hypemic) is =¥¥()+¥() 1 . 34 Hb SaO22 PaO 0., 0031 present. Histotoxic hypoxia occurs when the utiliza- where CaO2 = oxygen content of arterial tion of oxygen by the body tissues is hindered. blood, Hb = hemoglobin, SaO2 = % arterial This includes carbon monoxide poisoning, oxygen–hemoglobin saturation, and PaO2 = partial pressure of arterial oxygen. cyanide poisoning, and alcohol ingestion. For At a sea level equivalent of 760mmHg, with the AE patient, this is not in general a contributing factor except in specific cases of a PaO2 of 102mmHg, Hb of 15g/dL, and SaO2 of 98%, each 100mL of blood could carry known exposure, such as burn victims (carbon approximately 20mL of oxygen. This is reduced monoxide) and cyanide (sodium nitroprusside) to 19mL per 100mL of blood due to venous toxicity. admixture with unsaturated blood. The content drops by one half when the hemoglobin drops Gas Expansion from 15 to 7g/dL; however, the extraction remains constant at 5 to 6mL of oxygen per Changes in barometric pressure produce effects 100mL of blood. Thus, the venous saturation beyond hypoxia. According to Boyle’s Law pre- drops from 75% to less than 50%, leaving no sented above, a volume of gas is inversely pro- reserve for additional oxygen demands when portional to the pressure surrounding it there is an associated drop in inspired oxygen. (Fig 9.2). This resulting gas expansion can Stagnant hypoxia occurs when there is a adversely affect not only the medical crew but reduction in total cardiac output, pooling of the patients and equipment as well. The end blood, or restriction of blood flow reducing product of gas expansion in patients and crew oxygen delivery. This includes problems com- can be actual tissue damage or pain that will monly found in critically ill or injured patients affect mission performance. 9. Critical-Care Air Transport: Physiology and Organizational Considerations 115

Figure 9.2. Impact of altitude on gas expansion. At the highest cabin altitude expected during ﬂight in a pressurized aircraft (10,000ft), gas expands to 1.5 times the original volume.

The terms used to describe the effects of opening of the Eustachian tube using positive barometric pressure changes include dysba- pressure from the nasopharynx or by using the rism, barotrauma, and decompression sickness. jaw muscles usually suffices to equalize the Dysbarism represents the general topic of pressure differential: yawning, swallowing, or pressure-related injuries. Barotrauma refers the Valsalva maneuver. to the direct injuries that are a result of the This process of expansion and contraction mechanical effects from an applied pressure can cause significant complications if the nor- differential. Finally, decompression sickness re- mal corrective procedures are ineffective or lates to the complications associated with the impaired. Severe pain, nausea, vertigo, tinnitus, evolution of gas from tissues and fluids of the perforation of the eardrum, and bleeding can body. occur with an associated temporary impairment The most common sites of trapped gas disor- of hearing. Medical crew members should be ders in the typical patient or medical crew aware of the early symptoms of barotitis media. member involve the ears, sinuses, gastrointesti- In patients or crew with congestive symptoms, nal tract, and, rarely, teeth. When considering topical vasoconstrictors such as 0.25% phenyle- the potential for problems with the air trans- phrine spray may be beneficial when used 15 port of patients, you may need to consider other minutes before descent or take-off. Severe areas, including medical equipment and air symptoms should be reported to the director of introduced into other anatomic sites as a result the aeromedical crew because the aircraft may of injury or operation. have to increase altitude again to allow equal- Barotitis media or “ear block” is an acute or ization of pressure in the middle ear before chronic trauma of the middle ear caused by the reattempting descent. Finally, politerization difference of pressure between the air in the may be required to equalize pressures. This tympanic cavity and mastoid air cells and that involves the delivery of pressurized air using a of the surrounding atmosphere. During ascent, handheld compression device (Politzer bag) or expanding gas within the tympanic cavity is compressed air through the nose to open the vented. The Eustachian tube usually functions Eustachian tube. as a one-way valve to allow this gas to escape The implications of gas expansion and baroti- from the middle ear. On descent, however, the tis media are less clear for the comatose, volume within the middle ear contracts, causing psychotic, or disoriented patient. Do not forget the tympanic membrane to retract. Active to evaluate those patients who have been 116 T.E. Grissom nasotracheally intubated or who have nasogas- vomiting, shortness of breath, and, in extreme tric tubes in place because they are prone to cases, vagal symptoms. Preflight placement of a develop edema and Eustachian tube dysfunc- nasogastric tube, if not already done, should tion. You should observe patients for evidence be accomplished in these patients and be left of increased irritability or agitation during unclamped during flight. Some recommenda- descent, which may accompany the discomfort tions suggest avoiding high-altitude exposure in associated with increased middle-ear pressures. postabdominal surgery patients for 24 to 72 Direct examination of the tympanic membrane hours following surgery due to the potential for for significant retractions may rule out this associated intrabdominal air trapping.6 The problem. pregnant patient, in particular in the third Barosinusitis occurs when there is obstruc- trimester, may also be at higher risk of hav- tion of airflow that normally passes in and out ing discomfort related to gastrointestinal gas of the sinus cavities without difficulty. The pres- expansion. ence of an upper-respiratory infection may Intrathoracic air presents a special consider- produce swelling of sinus mucosal membranes ation because it is contained within a fixed that will obstruct normal venting. On ascent, space. The management of the patient with a this will produce pain or pressure below (max- pneumothorax requires the medical crew to illary), above (frontal), or behind the eyes. consider several issues. Even patients with an More commonly, problems occur during asymptomatic pneumothorax can develop sig- descent. The use of the Valsalva maneuver will nificant decompensation with gas expansion frequently provide at least temporary relief. inside the thorax. An untreated pneumothorax Vasoconstrictors and return to a higher altitude is considered an absolute contraindication to may also be necessary. When considering the movement by aircraft except in the absence of AE patient, barosinusitis may occur in patients respiratory compromise and ability to maintain with abnormal nasal pathology or inflammation cabin altitude equal to that at the point such as facial trauma or nasal instrumentation of origin. Even under these circumstances, (intubation, nasogastric tubes). the medical team should have the capability Barodontalgia occurs when trapped air in to provide definitive treatment should the abscesses, dental fillings, or caries expands, re- patient’s condition change. The safest approach sulting in severe pain during ascent. This is an is to electively place a chest tube before flight uncommon problem and can be confused with with an appropriate collection system. barosinusitis involving the maxillary sinuses. In In a patient requiring air transport, if already the case of barodontalgia, only one tooth is present, the chest tube should be left in place usually involved whereas several of the upper before flight even if it could otherwise be teeth on the affected side are symptomatic with removed. If recently removed, a minimum of 24 maxillary barosinusitis. Therapy is limited to hours should elapse before transport and an descent and pain control with appropriate expiratory chest radiograph showing no reac- follow-up. cumulation of the pneumothorax is obtained Barogastralgia or gas expansion in the gas- before flight.6 In addition, an occlusive dressing trointestinal tract is rarely serious with cabin should be applied to the chest tube site. altitudes less than 10,000ft (3045m) where gas For all patients with chest tubes, they should expansion is typically 1.5 times the volume at be connected to a rigid, nonglass collection sea level (Fig 9.2). Patients or crew who eat system with a Heimlich or other one-way valve. hasty, large meals with foods and carbonated Water levels should not be changed during beverages known to produce gas may on occa- ascent or descent although the suction level, if sion experience problems related to gas expan- used, should be checked frequently. sion. In patients with gastrointestinal problems Intracranial air is one of the rare areas of gas such as bowel obstructions, ileus, or motility expansion that can be potentially devastating. problems, the amount of expansion may be Whether it is from a penetrating injury, surgery, excessive and produce symptoms of discomfort, or diagnostic study, the presence of intracra- abdominal pain, belching, flatulence, nausea, nial air requires close monitoring of the air 9. Critical-Care Air Transport: Physiology and Organizational Considerations 117

Figure 9.3. Changes in tra- 300 CUFFS cheal wall pressure associated = 9.5mm I.D. FOREGGER SLIP-ON with changes in altitude for = 10.0mm I.D. RUSCH air-inﬂated cuff (Foregger and 200 = 9.5mm I.D. KAMEN-WILKINSON Rusch), foam cuff (Kamen- = 9.0mm I.D. McGINNIS WITH Wilkinson), and pressure- CONTROL BALLOON regulated cuff (McGinnis) ± 100 = 1 S.D. endotracheal tubes in an animal model (used with permission from Stoner and Cooke7). 0 35,000 FT.

8,000 FT. GROUND LEVEL CUFF PRESSURE AGAINST TRACHEA (TORR) TRACHEA AGAINST CUFF PRESSURE 0 100 200 300 400 TIME (SECONDS)

transport patient. If the patient needs to be tubes (Fig 9.5). We currently recommend that moved, you should consider maintaining cabin the endotracheal tube or tracheostomy tube pressure equivalent to the point of origin. In cuff be inflated with sterile saline using addition, the presence of a cerebrospinal fluid the “minimal leak technique” to avoid tissue leak from the ears or nose raises theoretical damage or air leak due to gas expansion and concern for drawing in air or bacteria during compression during ail phases of flight. If air is ascent/descent. used, the cuff pressure should be checked and Medical equipment that contains air can also adjusted with changes in cabin altitude. be adversely affected by gas expansion. Items Other equipment considerations include such as MAST garments and pneumatic splints dlstention of balloon bladder catheters, intra- may become excessively distended on ascent or venous (IV) solution bags, and aortic balloon may not function as intended with volume loss pump function. Finally, some research has been during descent. Endotracheal tube cuff man- conducted on the performance of mechanical agement presents a particular problem. Cuff ventilators at altitude. Special attention should expansion at decreased barometric pressures be paid to the delivered tidal volume of trans- can result in excessive pressure on the tracheal port ventilators used during AE when the cabin mucosa and rapid decompression could theo- pressure is decreased. While some ventilators retically lead to tracheal injury or rupture. have automatic compensation, others do not Stoner and Cooke demonstrated this in 1974 and the adelivered tidal volume and/or rate using an animal model and suggested that may change with alterations in cabin altitude endotracheal tubes with pressure-regulating (Fig 9.6).8–10 valves on the pilot balloon or foam cuffs be used to avoid the problems related with cuff Cabin Altitude/Pressurization expansion (Fig 9.3).7 Another recommendation is that saline be used to expand the cuff dur- To reduce the problems associated with hypo- ing aeromedical evacuation because expansion xia and gas expansion, most aircraft have a would be minimal. Figure 9.4 shows the cuff system to produce cabin pressurization using pressure response from 0- to 15,000-ft altitude engine bleed air. The pilot can sometimes reg- with air, saline/air, and saline. Care must be ulate the cabin pressure and ventilation by taken when using saline expansion because varying the amount of air forced into the cabin there is a variable and steep volume–pressure and adjusting the overflow while correcting for response curve in commonly used endotracheal the known leak rate. Malfunction of this system 118 T.E. Grissom

Figure 9.4 Changes in mean cuff pressure associ- circles), saline plus 2cc air (open circles), and saline ated with changes in altitude for a standard 8.0-mm (solid squares) ﬁlled cuff using a laryngeal model. ID endotracheal tube (Portex) with air (solid

Figure 9.5. Pressure responses for saline-inﬂated endotracheal tube cuffs in a laryngeal model (unpublished data courtesy of the author). 9. Critical-Care Air Transport: Physiology and Organizational Considerations 119

Figure 9.6. Effect of changing altitude on the tidal ambient pressure (used with permission from volume delivered by the Impact 750 transport venti- Grissom et al10). lator when not recalibrated following changes in

or aircraft structural damage may result in a Altitude Restrictions loss of cabin pressure or decompression. The cabin volume, size of the defect, altitude, and The decision for an altitude restriction or the pressure differential will then impact on prob- need to provide supplemental oxygen adminis- lems related to the decompression. tered at altitude should be based on several Aircraft such as the USAF C-9A maintain a considerations. Most fixed-wing aircraft nor- constant cabin pressure (isobaric system) as air- mally used for AE must fly at altitudes much craft altitude increases. With this type of lower than their normal cruise to maintain sea- system, the pressure differential between cabin level pressurization in the cabin. Flying at lower pressure and ambient pressure increases with altitudes increases their fuel consumption, de- altitude. The C-9A maintains a pressure sched- creases their range, and increases the probabil- ule slightly greater than ambient to 8000ft and ity of turbulence. Inappropriate cabin altitude then maintains 8000ft through its certified restrictions can result in the use of alternate ceiling. The C-141, on the other hand, uses routes that lengthen air miles flown and an 8.6-psi isobaric-differential pressurization increase time and cost of flight. Individuals system. The cabin altitude will remain at sea- with a PaO2 at or below 60mmHg (90% evel or ground-level pressure until the aircraft saturation) at sea level will probably demon- reaches 21,000ft. Above this level, the system strate hypoxia at or above 2000 to 4000ft. The maintains a pressure f differential of 8.6psi to treatment for problems of oxygenation is not an the service celling of the aircraft. For example, altitude restriction but the appropriate man- at 40,000ft the ambient pressure is 2.72psi with agement of inspired oxygen via an approved a cabin pressure of 11.3 (8.6 + 2.72) psi. This delivery system. corresponds to an altitude of 8000ft. Figure 9.7 During aeromedical flights, patients with de- graphically demonstrates these two pressuriza- creased pulmonary perfusion and those with tion schemes. cardiac conditions should be closely observed. 120 T.E. Grissom

COMPARISON OF PRESSURIZATION SCNEDULES Figure 9.7. Isobaric and isobaric- AIRCRAFT differential aircraft pressurization 50,000 ALTITUDE schedules (used with permission from ISOBARIC DeHart RL, ed. Fundamentals of SCHEDULE 40,000 Aerospace Medicine. 2nd ed. Balti- more: Williams & Wilkins; 1996:109). 30,000

20,000

CABIN PRESSURE ALTITUDE (ft) ALTITUDE CABIN PRESSURE 10,000 CABIN ALTITUDE

0 10,000 20,000 30,000 40,000 50,000 AMBIENT PRESSURE ALTITUDE (ft) 50,000 AIRCRAFT ALTITUDE ISOBARIC DIFFERENTIAL 40,000 SCHEDULE (8.6 PSID) 30,000 8.6 PSID DIFFERENTIAL 20,000

CABIN PRESSURE ALTITUDE (ft) ALTITUDE CABIN PRESSURE 10,000

ISOBARIC 0 10,000 20,000 30,000 40,000 50,000 AMBIENT PRESSURE ALTITUDE (ft)

Patients having a pulmonary disease with an variations from 15°C or lower to 25°C should undetected coronary artery disease may be be expected in winter flying, and in summer affected significantly by hypoxic hypoxia. In 20°C to greater than 35°C is not uncommon. addition, patients with chronic obstructive These wide variations require the medical pulmonary disease (COPD) should be ad- crews to be aware of cabin temperature ministered low-flow oxygen therapy (1 to changes in relation to performance and patient 2L/min) via nasal cannula or 24% to 31% care/comfort. In addition, there can be de- Venturi mask to regulate the delivered oxygen gradation of equipment performance at the concentration.11 extremes of temperature. The effects of thermal exposure can be mag- Temperature nified by other stresses, including vibration, dehydration, and alcohol/drug intoxication. In Ambient temperature decreases with increas- addition, climatic temperature variations may ing altitude at a rate of 2°C per 1000ft up to create air turbulence that can impact negatively 35,000ft (about 1°C per 100m).12 As a conse- on the aircraft, crew, or patient. quence, aircraft cabin temperature fluctuates considerably depending on the temperature Noise outside the aircraft. This is caused by the inability of aircraft temperature controls to respond Noise represents one of the more troublesome rapidly and the necessity to open aircraft doors stresses encountered during AE operations. It at en route stops. Inside aircraft temperature is can be defined as any sound that is unpleas- 9. Critical-Care Air Transport: Physiology and Organizational Considerations 121 ant, distracting, or in some other way unde- with the other stresses of flight, the overall sirable. Unprotected exposure to noise can effect is magnified. produce one or more of the following undesir- Because there is little that the pilot or crew able effects: (1) degraded communications and can do to eliminate or decrease the amount of patient evaluation, (2) temporary auditory vibration, care should be taken in minimizing threshold shifts (auditory fatigue), (3) perma- its effects. Patients should be properly secured, nent threshold shifts (sensorineural hearing encouraged and assisted with position changes, loss), or (4) fatigue. and provided with adequate padding and skin Interference with effective communications care. Special care should be taken in the move- between providers and between the medical ment of neonates because they may be more crew and the awake patient can disrupt the susceptible to direct injury from both noise and detection of changes in symptoms or condi- vibration.17 In addition, vibration may cause tions. As a result, the crew must frequently rely dysfunction of activity-sensing pacemakers18 on other means to monitor and assess the although other types of pacemakers should not patient’s condition.13 With high levels of noise be affected. such as that present on rotary-wing and military The potential deleterious effects of vibration aircraft, close observation of the patient and extend to the equipment used during transport. visual alarms will supplement the usual forms Although evaluation of several pulse oximetry of patient interaction and assessment. The units demonstrated their capability to function ability to auscultate for breath sounds is almost in the flight environment, they are sensitive to impossible under most circumstances in flight.14 motion and may display artifactual readings on Auditory fatigue induced by noise is fre- occasion.19,20 Similarly, noninvasive blood pres- quently accompanied by a feeling of fullness, sure (BP) monitors will work well under most high-pitched ringing, buzzing, or a roaring in-flight circumstances; however, they are still sound (tinnitus) in the ears.15 These symptoms subject to the same accuracy limitations seen in usually resolve within a few minutes of noise the hospital.21 cessation but may take hours in some circumstances. Most of the significant symptoms of Decreased Humidity noise exposure, such as nausea, disorientation, One of the more subtle stresses of flight is a and fatigue, in general occur with exposure to decrease in cabin humidity.As altitude increases noise levels in excess of those seen during AE and air cools, moisture in the air decreases missions. Nonetheless, it is recommended that significantly. Thus, the fresh air supply drawn all personnel wear hearing protection during into the aircraft cabin comes from a very dry patient transport operations. atmosphere. This dry air also replaces the moisture-laden cabin air such that the relative Vibration humidity is less than 10% to 20% on most commercial flights.4 Vibration, like noise, is inherent in all transport Medical crew will develop chapped lips, vehicles and may interfere with patient assess- scratchy or slightly sore throat, hoarseness, and ment and some routine physiological functions. general moisture loss. The patient with respira- The most common sources of vibration during tory complaints or who is already dehydrated air transport are the engines/rotors and air tur- may have more significant problems. Patients bulence. When in direct contact with a source requiring oxygen should receive humidified gas, of vibration, mechanical energy is transferred, and fluid intake of both the crew and patients some of which is degraded into heat within should be monitored to minimize problems those tissues that have dampening properties. with dehydration. The whole body response to sustained vibration is a slight increase in metabolic rate that is Acceleration similar to mild exercise. Low-frequency vibration may also promote the onset of fatigue, irri- Gravitational force,or acceleration,is negligible tability, and motion sickness.16 In conjunction under most circumstances when discussing the 122 T.E. Grissom type of airframe used for patient transport. The exposure to altitude is fatigue. Performance longitudinal axis (fore to aft) is the most impor- degradation with loss of attention and decrease tant aspect of force to be considered during AE in reaction time can be a significant contributor and is of interest primarily during take-off and to a decrease in operational capability. This landing. The implications for patient care are problem is often made worse by self-imposed mostly theoretical although they are important stress such as the use of drugs, (including over- in regard to routine operations, accident pre- the-counter drugs, prescription medications, vention, and accident survival. and stimulants such as caffeine), exhaustion, Federal regulations stipulate that each item alcohol, tobacco, and poor dietary habits. of mass inside the cabin that could injure an occupant be restrained when subjected to load factors seen during flight. This includes all Organizational Issues medical equipment and monitoring devices. Care should be taken to secure all equipment Team Composition bags opened during flight to prevent injury in The “ideal” air medical crew composition has the event of turbulence or during deceleration been a topic of discussion for a number of years (landing). without resolution.22–27 The mission require- Theoretical implications regarding patient ments, scope of medical responsibilities, and positioning during take-off and landing center personnel availability all contribute to the com- around the impact these forces have on blood position of the flight crew. A recent survey of pooling and central hemodynamics. Head posi- civilian hospital-based flight programs in the tion toward the front or rear of the aircraft may United States shows that a nurse–paramedic affect intracranial pressure and cerebral perfu- composition is the most common combination sion pressure in different ways although there although physicians, respiratory therapists, and is no scientific evidence to support this as a clin- emergency medical technicians are occasional ically significant problem. Increased intracra- team members.28 nial pooling of blood during take-off may Currently, there are no national standards for transiently increase intracranial pressure if the the qualifications of medical personnel actively head is pointed to the rear. When the head participating in the air transport of critically ill is positioned to the front of the aircraft, a or injured patients.29 Recommended training decreased cerebral perfusion pressure may for these aeromedical crewmembers include occur due to pooling in the lower extremities education and experience in altitude physiol- with a decrease in venous return and mean ogy, management of patients in the prehospital arterial pressure. setting, and flight communications and safety. In the patient with poor myocardial function, In addition, for nonphysician personnel, “they myocardial perfusion may be improved during should have the ability and training to function acceleration by positioning the patient with autonomously in a variety of settings with treat- their head to the back of the aircraft. More ment protocols if immediate communications likely, however, the patient with congestive with a physician is not possible or if immediate heart failure or volume overload will bene- life saving actions are required.”30 fit from a head-forward position to avoid more central blood pooling (increased preload) Nurses during take-off. As with head injury, these are mostly theoretical concerns and the transient By far, the majority of flight teams include a nature of the acceleration pattern may be far registered nurse (RN) as the team leader. In the outweighed by other patient and environmen- evolution of air medical services, the majority tal factors. of air transports in the United States have been interhospital transports where patients are moved from the source hospital to one Fatigue capable of providing a higher level of neces- The end product of all the physiological and sary care. As such, patients should anticipate psychological stresses of flight associated with receiving a level of care comparable to that 9. Critical-Care Air Transport: Physiology and Organizational Considerations 123 of the sending facility. The inclusion of designed for flight personnel and including RNs with specialized skills meets this need specific air medical modalities and issues. in most instances. According to the American 5. Three years’ experience in the field as an Society of Hospital Based Emergency Air EMT working as an advanced life support Medical Services’ (ASHBEAMS) recom- provider. mended standards, “staffing the aircraft shall Another development that will contribute to be commensurate with the advanced life sup- the increased use of paramedics in transport is port environment afforded by the airborne the development of Critical Care Paramedic emergency care facility.”31 This staffing should (CCEMT-P) training programs. A recent study include, at a minimum, “at least one specially examined the impact of a paramedic-staffed trained registered nurse.” mobile intensive-care unit performing inter- Now, the “specially trained registered nurse” facility transports.35 The authors concluded that is most commonly a flight nurse. The National specially trained paramedics “can monitor and Flight Nurses Association has established prac- treat patients appropriately during interfacility tice standards for flight nurses and provided transfers that traditionally would have required numerous position statements regarding the supplementation with additional hospital staff.” role of flight nurses in the delivery of care While this was a small study,the potential to use during air transport.30,32,33 The USAF has a six- less costly personnel may cause some transport week training program to provide registered services to re-examine their current staffing nurses with the additional skills and experience mix. to become military flight nurses. By covering the additional training and education described Physicians above, these individuals are better prepared to transport the critically ill and injured patients Few transport teams include routine, direct needing a higher level of care than that pro- physician support on the aeromedical crew. In vided by basic transport services. an attempt to determine whether the presence of physicians improves patient outcome, a Paramedics/Other Technicians number of studies have examined various programs with differing results. For example, The most common air medical crew configura- Wright et al failed to demonstrate a change in tion for use in the United States includes mortality with physician involvement during one RN and one paramedic.28 During the the aeromedical transport of patients with trau- mid-1980s many flight programs turned from matic cardiac arrest.36 In contrast, Baxt and predominantly RN crews to ones that incorpo- Moody reported a decrease in mortality for rated the prehospital skills of the paramedic. blunt trauma patients without traumatic arrest The National Flight Paramedics Association when a physician was part of the transport (NFPA)34 has stated that minimal training stan- team.22 The majority of studies of this type deal dards and qualifications for paramedics in this with prehospital management and scene field should include: responses where stabilization prior to transfer 1. Successful completion of an approved emer- is the key issue. In a review of aeromedical gency medical technician (EMT)-paramedic transportation, Moylan observed that available course that utilizes Department of Trans- data “demonstrate clearly that the interval portation EMT-paramedic course guideline. between the accident and arrival of the heli- 2. Biennial successful completion of an copter medical personnel at the scene of the American Heart Association advanced accident or outlying hospital—not the speed cardiac life support provider course. with which the patient is delivered to the 3. Successful completion of either a basic tertiary care facility—is the key factor in trauma life support course or prehospital improving survival.”37 If physician involvement trauma life support course with respective has an impact on patient outcomes in most sce- refresher courses as required. narios, it lies in the preflight stabilization of the 4. Successful completion of an additional critically ill or injured patient. This is not a course of instruction (when available) trivial consideration because 24% to 70% of 124 T.E. Grissom transferred patients may be inadequately stabi- stabilization prior to transport or while en lized prior to transport.38 route. For longer, fixed-wing transport, the same Beyond direct contributions to the transport controversy exists. The USAF has employed a team, physicians also provide support as air mix of flight nurses and AE technicians since or transport service medical directors with the 1960s for the movement of patients by air. established programs. A well-prepared medical With recent changes in missions and logistic director contributes greatly to the development support, there has been increasing emphasis on of treatment protocols, quality processes, crew physician involvement. During Operation Just training, and administration. The degree of Cause, when US Forces went into Panama, the involvement, however, varies widely.43 Cur- AE system designed to move stable patients rently, most physician directors lack experience found itself with a requirement to transport in air medical practice, in particular in the areas fresh casualties.39 The inclusion of physicians on of medical training, practical experience, and these flights and those generated during longevity in their current position. Many of the Gulf War40 has led to the creation of the these positions are unpaid and performed on a Critical Care Air Transport (CCAT) Teams. part-time basis with responsibility for a wide CCAT Teams are composed of an “intensivist” range of skills not typically acquired during physician, critical-care nurse, and cardiopul- medical training. These deficits are similar to monary/respiratory therapy technician (Fig those associated with the aircrew members, 9.8).41,42 The definition of an intensivist includes where there is a lack of standardization in anesthesiologists, emergency medicine physi- training, education, experience, and function. cians, and pulmonary/critical-care medicine Organizations such as the Association of Air specialists. These are the physicians whom Medical Services (AAMS) and the Commission are more likely to be dealing with critical on Accreditation of Medical Transport Systems patients on a daily basis and be able to provide (CAMTS) have published standards that the degree of support necessary to establish should improve this process.

Figure 9.8. An emergency room nurse and a trauma surgeon monitor the temperature of a trauma casualty aboard a C-141 (USAF photo by Dewey Mitchell). 9. Critical-Care Air Transport: Physiology and Organizational Considerations 125

Equipment recommendations exist for equipment used in air ambulances.46 The care and monitoring of patients in the One of the more unique considerations in the aeromedical environment commonly requires flight environment is the power requirement the use of modern biomedical equipment. for biomedical equipment. Unlike commercial Devices that work perfectly fine in the power, which provides 110 VAC at 60Hz, most intensive-care unit on the ground may not func- fixed-wing aircraft operate on 110 VAC at 400 tion as expected when taken to even moderate Hz or 12-V DC while rotary-blade aircraft altitudes or may experience total dysfunction in general operate on 28-V DC systems. With following loss of cabin integrity and rapid average rotary-wing missions in the United decompression. Beyond being able to tolerate States taking a little less than 2 hours and fixed- the direct effects of altitude and other stresses wing transports lasting over 4.5 hours,47 trans- of flight, aeromedical equipment must also be port equipment must have long-lasting battery able to function safely in conjunction with support or be able to convert aircraft power to the radiofrequency (RF) transmitting equip- conventional 110 VAC at 60Hz. This can be ment found on the airframe. Not only must the accomplished through frequency inverters or medical devices not interfere with the commu- direct DC-to-DC conversion adapted to equip- nication and navigation systems found on the ment battery packs.48 aircraft, those same systems should not produce Although frequency inverters are large and electromagnetic interference (EMI) with the heavy, fixed-wing flights may necessitate their monitoring equipment. In 1989, 70% of neona- use due to the length of the mission. If lead-acid tal transport equipment failed military-specific 44 batteries are used, they must be sealed and testing for potentially excessive EMI. protected to ensure case integrity. When esti- As discussed earlier in this chapter, the phys- mating transport time in relation to battery life, iological stresses of flight can have a significant do not forget ground transportation time as this impact on a patient’s condition and the care he will most likely be accomplished on batteries receives during transport. Beyond the effects of and can take a significant period of time. altitude on equipment outlined in the previous section, each of the stressors has the potential Monitors to alter the functionality of aeromedical equipment. At Brooks AFB in Texas, the USAF In 1993, the American College of Critical Care has the Aeromedical Research Group, which is Medicine and other groups published guide- devoted to evaluating and certifying biomedical lines for the transfer of critically ill patients.49 equipment for use in military air transports.45 While these guidelines were targeted to generic The testing procedures evaluate the impact intra- and interhospital transports, many of the of vibrations, acceleration/deceleration, rapid recommendations are directly applicable to the barometric pressure changes, and wide temper- movement of patients by air. In their approach ature shifts on a variety of medical devices to monitoring, the basic tenet was to provide (Table 9.2). Testing requirements are less the same physiological monitoring during stringent in the civilian community although transport as received in the intensive-care unit

Table 9.2. Environmental tests for aeromedical equipment.

Altitude testing 10,000ft manned Rapid decompressions 45,000ft at 60, 7, and 1s High-temperature operation 49°C (120°F) for 2h Low-temperature operation 0°C (32°F) for 2h High-temperature storage 60°C (140°F) for 6h Low-temperature storage -40°C (-40°F) for 6h Humidity 94% at 29.5°C for 4h Vibration X, Y, Z Sine @ 2.5G from 5–500Hz X, Y, Z Random @ 9G from 20–2000Hz 126 T.E. Grissom prior to transfer, if technologically feasible. light,unsuitability for hypotensive patients,high They further established a minimal level of power requirement, and lack of compatibility monitoring to include continuous monitoring with disposable cuffs.54 They are, however, more with periodic documentation of electrocardio- accurate than those obtained by palpation.21 gram (ECG) and pulse oximetry and intermit- Alternative methods for the noninvasive tent measurement and documentation of BP, assessment of BP include the use of Doppler pulse rate, and respiratory rate. In addition, and pulse oximetry occlusion techniques where certain patients based on their clinical status systolic BP determination following BP cuff might benefit from monitoring by: capnogra- release is detected by the return of blood flow phy; continuous measurement of blood, pul- or oximetry waveform, respectively.55,56 Alter- monary arterial, or intracranial pressures; and natively, invasive BP measurements may be intermittent measurements of central venous desirable, in particular in those patients at and pulmonary arterial occlusion pressures or risk for significant hyper- or hypotension during cardiac output. transport. Current transport monitors such as The most basic of monitoring skills require the ProPaq Encore (Protocol Systems, Inc, no mechanical devices beyond a stethoscope Beaverton, Ore) include two channels of inva- and sphygmomanometer. In the flight environ- sive pressure monitoring in addition to non- ment, however, noise significantly limits the invasive measurement using oscillometric ability of the provider to use these simple tools techniques (Fig 9.9). for assessing BP and heart/breath sounds. The ECG monitoring, a fundamental require- noise level typically seen in medical helicopters ment in most transport situations involving the is 95 to 100dB and is approximately 2000 times critically ill and injured, is prone to mechanical louder than heart tones and breath sounds.50 and electrical interference.45 While the ECG is Even transport by fixed-wing aircraft does not useful in the diagnosis of pulseless electrical guarantee an environment that will be ade- activity and arrhythmias, during long-term quate for auscultation. Military aircraft such transports the ability to monitor for myocardial as the C-130 Hercules and C-141 Stratolifter injury and ischemia is also highly desirable. have noise exposures approaching those seen in Unfortunately, many transport monitors lack rotary-wing aircraft.51 Assessment during trans- the resolution required to detect subtle port by quieter commercial aircraft is not changes. Some units, such as the ProPaq immune from interference either.52 The use of Encore, provide an extended bandwidth where amplified stethoscopes and monitoring devices ST segments may be accurately displayed and has not solved this problem14,50 although the printed. The lack of automated ST segment advent of new techniques, such as esophageal monitoring, however, means that the transport stethoscopy, may resolve some of these team is directly responsible for detecting and limitations.53 analyzing any changes in this parameter. Care To compensate for the noise factor, other should be exercised in this regard because erro- monitoring techniques must be used. Use of neous determinations can be made in patients palpated systolic BPs taken at the radial or based on ST segment monitoring using trans- brachial site can be readily accomplished port equipment.57 although they are notably inaccurate in the The measurement of oxygen saturation and 21 critically ill even when they can be obtained. end-tidal CO2 (EtCO2) do not replace the need Automated BP monitors, either as stand-alone to assess the quality and distribution of breath devices or as components of an integrated mon- sounds although these values can be useful in itoring package, using oscillometric or other managing the critically ill patient. Pulse oxime- methods of noninvasive measurements, are try has been used in the aeromedical evacua- commonly used in this environment. Reported tion environment for a number of years with problems with the use of this technology in the great success5,19,58–60 although not all models are air transport environment include unreliability suited for use in transport.20 With one model, due to vibration or movement, difficulty visual- as much as 25% of the measurement time was izing screens due to positioning and ambient subject to interference during helicopter trans- 9. Critical-Care Air Transport: Physiology and Organizational Considerations 127

Figure 9.9. The ProPaq Encore monitor is representative of the transport monitors available that offer multiple options, including invasive and noninvasive BP assessment.

port.61 The ProPaq Encore and some other Hayward, Calif) (Fig 9.10). This simple device models incorporate electrocardiograph syn- incorporates metocresol purple into a detection chronization that signiﬁcantly reduces motion chamber where the presence of CO2 changes artifacts in pulse oximetry measurements the color of the detection paper from purple to during rotary-wing patient transport.62 yellow with some quantitative capability based

Similarly, EtCO2 monitoring provides infor- on the degree of change. A significant limita- mation on the adequacy of minute ventilation tion in the traumatized patient with significant and the position of the endotracheal tube. airway secretions or the intubated patient While breath-to-breath values may be mislead- receiving humidified gas is inactivation of the ing, tending the EtCO2 provides a better esti- indicator strip if it becomes moist. The princi- mate of CO2 exchange and minute ventilation ple use of this device is the confirmation of requirements.63 The presence of sustained tracheal placement of the tube following

EtCO2 following intubation provides evidence intubation. of correct positioning when other methods such Other monitoring modalities such as cardiac as auscultation are not available in the ﬂight output, temperature, and neuromuscular func- environment. In addition, the presence of tion, commonly used in the ICU, may still be

EtCO2 may help with assessment of cardiopul- useful in the transport environment. Currently, monary resuscitation because poor cardiac there are no portable monitoring systems with output is associated with a marked decrease in integrated cardiac output measurement capa-

EtCO2. Evaluations of several different models bility. The use of a portable blood gas analyzer show that they will have a role in the air trans- to assess arterial and mixed venous oxygena- port of intubated patients in particular when tion in combination with oxygen consumption combined with an integrated monitoring calculations based on the Fick equation is pos- 64,65 package. An alternative EtCO2 detection sible during longer, ﬁxed-wing transports pro- device is the disposable colorimetric CO2 vided a pulmonary arterial catheter is in place detector, such as the Easy Cap (Nellcor Inc, to obtain samples. Temperature monitoring is 128 T.E. Grissom

Figure 9.10. The Easy Cap employs a chemical detection paper that changes color in the

presence of CO2.

possible through a number of approaches ronment with the loss of auditory signals.13 In including liquid crystalline probes, thermistors, addition, many of the information displays and infrared thermometers. Potential monitor- used in transport-capable equipment were not ing sites include aural, oral, nasopharyngeal, designed for use in direct sunlight. Many of rectal, bladder, skin, and esophageal locations. these screens can be visualized at limited The exact location chosen will depend on the angles, if at all, when used in an outdoor envi- equipment available, patient tolerance, and the ronment under direct sunlight conditions. degree of core temperature accuracy required for patient management. Beyond patient Ventilators comfort, effective temperature management plays a role in the patient’s outcome, in partic- The need to develop special transport ventila- ular in the trauma setting.66 tors for the movement of military casualties was In addition to the reliability and utility of dif- recognized during the United States’ involve- ferent monitoring modalities in the flying envi- ment in Vietnam.67 Branson and McGough ronment, other factors of equipment design outline the definitions, characteristics, classifi- may limit the ability of specific monitors to cations, and necessary criteria for an ideal function outside of their normal area of use. As system in a 1990 review of transport ventilators previously noted, noise may significantly impair (Table 9.3).68 When addressing the special the ability to assess the patient directly. The requirements for transport by air, the ideal ambient noise in the aircraft cabin will also ventilator should also deliver a continuous limit the ability of caregivers to detect auditory mechanical ventilation (MV), without alter- alarms seen on most medical systems. This puts ation in tidal volume (TV) or rate, across a wide increased emphasis on the visual alarms and range of barometric pressures. The newer trans- data presented by on-board medical systems port ventilators in use and under development such as ventilators, monitors, and other pieces incorporate all of these features and more. of equipment. The adequacy of visual scanning Desirable additions such as built-in air com- may be hampered with the absence of auditory pressors or other mechanisms to allow for the signals because this requires direct attention delivery of a variable FiO2 are also available on as opposed to noting auditory clues without many of the current models without the need having to divert from other tasks. Fromm et al to carry a separate air compressor. noted the potential for significant delay in When mechanical ventilatory support is observation of visual alarms in the flying envi- required, how will altitude and the other flight 9. Critical-Care Air Transport: Physiology and Organizational Considerations 129

Table 9.3. Ideal characteristics for a transport dicted by the application of Boyle’s Law (Fig ventilator. 9.6). Because the delivered TV comes from a Variable tidal volume (eg, 100–1500mL) pressurized gas source at 45 to 55psi, a certain Variable ventilator rate (2–30 breaths/min) “mass”of gas is delivered in the microprocessor- Variable minute ventilation (4–20L/min) controlled time interval that expands by a factor Intermittent mandatory ventilation and controlled of two at an altitude equivalent of 18,000ft. This mechanical ventilation problem, however, is readily avoided in the field Low- and high-pressure alarms by disconnecting the patient from the ventilator Continuous positive airway pressure (1–20cm H2O) Demand-flow valve (eg, 100L/min peak flow rate on and performing a recalibration of the ventila- demand) tor after significant changes in cabin altitude. Monitoring of airway pressure Because the calibration process takes almost 60 Source: Branson RD, McGough EK. Transport ventilators. seconds to perform,certain patients may require Prob Crit Care 1990;4:254–74. manual ventilation during this procedure. The Univent Eagle avoids this potential problem by the inclusion of an internal barom- stressors impact ventilator performance? The eter. Changes in barometric pressure are con- potential for a decreased (or increased) baro- tinuously fed to the on-board microprocessor. metric pressure to affect transport ventilator In the microprocessor, the current pressure is function has long been recognized.69 In 1969, compared to those located in a lookup table. At Kirby et al reported on the function of the 5000-ft intervals, the microprocessor automati- Bird Mark VIII Respirator at altitudes up to cally adjusts the flow rate to compensate for 34,000ft equivalent (barometric pressure of the change in barometric pressure based on 188mmHg) in dogs.9 They noted a decrease in the correction factors in the lookup table (Les ventilator rate and an increase in TV. The drop Sherman, personal communication, Impact in the ventilator rate was attributed to alter- Instrumentation, Inc, August 1997). These cali- ations in the performance of the expiratory bration factors are set at 5000-ft intervals up to timer cartridge, which became overpressurized 25,000ft. Beyond the preset range, the ventila- with the decrease in barometric pressure. The tor can be expected to show an increase in tidal increase in tidal volume was only moderate and volume similar to that seen in the Univent the overall MV was relatively unchanged. Model 750. In the event of decompression at a More recently, Thomas and Brimacombe high altitude, the increase in peak airway pres- evaluated a modern transport ventilator, the sures should be blunted by the preset peak Dräger Oxylog, under hypobaric conditions.8 pressure limits. When these limits are exceeded, This ventilator is a time-cycled, volume- the ventilator stops the delivery of gas to constant ventilator with pneumatic logic con- decrease the risk of barotrauma. Both ventila- trols. Like the Bird Mark VIII Respirator, the tors have this pressure-limiting feature. Dräger Oxylog showed a moderate increase in In addition to the automatic compensation TV from 700 to 1442mL at 30,000ft with a for changes in barometric pressure, the Univent decrease in ventilator rate from 12 to a little Eagle incorporates a built-in air compressor to over 8 breaths/minute. The overall effect was an allow for an FiO2 of 0.21 to 1.0. The air com- increase in MV of 13% and 45% at 6676 and pressor output is minimally affected up to 30,000ft, respectively. Neither of these ventila- 15,000ft and should perform well in the AE tors is microprocessor controlled, and the inter- role. The Aeromedical Research Group has play of pneumatic controls limits the impact of accomplished additional testing of these and altitude on the delivered TV. other ventilators at Armstrong Laboratories The Univent Model 750 and Univent Eagle (Brooks AFB, Tex). Model 754 (Impact Instrumentation, Inc, West Caldwell, NJ) are electronically controlled, Infusion Devices time-cycled, pressure-limited transport ventilators. The observed increase in tidal volume of Infusion pumps are the most common piece the Univent Model 750 comes close to that pre- of equipment available in today’s air medical 130 T.E. Grissom services.54 There are a large number of trans- Armstrong Laboratories have approved this portable infusion devices available for use system for use in military AE missions. during patient transport. While patients can receive IV fluids through a passive, flow- Point-of-Care Testing Devices controlled system, any change in pressure in the IV fluid bag as a result of gas expansion can More recent additions to the equipment avail- affect the delivery rate.Although this should not able for in-flight use are the point-of-care be a significant problem at usual cabin altitudes, testing (POCT) systems. POCT allows medical cabin decompression can significantly alter the providers to assess a wide range of clinical con- flow rate. In addition, rapid decompression ditions in a rapid fashion at the site of patient can lead to rupture of pressurized bags used to interaction. While POCT has begun to impact drive higher flow rates when infusion pumps are on the delivery of care in the hospital setting, not available.45 Thus, infusion devices are the its potential for use in remote, field environ- preferred method of delivering both mainte- ments or during AE is just being realized. There nance fluids and emergency medications. are, however, challenges to providing this capa- Key considerations for selection of a trans- bility in the field. The environmental consider- port infusion device include robustness, op- ations are among the greatest threats for the eration in multiple orientations, adequate use of POCT in remote or hostile environ- anchorage, extended battery life, pressure- ments. Not far behind is the issue of ensuring activated occlusion alarms, and a lightweight, the repeated accuracy of the equipment. compact size. Devices such as the IVAC Both the IRMA (Diametrics Medical, Inc., MedSystem III (IVAC Medical Systems, San St. Paul, MN) and i-STAT (i-STAT Corp., Diego) are well suited for this environment Princeton, NJ) systems have operating temper- with the capacity for three independent deliv- ature ranges that can easily be exceeded in field ery channels and 6-hour runtime using all and flying conditions. The IRMA will operate channels at a rate of 125mL/hour (Fig 9.11). from 15 to 30°C while the i-STAT has recently

Figure 9.11. The IVAC MedSystem III is representative of available small battery-operated infusion pumps that offer many attributes suitable for use in AE of the critically ill patient. 9. Critical-Care Air Transport: Physiology and Organizational Considerations 131

Figure 9.12. The i-STAT system is one of several electrolytes, hemoglobin, and glucose during short- portable blood analysis systems available that allow and long-distance moves. transport teams to assess arterial blood gas values,

been upgraded to 16 to 30°C. In our experience, one in an ambulance service and the other in a this is one of the more common operating helicopter rescue unit. The i-STAT performed errors encountered when using the IRMA or well, with excellent consistency between i-STAT outside of the hospital setting. Both samples obtained “on the move” and those run devices are capable of working in a low- in the emergency department. However, both humidity environment down to 0%; however, studies reported problems when the ambient their upper limit is around 65% according to the temperature was cold and had to design special, manufacturer’s recommendations. Barometric insulated bags to protect the analyzers. pressure should not be a problem under most operating conditions. The IRMA is reported to Drugs function from 350 to 900mmHg (59 to 86kP). An on-board barometer calibrates the system The same space limitations that dictate the for the current barometric pressure prior to each need for compact, efficient hardware also limit use. The i-STAT (Fig 9.12) has recently com- the amount of medications available during a pleted testing at the Armstrong Laboratories, transport mission. Thus, it is important to carry where there were no reported problems when a range of medications that provide adequate using both electronic and liquid controls in a coverage for emergent efforts to stabilize cir- hypobaric environment. This testing resulted in culation, improve respiratory function, abolish an “approved” rating for its use aboard selected seizures, reduce pain or stress, and treat toxici- USAF aircraft used for AE. ties. In a survey of 230 German physicians In two studies that have taken this type of involved in emergency medical services, 10 analytic capability out of the hospital and into essential emergency drugs and 13 important the field setting, environmental temperature drugs (according to >70% of respondents) were was a consistent problem.70,71 Both studies identified for inclusion in a transport kit (Table examined the utility of the i-STAT in this role, 9.4).47 For longer flights that include a larger 132 T.E. Grissom

Table 9.4. Emergency drugs recommended by When transporting patients on extended survey. flights, do not forget the need to plan for unex- Essential Important pected occurrences. An adequate amount of Oxygen Nifedipine required medications, a two-day supply for in- Crystalloid infusion Atropine country moves and five-day supply for interna- Epinephrine Dexamethasone tional moves, should be available in the event Nitroglycerin Diazepam (rectal) of diversion to an unanticipated location due Morphine Dobutamine to aircraft malfunction or hostile weather Ketamine Dopamine Midazolam Theophylline conditions. Lidocaine Dextrose 40% Furosemide Verapamil Personal Equipment Dextrose Sodium bicarbonate Beyond those items necessary to provide direct Atropine Naloxone patient care, air medical crews have a requirement to maintain personal protective gear for use in the flying environment. Depending on the mode of transport, fixed- vs. rotary-wing, these items can include helmets with face visors, long-sleeved Nomex uniforms, flame- number and variety of patients, the USAF also retardant gloves, natural leather high-top boots, has a recommended list of medications for in- flight use (Table 9.5). Table 9.5. Routine medications available on USAF Note that neither list provides for the rou- AE flights. tine availability of neuromuscular blocking (NMB) agents despite the fact that they are the Controlled drugs Demerol inj tubex 50mg, 100mg most commonly administered medication Morphine sulphate inj tubex 10mg 72 during preparation for interhospital transfer. Percocet tabs 5mg Because they induce apnea, these agents pre- Tylenol #3 tabs sent risks for serious complications and their Valium inj 10mg use by inadequately trained personnel can be Valium tabs 5mg Routine drugs disastrous. The use of NMB agents during Pseudoephedrine nasal spray patient transport will typically be driven by one Atropine 0.1mg/cc of two considerations. First, they are often used Diphenhydramine caps 25mg to facilitate airway management and endotra- Diphenhydramine inj 50mg/cc cheal intubation. In the out-of-hospital setting, Chlorpromazine inj 25mg/cc Dextrose 50% inj their use is controversial although a number Digoxin 0.25mg/cc of studies have documented protocols that are Digoxin tabs 0.25mg effective when combined with adequate train- Phenytoin caps 100mg ing, even by nonphysician air medical person- Phenytoin inj 50mg/cc nel.46,73–75 Alternatively, a patient with a secured Dopamine 40mg/cc Dramamine tabs 50mg airway may require muscle relaxation as part of Epinephrine inj 1:1000 & 1:10,000 their in-flight management plan or continuation Haldol inj 5mg/cc of preflight treatment.23 This includes the use of Heparin lock flush 100U/cc NMB agents as “chemical restraints” when a Inderal inj 1mg/cc combative patient poses a threat to the crew.76 Isuprel 0.2mg/cc Furosemide 10mg/cc While the use of NMB agents in combination Liquid tears with a sedative/amnestic agent can produce the Antacid desired control, this does not obviate the need Naloxone (adult) 0.4mg/cc to evaluate for other, reversible causes of Nitroglycerin 2% paste agitation such as hypoxia, hypoperfusion, and nitroglycerin IV 50mg/vial Potassium chloride (kcl) 2meq/cc central nervous system derangements. 9. 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high noise environments. J Acoust Soc Am carbon dioxide monitor during pediatric 1998;103:2483–2491. interhospital transport. Pediatrics 1995;95: 52. Bishop LC. Aviation auscultation. JAMA 1990; 875–878. 263:233. 65. Donnelly JA, Smith EA, Hope AT, Alexander 53. Stone CK, Stimson A, Thomas SH, Hume WG, RJT. An assessment of portable carbon dioxide Hunt R, Cassell H, et al. The effectiveness of monitors during interhospital transfer. Anaes- esophageal stethoscopy in a simulated in-flight thesia 1995;50:703–705. setting. Air Med J 1995;14:219–221. 66. Jurkowich GJ, Greiser WB, Lutterman A, 54. Eljaiek LF. Medical equipment used in the air Curreri PW. Hypothermia in trauma victims: medical environment: Survey and database An ominous predictor of survival. J Trauma results. Air Med 1998;4:34–38. 1987;27:1019–1024. 55. Peacock JB, Webber GR, Kuhn W, Waits JN. A 67. Sweeney DF,Garrison FW. Portable intermittent technique for measuring blood pressure in a positive pressure breathing apparatus. Anesthe- medical evacuation helicopter. J Trauma 1975; siology 1966;27:508–509. 15:999–1002. 68. Branson RD, McGough EK. Transport ventila- 56. Talke PO. Measurement of systolic blood pres- tors. Prob Crit Care Med 1990;4:254–274. sure using pulse oximetry during helicopter 69. Ross JA, Manson HJ. Behaviour of three resus- flight. Crit Care Med 1991;19:934–937. citators under hyperbaric conditions. Aviat 57. Hebel GA, Hutton K, Kanowitz A, Neuman T, Space Environ Med 1977;48:26–28. Martinson L, Rosen P. The accuracy of ST 70. Herr DM, Newton NC, Santrach PJ, Hankins segment deviation in prehospital cardiac moni- DG, Burritt MF. Airborne and rescue point- toring. J Emerg Med 1994;12:207–211. of-care testing. Am J Clin Pathol 1995;104: 58. Mehm WJ, Dillard TA, Berg BW, Dooley JW, S54–S58. Rajagopal KR. Accuracy of oxyhemoglobin sat- 71. Tortella BJ,Lavery RF,Doran JV,Siegel JH. Pre- uration monitors during simulated altitude expo- cision, accuracy, and managed care implications sure of men with chronic obstructive pulmonary of a hand-held whole blood analyzer in the pre- disease. Aviat Space Environ Med 1991;62: hospital setting. Am J Clin Pathol 1996;106: 418–421. 124–127. 59. Mulrooney P. Monitoring during aeromedical 72. Runcie CJ, Reeve WR, Wallace PG. Preparation transfer. Anaesthesia 1990;45:256. of the critically ill for interhospital transfer. 60. Talke P, Nichols RJJ, Traber DL. Monitoring Anaesthesia 1992;47:327–331. patients during helicopter flight. J Clin Monit 73. Rose WD, Andersen LD, Edmond SA. Analysis 1990;6:139–140. of intubations before and after establishment 61. Helm M, Forstner K, Lampl L, Bock KH. Pulse of a rapid sequence intubation protocol for air oximetry in the air rescue service. 1. Quantita- medical use. Air Med J 1994;13:11–12. tive detection of interfering factors on the 74. Lowe L, Sagehorn K, Madsen R. The effect of a method. Anaesthesiol Intensivemed Notfallmed rapid sequence induction protocol on intubation Schmerzther 1993;28:86–90. success rate in an air medical program. Air Med 62. Helm M, Forstner K, Lampl L, Bock KH. Pulse J 1998;17:101–104. oximetry in the air rescue service. 2. Methods of 75. Ma OJ, Atchley RB, Hatley T, Green M, Young increasing the stability of pulse oximetry mea- J, Brady W. Intubation success rates improve surements—ECG synchronized pulse oximetry for an air medical program after implementing and adhesive sensors. Anaesthesiol Inten- the use of neuromuscular blocking agents. Am sivemed Notfallmed Schmerzther 1993;28:174– J Emerg Med 1998;16:125–127. 178. 76. Brauer KI, Hutton KC. Use of restraints in air 63. Marini JJ, Truwit J, Hall JB, Schmidt GA, Wood medical transport: A survey. Air Med J 1997; LDH, eds. Principles of Critical Care. New York: 16:105–107. McGraw-Hill; 1992:197–219. 77. National Flight Paramedics Association. Posi- 64. Bhende MS, Karr VA, Wiltsie DC, Orr RA. tion statement on personal protective gear for Evaluation of a portable infrared end-tidal air medical providers. 1996. 10 Nursing Care in Flight

Susan B. Connor

In-flight nursing care during long-distance have an accurate primary diagnosis, know both aeromedical evacuation (AE) requires clini- the medications that the patient is allergic to cal expertise, personal fitness, knowledge of and is currently taking, and be aware of signi- airframe capabilities, an understanding of the ficant past medical history that may complicate physiological effects of flight, quick critical the patient’s current condition or transport. The thinking skills, and a “large roll of duct tape.”1–3 use of the mnemonic “AMPLE”is a helpful way The movement of a patient by air should not be to make sure a complete general history is col- considered a mere event but rather the contin- lected (Table 10.1). This information is useful uation of the care plan and process that began in alerting the aeromedical crew to potential with the initial patient contact. The collabora- problems that may develop during transport. tive abilities and efforts of the ground-based medical teams, aeromedical crew, and flight Physical Assessment crew determines the successful movement of a patient by air. After the history is obtained, a primary physical assessment of the patient helps confirm the patient’s condition, alerts the aeromedical crew Preflight Preparation to potential problems that might present during flight, and directs clinical interventions. A thor- When the plan of care requires airlift, careful ough secondary survey will provide more clini- preparation must occur to minimize the effects cal information but may not always be possible on the human body of the harsh, relatively prior to flight and is difficult during flight due isolated, and hypobaric environment com- to the noise and cramped environment. mon during AE.4 Meeting in-flight care goals After the initial treatment plan is established, requires synergy between the on-the-ground the aeromedical and flight crew must then medical team, flight crew, and aeromedical make plans to minimize the effects of flight that crew. In-flight care is very reliant on an accu- could be antagonistic to the traditional ground- rate patient history, a primary physical assess- based care plan. Patient preparation includes ment, and continued reassessment throughout not only continuation of all medical treat- the flight. ment but also anticipation of what may occur based on the patient’s history, physical assess- Patient History ment, and the initial interventions performed. In some cases, the pretransport assessment and A good patient history is vital and, in some care may have to be accomplished in an austere cases, may provide more information about environment with limited available resources, the patient’s present condition than does such as a mobile aeromedical staging facility the primary physical assessment. It is critical to (see chapter 7). With diagnostic and medical

136 10. Nursing Care in Flight 137

Table 10.1. The mnemonic “AMPLE” is helpful The patient’s energy should be safeguarded by when collecting essential patient history information a combination of exercise conservation and rest. before coordinating a patient care plan. New bold therapies should not be initiated just A Allergies: What medications is the patient prior to or during transport, and administration allergic to? of medication and treatment should be timed M Medications: What medications is the patient throughout the flight to maximize rest. Supple- currently taking? mental oxygen can be used to counter the P Past history: Are there previous medical conditions that will compound this event or cumulative effects of the hypobaric environ- transport? ment over a long period of time. Finally, oral L Last meal intake of appropriate calorie and nutrient sup- E Events/Environment related to injury plements that are easily and safely stored, prepared, and served can prevent the deleterious effects of a catabolic state. capabilities limited both there and during flight, Countering the Stresses of Flight anticipatory planning is vital for the safe transport of patients. Patient responses to treatment The common stresses associated with flight and the stresses of flight can be difficult to may be especially deleterious due to certain predict, and thus all preflight planning should conditions (Table 10.3).5,6 Although all have incorporate strategies to minimize and counter well-recognized countermeasures, these often the affects of the airborne environment. have significant bearing on the overall airlift. A useful management tool for this purpose is The stresses of flight can increase the risk the “HERO” pneumonic (Table 10.2),2 which is of both hypoxia and hypercapnea, which fre- based on the concept that the combination of quently complicate in-flight management of a the patient’s disease or injury and the flight patient who was only marginally stable on the environment can stress and fatigue the patient’s ground. A mild reduction in oxygen saturation, systems just as much as a workout at the gym. which can occur during airlift in any pressur- An effective plan to hydrate the patient is ized aircraft, may prove unexpectedly damag- crucial because of the extremely low cabin ing to a marginal patient’s fragile condition. humidity and the duration of many missions. The risk for hypercapnea and hypoxia may be increased in any patient who has a decreased ability to transport vital nutrients, increased cardiorespiratory workload, or decreased level Table 10.2. Preflight planning incorporates strate- of consciousness. The airborne environment gies that minimize affects of the airborne environ- can pose a significant threat to these patients, ment using the “HERO” pneumonic. even if they are asymptomatic at ground level. H Hydration is critical; intravenous therapy should Supplemental oxygen, or in extreme condi- be considered for patients who will not or tions a restricted cabin altitude during flight, cannot take additional fluids by mouth may be required for patients who are at E Exercise conservation; a patient may respond to high risk of decompensating as a result of flight as they would a stress test; limit stressful treatments when possible altitude-induced hypoxia. Because both hyper- R Rest; if possible, medicate prior to flight and ventilation and hypoxia present with similar adjust dosages to counter the continuous signs and symptoms, anxious patients treated vibration and poor circulation some patients with oxygen may have to be coached to slow experience during flight their rate of breathing.1,7 An especially danger- O Oxygen; additional oxygen may need to be provided during flight to maintain desired ous condition during flight is severe chronic saturation levels; oxygen should be humidified. pulmonary disease, where mild hypoxemia may O Oral intake; diet plans should steer clear of be the primary central drive for respiration.8 In caffeinated drinks and gas-forming foods; these cases, the crew must carefully adjust sup- small frequent meals should be planned for plemental oxygen as the cabin altitude changes patients prior to flight. to avoid oxygen-induced apnea. 138 S.B. Connor

Table 10.3. Stresses of ﬂight, their countermeasures, and the impact on the overall airlift mission. Flight stressor Patients most impacted Countermeasure Flight consideration

Decreased partial Cardiopulmonary disease, Supplemental oxygen, Increased fuel required; longer pressure of anemia, trauma, burn altitude restriction flying time; route may be oxygen patients, the elderly, different than nonrestricted and neonates. aircraft traffic Decreased Postoperative, trauma, Decompression tubes, Increased fuel required; longer barometric orthopedic, any trapped Heimlich valves, altitude flying time; route may be pressure gasses, and ENT patients restriction, bivalve casts, different than nonrestricted deflate balloons/cuffs aircraft traffic or fill with saline Extreme changes Newborn/pediatric, burn, Dress warmly, blankets, Some aircraft (C-9A, C-21, C-17) in temperature postoperative, trauma, medication dosage and have much better cardiopulmonary diseases, route, placement on temperature control than and arthritic patients airframe others (C-130, C-141, KC-135) including the elderly

Decreased Postoperative, pregnant, Humidiﬁed O2 hydrate, and Jet aircraft (C-9A, C-21, C-141, humidity pediatric, burns, elderly, eye/mouth care C-17, KC-135) are faster and pulmonary disease, and thus have less time en route comatose patients than turboprop aircraft (C-130) Increased noise Psychiatric patient; newborn; Hearing protection, Some aircraft (C-9A, C-21) have decreased ability to medication, special lower cabin noise levels than auscultate heart, lung, brieﬁngs others (C-130, C-141) bowel sounds, or fetal heart tones; decreased verbal communication Vibration Psychiatric, orthopedic, Medication, extra padding, Some aircraft (C-9A, C-21) have postoperative, and trauma patient position on less vibration than others patients aircraft (C-130, C-141) Fatigue All patients and crew Hydrate, supplemental Integral to long-distance AE oxygen, small frequent nutritious meals, rest (“get-down litter”) G-forces Pregnancy, cardiac, Supplemental oxygen, Varies by type of aircraft; may postoperative, trauma, reduced cabin altitude, be decreased by decreasing and brain injury (sensitive small frequent meals, angle for take-off and landing to forward acceleration) placement on airframe patients

Altitude restrictions should be considered During ascent and descent, some patients for patients with conditions where expanding may have problems equalizing as the cabin air in a closed space can significantly limit per- pressure changes. The potential risk for baroti- fusion or increase pressure. Penetrating head, tis media (eg, ear block) may be determined face, chest, or ocular injuries with gas trapped by having patients attempt to clear their ears in a closed rigid space will require an altitude prior to flight. This may be difficult for patients restriction due to the risk of expansion and with upper-respiratory infections or whose jaws resulting pressure on surrounding vessels and are wired shut. In addition, the Valsalva ma- tissues. Patients suffering from decompression neuver should be avoided in patients with sickness (eg, the bends) will also require an alti- ocular injuries or aneurysms because it can tude restriction with supplemental pressurized cause momentary increases in cranial, ocular or oxygenation during flight to avoid expansion of intrathovacic pressure. Finally, it should be trapped nitrogen bubbles in the joints and remembered that agitation during descent other areas of the body. might be a symptom of ear block in patients 10. Nursing Care in Flight 139 who are noncommunicative because of age or accomplishing the desired affect on behavior altered mental status. When transporting while avoiding physical injury.11 patients known to have significant problems Pregnant patients offer unique challenges with ear block, a slower than normal descent or, during airlift, as discussed in chapter 22. The in extreme cases, altitude restriction may be mother is prone to hypoxia and dehydra- required. tion during flight due to her increased cardiac Medication dosages, routes, times, and diet workload, diaphragmatic impingement, possi- supplements may need to be altered to help ble occlusion of the ascending vena cava by the counter the effects of the airborne environ- fetus, and increased nutritional and fluid needs. ment. The dry environment during flight can Allowing the mother to sit or lie tilted to the result in thickened secretions and can cause left will help decrease the effect of the fetus on ocular injury when the patient is unable to the vena cava. Supplemental oxygen may also tear. All patients should receive additional oral be added to ensure adequate perfusion. Small hydration and, when required, humidified snacks with drinks need to be offered at least oxygen. Patients should be kept comfortably every 2 hours of flight. Mothers may be reas- warm because a cool environment can slow sured that it is normal for the fetus’ activity vascular perfusion and alter medication ab- level to change during flight in response to a sorption. The combination of these and other change in environment. stresses of flight can increase the risk of motion sickness, especially during a turbulent flight. The psychological response of patients to Flight Preparation flight is often more difficult to predict than their physical responses. For patients known to be In addition to medical considerations, several at risk for psychological problems, placement other factors need to be added to the care on the aircraft should take into account cabin planning equation as outlined in Figure 10.1. lighting, sounds, security, and capability (see The flight crew and aeromedical crew must chapter 8). Various types of auditory and visual have a common understanding of required alti- stimulations may trigger seizures or hallucina- tude restrictions, flight route, alternate landing tions, especially on propeller aircraft. Patients site capabilities, en route weather forecast, who become easily confused, such as elderly expected delays, weight, and balance consider- patients with “sundowner syndrome” or de- ations, and the estimated flight time.1 By com- mentia, and patients recovering from drug- bining conservative ground-based treatments related hallucinations may manifest symptoms with treatments aimed at minimizing the effects during flight regardless of the time of day.These of a dry, dimly lit, vibrating, noisy, hypobaric patients may benefit from techniques that keep environment, the patients should arrive at their them appropriately oriented to time and space. definitive care location ready to move forward Careful preflight screening will identify in their medical care and treatments. patients who are dangerous to themselves or Meticulous planning is critical for patient others and thus require constant observa- safety and it begins with the initial transport tion during flight. If one-on-one observation is request. Once all the teams have established required for safety, the referring facility will the patients’ expanded care plan for the flight, need to provide an attendant. The patient’s the airlift crew will need to assemble an airlift plan of care, including the use of seclusion, package that is easy to transport, allows for sedation, and restraints, should be continued continued patient assessment over a variety of throughout the flight until the final destination parameters, and will remain secured during all is reached. The efficacy of patient restraint phases of flight. The proper monitoring and life- remains controversial, and thus the decision support equipment, including oxygen, must be to restrain a patient in-flight must carefully obtained. The on-board electrical power must weigh physical, psychological, ethical, and be compatible with the required equipment in safety issues.9,10 When used, restraints must be terms of voltage, phase, and amperage. Appro- continually re-evaluated to ensure they are priate types and amounts of medical supplies 140 S.B. Connor

Figure 10.1. Basic planning tree for flight preparation. and medications must be obtained and stored The flight environment is associated with and include those needed for anticipated emer- many unique hazards that are not encountered gencies. Infection control and dietary needs in ground facilities. Equipment used at ground must also be taken into account during the facilities may not be suited or could even planning process. In addition to the basic pa- be dangerous when used at altitude. For this tient needs, all food, supplies, and medications reason, medical equipment must meet rigorous must be adequate to last for several days standards and testing to verify that it will con- because delays or diversions due to mechanical tinue to operate at altitude and during and or weather problems are common. following rapid decompression and tolerate 10. Nursing Care in Flight 141 constant vibration. It also cannot emit electro- drip sets. Plastic containers are preferred for magnetic pulses that can interfere with other flight because they are easy to handle, secure, aircraft systems.5,12 Equipment should oper- do not break, and can expand or contract with ate at any angle and be easily decontaminated barometric changes. between patients. When flying over water, patients and crew In-Flight Infection need to ensure adequate numbers and types of Control Considerations floatation rescue devices are available, especially those tailored for immobile patients. The diversity of airframes and the nature of Medical supplies that are filled with air or that infectious disease challenge the airlift team and use air-filled balloons (such as cuffed endo- their infection control procedures. Knowledge tracheal tubes or Foley catheters and MAST of epidemiology, airflow, and equipment is trousers) must be monitored during flight be- important when trying to decrease the chance cause of gas expansion at altitude. Balloon of exposure (see chapter 11). Given the nature devices can be used after the air has been of patient care, prudent infection control and replaced with normal saline. Chest tubes must use of personal protective apparel is a must. have either a one-way valve or an equivalent Standard precautions are well defined and device in place for flight to prevent reflux of air should be universally applied. Strict reverse or or fluid back into the pleural cavity.12 Water- protective isolation cannot be provided during sealed chamber levels will vary during flight routine AE flights. For this reason, patients due to pressure changes and will require close with compromised immune status may need to observation. Intravenous solutions should be be positioned in specific areas on the aircraft contained in plastic containers with nonvented where airflow minimizes risk (Fig 10.2).

Figure 10.2. Examples of equipment use and secu- observation and in-flight treatment (USAF photo by rity. A litter is placed over a burn patient to deflect Dewey A. Mitchell). direct airflow, provide a shield, and permit patient 142 S.B. Connor

Individualized patient instruction on in-flight the patient should wear protective apparel and hygiene and personal item disposal is especially handle all potentially contaminated articles important for patients known to have infectious appropriately.16,17 secretions. Although hand-washing remains the cornerstone of infection control, running water Medicolegal Considerations is not available on many AE aircraft. In these cases, antimicrobial hand wipes should be used. Despite the unique setting of AE, in-flight All contaminated linen and supplies need to be medical care is governed by the same legal disposed safely, and this may require preflight regulations that govern medical care on the coordination to ensure contaminated items are ground. Care and practice decisions during AE transferred and disposed of appropriately.1,5 An are governed by several standards, including (1) effective approach is to off-load all contami- patient rights and responsibilities as outlined nated items along with the patient at their des- by the Joint Commission for the Accreditation tination facility. The AE transport of patients of Healthcare Organization, (2) scope of prac- with infectious airborne diseases, such as ac- tice laid out by medical and nursing practice tive pulmonary tuberculosis, can be hazardous. acts, (3) care guidelines established by the Special arrangements must be arranged prior to Federal Aviation Administration and Federal the flight to protect both the crews and other Communications Commission, and (4) the passengers. Consolidated Omnibus Reconciliation Act.1 In addition, Flight Nurse Performance Stan- Chemical and Biologic Contamination dards have been published by the Nation- al Flight Nurses Association (Table 10.4).18 The Emergencies involving hazardous materials United States Department of Transportation occur frequently worldwide and the threats of (USDOT) in conjunction with the National biologic contamination, warfare, and terrorism Highway Traffic Safety Administration are growing daily. Despite these known risks, (NHTSA) are publishing education guide- the lack of adequate decontamination facilities lines,19 and the Commission of the Accredita- and protocols increases the risk that contami- tion of Medical Transport Systems recently nated patients may arrive at the flight line published new standards.20 for AE.13,14 Failure to adequately prepare for Legal jurisdiction is complicated when air- this situation can result in toxic exposure of craft cross state and international bounda- both the ancillary health-care providers and the ries. When the AE flight involves planned or flight crew, not to mention potential contami- unplanned landings in foreign countries, the nation of the flight line and the aircraft.15 medical teams and aircrew must be familiar Providing care to patients contaminated with with immigration, customs, and agricultural a hazardous material requires advanced plan- regulations and guidelines. AE systems that ning and specialized training and equipment. routinely make international flights must estab- Prior to accepting a contaminated patient, the lish consistent policies and practices for such flight crew must verify that the patient, linen, common nursing care practices as managing clothing, and equipment have been decontami- controlled drugs. Failure of the medical and nated. A transport vehicle should never bring a flight crews to understand and follow the rules patient directly from the “hot” zone to the flight can result in AE delays and cause undue hard- line. ship for the patients and their families. Even after decontamination, patients ex- AE crews will have to consult with their legal posed to hazardous material with a high vapor liaison when specific patient transit issues or pressure may continue to release toxic sub- dilemmas arise. Common issues include obtain- stances during transport. Decontaminated ing permission for the nonemergency transport patients should be placed in the aircraft such of unaccompanied minors or incompetent that airflow patterns offer the most protec- patients or informing a patient that, due to his tion to others aboard the flight. Aeromedical or her body size or medical condition, the crew crew members who have direct contact with cannot assure safe egress during an aircraft 10. Nursing Care in Flight 143 emergency. Both the attending physician and tion.19–21 The referring agency must arrange for legal liaison should be notified when a patient any special equipment needed, such as refriger- requests release from the airlift before com- ation units, oxygen systems, or storage solutions, pleting the transfer. because these are not routinely available.22,23 If A “do not resuscitate” (DNR) directive for a transportation will be labor-intensive, the crew patient with a terminal condition represents an should be augmented with additional trained important circumstance. When the attending personnel. All limbs and organs should be listed physician writes a DNR order, the aircrew will on the manifest prior to flight. The appearance provide all other general care as indicated. and condition of forensic evidence should be However, the family or patient may revoke the documented prior to exposure to the airborne DNR order at any time during the flight. environment. To help maintain chain of custody, Another important consideration is prisoner a trusted agent of the investigating organization patients. When the patient being transported should carry legal evidence in most cases. If requires a guard, the referring agency is respon- organs for transplantation are being trans- sible for providing the guard. If the guard ported internationally, thorough preplanning is is armed, the aircraft commander must be required to prevent administrative delays that informed so the guard’s weapons and ammuni- could result in the organ being held by local tion can be under his or her control and stored authorities until viability is lost. the during flight.5 At no time should any patient be physically attached to any part of the aircraft by handcuffs or restraint. Safety and Security Two other special problems are in-flight Aircraft safety and security is a shared respon- births and deaths. Most commonly, the flight sibility of the ground-based medical teams, will need to make an emergency landing so that aeromedical crew,and flight crew. All members’ the situation can be medically and legally actions affect not only their own safety but also managed. If childbirth occurs in flight, the the safety of the patients, other team members, geographic location of the aircraft in latitude and the entire aircraft. A lapse in safety can sig- and longitude at the time of birth should nificantly undermine the ability of the crew to be recorded to determine the appropriate reg- perform the diverse responsibilities required istration and citizenship requirement. After for patient care. completing the mother’s and infant’s care, the Patients need to be adequately prepared newborn will need to be added to the passen- for flight. Standard antihijacking procedures ger list on the manifest. If an apparent death should be used to verify that weapons are not occurs in-flight, the patient should not be offi- carried onto the aircraft. All personal items and cially pronounced dead until the aircraft has any medical supplies the passengers bring onto landed because an accurate patient assessment the aircraft need to be inspected and secured to is difficult during flight and the crew will need prevent tampering or theft. Hearing protection to ensure legal considerations are completed at needs to be provided to all patients prior to the location where death is pronounced. If a arriving at the aircraft. birth or death occurs over a foreign country, Patient boarding for AE takes special prepa- it is important to know the policies of the ration. Prior to boarding, all crew members country before landing to avoid flight delays or need to review the plans for patient enplaning, other problems. positioning, deplaning, and emergency egress. Staging personnel familiar with flight line poli- Laboratory Considerations cies and safety considerations must be available to ensure safe patient enplaning and deplan- At times, laboratory specimens, pharmaceuti- ing. Litter patients need special preparation cals, limbs, or organs for transplant may need to for enplaning by the creation of an “air- be added to the airlift equation. Appropriate lift package” designed for patient observation, care of the specimens and documentation safety, and environmental stress protection (Fig often requires considerable preflight coordina- 10.3). Special precautions should be taken with 144 S.B. Connor

Figure 10.3. Meticulous care, planning, and accom- visibility missions, aircraft safety and patient privacy plishment of safe patient on- and off-loading is require crew attention to detail (USAF photo by crucial to the success of the airlift. During high- Dewey A. Mitchell).

excessive equipment and patient weight or tered and the risk of midair collision. Prior when on- or off-loading is performed with the to in-flight refueling, patient care activities engine running or during inclement weather. must be completed, all nonessential equip- During taxi, take-offs, and landings, patients ment turned off, and patients, crew, and sup- and crew need to be seated or supine with plies secured. Nonessential communications safety restraints in place and all equipment between the medical crew and pilot during the needs to be secured. If an aeromedical crew critical phases of flight are prohibited, and only member needs to remain standing to provide essential personnel are allowed on the flight medical care during these critical phases of deck.24 Throughout the flight, the aircraft com- flight, such as approach to landing, the aircraft mander and AE crew director should coordi- commander needs to be informed. nate on all patient or medical team visits to the Refueling is considered a hazardous time for flight deck. military aircraft because of the remote, but real, risk of fire. Almost always, refueling will oc- Patient Care During and Following cur prior to patient boarding. If patients must In-Flight Emergencies remain on-board during refueling, all nonessential electrical equipment must be turned off. In addition to medical emergencies, the aero- The fire protection personnel will need to know medical crew must be prepared for aircraft- how many people are on-board, and a fire truck related emergencies as well. Immediate actions should be positioned in full view of the aircraft. will be required to stabilize and possibly evac- In-flight refueling, required for time-critical uate patients in the event of an aircraft fire long-distance transport, is hazardous both crash landing, or ditching.25,26 Evacuation plans because of the turbulence routinely encoun- for each of these situations are a routine part 10. Nursing Care in Flight 145 of every preflight crew briefing. During any in- ground medical crew need to known the exact flight emergency, the aircraft may experience landing times and required ground-based trans- extreme changes in attitude (ie, pitch, roll, or port needs. The flight line personnel will need yaw). The first priority is to ensure cabin secu- final instructions prior to landing regarding rity regardless of the phase of flight. Once the patient deplaning plans, fleet services, and any aircraft commander decides it is safe to move decontamination cleaning needs. around the cabin, each patient should receive a Once on the ground, the first priority in primary assessment, followed by a quick equip- a foreign country is to meet all agricul- ment check. If smoke is present in the cabin, the tural, customs, and immigration requirements patients should be moved to the lowest possi- as quickly as possible. Staging personnel then ble position and their faces covered with moist- off-load patients, along with their records, sup- ened towels because medical oxygen masks plies, and life support equipment, and the do not protect from smoke. In the event of aeromedical crew gives a patient report to the a sudden decompression, intravascular lines accepting medical authority. Aircraft discrep- should be temporarily closed to prevent a fluid ancies are reported directly to the flight crew bolus and devices such as chest tubes or oral and any mission discrepancies documented and gastric tubes should be checked as soon as pos- reported as required.27 The aircraft, equipment, sible. If patients need to be evacuated, the crew and supplies are then cleaned and restocked for should first direct ambulatory patients out of the next mission. the aircraft to a safe area and then assist litter patients. Another unique aircraft hazard is hijacking. Conclusion If the plane is still on the ground when a hijacking attempt occurs, every attempt should be There are few absolute contraindications to made to delay the movement of the aircraft. AE if both the patient and flight environment This will allow time for all appropriate agencies are appropriately prepared. The flight nurse’s to coordinate a plan to prevent the hijacking special skills and knowledge are crucial for and minimize danger to all on-board. Deadly the safe,expeditious transport in a relatively iso- force should be used to prevent or end a hijack- lated, hostile environment. Through coopera- ing only as a last resort.26 tive planning and communication, ground- based medical teams and AE crews can ensure a seamless continuation of the patient care plan Postflight Considerations that meets established standards.

The movement of a patient by AE is not an isolated event but part of a continuum that begins References when the decision for air transportation is 1. Holleran R. Flight Nursing: Principles and Prac- made and ends when the patient reaches the tice. 2nd ed. St. Louis, Mo: Mosby; 1996. accepting medical facility. Both patient plan- 2. Miller M, Babcock D. Critical Thinking Applied ning and communication are crucial throughout to Nursing. St Louis, Mo: Mosby; 1996. this process, with goals of optimizing patient 3. Wraa CE, O’Malley JO. Flight nurse physical care, ensuring privacy, and promoting safety. requirement. J Air Med Transport 1992;11(10): Patient care planning must focus on meeting 17. the physiological needs of the patient. How- 4. Rayman RB. Passenger safety, health, and ever, it should also take into consideration the comfort: A review. Aviat Space Environ Med 1997;68:432–440. need of the patient’s family and the legal issues 5. Department of the Air Force. Aeromedical related to patient movement. Evacuation. Scott AFB, Ill: AMC; 1991. AMC Coordination between the aeromedical crew Regulation 164-1. Note: this reference will be and ground medical team begins during the replaced by Department of the Air Force AE initial phases of planning and is reiterated by Patient Cosiderations and Standards of Care. radio within the last 2 hours before landing. The AFE 41–307, 2002. 146 S.B. Connor

6. Department of the Air Force. Aeromedical of NBC Defensive Operations. AMedP-6 (B) Evacuation. Scott AFB, Ill: AMC; 1993. AMSCP Part II—Biological. Washington, DC: USAF; 164-50, vol 4. Same note as above (AFI 41–307). 1996. 7. Sheffield PJ, Heimbach RD. Respiratory physi- 17. Department of the Army. Medical Manage- ology. In: DeHart RI, ed. Fundamentals of Aero- ment of Biological Casualties Handbook. 4th ed. space Medicine. 2nd ed. Philadelphia: Williams Bethesda, Md: US Army Medical Research Insti- & Wilkins; 1996:69–108. tute of Infectious Diseases; 2001. 8. Hart K. The passenger and the patient in flight: 18. Hepp H. National Flight Nurses Association. In: DeHart RI, ed. Fundamentals of Aerospace Standards of Flight Nursing Practice. St. Louis, Medicine. 2nd ed. Philadelphia: Williams & Mo: Mosby; 1995. Wilkins; 1996:667–683. 19. U.S.D.O.T. Guidelines for Air-Medical Crew 9. Quinn CA. The four A’s of restraint reduction: Education. Washington D.C. NHTSA 2002. Attitude, assessment, anticipation, avoidance. 20. Commission on the Accreditation of Medical Orthoped Nurs 1994;13(2):11–19. Transport Systems. Accreditation Standards of 10. Ortiz-Pruitt J. Physical restraint of critically ill CAMTS. 5th ed. 2000. patients: A human issue. Crit Care Nurs Clin 21. Raskin KB, Weiland AJ. Current concepts of North Am 1995;7:363–373. replantation. Ann Acad Med Sing 1995;24 11. Marks W. Physical restraints in the practice of (suppl 4):131–134. medicine. Current concepts. Arch Intern Med 22. Layug ML, Barrett EJ, Kenny DJ. Interim 1992;152:2203–2206. storage of avulsed permanent teeth. J Can Dent 12. Department of the Air Force. Aeromedical Assoc 1998;64:375–363. Evacuation. Scott AFB, Ill: AMC; 1993. AMSCP 23. Zemmel NJ, Amis LR, Sheppard FR, Drake 164-50, vol 2. DB. A temporal analysis of the effects of pres- 13. Burgess JL, Blackmon GM, Brodkin CA, surized oxygen (HBO) on the pH of amputated Robertson WO. Hospital preparedness for haz- muscle tissue. Ann Plast Surg 1998;40:264– ardous materials incidents and treatment of con- 629. taminated patients. West J Med 1997;167: 24. Federal Aviation Administration. Code of 387–391. Federal Regulations. Washington, DC: US 14. Cox RD. Decontamination and management of Department of Transportation; 1996. hazardous materials exposure victims in the 25. Mayberry RT. Medical air crew roles and emergency department. Ann Emerg Med 1994; responsibilities during aircraft emergencies. 23:761–770. Aero Med J 1998;3(4):16. 15. Headquarters Departments of the Army, the 26. Department of the Air Force. Aeromedical Navies and the Air Force and Commandant, Evacuation. Scott AFB, Ill: AMC; 1993. AMSCP Marine Corps. Field manual: Treatment of Bio- 164-50, vol 1. logical Warefare Agent Casualties, Washington 27. Frazer R. Operational quality assurance; a new D.C., 2000. concept defined. J Air Med Transport 1991; 16. Departments of the Army, the Navy, and the Air 10(3):19. Force. NATO Handbook on the Medical Aspects 11 Aeromedical Evacuation of Patients with Contagious Infections

Mark R. Withers, George W. Christopher, Steven J. Hatﬁll, and Jose J. Gutierrez-Nunez

The operational decision to evacuate patients warfare casualties. Unresolved issues will be with communicable diseases or those who are identiﬁed with the goal of stimulating discus- biologic warfare casualties is complicated sion and future research. by many factors, including the etiologic agent involved. Unlike nuclear or chemical casualties, patients with contagious infections may trans- Airframe as mit disease after external decontamination. Microbial Environment Further, theater medical facilities might be overwhelmed by a mass-casualty disaster after The engineering parameters of aircraft ventila- an epidemic or biologic warfare attack, neces- tion and pressurization are well known and sitating rapid evacuation (Fig 11.1). tested extensively by aircraft manufacturers. Little has been published regarding the While most studies of aircraft cabin air quality aeromedical evacuation (AE) of patients with have focused on tobacco by-products and other communicable diseases or biologic warfare chemical contaminants, few have addressed the casualties. A recent search of the MEDLINE ecology of airborne microbes. The few available electronic database (1966 through January studies of the aerobiology of aircraft interiors 2000) that queried the intersection of keywords suggest that the modern aircraft interior is a “biological warfare” and “aeromedical evacua- less likely venue for disease transmission than tion” or “transportation of patients” yielded but most public places.1 a single citation.1 A comprehensive review of the AE of such Ecology of Aircraft Cabin Air patients would have to contain elements from several diverse disciplines. These would include Air vented into most aircraft cabins is sterilized disaster medicine, air transport medicine, during pressurization. To maintain an internal critical-care medicine, the ergonomics and aer- cabin atmosphere equivalent to about 8000ft obiology of aircraft interiors, infection control, above mean sea level while at altitude, pressur- international aviation law and diplomacy, and ized air is extracted from the main jet engine the operational requirements and constraints of compressor, where it has been subjected to the USAF and other military and civil services. both high temperature (more than 250°C) and We have limited the discussion in this chapter pressure (450psi). The air is then cooled by a to the ecology of aircraft interiors, disease series of heat exchangers and vented into the transmission on-board aircraft, and highlights cabin.2 of the elements of military AE plans and capa- Microbial survival times are also altered by bilities and the emerging US military doctrine variations in relative humidity.3 Because air as they apply to the feasibility of the AE of at altitude has low relative humidity (10% to patients with contagious infections and biologic 15%), the resultant compressed cabin air does

147 148 M.R. Withers et al.

Figure 11.1. Aeromedical isolation team members stretcher isolator, a lightweight unit designed for in field-protective suits equipped with battery- initial patient retrieval (from Christopher and powered HEPA-filtered respirators transporting the Eitzer51). also. Low humidity inhibits bacterial growth The mechanism by which air is circulated and stability but increases the survival and though most large aircraft cabins depends on infectivity of certain airborne viruses.4 The several factors. When on the ground, fans recir- influenza virus was found to survive longer culate cooled or conditioned air throughout the in dry air (relative humidity <50%), while cabin. When the engines are off, ventilation is poliovirus survived longer in humid air (rela- provided in one of two ways: Either an aux- tive humidity >50%).5 iliary power unit runs the cabin ventilation system or preconditioned air is supplied by con- Ventilation: Air Distribution Systems necting a ground air-conditioning unit to an air manifold. In some aircraft, no fresh air is taken and Airflow in until pressurization is begun at altitude. The three most important factors that deter- However, older military transport aircraft (such mine the incidence of infections spread by air- as the C-130 Hercules) use pressurized air borne particles in an enclosed space are the from the engines for ventilation whether on the susceptibility of those exposed, the duration of ground or aloft. At altitude, compressed air exposure, and the concentration of infectious enters continually while air is vented overboard droplets or droplet nuclei. The concentrations via an outflow valve. First-generation jet air- of droplets and droplet nuclei increase when liners (eg, Boeing 707s, Boeing 727s, DC-9s) the generation rate is high, when the static and most military transports use 100% ambient volume of enclosed air is small, and when (fresh) air for cabin supply.7 fresh air ventilation is low. Ventilation of any The airflow design for most large aircraft enclosed space decreases the concentration of is either circumperipheral or longitudinal. For airborne organisms logarithmically, remov- both designs, conditioned air typically enters ing approximately two thirds of the airborne the cabin at standing head level. With the droplets per air exchange.6 circumperipheral design, air circulates from 11. Aeromedical Evacuation of Patients with Contagious Infections 149 aircraft skin to midcabin, then down and back most cabins feature a flow design that is both to the vents near the skin at floor level on the circumperipheral and laminar, with air entering same side. With the longitudinal design, air cir- overhead, flowing down the sides, and exiting culates from the aircraft skin in the midsection through vents above the floor. Second, they to outflow valves either fore or aft. The outflow have relatively high air exchange rates, typically valves are sometimes along the hull (two on the ranging from 15 to 20 exchanges per hour. This Boeing 707: one at the forward edge of the exceeds both the 12 air exchanges per hour that wings and the other near the tail) or elsewhere maintain air quality in modern office buildings along the fuselage (below the right cockpit and the 6 exchanges per hour recommended by floor in the C-130). the Centers for Disease Control and Preven- The type and direction of airflow during tion (CDC) for the hospital isolation rooms an AE flight has important implications for of patients with active tuberculosis.11 Unfortu- airborne spread of infection. In general, the nately, the purging of air within the cabin may circumperipheral mode is preferable to the lon- not always be uniform because of the laminar gitudinal because it minimizes aircrew expo- flow design. There may be decreased air circu- sure to contaminated air. With the longitudinal lation in fore and aft areas, resulting in stagnant design, the direction of airflow should be zones while animal studies demonstrate that adjusted so that it is aftward by closing the increased ventilation decreases airborne trans- forward outflow valves. In the C-9A Nightin- mission in confined spaces.12,13 It is important to gale, cabin airflow is “top to bottom, front to remember that ventilation alone is not suffi- back” and therefore contagious patients are cient to prevent all transmission of airborne placed as far aft and as low as possible. pathogens.14 The airflow for the C-141 takes on special importance because it is the main strategic AE High-Efficiency Particulate Air Filtration airframe for the US military. This aircraft also has a longitudinal airflow design, where the Jet engine efficiency is decreased by the extrac- air enters both on the flight deck and the aft tion of compressor air for delivery to the cabin cargo compartment. Air then flows toward two because this air is not available for additional outflow valves located above the aft pressure thrust. To economize, commercial airliners use bulkhead.8 Therefore, potentially infectious systems that partially recycle cabin air, rather patients should be placed as far aft and as high than continuing to supply 100% fresh air from as possible. The ventilation patterns of the C-17 the engines. The fraction of recirculated air transport, which may assume some of the ranges from 24% to 66%.15 The use of recir- strategic AE missions in the future, remain to culated air may reduce air quality due to the be characterized.9 recirculation of aerosolized contaminants. To The risk of airborne infection to the flight counter this, most airlines have installed high- crew is related to the flight deck airflow design. efficiency particulate air (HEPA) filters in their In many commercial airliners, such as the recirculation systems. These are 99.7% effec- B-707, the flight crew is somewhat protected tive for removing particles of 0.3mm diameter by the independent flight deck ventilation or larger. system. As noted above, the C-141 flight crew Although HEPA filters were originally is protected by the longitudinal system, where installed for passenger comfort (eg, for remov- the air enters on the flight deck and flows ing tobacco smoke), they also appear to reduce aftward through the cabin. This is in contrast the risk of transmission of airborne pat- to the C-130, where the flight deck personnel hogens.16,17 The droplet nuclei carrying measles, may be at increased risk because all cabin varicella, and tuberculosis are typically 5mm or air is drawn to the cockpit, where it is vented less in diameter. A study commissioned by the out.10 US Department of Transportation to evaluate Commercial airline cabin airflow has two the levels of bacteria, fungi, carbon dioxide, important design features that may reduce res- ozone, and tobacco products in recirculated air- piratory droplet or airborne transmission. First, liner cabin air found that of microorganism 150 M.R. Withers et al. concentrations did not reach levels considered optimal location for placing a highly infections hazardous to health.18 patient in the 707 would be the left rear of the cabin. When the aircraft was pressurized and the forward outflow valve was closed, contamination was largely restricted to the rear area, Microbial Aerosols in Aircraft placing the flight crew at minimal risk if they Because of concerns generated by lethal and stayed forward. untreatable viral hemorrhagic fevers, and a pos- In view of its airflow design, it was no sur- sible need to transport victims of these diseases prise that there was substantial drift of smoke by air, the ventilation and air-conditioning from the cargo hold of the C-130 into the flight systems on pressurized, long-range transport deck.19 Approximately 3% of the spores re- aircraft were studied to evaluate the aerody- leased in the aft cabin reached the flight deck, namics of aerosolized microorganisms.19 The probably enough to transmit infection over a two aircraft evaluated were the Lockheed prolonged flight if the organism had been in- Martin C-130E Hercules (the aircraft used for fectious. The relative locations of the bleed most tactical AE) and the Boeing 707-347C. At valves and outflow valve would make plastic the time, the aviation engineering knowledge diaphragms impractical. One conclusion of the of ventilation and air pressure changes on these study was that high-containment isolators aircraft was extensive. The movement of smoke would be required to evacuate patients with particles was observed and the dispersion of potentially lethal contagious diseases in a C- aerosolized spores of a nonpathogenic organ- 130. These isolators would protect the flight ism (Bacillus subtilis var. globigii) was assayed crew and medical workers and allow refueling at multiple cabin sites under various pressure stops without alarming foreign governments, and ventilation conditions. Results of both which might otherwise refuse international smoke and spore studies suggested that the landing clearances (Fig 11.2).

Figure 11.2. Vickers aircraft transport isolator, designed for prolonged patient transportation and in-ﬂight care (from Christopher and Eitzen51). 11. Aeromedical Evacuation of Patients with Contagious Infections 151

A second conclusion of the study was that Control samples were taken at urban loca- such patients should only be transported in tions such as buses, malls, streets, and airports. long-range jet aircraft with the air distribution Microorganisms were quantified by counting characteristics similar to those of a Boeing 707. colony-forming units (CFUs) after 72 hours However, significant air contamination occurs incubation, but no attempt was made to iden- within the cabin while these aircraft taxi for tify the organisms. take-off with the recirculation fans functioning. This study found no significant differences To avoid this, the starboard engines should be between air at seat level and higher sites, nor operated with the forward outflow valve closed, between coach, business, first-class, or galley thus ensuring rapid air exchanges within the sections.21 The highest counts came from cabin. Potentially infectious patients should be samples taken near outflow vents, about 1ft boarded through the rear passenger hatch and above floor level. Interestingly, the microbial then placed in the left rear of the cabin facing air contamination found during flight was sig- aft. To protect the flight crew, patients and nificantly lower than that found in cities, buses, medical workers should venture no further and public buildings. Decreased passenger forward than midcabin and flight crew no movement (ie, during sleep) correlated with further aft than that same point. lower numbers of CFU. The authors concluded These concepts were applied, without em- that “the small number of microorganisms piric validation, in 1974, when the aft area in a found in US airliner cabin environments does 707 was used to transport a patient with Lassa not contribute to the risk of disease transmis- fever.20 A 707 was selected because it was sion among passengers.”21 capable of a nonstop flight to Germany, obviat- ing potential difficulties obtaining permission to refuel in a third country. This dedicated Survey of Infectious Disease AE utilized extensive and unprecedented pre- Transmission in Aircraft cautions to transport the patient (a German physician) from Lagos, Nigeria, to Hamburg. The risk of transmitting infections in aircraft The patient was isolated in the rear of the has probably been exaggerated.22 Most reports cabin and a “neutral zone” was created using of disease transmission on-board aircraft de- two polyvinyl chloride partitions. The outflow scribe foodborne outbreaks on commercial air- valves were configured to create a longitudinal liners,23 a discrete area of relevance to AE. The pressure gradient in the cabin so that airflow following is a brief summary of the transmission was from the forward to the aft section. Finally, of several common pathogens. to avoid microbial dissemination via recirculated air the starboard engines were started Tuberculosis to allow pressurization prior to boarding the patient through the aft door. After, the aircraft Tuberculosis is an obvious concern aboard AE interior was fumigated with vaporized formalin aircraft because it is a common and serious for 6 hours, and there were no secondary disease usually spread via airborne transmis- cases. sion, especially in confined spaces.24 Three con- The air was sampled for microorganisms on clusions about the risk of tuberculosis spread 36 domestic and international flights, including can be drawn from the limited number of pub- small and large jet airliners and turboprop com- lished retrospective cohort studies of tubercu- muter aircraft, between 1987 and 1994.21 It was losis exposures aboard aircraft. First, the risk of assumed that all microbial contamination orig- tuberculosis transmission aboard an aircraft is inated from passengers and crew because the apparently no greater than in other confined air taken in from the engines was presumably spaces, with reported conversion rates of 2% sterile. It was also assumed that lower levels to 4%.25,26 Second, the duration of exposure of microbial air contamination would correlate appears to be important, with several studies with a lower risk of disease transmission, reporting no tuberculosis transmission after although this has not been validated clinically. exposure to an infectious patient after flights 152 M.R. Withers et al. less than 9 hours in duration.27,28 Finally, the risk well-ventilated airliner appears to be higher of conversion appears much greater for those than the general community attack rate dur- seated within two rows of an infectious passen- ing epidemics (10% to 20%) but less than the ger on airlines with a laminar air flow system.29 rate for boarding schools or nursing homes Based on this information, the CDC recom- (>50%).31 mended that “those known to be infectious travel by private transportation rather than by Measles commercial aircraft.”25 The CDC has also suggested three criteria to Measles is one of the most contagious infec- determine which passengers and flight crew tious diseases, with an attack rate of about 80% members should be notified of the possibility of among susceptible, casual contacts. Spread by tuberculosis exposure.25 First, the person with droplet nuclei, virions can survive in the air for tuberculosis was infectious at the time of the several hours. During the early 1980s, over 500 flight. Infectiousness can be assumed if the measles cases per year were either imported to person was symptomatic with AFB smear- the United States, or acquired from imported positive, cavitary pulmonary, or laryngeal cases. Most of the imported cases were associ- tuberculosis or has transmitted the disease to ated with air travel, and several secondary cases household or other close contacts. Second, the were acquired during flight.32 exposure was prolonged (ie, duration of flight An important aspect of measles transmission exceeded 8 hours). Finally, passengers and is that it may occur before the patient becomes flight crew who were at greatest risk for expo- symptomatic, a day or two before the end of the sure based on proximity to the infectious pas- incubation period. In one report, eight passen- senger should be given priority for notification. gers became infected on a single flight even Routine tuberculosis screening for airline crew though no ill or coughing passengers were members has not been recommended as an observed during the flight.33 occupational health measure. Smallpox Influenza During the Intensified Smallpox Eradication Air travel has significantly altered the epidemi- Program (1967 to 1980), concern was extremely ology of influenza. Since the 1950s,it has become high that smallpox would be reintroduced to clear that influenza pandemics have followed Europe or the United States from endemic major air transportation routes. Influenza has areas by air travel. Consequently, smallpox vac- also been transmitted during flight. Because cinations and boosters were recommended for of confinement in a closed space associated national and international flying personnel.34 with flight, these cases most likely consti- From 1959 to 1973, 27 of the 29 known cases of tute common-source,single-exposure outbreaks smallpox imported to Europe were associated rather than the usual linear “person-to-person- with air travel. None were acquired during to-person” epidemics. flight, as all case patients traveled during the Based on published reports, several conclu- incubation period.35 There is one case of poten- sions can be drawn. First, prolonged ground tial infection during air travel, but it is unclear delays may increase the risk, especially if the air whether transmission occurred in the air or in ventilation system is not functioning. In one a terminal.36 such report, 72% of the passengers became ill and there was a strong association of the rate Viral Hemorrhagic Fevers of illness with the duration of exposure to the ill passenger.30 Thus, a second conclusion is that Viral hemorrhagic fevers (VHFs) are caused by the length of exposure is important. But, in con- a taxonomically diverse group of RNA viruses trast to tuberculosis, even patients exposed for and feature a febrile syndrome with severe vas- less than 1 hour appear to be at significant risk. cular abnormalities. In general, they are associ- Third, the attack rate of influenza aboard a ated with high rates of morbidity and mortality. 11. Aeromedical Evacuation of Patients with Contagious Infections 153

With the exception of Lassa fever, little is cautions be promptly implemented. Attempts known about their transmissibility during air are currently underway to develop portable, transport. rapid diagnostic tests, such as enzyme-linked The mortality and communicability of Lassa immunosorbent assays and genetic typing, fever has engendered a cautious approach to which can be used in the field. In the presence these patients in the west from both the medical of a biologic warfare threat, patients will be and aeromedical communities. As reported screened for incubating infections (eg, small- above, an infected patient transported from pox) prior to being transported for other indi- Lagos to Germany was the sole patient on a C- cations to minimize the risks of evacuation 141, and the patient together with the aero- related epidemics. medical crew were quarantined from the flight When a casualty is determined to be infec- crew.21 Perhaps the most unusual AE in history tious, the most obvious preventive measure occurred when a CDC worker with Lassa fever would be to defer AE until after the communi- and his wife were transported from Sierra cable period. However, such casualties might Leone to the United States on a C-141.37 For need evacuation sooner for tactical or other lack of an isolation chamber, they were both reasons. The use of restricted flights for trans- sealed for the duration of the flight in an Apollo portation of cohorts with specific commu- space capsule that had been flown from a US nicable diseases would obviate the risk of military warehouse in Germany. patient-to-patient transmission but offer little Fortunately, the risk of transmission of Lassa protection to either the aeromedical or flight fever, both on the ground and during commer- crews. cial flight, appears to be low. There have been When transporting any infectious patient, two reports of inadvertent exposure of large standard infection control practices are essen- numbers of susceptible individuals to patients tial. Additional transmission-based precautions with Lassa fever in western hospitals without necessary for certain infections. CDC guide- evidence of secondary transmission.38,39 On at lines mandate the use of surgical masks for dis- least four occasions, passengers with Lassa eases transmitted by droplets (eg, influenza) fever have traveled on commercial overseas and fit-tested HEPA-filtered masks for diseases flights without a single secondary case occur- transmitted by droplet nuclei (eg, tuberculosis) ring.40–43 This suggests that the apparently high in hospitals. These guidelines can be adapted transmission rate of Lassa fever in West African for use in aircraft. The USAF is currently devel- hospitals may be due to local infection control oping a comprehensive regulation on infection practices.38,44 control on aircraft. Based on these reassuring reports, it has been Judicious patient placement should be used suggested that Lassa fever patients can be to minimize the transmission of disease by safely transported by AE using simple barrier respiratory droplet or droplet nuclei based on infection control techniques.38,45 However, the the ventilation characteristics of the specific World Health Organization (WHO) strongly aircraft. For example, infectious patients are discourages the transport of Lassa fever pa- placed as far aft and as low as possible in the tients from endemic to nonendemic areas, C-9A but as far aft and as high as possible in a stating that this should be undertaken only C-141.8 The ventilation pattern of the C-17 in exceptional circumstances and should be transport remains to be characterized.9 accomplished using special precautions includ- The C-130 is potentially the most problem- ing high-containment isolators.46 atic from an infectious disease perspective because cabin air is vented out through the cockpit.10 In high-risk situations, the flow of In-Flight Preventive Measures cabin air can be reversed aftward by opening the safety valve located in the cargo door.47 Early diagnosis of communicable diseases is Unfortunately, the aircraft can not be pressur- the key to prevent transmission. Only then ized in this configuration, necessitating an alti- can disease-specific, transmission-based pre- tude restriction. As an additional protective 154 M.R. Withers et al. measure, the recirculation fan in the cargo com- by batteries. The AERP system is available in partment can be turned off to prevent recircu- most aircraft used for military AE, and all lation of droplet nuclei. aeromedical crew members routinely train The HEPA filtration used in most commer- for its use during emergencies.55 cial airliners may confer additional protection. This may become an important factor in a large conflict, where Boeing 767 passenger aircraft US Military Policies for will be converted into air ambulances as part of Evacuating Contagious Patients the Civil Reserve Air Fleet (CRAF). and Biologic Warfare Casualties Airflow compartmentalization with plastic partitions, neutral zones, contaminated zones, Historical Review and pressure gradients should be considered only in exceptional cases.21 Because they have Aeromedical evacuation of US service yet to be proven effective in practice, no such members with contagious diseases has been precautions are at present recommended for routinely undertaken virtually since the estab- use in US AE aircraft. lishment of a military AE service in 1942. High-containment isolators can be used for During World War II, C-46 Commandos, C-47 transporting patients with highly contagious, Skytrains, and C-54 Skymasters were reconfig- potentially lethal diseases. Unfortunately, they ured to carry litters after unloading military are limited in number and capability and cargo, becoming air ambulances on their return require specially trained teams of medical flights to the United States.56 personnel. These isolators are necessary for Air transportation was soon determined to the implementation of the extremely strict be the most desirable method of evacuation CDC infection control guidelines for the care for all but the sickest of active tuberculosis and AE of patients with infections such as patients.57 Those with large tension cavities or Arenavirus, Filovirus, and Bunyavirus hemor- therapeutic pneumothoraces could not be rhagic fevers.32,48–51 They have been deployed for moved by air because intrapleural gas volume evacuating patients with suspected or proven would double as these unpressurized aircraft VHF and active pulmonary tuberculosis.52,53 ascended from sea level to 18,000ft. In most Although valuable for evacuating limited num- cases, patients were held at hospitals of bers of patients, they would not be suitable for embarkation until a sufficient number accumu- evacuating mass casualties. lated to fill a dedicated flight of tuberculosis The USAF has anticipated the possible patients. A trained nurse was usually present, future challenge of operating in a chemically and strict “sanitary precautions” and “proper contaminated environment by introducing the isolation” were practiced. However, the aero- Aircrew Eye/Respiratory Protection (AERP) medical personnel were not screened with system.54 Transport aircraft have been equiped tuberculosis skin tests.57 Consequently, the with the AERP systems, and these could be number of new tuberculosis infections oc- used to protect aeromedical crew members curring during these early air evacuations is from infection. The system consists of a unknown. mask–hood assembly, a blower, and an inter- In 1954, the first aircraft specifically designed communication unit. The C-9A is equipped and dedicated to routine air medical transport, with eight AERP stations located throughout the C-131A Samaritan, entered service. It could the aircraft. There are fewer such stations on carry specialized medical equipment and was the C-17, C-130, and C-141 aircraft. During capable of cabin pressurization. In 1961, the flight, regulated aircraft oxygen is passed Boeing 707 jet was modified by the military to through the filter/manifold subassembly to the become the C-135 Stratolifter and soon became mask for breathing while filtered ambient air is the mainstay of the first permanent interconti- used to provide visor defogging. On the ground, nental airlift system. Meanwhile, the C-130 filtered ambient air is used. The AERP blower Hercules began to see use for tactical AE. In is powered by the aircraft electrical system or 1965, the C-141 Starlifter began to replace the 11. Aeromedical Evacuation of Patients with Contagious Infections 155

C-135 for strategic (ie, overseas) AE. This jet approved by the appropriate theater comman- aircraft represented a quantum increase in der-in-chief (a nonmedical general officer) and patient load, range, speed, and control of cabin theater surgeon. environment. In Vietnam, helicopters moved A key element of any successful approach to wounded from the battlefield to medical treat- the treatment and transportation of biologic ment facilities in rear areas. From there, C-130 warfare casualties is early and rapid identifica- Hercules, C-123 Providers, and C-7 Caribous tion of exposure, clinical diagnosis, and labora- moved them to rear airfields, where C-141 Star- tory confirmation using field diagnostic tests.58 lifters embarked on intercontinental routes. To meet this need, the USAF is preparing to AE became so efficient that evacuees were deploy multiple specialized teams and has sometimes received in a continental US developed a portable device that can quickly medical facility within 24 hours of wounding. identify organisms by genetic typing. It is now Large-scale actions in Vietnam in 1968 demon- projected that these teams will interface with strated the ability of the AE system to success- the AE system as integral components of fully respond to periodic surges of patients. aeromedical staging facilities. In 1968, the USAF received its first C-9A Nightingale, a military version of the McDonnell Douglas DC-9 specifically designed International Legal and and dedicated for AE. New features included a Regulatory Aspects special area for patient isolation and intensive care, a hydraulic ramp to facilitate enplaning In the 1970s, widely publicized outbreaks of of litter patients, integrated electrical and Lassa and Ebola fevers in Africa spurred con- suction outlets, and medical supply and storage siderable interest among airline officials and equipment cabinets. public health authorities. In retrospect, in- The cornerstone of the current infection appropriate and unnecessary measures were control program is adherence to the CDC instituted at airports in many countries to min- guidelines for infection control. Any infections imize the risk of disease importation. In com- thought to have been acquired during AE are menting upon what he considered a deplorable to be reported to the Air Mobility Command state of affairs, Michel Perin of Air France’s Surgeon’s Office, Scott AFB, Ill. To date, no Central Medical Service wrote: cases have been reported. Most airline companies refuse to admit aboard passengers known, or believed, to have contagious Biologic Warfare Casualties diseases. Such stringency can scarcely be justified by reference to laws or regulations, whether national Military doctrine regarding all aspects of the or international. It introduces the risk of arbitrary, medical management of biologic warfare casu- mistaken, or prejudiced conduct. It does not seem alties, including AE, is currently under devel- logical because airlines learn about only a small opment. Much of the existing joint and USAF fraction of the contagious persons who travel, and doctrine relevant for the AE of nuclear, public health is much more greatly endangered by biologic, and chemical casualties does not unknown infectious persons. Normal hygienic conditions aboard planes usually suppress the risk of con- clearly differentiate between these three tagion of most diseases. The possibility of refusing groups. Clearly, there are significant differences admission should be given to airlines in certain cases, among the diseases produced by these three according to their doctor’s appreciation.59 weapons of mass destruction. The USAF Surgeon General has developed Perin suggested that exclusionary rules interim guidelines for the AE of biologic should be applied “only against someone who warfare casualties. These guidelines are based refuses to comply, or seems incapable of on rational infection control procedures re- complying, with the conditions intended to commended for the infectious diseases caused make him harmless, or against someone who by potential agents. Before these interim guide- has such an infectious disease that it would be lines can be implemented locally, they must be impossible to make him harmless to others.”59 156 M.R. Withers et al.

Insight into how the international commu- US Military Regulations nity reacts to even rumors of highly contagious diseases among airline passengers can be The US Military services have regulations that gleaned from events of August and September govern the transport of infected passengers. 1994. An epidemic of plague in the Indian city One the most relevant of these regulations for of Surat resulted in panic and chaos. Many the AE of potentially contagious patients is of the inhabitants including most physicians, USAF Regulation 161–4, which requires air- evacuated themselves from the city. Panic craft commanders to request an inspection by a spread rapidly to commercial air carriers, with quarantine official when an ill passenger has all but two international airlines canceling any of the following symptoms and signs: (1) a flights to India. Indians deplaning at airports temperature of 100°F (38°C) or greater accom- around the world were evaluated for signs of panied by a rash, lymphadenopathy, or jaundice plague and, in Canada, airport workers donned or that has persisted for over 48 hours; (2) diar- gloves and masks.60 Eleven febrile Indian pas- rhea defined as three or more loose stools or sengers were promptly quarantined when they a greater than normal amount of loose stool for that person in a 24-hour period; (3) death deplaned in New York City. None had plague, 64 but four were found to have malaria, one had due to illness other than physical injuries. dengue fever, and one had typhoid fever.61 The implications of this relatively imprecise Health officials of any country can deny and abstruse statement could be considerable. clearance for an aircraft to land or for the crew Medical planners must be aware of these regu- or passengers to disembark. There is a real lations because failure to implement their pro- possibility that an aircraft commander whose visions may have international repercussions. aircraft carries infectious patients or biologic warfare casualties might be denied permission Unanswered Questions to land in a foreign country or might find that his crew and aircraft are quarantined upon Certain aspects of our current understanding arrival. of the AE of contagious patients remain unre- The International Health Regulations of the solved. We offer the following questions about WHO specify that permission to land can issues that may warrant future research: be denied for three quarantinable diseases: plague, cholera, and yellow fever (smallpox was 1. Will additional smoke and simulant dis- removed from the list in 1981). In addition, the persal studies be done in various current AE following diseases must be reported: louse- aircraft to determine optimal aircraft type and borne typhus, relapsing fever, poliomyelitis, patient configurations for AE of patients with influenza, and malaria.62 contagious diseases? These International Health Regulations are 2. Would the use of HEPA-filtered recircu- being revised “in view of the growing global lated air reduce the risk of disease transmission threat to public health posed by infectious in USAF aircraft that could potentially be used diseases and the increase in emerging and for tactical or strategic AE? re-emerging infectious disease.”63 The pub- 3. What is the utility of UV light in reducing lished draft requires reporting (and possible transmission of airborne infections in aircraft? quarantine) of additional “diseases” of inter- 4. Should the United States pursue international importance, including “acute hemor- national agreements regarding the entry of rhagic fever syndrome, acute respiratory military aircraft carrying contagious disease distress syndrome, acute diarrheal syndromes, patients into other countries under certain acute jaundice syndrome, and acute neurologi- conditions? cal syndrome.” There is a potential for these 5. Can a computer-based tracking system revised regulations to have a considerable be developed for epidemiologic surveillance of impact on international air travel and military AE patients, to enhance reporting of nosoco- AE. mial infectious potentially acquired during AE? 11. Aeromedical Evacuation of Patients with Contagious Infections 157

Conclusions aircraft. Aviat Space Environ Med 1976;47: 471–482. 3. Harper GJ. The influence of environment on the Under normal conditions, the risks of transmit- survival of airborne virus particles in the labora- ting infections in aircraft are probably equal to, tory. In: Des Archiv Fur Die Virusforschung. or lower than, the risks in other crowded enclo- Vienna: Springer Verlag; 1963:1–3 (monograph sures. This is most likely related to the excellent printed in English). ventilation systems built into most modern 4. Buckland FE, Tyrell DAJ. Loss of infectivity aircraft. However, when the ventilation system on drying various viruses. Nature 1962;195: is not functioning (as is often the case prior 1063–1064. to take-off) the aircraft cabin environment 5. Hemmes JH, Winkler KC, Kool SM. Virus sur- increases the risk for transmission of airborne vival as a seasonal factor in influenza and viruses such as measles and influenza. poliomyelitis. Nature 1960;188:430. The most effective method to minimize 6. Nardell EA. Dodging droplet nuclei: Reducing the probability of nosocomial tuberculosis trans- disease transmission is to defer AE of infec- mission in the AIDS era. Am Rev Respir Dis tious patients until after the period of commu- 1990;142:501–503. nicability. Unfortunately, there are many 7. Harding RM,Mills EJ.Aviation Medicine. 3rd ed. situations in which infectious patients must be London: BMJ Publishing Group; 1993:120–122. evacuated, and AE planners must be ready to 8. Flight Manual, USAF Series C-141B Aircraft respond. (TO 1C-141B-1). Washington, DC: US Govern- Most patients with infectious diseases, ment Printing Office; 1998:1-31–1-38. including biologic warfare casualties, can be 9. Ewing JR. C-17 Globemaster III: AMC’s Air- safely evacuated using standard precautions. lifter of the Future. Abstract presented at the However, certain contagious diseases (ie, tuber- Aerospace Medical Association’s 69th Annual culosis, pneumonic plague, VHF) require trans- Scientific Meeting. Seattle; 1998. 10. Flight Manual, USAF Series C-130-B, mission-based precautions to protect the other C-130E, and C-130H Aircraft (TO 1C-130-B-1). patients, medical personnel, and aircrew. AE Washington, DC: US Government Printing planning for these patients must take into Office; 1995 (revised 1996):4-11–4-15. account international public health regulations. 11. Centers for Disease Control. Guidelines for Given adequate resources, foresight, and exper- preventing the transmission of tuberculosis in tise, the AE of infected patients and biologic health-care facilities, 1994. MMWR 1994;43 warfare casualties can be safely accomplished. (suppl):RR-13. 12. Schulman JL, Kilbourne ED. Airborne trans- Acknowledgments. An earlier version of this mission of influenza virus infection in mice. chapter was prepared while Mark R. Withers Nature 1962;195:1129–1130. was a resident in Aerospace Medicine at the 13. Andrews CH, Glover RE. Spread of infection USAF School of Aerospace Medicine, Brooks from the respiratory tract of the ferret. I. Trans- AFB, Tex. The opinions and assertions herein mission of influenza A virus. Br J Exp Pathol are those of the authors and do not purport to 1941;22:91–97. reflect official positions of the Department of 14. Nardell EA, Keegan J, Cheney SA, Etkind SC. the Army, Department of the Air Force, or Airborne infection: Theoretical limits of protec- Department of Defense. tion achievable by building ventilation. Am Rev Respir Dis 1991;144:302–306. 15. Harding R. Cabin air quality in aircraft. Br Med References J 1994;308:427–428. 16. Driver CR, Valway SE, Morgan WM, Onorato 1. Martin TE. Al-Jubail—an aeromedical stag- IM, Castro KG. Transmission of Mycobacterium ing facility during the Gulf conflict: Discus- tuberculosis associated with air travel. JAMA sion paper. J Roy Soc Med 1992;85:32–36. 1994;272:1034. 2. Clayton AJ, O’Connell DC, Gaunt RA, Clarke 17. Hendley JO. Risk of acquiring respiratory tract RE. Study of the microbiological environment infections during air travel. JAMA 1987;258: within long- and medium-range Canadian Forces 2764. 158 M.R. Withers et al.

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50. Wilson KE, Driscoll DM. Mobile high- 58. Reed K (Battelle Corp). Draft of United States containment isolation: A unique patient care Air Force Concept of Operations (CONOPS) modality. Am J Infect Control 1987;15:120–124. for Management of Biological Warfare Casual- 51. Christopher GW, Eitzen EM, Jr. Air evacuation ties. Unpublished 2nd draft. 1997. under high level biosafety containment: The 59. Perin M. Transportation in commercial aircraft Aeromedical Isolation Team. Emerg Infect Dis of passengers having contagious diseases. Aviat 1999;5:241–246. Space Environ Med 1976;47:1109–1113. 52. Clausen L, Bothwell TH, Isaacson M, et al. Iso- 60. Wills C. Yellow fever, black goddess: The co- lation and handling of patients with dangerous evolution of people and plagues. Reading, Mass: infectious disease. South Afr Med J 1978;53: Helix Books, Addison-Wesley Publishing Co; 238–242. 1996:13–14. 53. Clayton AJ. Containment aircraft transit isolator. 61. Centers for Disease Control. Detection of noti- Aviat Space Environ Med 1979;50:1067–1072. fiable diseases through surveillance for imported 54. Human Systems Center (Brooks AFB, Tex), plague—New York, September–October 1994. Products and Progress. http://www.brooks.af. MMWR 1994;43:805–807. mil/hsc/ya/yac/aerp.htm. 62. World Health Assembly. International Health 55. Flight Manual, USAF Series C-9A Aircraft (TO Regulations (IHR). 22nd WHA. 1969, 1983 (3rd 1C9-A-1). Washington, DC: US Government annotated ed), 1992 (updated reprint). Printing Office; 1997:1-346–1-348. 63. Provisional Draft of the Revised International 56. Merwin CA. US Air Force patient airlift: From Health Regulations. Geneva: World Health balloons to high-speed jets. J Air Med Trans Organization; 1995. 1990;19:18–25. 64. Department of the Air Force. Quarantine Regu- 57. Coates JB. Internal Medicine in World War II. lations of the Armed Forces. Departments of vol II. Infectious Diseases. Washington, DC: the Navy, Army, and the Air Force. Washington, Office of the Surgeon General, Department of DC: US Government Printing Office; 1992. AFR the Army; 1963:342, 378–381. 161–4. 12 In-Flight Emergencies: Capabilities and Limitations

R.T. Ross and M. Gage Ochsner, Jr.

The goal of aeromedical evacuation (AE) is Given a preliminary patient status report and a the safe, efficient transport of all patients while brief description of the mechanism of injury, maintaining adequate medical care with fre- astute aeromedical caregivers should be able to quent reassessment. AE is often complicated predict injury patterns and anticipate potential and logistically demanding, requiring meti- problems. culous preplanning and flawless execution by a cohesive team composed of individuals with diverse skills. The need for AE was first recog- AE Environment nized by military commanders who desired the rapid evacuation of seriously injured troops Caring for a patient in a moving aircraft is a directly from the battlefield to skilled treat- complex challenge that requires a combination ment facilities. Later, civilian hospitals adopted of resourceful evaluation and good tactile skills. this military practice and developed a model of Distractions, limited resources, and flight safety peacetime AE. The means by which AE is operational issues all impact the receipt, evalu- accomplished involves calculated risk because ation, transport, reassessment, and disembar- human flight is inherently dangerous. The pur- kation of AE patients. Preflight preparation, pose of this chapter is to familiarize the reader communication, and teamwork are imperative with common in-flight emergency situations, for the safe and efficacious transport of seri- highlight clinical clues that facilitate rapid diag- ously injured or ill patients. Medical personnel nosis using the Advanced Trauma Life Support must anticipate the unique AE environment to (ATLS) primary survey as a model, and outline minimize their influence upon the diagnosis treatment options. and treatment of in-flight emergencies.

Definition Stress Factors There are numerous stress factors during AE. An in-flight emergency can be defined as any The gravitational forces associated with take- urgent condition or change in an existing con- off, changing direction, and landing can alter dition that, during the course of aerial trans- equilibrium and affect blood flow. Air turbu- portation, requires immediate evaluation and lence may induce motion sickness in both care- definitive intervention. Most of these emergen- givers and patients. Reduced cabin pressure, cies are respiratory or circulatory in nature and common during most fixed-wing and some can occur with little, if any, warning. Vigilant rotary-wing AE, promotes hypoxia and causes reevaluation of patients is crucial so that life- trapped gases to expand, sometimes painfully. threatening changes in the patient’s condition In many aircraft, the cabin temperature can be recognized early and managed promptly. may decrease because of the drop in ambient

160 12. In-Flight Emergencies: Capabilities and Limitations 161 temperature associated with altitude (appro- transport is from site of injury to medical facil- ximately 2°C per 1000ft). Aircraft noise and ity or in between medical facilities. vibration can impede evaluation and communication, promote nausea and vertigo, and cause Primary Survey temporary and permanent hearing loss. Simi- larly, noise and vibration mildly stimulate the Seriously ill or injured patients must be moni- cardiovascular system. All of these factors lead tored and re-evaluated in a timely, standardized to fatigue for both the aeromedical crew and fashion. The primary survey, as outlined in patients. the ATLS Program for Physicians, serves as a template for a logical, sequential approach to patient assessment and surveillance.1 This Limitations primary survey quickly identifies, prioritizes, Restriction in cabin space and the standard and simultaneously treats all life-threatening safety practice of restraining personnel and issues (Table 12.1). equipment makes moving around the aircraft The primary survey algorithm is universal interior awkward, especially during emergency and can be applied to all patient types and situations. Because aeromedical equipment event scenarios. Patient care priorities remain must be light, durable, and field-hardened, it constant whether the patient is civilian or mili- often sacrifices precision for ease of application tary, trauma or medical, pediatric or adult, or and ruggedness. Although usually easy to use, pregnant. However, the differences in injury the equipment itself is on occasion inaccurate patterns and physiological status should always and prone to malfunction. be taken into account. For example, military patients tend to be younger and in general heal- thier than the “at large” population. Elderly Safety patients may have significant comorbid medical Flight safety remains an important additional conditions that necessitate a more aggressive duty of the aeromedical crew. Caregivers must approach. Pregnancy is associated with marked constantly maintain situational awareness and anatomic and physiological changes that re- communicate significant patient care events quire early and aggressive resuscitation of the (eg, defibrillation) to the aircraft commander. pregnant patient with parallel monitoring of Conversely, the pilot must inform the aeromed- the fetus. Despite these special considerations, ical crew of weather issues, aircraft emergen- the primary survey is the cornerstone for all cies, and changes in the flight plan that could patient evaluations that makes possible the impact the ease, type, or duration of in-flight rapid categorization and prioritization of life- medical care. Unsafe practices adversely affect threatening emergencies. the mission and jeopardize the safety and well- being of both the crew and patients. Airway The first priority of medical management during AE involves maintaining or securing the In-Flight Diagnosis and Treatment Table 12.1. Primary survey of Advance Trauma Life Diagnosis and treatment of AE emergencies Support. must be simultaneous rather than sequential A Airway control with cervical spine immobilization because most such emergencies will require B Breathing and ventilation prompt definitive intervention to avoid cata- C Circulation with hemorrhage control strophe. The following simple, time-proven pro- D Disability and neurological status tocols can be applied in any situation, whether E Exposure/environment the patient is a trauma or medical casualty. Source: Adapted from American College of Surgeons These protocols are applicable whether the Committee on Trauma.1 162 R.T. Ross and M.G. Ochsner, Jr. airway while protecting the cervical spine. If the airway option among emergency care person- patient can speak, the airway is not immedi- nel, is rarely used today. Instead, endotracheal ately endangered but frequent reassessment is intubation is the treatment of choice for airway wise. If there is any question of an adequate compromise, and all medical personnel should airway, the first step is to inspect the oro- be thoroughly trained in its indications and pharynx for potential obstructions and remove implementation. any secretions, loose teeth, dentures, or other Intubation. Intubation can be either nasotra- foreign bodies. cheal or orotracheal. Nasotracheal intubation The second step in securing an airway is to can be used in nonapneic patients without reposition the head. The chin lift, head tilt, and nasofacial trauma, but should not be used jaw thrust can serve as temporizing measures for more than 3 days. Orotracheal intubation until a definitive airway is secured. However, in under direct visualization with a laryngoscope a trauma patient extreme care must be used to remains the gold standard of securing an avoid any maneuver that applies force to the airway. This method is safe and effective cervical spine, such as hyperextension, hyper- although it may be difficult in some patients, flexion, or rotation of the neck, as this may such as those with laryngeotracheal trauma. result in iatrogenic spinal cord injury. Patients Regardless of the method used, all intubations who have suffered multisystem trauma, espe- must be performed while maintaining cervical cially involving the head, should be assumed to spine immobilization and ideally using the have cervical spine injuries. Even after thor- three-person technique. Specifically,one person ough medical evaluation has ruled out such maintains in-line cervical spine immobilization, injuries (ie, a “cleared neck”), high-risk patients one maintains cricoid pressure (ie, “Selinger should wear a rigid cervical collar during trans- maneuver”) to prevent aspiration of gastric fer for in-line cervical spine immobilization. contents, and the final person intubates the patient. Signs and Symptoms of Airway Compromise Cricothyroidotomy. Patients with maxillofacial A few patients will present with apnea as the trauma may be difficult to intubate and medical first sign of airway compromise but, more com- personnel should be ready to employ alterna- monly, the first signs will be subtle. Therefore, tive methods of managing the airway. Needle or caregivers must keep alert with patients at risk surgical cricothyroidotomy may be necessary, for developing airway problems. Semiconscious although these modalities are considered last and unconscious patients are at the highest risk or emergent use only and require a thorough and may suddenly lose their airways at any knowledge of neck anatomy. Needle crico- time. Narcotic analgesia may alter conscious- thyroidotomy is performed by identifying the ness and thus increase the risk of airway anterior cricothyroid membrane between the compromise, especially for patients with multi- thyroid and cricoid cartilages (Fig 12.1), immo- system trauma. Burn patients, in parti- bilizing it with the thumb and finger, and insert- cular those with facial burns or whose injuries ing a 12- or 14-gauge over-the-needle catheter occurred in closed spaces, are especially sus- through the membrane at a 45° angle caudal. ceptible to a compromised airway secondary to The needle is removed and high-flow oxygen oropharyngeal edema. administered through the catheter. A small hole in the tubing will allow intermittent venti- Treatment Options lation: Occluding the hole for 1 second (usually The first step is always positioning (as described with the thumb) results in lung insufflation with above), followed by placement of an oropha- oxygen and leaving the hole open for 4 seconds ryngeal or nasopharyngeal airway to optimize allows for expiration. airway patency. If this is not sufficient, a A more definitive method of securing decision should be made to secure an airway in an airway is surgical cricothyroidotomy. It is the most appropriate manner. The esophageal accomplished by placing a vertical incision obturator, once commonly employed as an directly over the cricothyroid membrane, 12. In-Flight Emergencies: Capabilities and Limitations 163

Figure 12.1. Relevant anatomy of cricothyroid membrane.

inserting the scalpel handle through the inci- because they allow for earlier re-evaluation of sion to dilate the intended airway, and placing the patient’s neurological status after intuba- an appropriately sized endotracheal or tration. The use of amnestic sedation is also rec- cheostomy tube in the trachea. This technique ommended in these patients. Other important requires specialized equipment and training. adjuncts are adequate suction and gastric decompression with a nasogastric or orogastric Laryngeal Mask. The laryngeal mask is an tube. Restraints should be available and used alternative method of maintaining a secure when deemed appropriate. Finally,all intubated airway that is gaining popularity (Fig 12.2). patients should be monitored with end-tidal Originally designed exclusively for surgical carbon dioxide devices if the devices are avail- anesthesia, it is now considered an excellent able because the absence of exhaled carbon alternative when direct endotracheal intuba- dioxide implies inadvertent esophageal intuba- 2 tion is not possible. Easy and simple to insert, tion or loss of a previously secured airway. it can be applied blindly with ease in only a few seconds. However, it is not considered a Breathing primary or ﬁrst-line technique at this time. The second priority of medical management during AE is adequate ventilation. Supplemen- Adjuncts for Maintaining a Secure Airway tal oxygen (O2) should be administered during There are several important adjuncts for AE for any patient at risk of hypoxia. Methods maintaining a secure airway in an emergency for delivering O2 include nasal cannula, non- situation. The ﬁrst is the use of paralytics for re–breathing mask, bag–valve–mask, continu- intubation, which should be considered during ous positive airway pressure (CPAP), and rapid-sequence induction in the conscious or mechanical ventilation. If hypoxia persists semiconscious patient. Shorter-acting paralytic despite O2 administration and a secured airway, agents, such as succinylcholine, are preferred other causes need to be discovered and treated. 164 R.T. Ross and M.G. Ochsner, Jr.

Figure 12.2. Laryngeal mask airway.

Etiology of Ventilation Problems sedation, or paralytics. Peripheral neurological problems are less common and include isolated Ventilation problems are in general categorized injuries to the nerves that supply the intercostal as either mechanical or neurological. Mechani- or diaphragmatic muscles. cal problems include airway obstruction or anything that restricts normal chest wall and lung movement. A partially or completely ob- In-Flight Emergencies structed airway restricts or prevents adequate Regular re-evaluation to verify adequacy of ventilation. The pain associated with chest ventilation is important during AE. In a noisy trauma (eg, rib fractures and flail chest seg- aircraft, observation of the symmetrical rise and ments) results in shallow breathing that impairs fall of the chest is a more reliable indicator the bellows action of the thorax. of adequate ventilation than is auscultation. Anything that increases intra-abdominal Tachypnea or labored respiration may be the pressure can impede diaphragmatic excursion. earliest signs of hypoxia. Clinical observation, Any condition that results in intraperitoneal the cornerstone of ventilatory surveillance, or retroperitoneal bleeding may hinder ventila- can be optimized by the use of technological tion, as can pneumatic antishock garments. monitoring devices, when available. When the latter is suspected, the device should In high-risk patients, pulse oximetry and end- be deflated to determine if this improves tidal carbon dioxide devices should be used to ventilation. allow early detection of ventilation problems. Intrathoracic processes, such as simple pneu- Normal pulse oximetry assures peripheral oxy- mothorax, tension pneumothorax, and hemoth- genation, but this monitoring device is of little orax, can seriously decrease ventilation by use for patients with suboptimal peripheral per- occupying intrapleural space and thus reducing fusion and gives many false alarms. When the vital lung capacity. This can be especially dele- patient is intubated, the gold standard is the terious for patients with suboptimal pulmonary end-tidal carbon dioxide monitor because it reserve prior to an injury, such as those with will quickly and accurately alert medical per- chronic obstructive or restrictive pulmonary sonnel to inadvertent esophageal intubation or disease. loss of a previously secured airway. Neurological problems that can lead to inadequate ventilation can be classified as either Medical Conditions. Any patient with chronic central or peripheral. Central neurological pulmonary disease should be monitored care- problems include intracranial injuries, which fully throughout flight for signs of pulmonary can suppress central respiratory drive, and compromise. All such patients should receive spinal cord injuries, which can decrease either supplemental O2 during AE, although this the intercostal or diaphragmatic contributions should be given cautiously in patents with to respiration. An underappreciated central chronic obstructive lung disease because hypo- cause is the inappropriate use of analgesia, xia may be their only respiratory drive. Status 12. In-Flight Emergencies: Capabilities and Limitations 165

Table 12.2. Emergency treatment of status flight a simple pneumothorax may develop into asthmaticus. a tension pneumothorax as a result of expansion of the trapped air associate with decreased 1. Ensure adequate humidified O2 2. Inhaled beta-2 adrenergic agents cabin pressure. For this reason, a thoracostomy 3. IV corticosteroids tube should be placed prior to flight in any 4. Optimize theophylline patients with known or suspected pneumotho- 5. Consider anticholinergic agents races and should be considered for any intu- 6. Consider endotracheal intubation bated patient with documented rib fractures. Source: Adapted from Nowak and Tokarski.3 Clinical clues associated with the development of a tension pneumothorax include dyspnea, ipsilateral absence of breath sounds asthmaticus, a true emergency, should be (this will be difficult to detect in-flight), tracheal treated aggressively with epinephrine, inhaled deviation, jugular venous distension, tachycar- beta-agonists, corticosteroids, and antihista- dia, and hypotension. Immediate decom- mines (Table 12.2).3 Acute respiratory depression of a tension pneumothorax can be compensation with most other chronic medical lifesaving and is accomplished by inserting a conditions will usually require emergency large-bore needle into the second intercostal intubation, as described above. space in the midclavicular line (Fig 12.3). The Pneumothorax. The most important potential simple pneumothorax that remains should be respiratory complication for trauma patients is treated with a thoracostomy tube. tension pneumothorax. On the ground, this Another related condition is the open pneu- condition evolves from a simple pneumothorax mothorax, where a defect in the chest wall when air entering the pleural space through a allows air to enter the pleural space. Lack of a defect in the lung or chest wall on inspiration is relative vacuum in the pleural space allows unable to escape. The resultant increasing the lung to collapse, resulting in ineffectual ven- intrathoracic pressure inhibits pulmonary per- tilation with loss of functional residual capacity fusion, venous return to the right side of the and ultimately hypoventilation and hypoxia. heart, and eventually tracheal airflow. During The open pneumothorax is treated with a

Figure 12.3. Needle decompression of tension pneumothorax. 166 R.T. Ross and M.G. Ochsner, Jr. sterile, occlusive dressing applied over the open Circulation wound, but secured only on three sides so The third priority of medical management that accumulated air can escape via a Heimlich during AE is to maintain adequate circulation flap valve. It is critical that caregivers monitor by stopping hemorrhage, establishing adequate respiration closely because an open pneu- intravenous access, and instituting aggressive mothorax can quickly evolve into a tension fluid resuscitation, if required. As with other pneumothorax. life-threatening, in-flight emergencies, circula- Flail Chest. Another trauma-related respiratory problems must be diagnosed quickly and tory emergency is a flail chest segment, result- treated immediately. ing from multiple fractures of contiguous ribs at two or more sites on each rib. This results in Shock severe pain, loss of thoracic cage stability, and paradoxical respiratory motion of the chest Shock is defined as hypotension associated with wall. A concomitant pulmonary contusion can decreased tissue perfusion, cellular hypoxia, further exacerbate the resulting respiratory and metabolic acidosis. At the cellular level, insufficiency. Initial therapy includes supple- inadequate oxygenation causes a shift from mental humidified O2 and judicious application aerobic to anaerobic metabolism and results in of intravenous (IV) fluids. These patients are at lactic acidosis. Cellular swelling results from high risk of worsening respiratory insufficiency massive fluid shift from the intravascular to the during AE and preparations should be made intracellular space. Hypovolemia secondary to for emergency intubation and mechanical ven- acute blood loss is quickly exacerbated by this tilation, if required. secondary compensatory fluid shift. Hemothorax. A life-threatening hemothorax Hemorrhagic Shock. The most common cause results when 1500mL or more of blood rapidly of shock is hypovolemia secondary to acute accumulates in the hemithorax. Patients with hemorrhage. Any trauma patient who has catastrophic intrathoracic vascular injury (eg, tachycardia and signs of peripheral vasocon- penetrating or blunt injuries to the great vessels striction should be presumed to have hemor- or pulmonary hilar vessels) are unlikely to rhagic shock. The key management principle present during AE because these are quickly of shock is prompt recognition and stopping fatal. However, several types of patients, includ- any ongoing hemorrhage. External hemor- ing postoperative patients, those with unrecog- rhage resulting from soft-tissue laceration, nized injuries to the internal mammary or amputation, or open fracture is usually obvious intercostal vessels, or those with lung paren- and should be treated with direct pressure, chymal lacerations, may develop a massive splints, and tourniquets, as required. Internal hemothorax during flight. hemorrhage can occur into the thoracic cavity, The signs and symptoms associated with this peritoneal compartment, or retroperitoneal injury include dyspnea, ipsilateral dullness space and may be occult. If unrecognized, to percussion, decreased breath sounds, and the initial signs of tachycardia and peripheral shock. General management includes imme- vasoconstriction can quickly progress to shock. diate fluid resuscitation and placement of a Basic management involves rapid adminis- thoracostomy tube. However, appropriate man- tration of isotonic IV fluids. However, the agement of massive hemothorax is difficult, massive amounts of fluid given to patients in especially during AE. Continued drainage by the past may not be appropriate.4 The recent lit- thoracostomy tube may result in exsaguination. erature suggests that normalization of systemic Alternatively, clamping the thoracostomy tube blood pressure for patients with internal may result in tension hemothorax. Any time hemorrhage may negate the natural protective 1000ml of blood is rapidly evacuated via thora- mechanism of relative hypotension. If the costomy tube, brief or intermittent clamping of length of time between recognition of shock the chest tube may help tamponade the bleed- and landing at an airport where the patient ing until thoracotomy can be performed. can be taken to a hospital is great, then consid- 12. In-Flight Emergencies: Capabilities and Limitations 167 eration should be given to minimizing fluid considered together. Neither of these types resuscitation. of shock are associated with acute trauma, but both can develop subsequent to trauma or Cardiogenic Shock. Cardiogenic shock is a resuscitation. Septic shock may result from nonhypovolemic state in which hypoperfusion infection after a grossly contaminated injury is caused by reduced cardiac output. Common related to combat. Anaphylaxis can result from causes are myocardial infarction or dysrrhy- transfusion of blood products, especially if it mia, cardiac tamponade, blunt cardiac trauma, has not been correctly cross-matched. In-flight tension pneumothorax, or massive pulmonary treatment consists of stopping the infusing embolus. Signs of tamponade include “Beck’s blood products, administering oxygen, aggres- triad” of muffled heart tones, hypotension sive fluid resuscitation, and a beta-2 adrenergic with tachycardia, and jugular venous disten- agent to relieve bronchospasm. If sepsis is sion. Pulsus paradoxus (“Kussmaul’s sign”) suspected, broad-spectrum antibiotics should is a more reliable sign for patients who are be started if not already in use. hypotensive. Chest pain, dysrrhythmias, and myocardial IV Therapy infarction should be promptly treated using Advanced Cardiac Life Support (ACLS) pro- Venous access is crucial during the transport tocols. If the patient’s hemodynamic status does of patients, and large-bore (14-gauge) IV not improve after routine resuscitation, cardiac catheters should be readily available at all tamponade should be assumed and immediate times. In high-risk patients, one or two IV lines pericardiocentesis performed. A long 16- or should be established in the forearm or ante- 18-gauge needle should be directed percuta- cubital veins prior to transport. If this access is neously toward the ipsilateral tip of the scapula. not possible, central venous access should be Aspiration of as little as 15 to 20mL of fluid will placed in these patients. immediately improve cardiac output. If peri- Medical personnel must be adept at quickly cardiocentesis is successful, the patient should obtaining peripheral venous access in a noisy, be transferred to a medical facility as soon as unstable, and cramped environment. If the possible for creation of a pericardial window patient is in shock, placement of a large-bore and possible thoracotomy. device into a femoral vein may be required. In children less than 6 years of age, IV fluids can Neurogenic Shock. Neurogenic shock is also be quickly and reliably given in an emergency nonhypovolemic in nature. Any head or spinal situation by placing an intraosseous needle cord injury may diminish systemic vasomotor through the anteriomedial surface of the responses. Peripheral vasodilatation results proximal tibia. in venous pooling of blood and hypotension. Decreased cardiac sympathetic innervation Isotonic Solutions. Isotonic crystalloid solu- prevents a compensatory tachycardia. Aggres- tions, such as lactated Ringer’s solution or sive fluid resuscitation is ineffective and may normal saline, are standard fluid therapy for in- lead to fluid overload with pulmonary edema. flight emergencies. The use of lactated Ringer’s Once hypovolemia is excluded, neurogenic solution is slightly preferred if large volumes shock can be carefully treated with vasopres- are required as it more physiologically ap- sors. Atropine may be effective in alleviating proximates human plasma, If large amounts bradycardia. Adrenergic compounds such as of normal saline are given, the patient must the alpha-agonist phenylephrine and the com- be evaluated for possible hypernatremia and bined alpha/beta-agonist norepinephrine may hyperchloremia and acidosis. Colloids such as play a role in the treatment of patients with hetastarch and dextran are less commonly used spinal cord injuries. because they have not been shown to improve patient outcome when compared with crystal- Septic and Anaphylactic Shock. Shock related loid infusion. Dextrose should never be used to massive infection is similar to the shock for fluid resuscitation as it promotes osmotic related to anaphylaxis, and thus they will be diuresis. 168 R.T. Ross and M.G. Ochsner, Jr.

Blood Products. The administration of blood During AE, neurological casualties must be products, in particular packed red blood cells, closely monitored for potentially rapid deterio- is important for the treatment of hemorrhagic ration. Clinical clues may include the deve- shock. However, before hypovolemic adults lopment of unilateral or bilateral mydriasis, receive blood products, the clinical response progression or development of lateralized to a 2-L challenge of crystalloid fluid should neurological signs, unusual breathing, vomiting, be evaluated. Hypovolemic children should combativeness, lethargy, increased confusion, receive two 20-mL/kg challenges of crystalloid or decreasing level of consciousness as deter- solution, after which an infusion of 40mL/kg mined by the Glasgow Coma Scale. Unfortu- of packed red blood cells should be given if nately, little more than supportive care can necessary. When time and facilities permit, be done in-flight. Diversion to an appropriate cross-matched blood should be used. In life- medical facility may be required for the new threatening emergencies, type-specific or type onset of significant symptoms. O Rh-negative blood may be required. Exposure/Environment Treatment of Coagulopathies The final step of the ATLS primary survey has Massive IV transfusions can result in dilutional a duel meaning. “Exposure” is a reminder that coagulopathy. Delayed coagulopathies are whenever a patient’s condition worsens it is uncommon during the first posttrauma hour, important to examine the patient thoroughly but it unfortunately becomes an issue several for potential sources of hemorrhage, as well as hours later.5,6 Warming the fluid may decrease other injuries that may have been missed in a this risk by minimizing hypothermia, whether field medical facility. “Environment” refers to crystalloids or blood products are given. Treat- factors in the patient’s environment that may ment consists of transfusion of fresh frozen adversely affect his or her health. Keeping the plasma, cryoprecipitate, and platelets. patient warm is especially important in large Cardiac Defibrillation AE aircraft, which may have significant swings in cabin temperature during flight. In hot A portable defibrillator should be present and climates, hyperthermia may on occasion be a ready for use at all times. Paddles are not concern, in particular during evacuation of commonly used for defibrillation in an air- combat casualties. However, hypothermia is craft because of the increased risk of accidental probably more common in trauma casualties, shock to a caregiver secondary to the cramped even in combat situations. quarters and unexpected movements common in aircraft. Instead, “hands-off” defibrillation is recommended using an external cable and adhe- Conclusions sive gel pads. ACLS protocols remain the standard approach. The flight environment places unique stresses on both patients and aeromedical personnel. Disability Meticulous and periodic reassessment of pa- “Disability” refers to the patient’s neurological tients and anticipation of potential problems is status. Patients with neurological injuries need required for safe AE. Early recognition and to maintain optimal cardiopulmonary status to treatment of complications that occur during limit secondary neurological insult. Adequate AE requires well-trained aeromedical person- supplemental oxygenation will also promote nel and appropriate resources. adequate cerebral oxygenation. Mild hyperventilation may be used during AE to reduce intracranial blood volume, limit intracranial References acidosis, and increase cerebral metabolism. 1. American College of Surgeons Committee on Finally, overhydration should be avoided be- Trauma. Advanced Trauma Life Support Student cause it may exacerbate cerebral edema. Course Manual. 1997:26–30. 12. In-Flight Emergencies: Capabilities and Limitations 169

2. Martin SE, Ochsner MG, Jarman RH, Agudelo Trauma. Baltimore: Williams & Wilkins; 1996: WE. Laryngeal mask airway in air transport when 195–206. intubation fails. J Trauma 1997;42:333–336. 5. Knudson MM. Coagulation disorders. In: Ivatury 3. Nowak RM,Tokarski GF. Adult acute asthma. In: RR, Cayton CG, eds. The Textbook of Penetrat- Rosen P, Barkin RM, eds. Emergency Medicine: ing Trauma. Baltimore: Williams & Wilkins; 1996: Concepts and Clinical Practice. 3rd ed. St. Louis, 1016–1022. MO: Mosby; 1992:1066–1093. 6. Rutledge R, Sheldon GF. Bleeding and coagula- 4. Mattox KL, Hirshberg A, Wall M. Alterna- tion problems. In: Feliciano DV, Moore EE, tive approaches to resuscitation. In: lvatury RR, Mattox KL, eds. Trauma. Stamford, Conn: Apple- Cayton CG, eds. The Textbook of Penetrating ton & Lange; 1996:1059–1080. Part 3 The Patients 13 General Surgical Casualties: Abdominal Wounds, Urogenital Trauma, and Soft-Tissue Injuries

J.D. Polk, Charles J. Yowler, and William F. Fallon, Jr.

Timing is critical in the treatment sequence of prevailed because the mortality rate of patients both battlefield and civilian casualties.1 In both undergoing laparotomy was approximately cases, rapid medical evacuation (MEDEVAC) 75% to 85%. Fortunately, military medicine from the site of injury to a medical facility and surgery continued to improve. has revolutionized trauma care. Likewise, aero- During World War I, the mortality rate for medical evacuation (AE) used for the trans- penetrating abdominal wounds dropped to portation of casualties over long distances to approximately 50%.7,8 This has been attributed access more sophisticated treatment has bene- to the development of new and more reliable fited the trauma casualty. AE is often employed surgical techniques for performing laparo- for surgical casualties with apparently similar tomy at frontline surgical facilities. This rate wounds but potentially different needs. During decreased to 25% in World War II with the AE, the type of injury, mode of transportation, advent of antibiotic therapy and the develop- and duration of the process will influence treatment of more capable forward surgical facili- ment status and needs. ties. By the Korean conflict, the mortality The focus of this chapter will be on AE con- rate for penetrating abdominal wounds had siderations for casualties with abdominal, uro- dropped to >12%. Although this was due in genital, and soft-tissue trauma and how they are part to surgical advances and improved antibi- managed, either surgically or nonsurgically. The otic therapy, the single greatest advance was history of these injuries will be followed by a the helicopter. This new form of casualty trans- discussion of the most common general surgi- portation, which saw limited use at the end of cal injuries to intra-abdominal and urogenital World War II, was used extensively during the organs. Safe AE depends on an understanding Korean conflict for the rapid MEDEVAC of of the injury, its treatment, and the distinctive battlefield casualties to forward mobile army complications that may occur. surgical hospitals. The Vietnam War saw even faster and more aggressive MEDEVAC of casualties from the battlefield, together with the Abdominal Trauma Care first jet aircraft use in AE. As a result of this aggressive MEDEVAC and AE, the mortality Historical Perspective rate for penetrating abdominal trauma has continued to decline to the present-day rate of 3%. During the Revolutionary War, the mortality In the past, abdominal wounds encountered rate for victims with abdominal trauma was on the battlefield and those seen in the civilian quite high.2 Far more patients died from com- sector were distinctively different. However, plications and sepsis than did from the actual there has been substantial blurring of these penetrating abdominal trauma itself.3–6 Con- differences, as pointed out by Norman Rich servative management of penetrating trauma in his Hume Memorial Lecture in 1993.2

173 174 J.D. Polk, C.J. Yowler, and W.F. Fallon, Jr.

High-velocity weapons are becoming more Unlike traditional definitive surgery, where common in the street violence that plagues reoperation is performed only for complica- society today. Automatic weapons and explo- tions, damage control surgery is limited such sives, whose use was once limited to acts of that reoperation is a planned event for defini- political terrorism, are now in use by common tive repair at a later time. Damage control criminals and disturbed children. Suddenly, surgery is most often used for hemorrhage civilian trauma surgeons find themselves in control of wounds associated with organ injury. “urban battlefields” applying lessons that have This has created obvious new challenges for been learned from centuries of battlefield medi- AE, as “stabilized” patients are transported cine. Compared to his military counterpart, the after damage control surgery to a larger civilian trauma surgeon is at a disadvantage of tertiary-care hospital thousands of miles away having patients that may be aged or very young, for the definitive repair (eg, Operation Just in addition to young healthy adults. Cause in Panama). Maintaining and caring for stabilized patients in the dynamic AE environ- Damage Control Surgery ment requires a firm grasp of aerospace physiology, surgical anatomy, and the types of The evolution of the modern trauma center has complications that may occur in these patients. allowed patients to be cared for in a concise and In an effort to increase the knowledge base of rapid fashion, but many of these patients must surgical priorities for abdominal trauma, we be transported over long distances to access this will review several important aspects unique to definitive care. Thus, both MEDEVAC and these patients. AE have established permanent roles in the modern approach to surgical casualties. A relatively new concept, termed “damage Surgical Approach control surgery,” has taken on a particularly Surgical exposure is of paramount importance important role in both the initial treatment for abdomen exploration after traumatic injury. and AE of patients with abdominal trauma. Adequate exposure of the abdomen allows the Damage control surgery is essentially taking surgeon to determine which injury will take an unstable patient to the operating room with precedence and allows for better control of vas- the sole purpose of providing hemostasis and cular and solid-organ hemorrhage. This is best drainage. This minimal but effective treatment accomplished with a midline abdominal inci- of major injuries is used either to buy time until sion that extends from the xyphoid to the pubic the patient can tolerate a prolonged surgical symphysis (Fig 13.1). Interestingly, this tech- repair or transport the patient to a trauma nique has remained relatively unchanged since center. Decisions to subject these stabilized the turn of the century, when George W. Crile, patients to the potentially fatal stresses of long- a pioneer in trauma surgery, determined this to distance AE must be made on a case-by-case be the incision of choice.8 basis (Table 13.1). The next step is careful exploration of the abdomen. Just as a pilot requires a routine for Table 13.1. Contraindications of elective AE. systematically checking the aircraft’s instruments, the surgeon also needs a systematic Patient in arrest or excessive shock state requiring approach for exploring the abdomen. A repro- aggressive vasopressors, bolus antiarrhythmics, or ducible, if not habitual, approach that explores continued electrical therapy Hemodynamic instability in a trauma patient the entire abdominal cavity will help minimize unresponsive to traditional fluid resuscitation the risk for missed injuries. Hypoxia with inadequate oxygenation or hypercarbia at sea level or inability to adequately oxygenate with portable devices Inadequate resources or materials available to care for Hollow-Organ Injuries and AE the patient in the event of an emergency or change in Hollow-organ injuries are of particular impor- flight plan tance to the aeromedical crew. Because of the 13. Abdominal Wounds, Urogenital Trauma, and Soft-Tissue Injuries 175

during or immediately after surgery. Both the surgical and aeromedical teams must be vigilant in the use of drainage devices in postoperative abdominal trauma patients.

Specific Injuries Upper Gastrointestinal Injuries Gastric Injuries Injury of the stomach, although rare in blunt trauma, is relatively common in penetrating trauma (especially in knife wounds from right- handed assailants). During surgery, the finding of an anterior wall laceration is an indication to carefully examine the posterior wall for per- forations as well. The laceration should be closed using two layers of interlocking sutures rather than a purse-string suture because the latter is not effective in controlling gastric wall bleeding. Asymmetrical tears should be converted to a linear closure. More extensive Figure 13.1. Midline abdominal incision for abdom- trauma to the stomach requiring gastric resec- inal exploration after traumatic injury. The incision should extend from the xyphoid to the pubic sym- tion or vagotomy may require a reanastomosis physis, and can be extended laterally at the apex, if procedure, such as a gastrojejunostomy or 9–12 necessary (used with permission from Blaisdell FW, gastroduodenostomy. Trunkey PD, eds. Abdominal Trauma. New York: It is important to determine if there has been Theime-Stratton; 1982). spillage of gastric contents. A simple gastric laceration without spillage requires minimal lavage and no subsequent drainage. When a gastric injury is associated with spillage of expansion of air that occurs at altitude, the gastric contents into the peritoneal cavity, clo- injured gut is in particular vulnerable to com- sure should be followed by copious lavage of plications due to AE. Expansion of trapped gas the peritoneal cavity to avoid abscess forma- from a paralytic ileus or repaired gut can cause tion, with special attention to the lesser sac. considerable pain or rupture of surgical anas- In addition, postoperative drains are usually tamosis or retention sutures. required. Altitude-associated decreases in pressure cause patients with gas trapped in hollow or- Duodenal Injuries gans to potentially experience problems in unpressurized aircraft at altitudes above 5000ft. Whenever a blunt or penetrating injury of the This is important because even pressurized upper abdomen occurs, duodenal injury should aircraft allow the cabin pressure to decrease to be considered. In the civilian venue, seat belt the equivalent of 8000ft altitude. Unquestion- injuries are common causes of a duodenal in- ably, gas expansion is a concern for postopera- jury, which is usually seen in conjunction with tive patients during AE. other organ injuries, including the pancreas, Because of gas expansion during flight, ade- gastric, hepatic, or biliary system. During la- quate drainage of both air and intestinal con- parotomy, the duodenum should be mobilized tents must be assured before, during, and after using the Kocher maneuver to allow adequate AE. It is extremely important that patients examination of both the anterior and poste- requiring AE have a nasogastric tube in place rior duodenum and the adjacent organs.13–17 176 J.D. Polk, C.J. Yowler, and W.F. Fallon, Jr.

A retroperitoneal hematoma or bile-stained connected to low intermittent suction through- tissues should prompt an extensive search for out the flight. pancreaticoduodenal injury. Prolonged transports should be avoided in Small penetrating injuries of the duodenum “stabilized” patients, who are at increased risk are closed in a simple two-layer fashion. The of lactic acidosis from ongoing bleeding or sub- wound edges are debrided and all other sur- acute hemorrhage. The aeromedical crew may rounding structures are evaluated. A serosal have blood and lactated Ringer’s solution, but patching for significant duodenal defects should usually will not have platelets and fresh frozen be used only for damage control surgery, as a plasma (FFP) if disseminated intravascular temporizing measure until the patient can be coagulopathy occurs as a result of the acidosis. taken to more definitive surgery. More exten- If possible, acid/base balance should be moni- sive surgery (eg, pancreaticoduodenectomy or tored at 4-hour intervals during transport and Roux-en-Y anastamosis) is used as last resort more frequently in patients who have under- for extensive damage to the duodenum, pan- gone damage control surgery. The aeromedical creas, and surrounding structures. crew will need to keep a close eye on patients who have had mesenteric resection for signs of Small-Bowel Injuries evolving ischemia, such as increased pain, lactic acidosis, and fluid sequestration into the gut. Small-bowel injury is almost always due to penetrating trauma, although blunt trauma can result in small-bowel injury at a point of rela- Colorectal Injuries tive fixation, such as the proximal jejunum. Wartime wounds of the colon are more likely During exploratory laparotomy, the entire to be caused by shrapnel injuries than civilian length of the small bowel should be inspected wounds, which are often the result of the blunt to rule out perforation or hematoma. The liga- forces associated with motor vehicle accidents. ment of Treitz should be taken down to care- For most penetrating colon injuries, colostomy fully evaluate each segment of the mesentery is commonly used to divert the fecal stream and and its associated vessels. Injuries from knife thus decrease the risk of sepsis or abscess for- wounds usually have clean edges and require mation due to fecal contamination (Fig 13.2). much less debridement than high-velocity pro- Broad-spectrum antibiotic coverage is also im- jectile wounds. Bowel resection is required for portant, especially for patients at high risk for areas that are crushed, avulsed, ischemic, or subsequent infection such as those with open torn. Drainage may be required for hematomas pelvic fractures, rectal injuries, or blunt colonic or contusions associated with blunt abdominal injury.18 trauma. Blunt colonic injuries may include serosal tears, contusions, mesenteric injuries, or frank Implications for AE rupture. Blunt injuries from motor vehicle After damage control surgery, rather than us- crashes are more likely to involve the sur- ing the standard layered abdominal closure, rounding structures and tissues compared to thought should be given to using a mass closure penetrating injuries, which usually are more technique with retention sutures. This will allow selective. Partial thickness contusions and for peritoneal expansion and will also allow the serosal injuries can be left to heal on their own. receiving surgeon to reinspect the bowel for Full thickness tears and mesenteric injuries vascular integrity if the mesentery has been with colonic involvement should be repaired in involved. a primary fashion, with colostomy for large or Placing a nasogastric tube for drainage is complicated cases. Rupture of the colon should absolutely necessary when transporting patients be treated with fully diverting colostomy and with gastrointestinal injuries by AE to avoid washout of the distal segment. the pain and danger of breaking down of a Rectal injuries are most commonly caused by repair because of overdilatation of expanding penetrating trauma. Digital rectal examinations gas at altitude. The nasogastric tube should be and/or proctosigmoidoscopy will identify most 13. Abdominal Wounds, Urogenital Trauma, and Soft-Tissue Injuries 177

further complicating the in-ﬂight care of the patient.

Solid-Organ Injuries Spleen The spleen is one of the most frequently injured organs in cases of blunt trauma. Abdominal pain and guarding are common for patients with acute splenic injury. Kehr’s sign (referred left shoulder pain) may be present when intraperitoneal bleeding has caused diaphragmatic irritation. Leukocytosis is also common, but decreases in the hematocrit may be relatively delayed. The patient may have acute physical signs of hemorrhage (eg, pain, tachycardia, and hypotension) before the hematocrit has a chance to equilibrate. Thus, physical exam, physical signs, and radiological studies are used to diagnose splenic injury and laboratory findings are considered secondary. With Figure 13.2. Surgical approach to traumatic injury the advent of spiral CT scanners and bedside to the colon in a field environment. After resection of the injured colon segment, the proximal end is ultrasound, splenic injuries can now be readily brought out as a colostomy. The distal end can be identified in a modern hospital setting. brought out as a mucus fistula or closed and left in Conservative management of splenic injuries the abdominal cavity (used with permission from has become more common in both pediatric Blaisdell FW, Trunkey PD, eds. Abdominal Trauma. and adult trauma centers because of the impor- New York: Theime-Stratton; 1982). tance of the spleen in fighting infection. In the pediatric population, nonoperative management is successful in greater than 75% of cases of blunt traumatic injury. In adults with grade I or II splenic injuries with an intact capsule, con- rectal injuries, although abdominal computed servative management is also possible. Total tomography (CT) scan is sometimes required. splenectomy is now reserved for those patients Diverting colostomy is the most common sur- in which complete rupture, loss of the vascular gical therapy for these injuries, although distal stalk, or uncontrollable hemorrhage has taken rectal washout and primary repair is used in place. some cases. Damage control surgery for hemorrhage control can be performed in unstable patients Implications for AE by using a combination of electrocautery, gel- Aeromedical crews must be trained in routine foam, thrombin, and packing. But, this is re- colostomy care because this operation is fre- served for splenic fractures that are deemed quently used in both the civilian and military easily repairable when the patient is stable. environments. In addition to care of the stoma, Otherwise, splenectomy is indicated in unstable proper care of the colostomy bag is important. patients for hemostasis purposes. Treatment of The bag must be periodically vented during moderate splenic injury differs between civilian ascent to avoid rupture of the colostomy bag and military practice. In civilian practice, the secondary to gas expansion. The colostomy bag surgeon can take whatever time is needed to should not be filled with saline or water, as the repair the injured spleen. However, in the fluid may be partially absorbed by the colo- combat arena of military medicine that time nic segment or cause an enema-like catharsis, spent on an extensive, elaborate repair might be 178 J.D. Polk, C.J. Yowler, and W.F. Fallon, Jr. better utilized on a rapid splenectomy of one use of platelets and FFP should be given to this patient to treat another. patient if AE anticipated. Injuries to the pancreatic tail usually require Implications for AE. The aeromedical consid- simple resection. Care should be taken to spare erations in moving postsplenectomy patients, or the splenic artery. Injuries to the body and head those with splenic injury managed conserva- may require either a Roux-en-Y or major resec- tively, mostly involve efforts to prevent bleed- tion of the duodenal segment. As stated previ- ing. These patients should be carefully managed ously, pancreaticoduodenectomy is a means of in the load plan, with litter placement in an area last resort, when the duodenum and pancreas where the potential for trauma is minimized. It have been so severely damaged as to leave no is also important that the AE crew have ready other alternative. access to monitor vital signs and start intravenous fluids as required. Implications for AE. Bleeding and latent disseminated intravascular coagulation (DIC) will Pancreatic and Hepatic Injury be the nemesis of the aeromedical crew in this Treatment of hepatic injuries has changed patient population. Although damage control somewhat over the past few years. Vascular surgery will not negate the need for AE for embolization of bleeding hepatic vessels in the definitive surgery, this approach can be rela- radiology suite has become a more common tively effective in stabilizing patients prior to site. However, battlefield medicine frequently transport. Generous use of blood products, does not have this luxury. For this reason, we including platelets and FFP, prior to transport will review the management of penetrating is paramount. Attempts should be made to trauma to the liver as it is performed in the field correct all coagulopathies prior to consider- hospital, as these are the patients most likely ation for transport. The aeromedical crew will to require AE. When managing superficial not be able to adequately combat DIC while en wounds to the solid organs, direct pressure is route during transport, as they more than likely often all that is necessary. More severe arterial will not have all the blood products needed for bleeding may necessitate the ligation of the this. Decompression of the gut is required by right or left hepatic artery. Packing large nasogastric tube for all patients with abdominal wounds with hemostatic material (Surgicel, surgery. Ideally, a prothrombin time/partial Gelfoam) for damage control and coadminis- thromboplastin time and hematocrit should be tration of FFP and platelets is often used as a evaluated at each stop during transport in these two-fold assault on large lacerations and patients. defects with uncontrolled hemorrhage. Direct pressure over the right and left arterial vessels is applied and then, dependent upon which one Urogenital Injuries controlled the hemorrhage, the vessel is ligated. If the Pringle maneuver is used (application of Urogenital injuries are less likely to be life a vascular clamp to the portal triad) and cessa- threatening than intra-abdominal visceral in- tion of bleeding occurs, this strongly suggests juries. However, recognition and appropriate the source of the hemorrhage is either hepatic treatment is crucial to avoid untoward morbid- artery or portal vein. If large defects or venous ity. Penetrating abdominal trauma is often asso- bleeding allows continued hemorrhage despite ciated with renal coinvolvement. In a combat the previously applied techniques, direct liga- situation, mine injuries are often associated tion of venous bleeders is performed. This with damage to external genitalia. The majority usually involves blunt dissection through the of urogenital injuries, whether internal or ex- penetrating defect with ligation of the individ- ternal, require some type of damage control ual hepatic veins as they are encountered. The surgery to prevent loss of viable organs and wound is then grossly packed with hemostatic tissue, with a planned revision at a later date. agents or a transposing vascularized flap of AE of these patients must be done in such a omentum is sutured into the defect. Generous way as to maintain adequate renal and uro- 13. Abdominal Wounds, Urogenital Trauma, and Soft-Tissue Injuries 179 genital function while attempting to avoid Bladder and Urethral Injuries sepsis and other complications prior to definitive care. Bladder injuries are usually repaired primarily and require continuous drainage afterward with either a large (24 French) suprapubic or Renal Injuries urethral catheter. Bleeding can be a problem, Renal injuries are classified as minor or major as clots may prevent drainage. Although this or as nonpenetrating or penetrating (Fig 13.3). can usually be remedied by irrigation, replace- Most nonpenetrating renal injuries are consid- ment of the tube of catheter may be required. ered minor (eg, contusions and hematoma) and Crush injuries of the pelvis often require the are usually managed without surgery because placement of percutaneous drains as well. surgical manipulation of the kidney carries some risk. Even a nonfunctioning kidney may Penile and Scrotal Injuries also be handled nonsurgically. Major renal injuries include severe blunt Penile lacerations may be closed primarily or renal trauma or penetrating injuries that result secondarily, depending on the degree of contain uncontrolled internal hemorrhage or injury mination and debridement required. A dressing to the renal vascular stalk. Blunt injuries re- impregnated with antibiotic ointment or petro- quire surgical management if an expanding leum is used to avoid tissue disruption upon flank hematoma, continued frank hematuria, or removal. A bladder catheter, either suprapubic drop in hematocrit accompany them or if sig- or urethral, is usually required and must be nificant vascular injury is demonstrated by arte- carefully secured to avoid excessive wound riogram. Penetrating injuries require surgical manipulation. If the penis is closed primarily or exploration in almost every case to look for sewn to a tissue or skin donor site, vascular other injuries. Prior to surgery, normal function integrity should be evaluated by checking for of the remaining kidney must be demonstrated adequate capillary, especially in the presence of by intravenous pyelogram (IVP) in case con- excessive edema. servation of the damaged kidney is required. Scrotal injuries often require debridement. Even with a contralateral functioning kidney, Depending upon how much viable albuginea nephrectomy is only performed if the pedicle is tissue remains, the scrotum may be closed or unrepairable or has been torn away or more the testicle may be placed or buried in the than 50% of the kidney has been obliterated. abdomen or thigh. These wounds must be carefully evaluated for signs of infection or abscess developing. Using a pressure dressing to sup- Ureteral Injuries port the scrotum may significantly reduce pain. Large ureteral injuries may require diversion Antibiotic coverage and drainage may also be of urinary flow to the skin by placement of a required. pyelostomy and ureterostomy tube. Intermedi- ate injuries are treated surgically with ureteral Implications for AE repair, reanastomosis, or reimplantation, followed by placement of a stent. Smaller ureteral For all urogenital injuries, adequate urinary injuries can sometimes be treated by stenting output is important for both treatment and alone. Stents and tubes present two challenges: management. Adequate urine output will verify First, stents usually cause painful ureteral patency of any catheter or nephrostomy tube spasms, requiring treatment with both antis- and increase the ability of the kidneys (or pasmodics and pain medication. The second kidney) to clear myoglobin related to the problem with stents, and especially nephros- trauma. Hydration is perhaps the single best tomy tubes, is that they are easy to dislodge and way to prevent obstruction by clots, debris, difficult to replace. Extreme care must be used or encrustation while affording an adequate when changing dressings or otherwise manipu- glomerular filtration rate to assure continued lating these devices. renal function. A good rule of thumb is to main- 180 J.D. Polk, C.J. Yowler, and W.F. Fallon, Jr.

Figure 13.3. Major and minor renal injuries. Minor surgical intervention (used with permission from injuries (A and B) can be managed without surgery, Blaisdell FW, Trunkey PD, eds. Abdominal Trauma. whereas major injuries (C through F) usually require New York: Theime-Stratton; 1982).

tain a urine output of between 50 and 100 should be irrigation of the catheter because cc/hour in a 24-hour period. This may reduce debris, blood, or mucous may have clogged the the need for continuous irrigation, assures the tubing. patient is adequately hydrated, and is evidence For patients with stents, aeromedical crews of continued renal function. However, the ﬁrst should make sure they have adequate pain diagnostic step for decreased urinary output medication and antispasmodics (Table 13.2). 13. Abdominal Wounds, Urogenital Trauma, and Soft-Tissue Injuries 181

Table 13.2. Supplies needed for in-flight care of injury, while associated vascular and orthope- urogenital casualties. dic injuries are discussed in those respective Ditropan chapters. Management of soft-tissue injury is Saline irrigation divided into immediate care at the trauma Toomey syringes scene and subsequent care during poststabi- Toradol 60mg (intravenous or intramuscular use) lization evacuation. Spare Foley catheter of same and one smaller size Intravenous fluids (saline or lactated ringers) Viscous lidocaine Immediate Care at the Trauma Scene Neosporin or suitable lubricating antibiotic ointment Ciprofloxacin or other suitable broad-spectrum antibiotic The immediate threats to life following a trau- with Escherichia coli coverage matic injury are in the areas of airway, breathing, and circulation. Unless a soft-tissue injury is the source of major blood loss, it should be addressed as part of the secondary survey. If Care should be taken with nephrostomy tubes ongoing extremity hemorrhage is contributing to ensure both patency and security because to hemorrhagic shock, it is best controlled by they are difficult to replace if dislodged and a properly placed compression dressing. This have a propensity toward obstruction. An unse- dressing should consist of a cotton trauma cured tube should be resutured prior to AE. dressing that is firmly wrapped with elastic For patients with bladder injuries, the crew compression gauze. It is important to realize should assure that the suprapubic or urethral that excessive gauze can decrease the pressure catheter is ≥24 French so that clots can be irri- on the site of hemorrhage and hide the blood gated from the bladder. Adequate irrigation loss from the evaluating physician. fluid and syringes should be on-hand to manage If a pressure dressing does not stop the an occluded catheter. A spare catheter should bleeding, the other treatment possibilities in- be available in case of persistent occlusion or clude a tourniquet, wound exploration, and vas- dislodgment. Antispasmodics may be required cular clamping. A tourniquet is rarely required for bladder spasm as well. except for complete amputations that cannot Foley catheters present special challenges. be controlled by a pressure dressing. There First, an air-filled balloon may expand and is no rote for wound exploration and direct rupture at altitude. For this reason, air should clamping except for an amputated extremity. be replaced with water or saline in all cases. For Vascular clamping in the field invariably catheterized men, antibiotic ointment should results in crushing of the neurovascular bundle be used to moisten the meatus to prevent fric- and the resultant nerve injury may be more tion between the catheter and urethra. The damaging to the limb than the vascular injury. foreskin of uncircumcised males must be re- Direct compression is the modality of choice placed after catheter insertion to prevent para- for bleeding control and vascular injury. Rarely, phimosis. a mangled extremity (such as a landmine Finally, contaminated wounds that have not injury) will require a temporary tourniquet. been closed primarily must be monitored This patient should be treated as a priority for closely for signs of infection. These patients are evacuation so that a formal operative wound at increased risk of abscess and sepsis and are exploration can be performed for vascular usually on broad-spectrum antibiotics. control. After hemorrhage has been controlled, the extremity should be stabilized. Motion in- Soft-Tissue Wounds creases bleeding and may compound any preexisting vascular or nerve injury, especially in Soft-tissue injury refers to damage to the skin, the presence of bone fracture. The limb may be subcutaneous fat, and muscular tissue of the secured to the backboard used for evacuation extremity or truncal wall. This section will out- or splinted temporarily in the field. After stabi- line management guidelines for soft-tissue lizing the limb, distal pulses must be checked 182 J.D. Polk, C.J. Yowler, and W.F. Fallon, Jr. to ensure adequate circulation. If pulses are and spread by the cavitating effect of the pro- absent, the splint should be inspected and any jectile as it traverses the soft tissue. The pres- binding that may be acting as a tourniquet ence of soil in a wound decreases the absolute should be adjusted. During MEDEVAC or AE, number of bacteria required for an infection. these patients should be placed in litter posi- Soil has been shown in animal models to: (1) tions that minimize trauma to the injured part interfere with normal leukocyte phagocytosis, and give maximum accessibility for in-flight (2) impair nonspecific bactericidal activity in care. serum, and (3) possibly inactivate antibiotics.19 If these stabilized patients are to be evacu- Specific organisms present at the time of injury ated long distances (eg, transoceanic AE mis- also influence the nature of any resultant infec- sions), broad-spectrum antibiotics should be tion. The heavily manured fields of Flanders in administered prior to and during the flight. World War I gave rise to infections far different A first-generation cephalosporin is sufficient from those seen today in modern urban trauma for most soft-tissue injuries. Extensively soiled centers. This effect of the local microbiology wounds or crush injuries may benefit from the plays a major role in the virulence of any addition of antibiotics with Gram-negative wound infection. anaerobic coverage. The key to infection pre- Delay in initial debridement will result in vention, however, remains rapid MEDEVAC increased wound infection rates. The initial to a medical facility where definitive wound hematoma and devitalized tissue provides the debridement and washout can be done. media for bacterial growth while the compro- Myoglobinuria may complicate crushing mised local circulation and resultant hypoxia soft-tissue injury. In the field, it will manifest as inhibits any host response. Unfortunately, delay pigmented urine, which varies in appearance in immediate MEDEVAC may be unavoidable from grossly blood-like to the color of tea. and patients entering the AE chain may be at Intravenous solutions should be administered increased risks for infection. to maintain a urine output of >100 to 150 Prior to antibiotics, soft-tissue wound debri- mL/hour. Administration of adjuvants, such as dement involved radical debridement of all mannitol and bicarbonate, should be deferred potentially contaminated tissue. The resultant until a medical facility is reached because deformity and disability may have been accept- administration of mannitol to an acutely hypo- able in the pre–anti-biotic era, where most volemic trauma victim may result in further wound infections would be fatal, but is an fluid loss and hypotension. unacceptable outcome with modern surgical therapy. Serial wound explorations and debri- Implications for AE dement with appropriate antibiotic coverage is the current standard of care. In this manner, the Following resuscitation and operative debride- maximum amount of soft tissue is preserved ment of a soft-tissue injury, the patient may and the resulting muscular dysfunction mini- require urgent or contingency AE. After initial mized. However, stabilized patients must often surgical treatment of soft-tissue injury,infection be evacuated in the midst of this staged surgi- and sepsis are the primary complications. The cal therapy, and any delay during the evacua- risk of infection is increased by several vari- tion process will increase the risk of infectious ables: (1) initial contamination of the wound, complications. (2) a large bacterial burden in the wound, (3) Thus, the flight crew taking care of patients initial delay in debridement, and (4) inadequate during the urgent or contingency AE must be debridement. sensitive to the early signs and symptoms High-velocity wounds (military or hunting of wound infection, including fever, chills, rifles) and wounds associated with high-energy increased thirst, decreased urine output, rela- transfers (landmines, shotguns) are associated tive hypotension, increasing agitation or confu- with increased amounts of devitalized tissue sion, and change in drainage from the wound. and penetration of contaminants. Clothing and Patients developing evidence of wound infec- soil may be carried deep into the wound tract tions should be diverted to a medical facility 13. Abdominal Wounds, Urogenital Trauma, and Soft-Tissue Injuries 183 for prompt surgical consultation. A delay in 5. Blaisdell FW. Medical advances during the Civil prompt surgical intervention may result in a War. Arch Surg 1988;123:1045–1050. necrotizing infection and possibly the loss of 6. Holt DM, Greiner JM, Coryell JL, Smither JR, limb or life. eds. A Surgeon’s Civil War. Kent, Ohio: The Kent State University Press; 1994. 7. Whelan TJ. Surgical lessons learned in the care Conclusion of the wounded. Med Bull US Army Eur 1981; 38:4–12. 8. Crile GW, Rowland AF, eds. Notes on Military In addition to knowing what injuries their pa- Surgery. Cleveland, Ohio: The William Feather tients have sustained, the aeromedical transport Co; 1924. crew must also know what therapies have been 9. DeMuth WE. Bullet velocity and design rendered in an attempt to stabilize the patient. as determinants of wounding capability: An This is in particular true in the trauma patient. experimental study. J Trauma 1965;6:222–231. The crew must understand modern techniques 10. Fackler ML, Bellamy RF, Malinowski JA. for surgical correction because they are likely The wound profile: Illustration of the missile– to impact therapies needed for aeromedical tissue interaction. J Trauma 1988;28(suppl): transport. The evolution of aeromedical trans- S21–S29. port has allowed surgical facilities and definitive 11. Fackler ML, Bellamy RF, Malinowski JA. A care to be moved farther from the front. In reconsideration of the wounding mechanism of very high velocity projectiles: Importance essence, advances in aeromedical transport and of projectile shape. J Trauma 1988;28(suppl): surgical techniques have extended the reach of S63–S67. advanced medical care from the tertiary-care 12. Mendelson JA. The relationship between centers to the field. This has placed a greater mechanisms of wounding and principles of burden on the flight crew to be skilled and adept treatment of missile wounds. J Trauma 1991;31: at critical care. Treatments and modalities 1181–1202. previously rendered in hospitals are now 13. Erichsen J. The Science and Art of Surgery. routine for in-flight care. Patients previously Philadelphia: Blanchard and Lea; 1859. thought to be unstable for transport are pushing 14. Fackler ML. Misinterpretations concerning the envelope and boundaries of conventional Larrey’s methods of wound treatment. Surg care, and military budget restraints are not Gynecol Obstet 1989;168:280–282. 15. Wangersteen OH, Wangersteen SD. The Rise of allowing the massive medical units of the past. Surgery. Minneapolis: University of Minneapolis This is necessitating aeromedical crews to Press; 1978. provide care farther, faster, and to more critical 16. Fackler ML, Dougherty PJ. Theodore Kocher patients than they have ever done before. and the scientific foundation of ballistics. Surg Gynecol Obstet 1991;172:153–160. References 17. Carey ME. Analysis of wounds incurred by U.S. Army Seventh Corps personnel treated in corps 1. Fallon WF. Surgical lessons learned on the bat- hospitals during Operation Desert Storm, Feb. tlefield. J Trauma 1997;43:209–213. 20 to March 10th, 1991. J Trauma 1996;40(suppl): 2. Rich NM. Surgeon’s response to battlefield S165–S169. trauma. Am J Surg 1993;166:91–96. 18. Fallon WF. The present role of colostomy in the 3. Hardaway RM. Care of the wounded of the management of trauma. Dis Colon Rectum United States Army from 1775 to 1991. Surg 1992; 35:1094–1102. Gynecol Obstet 1992;175:74–88. 19. Haury BB, Rodeheaver GT,Pettry GT,Edgerton 4. Greisman HC. Wound management and medical MT, Edlich RF. Inhibition of nonspecific de- organization in the Civil War. Surg Clin North fenses by soil infection-potentiating factors. Surg Am 1984;64:625–638. Gynecol Obstet 1977;144:19–24. 14 Air Evacuation of the Neurosurgical Patient

Mick J. Perez-Cruet and Rose Leary

The Air Evacuation System was first used in Initial Evaluation of the World War I by the USA Air Corps and was organized into a military patient airomedical Head Injury Patient evacuation (AE) system during the Korean conflict. Rapid transport by air with effective Once the patient’s airway is secured and they medical care en route has markedly changed are hemodynamically stable, an initial neuro- the way in which head- and spine-injured pa- logical assessment should be performed. The tients can be managed and transported from Glasgow Coma Scale8 (GCS) is the most widely the field to facilities that offer definitive neuro- used and accepted method by which the phy- surgical care. In many metropolitan areas, heli- sician and ancillary health-care personnel copter transportation of patients with blunt can rapidly assess the neurological status of a or penetrating head trauma and spinal injury trauma patient (Table 14.1). For an accurate has become routine.1–3 Many studies have GCS score, no paralytics, sedatives, or other shown the benefits of rapid AE of critically ill medications that may blunt the patient’s ability patients.4–7 to respond should be administered. The exam Currently, the US military operates a state- can be performed quickly and communicates of-the-art system for transporting personnel vital information relative to the severity of injured in the field to air transportable hos- the head injury to personnel at the receiving pitals (ATKs) or regional hospital facilities medical facility. The GCS is comprised of three for large-scale military operations. Due to the parts: the best eye opening, verbal, and motor increasing frequency of contingency opera- evaluation with a maximum combined point tions (eg, “military operations other than score of 15 and a minimum of 3. In general, mild war”; MOOTW), a system is being developed head injury patients have a GCS of 13 to 15; whereby critically injured patients are trans- moderate head injured patients a score of 9 ported long distances relatively soon after their to 12; and severe head-injured patients have injuries, often before they have received defin- scores of 8 or less. itive care. One result has been an increased The eye assessment determines whether the need for long-range transportation of critically patient is able to open his eyes spontaneously ill neurosurgical patients. In response, the US (4 points), to voice (3 points), to pain (2 points), military medical system is developing new or unable to open eyes (1 point). Verbal evalua- standards for managing these critically injured tion determines whether the patient is oriented patients in-flight while en route to definitive (5 points), confused (4 points), inappropriately care facilities. This chapter will cover initial verbal (3 points), incomprehensibly verbal evaluation, stabilization, and in-flight manage- (2 points), and nonverbal (1 point). The letter ment of the neurosurgical patient with intra- “T” after the verbal score indicates the patient cranial and/or spinal injury. is intubated. The best motor response deter-

184 14. Air Evacuation of the Neurosurgical Patient 185

Table 14.1. GCS scoring system. Severity Characteristic Response level Score The GCS has been developed to provide objec- Eye opening Spontaneous 4 tive uniformity to the evaluation of the head- To verbal command 3 injured patient. Those patients suffering from To pain 2 mild, moderate, and severe head injury have No response 1 Best motor Obeys verbal command 6 GCS scores of 13 to 15, 9 to 12, and 8 or less, response Localizes pain 5 respectively. In patients with severe head injury Flexion withdrawal to pain 4 (GCS score of 8 or less), 90% were found to be Flexion abnormal to pain 3 in a coma (ie, unable to obey commands, utter (Decorticate) words, or open their eyes).8, 12 Extension to pain response 2 (Decerebrate response) No response to pain 1 Mechanism Best verbal Oriented, converses 5 response Disoriented, converses 4 Head injury occurs by two basic mechanisms: Inappropriate words 3 blunt or penetrating trauma. Examples of blunt Incomprehensible sounds 2 trauma include motor vehicle accidents where No response 1 the head hits the windshield or a blunt object such as a baseball bat hits the head. Penetrat- ing trauma results when a projectile enters the cranium, such as a bullet or knife. The primary distinction between the two is the presence or absence of dural penetration. mines whether the patient is able to obey commands (6 points), localize to pain (5 points), Morphology withdraw to pain (4 points), decorticate flexion When classifying injuries by morphology, the (3 points), decerebrate extension (2 points), two broad categories are skull fractures and and has no response (1 point). It is important intracranial lesions.11 to recognize both decorticate flexion and decerebrate extension responses as these imply significant and severe head injury. The pupillary Specific Types of Head Injuries exam is extremely valuable as it can provide Skull Fractures information as to the existance of an intracerebral hematoma and impending brain hernia- Skull fractures may be linear or stellate, tion. The examination should be performed depressed or nondepressed, and open or closed. with a pen- or flashlight shined directly into Clinical signs that may indicate a skull fracture the eye to evaluate the size and reactivity of include targe scalp abrasions or stellate lacera- the pupil. A unilateral dilated pupil can be the tions. Scalp lacerations should be attended result of a mass lesion within the brain, such to promptly with irrigation, debridement, and as an epidural or subdural hematoma, which closure because significant blood loss can can result in irreversible brain damage and occur. At the least, the patient’s head should death without rapid medical and surgical be wrapped to prevent excessive blood loss. intervention. Gentle palpation of these areas with a gloved hand may reveal a bony step-off, or bone Classification of Head Injury fragmentation. Battle’s sign (redness/bruising behind the ear) or raccoon’s eyes (bruising Head injury can be classified by three methods: around the eyes) can indicate a basilar skull severity, mechanism, and morphology. There fracture. Other signs may include clear cere- is no universally accepted guideline; how- brospinal fluid (CSF) leaking from the ears ever, this approach has proven useful in the or nose or VII nerve palsy. Head computed diagnosis and management of head-injured tomography (CT) with bone windows clearly patients.9–11 demonstrates skull fractures (Fig 14.1). In 186 M.J. Perez-Cruet and R. Leary

Figure 14.1. Bone-windowed axial head CT showing depressed skull fracture. Note the inner table of the skull is below the outer table.

Figure 14.2. Axial head CT showing right-sided frontal epidural hematoma. general, these fractures are repaired surgically if they are open, to reduce the risks of meningitis, or when the outer table of the skull is below the inner table of the skull on imaging injuries; however, early recognition and evacu- studies.11 ation of the clot is important because outcome Skull fractures can also be associated with has been found to directly correlate with the an intracranial lesion such as a hematoma or clinical status of the patient before surgery. contusion. Intracranial lesions can be further Mortality increases from 0%, to 9%, to 20% for classiﬁed as focal or diffuse. Focal lesions patients not in coma, obtunded, and in deep include epidural and subdural hematomas, coma before surgery, respectively.13 Optimal intracerebral hematomas, and contusions. Dif- diagnosis and treatment within a few hours fuse lesions include diffuse axonal injury (DAI), decreases overall mortality rates of 20% to mild concussion, and classic concussion.11 55% to 5% to 10%.14

Epidural hematoma Subdural Hematoma An epidural hematoma is a blood clot located A subdural hematoma is a blood clot that between the dura (the covering of the brain) occurs between the dura and the brain, and and the undersurface of the skull, and has a these have a convex appearance on CT (Fig lenticular shape because the clot is pushing the 14.3). They are more common than epidural dura away from the undersurface of the skull hematomas, occurring in 30% of head-injured (Fig 14.2). It is usually the result of a skull frac- patients. This injury is frequently caused by ture and tearing of the middle meningeal artery, shearing of the bridging veins between the which runs on the inner surface of the skull, but draining sinuses and brain or lacerations of the venous bleeding can also cause an epidural brain surface. In many series, mortality is about hematoma. The patient may present with a 60% and there is usually associated underlying “lucent interval” after which the patient may brain damage. Rapid administration of medi- lapse into a coma.11 These injuries are un- cations to reduce intracranial pressure (ICP), common, representing less than 1% of head such as mannitol, and expedient evacuation of 14. Air Evacuation of the Neurosurgical Patient 187

temporal poles of the brain, where during rapid deceleration, such has after the head hits a windshield, the brain is pushed up against the skull. Over a period of hours to days, these can evolve to intracerebral hematomas causing mass effect, increased ICP, and require surgical evacuation.15 The distinction between a contusion and intracerebral hematoma is not always clear, as contusions can evolve and enlarge to form an intracerebral hematoma.11

Diffuse Axonal Injury (DAI) DAI is felt to be a result of the shearing of axons during a rapid deceleration of the brain. It is the most common injury seen in head- injured patients. This term describes prolonged posttraumatic coma that is not due to mass lesions or ischemic insults. Patients with severe DAI, which comprises 36% of all head-injured patients, often present after motor vehicle accidents with decorticate or decerebrate posturing and often remaining severely disabled if they survive.13 CT imaging may reveal small punc- Figure 14.3. Axial head CT showing right-sided tate contusions throughout the brain and mag- subdural hematoma. Note the shift in ventricles from netic resonance imaging (MRI) may show right to left. white matter changes, in particular in the corpus callosum. Distinguishing between DAI

11 and hypoxic brain injury is not easy in the the blood clot are the hallmarks of treatment. clinical setting, and the two may coexist.11 It was found in a series of 82 patients with acute subdural hematoma that patients operated on within 4 hours had a 30% mortality compared to 90% mortality if surgery was delayed more than 4 hours (“4-hour rule”).7 Therefore, rapid air evacuation of these patients is critical.

Intracerebral Hematoma Intracerebral hematomas are blood clots within the brain substance (Fig 14.4). They can cause signiﬁcant mass effect requiring evacuation, in particular when located near the brain stem in the temporal lobe.11

Contusions Contusions are frequently seen in head-injured patients and can be envisioned as “bruises” of the brain. They have the appearance of a “salt and pepper” pattern on head CT and are not as dense as intracerebral hematomas (Fig 14.5). Figure 14.4. Axial head CT showing left temporal They most commonly occur in the frontal or hematoma. Note the compression of the brain stem. 188 M.J. Perez-Cruet and R. Leary

• Rapid transportation to health-care facility. • Optimizing patient’s hemodynamic status and oxygenation during transport.

Episodes of hypoxemia and hypovolemia must be avoided to improve outcomes of patients with head and/or spinal cord injury, and the sig- niﬁcance of secondary injury on the outcome of head-injured patients has been well documented.16–28 Toward this end, specially trained personnel with appropriate equipment are required for the safe AE of patients with acute brain and spinal cord injuries (Table 14.2). An analysis of outcomes from severe head injury from the Traumatic Coma Data Bank revealed that mortality increases from 30% in patients without hypoxia and hypotension at admission to 60% with those who were hypotensive and 75% in those who suffered both insults.19

Figure 14.5. Axial head CT of right frontal contusion.

Table 14.2. Equipment required for AE of patients with acute brain and spinal cord injuries.

Avoiding Secondary Pulse oximeter Neurological Insults Face masks, nasal cannulas, endotracheal and tracheostomy tubes Upon Transport Ambu bags with appropriate adapters for endotracheal and tracheostomy tubes Primary injury to the brain occurs at the time Laryngoscope and oropharyngeal blades of impact and pertains to direct damage by Surgical kit to perform cricothyroidotomy or tracheostomy trauma to the skull, brain, and surround- Suction apparatus and cannulas ing tissues. Secondary injury occurs after the Firm cervical collars of various sizes, halo vests primary injury and includes the development of Sandbags or other means to immobilize the neck, cerebral edema or brain swelling, intracranial backboard hemorrhage, such as an epidural or subdural Appropriate traction devices without weights (eg, cervical halters) hematoma, and intracerebral brain hemor- Turning bed (eg, Stryker frame) or improvised from two rhage. Hypoxemia and ischemia can be due stretchers to increased ICP and/or shock.15 Although me- Padding for pressure points dical personnel have no control over the ICP monitoring equipment primary injury,they can help to reduce the dele- Fluids and drugs Mannitol, lasix terious effects of secondary injury. To reduce Sublingual nifedipine or nitroglycerin the harm caused by secondary injury, the fol- Dilantin, ativan, phenobarbital lowing principles should be followed: Methylprednisolone Fentanyl, morphine, pancuronium • Rapid stabilization of airway, breathing, and Antibiotics circulation (ABCs of the Advanced Trauma Pressors (ie, dopamine) Life Support [ATLS] protocol). Cystalloid IV Fluid • Spinal stabilization with use of cervical collar Collord IV Fluid Blood Products and backboard. 14. Air Evacuation of the Neurosurgical Patient 189

Hypoxia Increased ICP worsens outcome by two common mechanisms: decreased cerebral perfusion Maintenance of the airway is the single most pressure (CPP) and brain herniation. CPP is important management requirement in the un- the difference between mean arterial blood conscious patient. The most life-threatening pressure (MAP) and ICP and represents the aspect of unconsciousness is the loss of normal force pulsing blood through the brain (CPP = swallowing mechanisms, resulting in the inabil- MAP - ICP). Normally, cerebral perfusion ity to handle oropharyngeal secretions and pressure is approximately 70 to 90mmHg. If it keep the upper airway clear. In unconscious falls to less than 60mmHg, brain energy mech- patients, unrecognized hypoxia or anoxia may anisms begin to fail and neural cellular homeo- result in severe, permanent brain dysfunction static mechanisms deteriorate. When it falls to or death. Hypoxia and hypercarbia induce 0, blood flow to the brain ceases, resulting in vasodilatation of blood vessels, which results global ischemia and death. Although there are in increased cerebral blood volume, increased 16 not set guidelines, attempts should be made to ICP, and, potentially, cerebral herniation. maintain the CPP above 70mmHg.38 This can be performed by increasing the MAP with Hypotension fluids or vasopressors or by decreasing the ICP. Intracranial hypertension, if left untreated, Hypotension following brain trauma is another can have two effects on the injured brain: her- potentially avoidable cause of secondary brain niation and ischemia. Management of elevated injury. Every effort should be made to maintain ICP should begin early in the triage stages of normotensive blood pressure levels in brain- resuscitation, as it is a significant contributing injured patients. Cerebral autoregulation is im- factor to irreversible brain injury. paired after a head injury, resulting in cerebral hypoperfusion when systemic hypotension is Recognizing Increased ICP present.16 When brain injury is accompanied by systemic injury, mortality is doubled. The Herniation Syndrome effect of visceral or lower-extremity injury on Increased ICP, most commonly from either mortality was found to result from hypovolemic cerebral edema or a brain hemorrhage, may 20 hypoperfusion. On occasion, the scalp is a cause herniation of brain tissue out of its potential cause of hypovolemia, as it is a very normal position in the cranium. The two most vascular structure. Lacerations should be common types are temporal lobe and tonsil- inspected, cleaned, and closed to prevent blood lar herniation. Temporal lobe herniation, if loss, as these can be a potential cause of hypo- unchecked, may permanently damage the brain volemia. This is especially important if the AE stem, leading to death or permanent coma. Uni- is expected to take hours. lateral pupil dilation (ie, a “blown pupil”), caused by compression of the third nerve, may Increased ICP be the first indication of temporal lobe dis- placement. Tonsillar herniation compresses the There is a close relationship between increased medulla in which resphatory centers are con- ICP and brain damage from head injury.9,29–36 tained, thus causing death by inhibiting respi- Increased ICP can result from a number of ratory drive. causes: expanding intracerebral hemorrhage, Acute unilateral or bilateral pupillary dila- cerebral edema, poor venous drainage, and/or tion in a patient with brain injury is a neuro- hydrocephalus. Normally, the ICP within the surgical emergency. The most widely accepted cranial vault is less than 20mmHg. Because the theory for the cause of the pupillary dilation is skull acts like a solid box with a fixed volume, that an intracranial mass lesion (eg, hematoma a mass lesion within the brain can cause a rapid or tumor) compresses the third cranial nerve as increase in the pressure within the skull. Sus- the uncus is herniated downward and medially. tained ICP elevations of >50mmHg are associ- Continued compression of the medial tempo- ated with a mortality rate approaching 100%.37 ral lobe into the brain stem results in loss of 190 M.J. Perez-Cruet and R. Leary

Figure 14.6. Codman intraventricular ICP monitor.

consciousness, decerebrate posturing, and car- whether the pressure inside the head is ele- diovascular collapse. More recent data suggests vated is by placing an ICP monitor. ICP moni- that pupillary dilation is actually the result of toring is not routinely indicated in patients compromised brain stem circulation.33 with mild or moderate head injury. The most Changes in blood pressure, pulse, and respi- common devices used are the ventriculostomy ratory rates may also indicate elevated ICP. A catheter and intracranial parenchymal monitor. Cushing’s triad can be seen with an increased The ventriculostomy is a small catheter that can ICP and includes hypertension, bradycardia, be passed through the brain with the tip lodging and respiratory irregularity. Another early sign inside the ventricle of the brain (Fig 14.6). The of increased ICP is a change in respiratory advantage of this type of monitor is that it not pattern. The most common change in breathing only measures ICP but can also be used to treat can be confused with snoring. Because a clear increased ICP by draining CSF into a drainage airway and satisfactory oxygen exchange are system (Fig 14.7). The second type of monitor paramount for brain function, patients should is placed directly into the brain substance just always be given supplemental oxygen and intu- under the dura (Fig 14.8). The advantage to this bated if they are unable to protect their airway. monitor is that it is relatively easy to place, requiring only a small hole in the skull and tun- neling the catheter under the scalp. However, ICP Monitoring no CSF can be drained and therefore its use is The indications for placing an ICP monitor purely for monitoring purposes. ICP monitors include severe head injury (GCS score of 3 to should only be placed by experienced medical 8) when the patient is not following commands personnel because their placement, if not with an abnormal CT scan, or a normal CT scan performed properly, can result in serious or and age over 40 years, unilateral or bilateral life-threatening complications. However, once motor posturing, and systolic blood pressure placed these devices can be transported with <90mmHg. In this setting, the only way to tell the patient to help record and manage ICP. 14. Air Evacuation of the Neurosurgical Patient 191

Figure 14.8. Codman intraparenchymal ICP monitor.

improve outcomes in patients suffering severe head injuries. Figure 14.7. CSF drainage bag for intraventricular ICP monitor. Elevate Head of Bed One of the easiest methods of reducing ICP is to elevate the head of the bed. This improves Patients should receive intravenous (IV) anti- the jugular venous drainage of the brain and biotics such as a third-generation cephatos- thereby cerebral blood flow. The head should porin while the ICP monitor is in place. be raised approximately 30° and kept straight in the midline. Management of Increased ICP Hyperventilation Increased ICP can be treated by various means. However, before trying to treat increased ICP Hyperventilation reduces ICP by causing cere- it is important that mass lesions such as bral vasoconstriction and subsequent reduction intracranial hemorrhage that may require sur- in cerebral blood flow39; however, because of gical evacuation are ruled out. A CT examina- this there is an increased risk of causing cere- tion should be performed on patients with a bral ischemia with aggressive hyperventila- history of loss of consciousness and certainly in tion.40 Because of the risk of ischemic injury any patient with a severe head injury. It with hyperventilation, the current recommen- is important to understand that a head CT dation is to avoid chronic prolonged hype- can suggest, but not definitively determine, if rventilation therapy (PaCO2 of 25mmHg or increased ICP does in fact exist. At present, less) after severe traumatic brain injury in the only invasive ICP monitors can determine if the absence of increased ICP. Nevertheless, hyper- ICP is actually elevated. Treatment of increased ventilation therapy may be necessary for brief ICP should be started at a threshold of 20 to periods when there is acute neurological dete- 25mmHg. Although head CT is not always rioration, such as on the way to the operative available for in-field use, appropriate medical suite to evacuate an intracranial hemorrhage. management can be instituted during AE to More prolonged use may be necessary in the 192 M.J. Perez-Cruet and R. Leary setting of increased ICP refractory to sedation, of brain metabolism, inhibition of free radical- paralysis, CSF drainage, and mannitol. mediated lipid metabolism, and alterations in vascular tone. The most important is likely the CSF Drainage lowering of cerebral metabolic requirements. A ventriculostomy drain can be helpful in man- Barbiturate therapy is usually used as a last aging increased ICP by allowing drainage of resort after other methods such as sedation, CSF while also providing a measurement of the paralysis, hyperventilation, CSF drainage, and ICP. It can provide continuous drainage of CSF mannitol have failed to bring the ICP below or intermittent drainage as needed by opening 20mmHg. Before initiating this therapy, other up a stopcock device (Fig 14.7). Continuous causes of increased ICP—such as an expanding draining is in general used in the setting where mass lesion—must be ruled out, usually with a hydrocephalus exists with the burritrol bag head CT. There are a number of therapeutic being arbitrarily set at about 15cm above the regimens that all require a loading dose fol- patient’s ear and left open to drainage. For lowed by a maintenance dose. Because pento- treating increased ICP, 10 to 15 drops of CSF barbitol can cause cardiac arrhythmias and can be emptied as needed every 15 minutes to hypotension, it is important that a Swan–Ganz maintain the ICP below 20mmHg. The reason catheter be inserted before initiating therapy. If to avoid overdrainage is that it could result in the patient becomes hypotensive, the therapy ventricular collapse around the catheter tip, must be stopped. A fairly easy regimen is the which could cause occlusion of the ventricu- following: lostomy or inaccurate ICP recordings. • Loading dose: 10mg/kg over 30 minutes; then 5mg/kg every hour for 3 hours. Mannitol • Maintenance dose: 1mg/kg per hour. Mannitol is an osmotic diuretic that is felt to The goal is to reduce the ICP below be beneficial to severe head-injured patients 20mmHg and maintain a burst suppression with increased ICP in a number of ways, includ- pattern on electroencephalography (EEG). ing the following: increases cerebral blood flow, increases cerebral oxygen delivery, reduces hematocrit, and reduces blood viscosity.41,42 Special Considerations Based on Acting as an osmotic agent, mannitol causes Level of Consciousness “opening” of the blood–brain barrier, which can contribute to cerebral edema; therefore, it The amount of care and the intensity of moni- should be administered as repeated boluses toring required for the patient with acute brain rather than continuous infusion.43 Mannitol injury during AE are determined by the should not be administered in the setting of low patient’s level of consciousness. In all cases, blood pressure because further loss of volume the patient will require close observation for may lead to hypotension. The initial bolus dose changes in mental status, which will require is 1g/kg body weight. Subsequent bolus usually frequent neurological assessments. Changes in range from 12.5 to 25g every 4 to 6 hours as mental status may indicate increased ICP. needed to keep the ICP below 20mmHg. Man- nitol is stopped if the serum osmolarity exceeds 320mOsm to prevent renal failure. Furosemide, Air Evacuation of Head a diuretic, can also be used to treat elevated Injured Patient ICP by reducing cerebral edema and CSF pro- Once a severe head injury has been identified, 44 duction. A Foley catheter is essential in these neurosurgical treatment should be a priority. patients. Institutions without this capability should establish early consultation with a neurosur- Pentobarbital Coma geon at a definitive care facility, and arrange- Barbiturates appear to lower ICP through a ments for transport should begin as soon as number of different mechanisms: suppression a severe traumatic brain injury has been iden- 14. Air Evacuation of the Neurosurgical Patient 193 tified. Transfer should not be delayed for un- IV fluid management is an important aspect necessary diagnostic procedures.45 of care for brain-injured patients, with the goal Hypoxia, hypercarbia, anemia, and hypoten- of achieving both normal intravascular volume sion contribute to secondary injury, and early and adequate cerebral perfusion. In general, for recognition and treatment of these problems acute severe head-injured patients a solution will result in the best outcome.46 The task of the of normal saline plus 20mEq KCI/L is given transport team is to recognize subtle changes at a maintenance dose rate. Dextrose is not from the time of initiation of transport to the added to the solution because elevated levels of time of arrival. The three most important mea- glucose in acute severe head-injured patients sures are level of consciousness, pupillary func- can cause further brain injury. Hyperglycemia tion, and motion of the extremities. A decrease aggravates cerebral edema54,55 and may be ex- in the GCS of two points between examinations acerbated by steroids.15 An important point is is usually an indicator of significant worsening that deliberate dehydration is no longer rein neurological status. Any pupillary asym- commended for patients with acute brain injury metry of over 1mm should be regarded as to decrease the risk of brain edema. Sufficient secondary to intracranial pathology until hydration is required to assure the primary proven otherwise. This is especially important treatment goal of adequate CPP. Toward this to remember if there is concomitant facial or end, urine output should be carefully moni- orbital injury. Lateralizing lesions often cause tored in critically ill patients with the aid of an asymmetry of pupillary response and may in-dwelling Foley catheter.15 manifest in decreased extremity motion on the If ICP monitoring is performed, the guideline opposite side.47 threshold is 20 to 25mmHg. Measures to lower Once aboard the aircraft, airway main- ICP should be instituted if the ICP goes above tenance becomes the most important aspect the threshold. Maintaining a CPP greater than of care for the brain-injured patient. Unless 70mmHg is given as a therapeutic option if ICP the patient is ambulatory and fully alert, sup- is elevated.38,56,57 Routine measures to lower plemental oxygen should be administered. ICP include elevating the head of the bed 30 to Patients with endotracheal tubes or tracheos- 45° to reduce edema by encouraging venous tomies should receive humidified oxygen and drainage. Keeping the head midline will pre- scheduled suctioning of secretions. Changes in vent kinking jugular veins, which could also mental status, such as unconsciousness or not impair venous drainage. Avoid hypotension following commands, have a significant risk of by normalizing intravascular volume and using increased ICP and require intubation. Stabi- pressor support if needed. lization of the airway may be difficult during Early recognition of posttraumatic seizures transport, so it may be wise to intubate early to can prevent secondary injury from hypoxia prevent hypoxia and hypercarbia.48 In many and increased ICP. In a pharmacologically cases, neuromuscular blockade and sedation paralyzed patient, the only indication may be can prevent hypoxia, hypercarbia, and ICP tachycardia, hypertension, or pupillary changes spikes associated with coughing and “fighting (which could be misinterpreted as brain stem the ventilator” during transport.49–51 It will also compression due to herniation).48, 58 Phenytoin help to avoid accidental self-extubation en is useful in preventing seizures in the acute route, a potentially disastrous scenario.49, 52 The posttraumatic period59 and a short-acting ben- possibility of cervical spine injury must always zodiazepine is a reasonable initial treatment for be kept in mind because certain airway maneu- seizures.48 vers may worsen a preexisting injury. Airway compromise from blood, secretions, or loss of Unique Problems of AE mandibular tone accounts for a large percentage of unnecessary morbidity and mortality in AE has effectively reduced the time to trans- patients with head injury and should be sus- port patients from the field to hospital facilities. pected immediately if there is deterioration in Nevertheless, questions arise from transport the patient’s status.48, 53 personnel and physicians regarding air medical 194 M.J. Perez-Cruet and R. Leary patient safety. The flight environment is phy- oxygen tension, potentially contributing to sically different,60,61 and these implications secondary injury in the head-injured patient. deserve consideration when transporting a Therefore, pulse oximetry and supplemental head-injured patient. oxygenation should be in place to prevent Acceleration and deceleration forces are cyanosis.65 Also, any reduction in hemoglobin important in aircraft transport, as well as in can impair oxygen transport and affect the ground vehicles. For the supine patient, the oxygen available to the brain. Even in a pres- landing and take-off forces are in the long axis surized cabin, reduced PO2 increases the poten- of the body and may become significant. tial to become hypoxic.66 Seizures may be During ascent, the acceleration vector and precipitated by even mild hypoxia in the sus- steep climb angle create a sustained reverse ceptible patient.62 Trendelenburg position.62 It has been suggested Barometric pressure decreases with increas- that patients be positioned with the head ing altitude. High rates of ascent are well toler- toward the front of an airplane to avoid blood ated, but rapid descent can cause expansion of pooling during accelerations and toward the gases in an enclosed air-filled body cavity.65 rear of the plane on landing. This is obviously Medical devices such as cuffed endotracheal not always practical, but consideration of this tubes, balloon bladder catheters, and aortic with adjustment of the patient’s positioning balloons can produce problems with fluctua- during these times can assist with management tions in gas volumes due to pressure changes.62 of ICP by head elevation. The pilot should be Damage to middle-ear structures, paranasal requested to avoid the increased gravitational sinuses, lungs, and the gastrointestinal tract and centrifugal forces that may cause deterio- are fortunately rare in a pressurized cabin or ration in an already compromised patient.48 an unpressurized aircraft at low altitude.65 Pressurized cabins are maintained by con- Intracranial air (pneumocephalus), usually trolling the flow of compressed air out of the minimal in head trauma, can expand and cause cabin to the atmosphere. This flow also controls neurological deterioration. Patients at particu- the thermal environment, so the control of lar risk include those having major sinus frac- pressure and temperature are closely related. tures or skull base fractures. Attempts should The absolute pressure in an aircraft cabin is be made to maintain the cabin altitude at the almost always stated in terms of pressure alti- ambient altitude of the point of origin.62 tude. The maximum altitude consistent with Vibration can be a problem, especially in the flight safety in an unpressurized cabin is 5000 to transfer of patients by helicopter. The preflight 7000ft. Some patients may be unable to main- assessment should take into account the effects tain full oxygenation of tissues above 6000ft. of vibration and consideration to minimize its Hypoxia can affect not only the patients but the effects on the head-injured patient. A patient aircrew as well. The maximum cabin altitude of lying on the floor of an aircraft is exposed to passenger and AE aircraft should be kept as more vibration than one on a hanging stretcher low as possible (below 6000ft). Cabin pressur- or lying on an air mattress, which attenuates the ization controls environmental changes due to vibrational forces.67 ascent and descent of the aircraft.63 Flying at lower altitudes can put the aircraft into bad weather and turbulence that can otherwise be Air Evacuation of Spinal Cord avoided by pressurized cabins. The USAF Injury Patients worldwide AE system currently restricts cabin altitude to 5500 to 6500ft to ensure patient General Principles safety with a minimum impact on flight planning.62 This empirical limit also correlates with Spinal immobilization of patients with sus- the British Royal Air Force Institute of Avia- pected spinal cord injuries is initiated at the tion Medicine.64 scene of the accident with external bracing. A In an unpressurized aircraft, breathing air at general inspection will indicate whether the high altitudes can cause a marked reduction in patient is moving his hands or legs if conscious. 14. Air Evacuation of the Neurosurgical Patient 195

Table 14.3. Pinprick localization of key derma- cord injury may result in neurogenic spinal tomes to localize level of spinal injury. shock resulting in compromised sympathetic Level Dermatome tone, causing a decline in peripheral vascular C4 Shoulder resistance. Clinical indications of spinal shock C6 Thumb may include flaccid extremities, absent anal C7 Middle finger tone, priaprism, and sensory loss.68 Unlike C8 Little finger patients who are hypotensive from blood loss, T4 Nipples patients in spinal shock may appear well T6 Xiphoid 68 T10 Umbilicus perfused, with pink, warm extremities. These L3 Anterior thigh patients should be treated with fluids and L4 Medial malleolus vasopressors. L5 Great toe S1 Lateral foot S4–5 Perianal Cervical Immobilization Devices Spinal immobilization devices provide rigid fixation to prevent flexion, extension, and rotation of the spine when applied properly. The Inspection of the patient’s neck or back may cervical collar is the most commonly used show areas of abrasions or bruising suspicious device for immobilization of suspected cervical for spinal injury. If the patient is able to talk spine injuries during transport (Fig 14.9). The and answer questions, a simple pinprick exam collar is applied so that the chin rests snuggly can indicate the level of spinal injury (Table above the level of the collar (Fig 14.10). On 14.3). Like head injury, maintaining an ade- short-necked persons, a small “short” collar has quate airway and circulation are paramount to been developed to prevent head rotation. Once preventing further neurological injury. If naso- in a cervical collar, the patient can be transtracheal or orotracheal intubation is necessary, ported properly secured on a backboard to head and cervical manipulation should be min- minimize movement of the spine. It is impor- imized by performing a jaw thrust maneuver tant to keep in mind that lying on a backboard as described in ATLS protocol. Severe spinal is extremely uncomfortable and can lead to sacral and scapular decubitus ulcer formation very quickly. Therefore, the backboard should be removed as soon as the patient is transferred to the definitive care facility or onto a stable stretcher. Once at the definitive care facility,the patient can be logrolled slowly off the backboard. This is done by having one individual at the head, another at the torso, and a third at the foot of the bed that supports the individual while the backboard is tilted and removed slowly. The patient is then slowly rolled in a logroll fashion onto the supine position. More rigid cervical fixation devices include the SOMI brace and halo immobilization (Fig 14.11). The halo comes with a ring that is secured with pins into the skull of the patient (Fig 14.l2). Before application of the halo, aseptic preparation of the pin site on the scalp needs to be performed and the skin anes- thetized with local anesthetic as the application of the head frame can be painful. Once the halo Figure 14.9. Cervical collar. is in place, adequate alignment of the spine 196 M.J. Perez-Cruet and R. Leary

A B Figure 14.10. Correct placement of cervical collar: anteroposterior (A) and lateral (B) views.

needs to be assessed with a lateral, and antero- and water or a dilute hydrogen peroxide posterior plain radiograph. The patient can solution. then be transported to a deﬁnitive care facility. Reduction of an unstable or displaced cer- Pin site care during transport includes washing vical spinal column injury (ie, cervical subluxa- the area two to three times per day with soap tion) can be performed with Gardner–Wells

A B

Figure 14.11. Halo vest: anteroposterior (A) and lateral (B) views. 14. Air Evacuation of the Neurosurgical Patient 197

A B

Figure 14.12. Correct placement of halo vest: anteroposterior (A) and lateral (B) views.

skull tongs and requires only local anesthesia neurological injury. If the patient reports any and aseptic preparation of the scalp (Fig 14.13). neurological deterioration, the weight must Initial radiographic evaluation, which can be be reduced or removed. The weight is added performed at an air transportable hospital slowly, up to a maximum of in general 5lb per equipped with plain radiographic imaging vertebral body level above the level of injury. modalities, would include anterior–posterior, Therefore a C5–6 subluxation may require up lateral, and odontoid cervical views. Patients to 25lb of weight to reduce. During the dis- with persistent neck pain and negative ante- traction period, the patient can be given muscle rior–posterior, lateral, and odontoid views relaxants such as diazepam (Valium), which would undergo flexion and extension lateral will help in the reduction process but must be views to rule out ligamentous instability. Cervi- administered judiciously because the drug can cal reduction should only be performed by an lead to overdistraction and neurological injury experienced physician, once adequate imaging in the oversedated patient. Even gaining one radiographs have been performed. Although it functional level with traction can result in a may be impractical to reduce a patient during significant improvement in rehabilitation po- AE, patients can be reduced, immobilized in a tential. To gain a functional level from C6 to C7 halo vest, and then transferred to a definitive often means the difference between being able care facility. Placement of Gardner–Wells skull to use a wheelchair and not. Once the cervical tongs is as follows: The pin insertion site is spine is reduced to its normal alignment, an located 1cm above the ear in-line with the external immobilization such as a halo can be tragus. The pins are tightened by hand until applied for transport. the spring-load pin indicator protrudes 1mm. The pins may need to be retightened after 24 Thoracic and Lumbar Spinal hours. The skull tongs are then attached to a Immobilization pulley system, which supports weight behind the patient’s head. Small increments, 5lb or less, The majority of spine fractures occur at the are added to avoid overdistraction and possible thoracolumbar junction, usually T12 to L1 198 M.J. Perez-Cruet and R. Leary

Figure 14.13. Gardner–Wells skull tongs (A) with a close-up view of the pins that are inserted into the scalp (B).

because this is a transition zone between • Loading dose: 30mg/kg over 15 minutes. the relatively stabilizing chest cavity and the • Forty-five minutes after initial dose: continu- lumbar spine. Most of these patients are ous infusion 5.4mg/kg per hour for 23 hours. without immediate neurological injury and can An H2 blocker should also be given concur- be initially managed with a thoracolumbar– rently to prevent gastric ulcers. For paraplegic sacral orthotic (TLSO). Patients can be trans- or quadriplegic patients, pneumatic compres- ferred in the TLSO brace to a hospital facility sion hose or TED hose stockings should be in where more definitive radiographic and surgi- place to prevent venous pooling in the legs, cal intervention can be performed. which could lead to deep venous thrombosis and life-threatening pulmonary embolus. Methylprednisolone Administration Patients with significant spinal cord injury Early administration of IV methylprednisolone will need placement of an in-dwelling Foley is indicated for spinal cord injury patients.69 catheter acutely. Long-term management To be effective, the steroid needs to be admin- usually involves intermittent catheterization. istered within 8 hours from the time of injury, An important consideration for the care of the dose being as follows: paraplegic and quadriplegic patients is the 14. Air Evacuation of the Neurosurgical Patient 199 prevention of decubitus ulcers. Patients with careful attention to keep their airways clear of spinal cord injury cannot feel the discomfort of secretions. prolonged pressure, nor are they able to move because of paralysis. The loss of cutaneous Autonomic Dysreflexia spinal cord innervation results in an increased risk of skin breakdown at pressure points in as Autonomic dysreflexia is a life-threatening little as 2 hours. The resulting decubitus ulcers complication of spinal cord injury that occurs may take weeks or months to heal and greatly in patients whose injury is above the T6 level. impair the rehabilitation of spinal cord-injured It is an exaggerated autonomic response that patients. Therefore, all pressure points, espe- can occur following a mildly noxious stimu- cially overlying bony prominences (ie, heals, lus.70,71 The greatest time of occurrence is after hips, elbows, etc.), should be carefully padded the resolution of spinal shock injury and results to avoid decubitus ulcers. The patient should be from a disconnected feedback loop between turned every 2 hours during the entire evacua- the sympathetic and parasympathetic branches tion process to check for and prevent decubitus of the autonomic nervous system. The result ulcer formation. is that any significant stimulation below In addition, spinal cord-injured patients are the level of injury (eg, distended bowel or prone to constipation; therefore, they should bladder) provokes an unopposed autonomic receive stool softeners or suppositories as response, resulting most commonly in paroxys- needed. Adequate blankets should also be pro- mal hypertension. Other symptoms include vided because autonomic temperature control anxiety, diaphoresis, piloerection, headache, may be impaired. A final consideration for tachycardia, and erythema of face and chest. If patients with acute spinal cord injuries is the untreated, autonomic dysreflexia can cause a increased risk of developing gastrointestinal cerebral hemorrhage, cardiac arrest, blindness, complications, including paralytic ileus, gastric or even death. Treatment includes removal of dilatation, the body cast syndrome, peptic the offending stimulus (ie, catheterize bladder ulcer disease, and pancreatitis. Because patients or assure that the Foley catheter is not kinked) sometimes cannot feel pain related to these and elevation of the head of the bed (to problems, the presence of intra-abdominal decrease ICP). Antihypertensive drug therapy problems should be suspected in patients with can include sublingual nifedipine, hydralazine, other symptoms, including signs of autonomic or nitroprusside.72,73 dysreflexia, increased pulse rate, and shoulder pain. Conclusion Preparation for AE Patients with brain and spinal cord injuries can All patients with acute spinal cord injuries be air evacuated safely and effectively acutely should be thoroughly prepared for AE. This and after definitive neurosurgical care. An will usually include placement of an IV line for accurate evaluation of the patient’s neurologi- hydration, a Foley catheter into the bladder, cal condition, acute stabilization, and in- and a nasogastric tube because of the paralytic transport medical management during AE can ileus that often complicates this condition. help improve patient outcomes and reduce secondary brain and spinal cord injury. In-Flight Care Airway maintenance remains the highest prior- References ity for patients being transported after spinal 1. Hubschmann O, Shapiro K, Baden M, Schulman cord injury. Patients with high cervical lesions K. Craniocerebral gunshot injuries in civilian may often have some degree of respiratory practice—prognostic criteria and surgical man- compromise and may need to be intub- agement: Experience with 82 cases. J Trauma ated prior to AE. These patients will need 1979;19:6–12. 200 M.J. Perez-Cruet and R. Leary

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David G. Schall and John R. Bennett

Otolaryngology has had a long and close rela- performing the Valsalva maneuver. Passengers tionship with aviation. The environment of with upper-respiratory infections should avoid flight posed many physiological challenges that flying because their edematous Eustachian were noted with the earliest human flights. The tubes and mucus membranes put them at first ear block was described by J.A.C. Charles increased risk for both ear and sinus in 1783 when he experienced sharp ear pain barotrauma. upon descent in a balloon. A decade later, The Valsalva maneuver is performed by Benjamin Rush noted problems with epistaxis occluding both nares and exhaling against a in a French balloonist.1 The first physician closed mouth, thus forcing air into the assigned as a “Flight Surgeon” to the US Army nasopharynx to open the Eustachian tubes.2 Signal Corps (1917) was an otolaryngologist If this is unsuccessful and the difference from Philadelphia by the name of Robert J. between ambient pressure and middle-ear pres- Hunter.2 This close relationship has continued sure becomes ≥90mmHg, the Eustachian tube to this day. This chapter will begin with a dis- may become “locked” shut. If this pressure cussion of specific otolaryngologic problems of differential cannot be relieved, pressures flight. Next, it will address the aeromedical inside the middle ear may range from 100 to evacuation (AE) concerns regarding the move- 500mmHg and result in the rupture of the ment of patients who have relevant otolaryn- tympanic membrane.3 gologic diseases, sustained trauma to the head Ear pain, presumably related to a locked and neck, and undergone recent otolaryngo- Eustachian tube, can be experienced upon logic surgery. descent by >20% of adult air passengers and >50% of children.4 In this Danish study, 46% of adults and 33% of children who experienced Otolaryngologic Problems pain were able to clear their ears using the Associated with Flight Valsalva maneuver.A majority of the remaining adults and children who were unable to clear Middle-Ear Barotrauma their ears were found to have signs of barotrauma (eg, tympanic membrane redness, The most common otolaryngologic symptom retraction, clear fluid in the middle ear, or associated with flight is the “ear block.” During hemotympanum), but none had ruptured ascent, most passengers do not experience eardrums. problems as gas expansion in the middle ear The risk of middle-ear barotrauma can be forces open the normally closed Eustachian minimized through early and frequent attempts tube, thus releasing pressure. Upon descent, at ventilating the middle ear (eg, Valsalva however, the Eustachian tube must be actively maneuver, chewing gum, etc.) and the use of opened by chewing, swallowing, yawning, or topical nasal decongestants prior to the flight

203 204 D.G. Schall and J.R. Bennett and in anticipation of descent. Toward this end, repeated flying can delay closure of the perfo- sleeping passengers should be awakened before ration. The patient should not fly until the ear descent. Symptoms can also be controlled by has returned to normal, which may take several returning the aircraft to an altitude above the weeks or more. point at which symptoms developed, although Alternobaric vertigo is another form of this is rarely practical in large commercial air- middle-ear barotrauma that results in vertigo craft. Descent can then be attempted again at thought to be induced by unequal pressure a slower rate while the person continues to between the left and right middle ear. The equalize the pressure in the middle ear. vertigo is self-limiting and resolves with clear- Treatment of middle-ear barotitis includes ing of the pressure differential.5 Obviously, this topical nasal and systemic decongestants. In can have disasterous consequences if it occurs severe cases, a Politzer bag can be used to apply in pilots while they are taking off or landing an pressure to the nasopharynx (Fig 15.l). To use aircraft. this device, the mouth is closed along with one nostrill, the Politzer tip is placed in the other Inner-Ear Barotrauma nostril, and the patient is instructed to swallow while pressure is applied with the bag. Inner-ear barotrauma can occur from air travel, Perforation of the tympanic membrane nose-blowing, diving, or any other phenomena related to barotrauma will usually heal sponta- that can cause a middle-ear overpressure. neously as long as infection does not occur and The most common damage to the inner ear is water is kept out of the ear. The patient with an rupture of either the round or oval window acute tympanic membrane perforation will not membranes, which results in the loss of peri- experience further barotrauma in that ear as lymph fluid from the otic capsule and injury to long as the perforation remains; however, the hair cells of the auditory vestibular system. The clinical results can include sensorineural hearing loss and vertigo. Patients typically present with a “flat” hearing loss upon audiometric testing (all frequencies equally affected). In one study, only 15% of patients presented with vertigo or dizziness.6 The effects of inner-ear barotrauma may be permanent. However, if patients present for treatment within 2 weeks of their injury approximately 70% will have marked or almost complete improvement.6 Treatment consists of bedrest with the head of the bed elevated. Patients who have no improvement or worsening of their auditory or vestibular symptoms after 2 weeks of treatment may have a perilymph fistula. Exploratory tympanotomy and repair of the fistula will usually improve their vertigo; however, in some patients hearing will not improve.6

Inner-Ear Decompression Sickness Decompression sickness (the “Bends”) occurs Figure 15.1. Use of a Politzer bag. The patient closes when nitrogen bubbles form in various tissues mouth and occludes one nostril while the doctor following a deep saturation underwater dive. If places the tip in the opposite nostril and applies brisk nitrogen gas bubbles localize to the inner ear, pressure to the bag to open the Eustachian tube. the patient will present with audiovestibular 15. Otorhinolaryngology Head and Neck Surgery Patients 205 symptoms.7 Individuals involved in special Immediate treatment consists of returning operations duty should be aware that ﬂying the aircraft or cabin pressure to the altitude within 24 hours of diving signiﬁcantly increases where the symptoms began, if practical (Table their risk of developing decompression sickness. 15.1). Topical nasal decongestants and analgesics should be given if available and the Sinus Barotrauma Valsalva maneuver should be performed in an attempt to clear the affected sinuses. Further Sinus barotrauma results when pressure cannot changes in altitude should be done as gradually equalize, most commonly in the frontal or as possible.8 Recurrent sinus barotrauma may maxillary sinuses, and can be severely painful, require surgical intervention, as described later even potentially disabling. Symptoms can occur in the chapter. during either ascent or descent, although they are much more likely during descent. The most Table 15.1. Conditions requiring altitude common cause is obstruction of a sinus opening restrictions. by mucus membrane edema secondary to infection or allergic rhinitis. Polyps or tumors can Anemia less than 7g of Hg obstruct the sinus openings by a “ball valve” Frontal or maxillary sinus block unresponsive to medical therapy phenomenon (Fig 15.2).

Figure 15.2. Maxillary sinus ostia demonstrating pushed into the ostia, blocking the sinus and pre- ball valve action from a nasal polyp. At ground level venting equilibration. The pressure within the sinus (1), the sinus is equilibrated with ambient air. Upon can only be reduced by hemorrhage and dehiscence descent (2), the polyp is displaced as air ﬂows out of of the lining. At the conclusion of the ﬂight (5), sinus the sinus to equilibrate with the lower pressure. At pressure reequilibrates with continued hemorrhage altitude (3), the sinus equilibrates with the lower and lining dehiscence. cabin pressure. Upon descent (4), the polyp is 206 D.G. Schall and J.R. Bennett

Barodontalgia department 33% of facial injuries (primarily fractures) were missed.14 Barodontalgia is an infrequent condition where dental pain is precipitated by altitude change. The differential diagnosis of tooth pain during Airway Management flight includes sinus barotrauma because pain from this more common condition may be Airway control is crucial to victims of maxillo- referred to the teeth. The etiology is uncertain facial trauma, whether the trauma is to the face but appears to involve diseased pulp tissue. The or neck, penetrating or blunt, and a bony injury most commonly affected teeth are those of the or strictly a soft-tissue injury. Airway control is posterior maxilla that have recently undergone in particular important for unconscious patients an amalgam restoration. Definitive treatment and those with cranial vault trauma, facial usually requires removing diseased pulp and trauma, or inhalation burns. placing a new restoration.9 Any patient who is reasonably likely to need intubation should have an orotracheal or nasotracheal tube placed prior to AE. It is far better to intubate a patient in a controlled environ- Otolaryngologic Trauma ment on the ground than in an emergency situation in the turbulent and cramped envi- Military and Civilian Injury Patterns ronment of an aircraft. The types of maxillofacial traumas seen in warfare have changed throughout the years, Orotracheal vs Nasotracheal Intubation based on the changes in types of combat. During World War II, the massive application An airway can be secured by insertion of either of artillery and bombing resulted in 75% of an orotracheal or nasotracheal tube. Orotra- facial injuries from shrapnel, while only 10% cheal intubation has the disadvantage of requir- were from gunshot wounds.10 During the ing cervical spine manipulation and direct Vietnam War, close combat and in particular visualization of the trachea, which can be dif- guerilla warfare were more common, and thus ficult with massive trauma and bleeding of 58% of the maxillofacial trauma was secondary the lower face or oral cavity. Because victims to bullet wounds, only 30% from artillery, with of maxillofacial trauma are at increased risk the remaining 12% resulting from accidents.11 of coexisting cervical spine trauma, orotrcheal More recently during combat in the former intubation should be performed cautiously with Yugoslavia, approximately 12% of all combat in-line cervical spine immobilization in these injuries were to the head and neck and approx- patients. The advantages of nasotracheal intu- imately one half of these were from gunshot bation are that it can be done blindly with wounds and one half from explosive devices.12 a high degree of success and is better tolerated Maxillofacial trauma also constitutes a sig- by conscious patients.15 However, nasotracheal nificant proportion of the trauma treated in intubation is contraindicated in apneic patients. civilian trauma centers and may be initially It is also contraindicated in patients suspected overlooked in patients with multiple-organ of having a skull base fracture, as there is a system trauma. An Israeli study of prehospital risk that the endotracheal tube could pass diagnoses made by flight surgeons found that through the cribriform plate into the cranial 10% of trauma patients had facial injury, 3% vault. Evidence of possible skull base fracture had soft-tissue neck trauma, and 22% had includes midface and cranial instability or cranial head injuries.13 Approximately 26% of deformity and hemotympanum. the potentially identifiable facial trauma diag- Both orotracheal and nasotracheal intuba- noses were missed, compared to only 8% of tion are relatively contraindicated for patients the soft-tissue neck trauma and 7% of the who have had blunt anterior neck trauma head trauma. An Australian study found that of (eg, “clothesline” injuries) because laryngotra- head-injured patients seen in the emergency cheal separation or severe laryngeal fracture 15. Otorhinolaryngology Head and Neck Surgery Patients 207 may have occurred. Instead, a tracheotomy have trauma to the larynx and trachea, with should be done to stabilize the airway. Blunt possible tracheal disruption. Both needle and passage of the endotracheal tube into a par- surgical cricothyrotomy must be converted to tially separated larynx and trachea could sever tracheostomy when the patient has reached a any remaining soft-tissue attachments, thus surgical facility to minimize the long-term risk causing the trachea to partially retract into the of subglottic stenosis. chest with resultant loss of the airway. Hemorrhage Needle Cricothyrotomy Facial hemorrhage can be significant, but by Needle cricothyrotomy is useful to rapidly itself is usually not life threatening. Direct pres- provide limited and temporary airway access in sure is usually adequate to achieve hemostasis. any trauma scenario where the trachea cannot Penetrating wounds of the neck can cause rapid be readily intubated. A large-caliber angio- exsanguination or air embolism if the major catheter is placed through the cricothyroid vessels of the neck are involved. Surgical liga- membrane into the trachea. This should be tion may be necessary for emergent control. a 12- or 14-gauge catheter in an adult or a 16- or 18-gauge catheter in a child. The cannula Implications for AE with should then be connected to oxygen at 15 Specific Diagnoses L/minute at 40 to 50 psivia tubing with either a Y-connector or with a side hole cut in the Epistaxis tubing. Intermittent insufflation, 1 second on Epistaxis may be controlled by a number of and 4 seconds off, can be achieved by placing a methods, including pinching the nose, cautery, thumb over the Y-connector or hole in the tube. anterior packing, and on occasion posterior Patients can be maintained with this technique packing for persistent bleeds. Rarely is ligation for 30 to 45 minutes, assuming they previously or embolization required. Posterior packing has had normal pulmonary function and have no by tradition been accomplished with placement significant chest injury. Carbon dioxide will of a bulb catheter, such as a Foley catheter, build up, which will limit the usefulness of this through the nares and inflated with saline after technique in head-injured patients. Caution positioning in the nasopharynx. This is followed must also be used if there is complete airway by placement of multiple layers of Vaseline- obstruction at the glottic level, and if such soaked gauze to form the anterior pack and obstruction occurs the flow should be lowered then placement of a c-clamp, taking care not to 5 to 7L/minute. to put pressure on the nasal alae. Specially designed catheters with anterior and posterior Surgical Cricothyrotomy bulbs are also readily available. If the bulb Surgical cricothyrotomy is more dependable catheter is filled with air, the pressure fluctua- than needle cricothyrotomy and allows appro- tions associated with flight may cause either priate ventilation through a larger endotracheal increased pressure on the nasal mucosa or tube. Multiple studies have demonstrated the resumption of bleeding with decreased cuff efficacy and safety of this procedure in the pressure. For this reason, the bulb should be hands of appropriately trained caregivers in filled with water or normal saline instead. field condition.16–18 The technique consists of Because these patients are breathing pre- making either a horizontal or preferably a ver- dominantly through their mouths, they will tical skin incision and then a horizontal incision need increased humidification and hydration through the cricothyroid membrane, dilating during the flight. Usually blood has filled the the opening with a curved hemostat or the lower sinuses (maxillary and sphenoid) and blunt end of a scalpel, and inserting a 5- to 7- therefore sinuses are typically unaffected by mm endotracheal tube or tracheostomy tube. pressure changes of flight. Patients with poste- Surgical cricothyrotomy should not be per- rior packs must be closely monitored as the formed in children under the age of 12 due complication rate averages 17% with such to the risk of damage to the cricoid cartilage. It things as alar necrosis, sepsis, aspiration, and also should not be performed in patients who even cardiac arrhythmias and death.19 208 D.G. Schall and J.R. Bennett

Midfacial Trauma This can be in particular disconcerting to the aeromedical flight crew if they are unfamiliar Facial fractures are often overlooked in the with the particular procedure performed or if field, even in the presence of facial lacerations. written details of the operation are lacking. Fortunately, fractures of the sinus cavities are Familiarizing oneself with these procedures, as unlikely to cause sinus barotrauma during flight well as good communication with the otolaryn- because the sinus is no longer a fixed-wall cavity gologist, should alleviate concerns. and thus allows expansion of gas into the nose or surrounding tissue. Tracheostomy Skull Base Fracture There are many types of tracheostomy tubes, If a skull base fracture is suspected in a patient, but the typical tube consists of an inner cannula pneumocephalus must be considered and ruled with an outer sleeve (Fig 15.3). This inner out if possible prior to AE. A patient with cannula can be readily removed for cleaning, an unrecognized pneumocephalus may suffer while the outer sleeve maintains the patency of increased cerebral pressure or brain stem the tracheostomy. The cuff is inflated to isolate herniation due to expanding gases as the air- the trachea from the larynx and secretions craft ascends. If a patient with a documented above and allow for a seal during ventilator use. or suspected pneumocephalus must be trans- When the patient is spontaneously breathing, ported (ie, urgent or contingency AE), the cabin this cuff may be deflated to allow passage of should remain pressurized at the altitude of the air through the mouth. The patient may be able departure facility. In helicopters and smaller to speak if the cuff is deflated and the tube transport aircraft where this is not possible, the is occluded on exhalation, thus allowing air lowest possible altitudes should be flown. to pass through the larynx. All head-injured patients should be placed headfirst in the aircraft (ie, head toward the front) to lessen the risk of increased cerebral pressures (pooling of blood in the head) during the take-off acceleration and climb.20 Drugs to manage potential cerebral complications should be available if possible, as discussed in chapter 15.

Temporal Bone Trauma Temporal bone trauma may manifest as Battle’s sign (postauricular ecchymosis), tympanic membrane rupture, facial nerve paralysis, or hearing loss. If the middle ear is filled with blood, barotrauma during flight does not occur. In some cases, temporal bone fractures can breach the cranial vault, resulting in leakage of cerebrospinal fluid (CSF) and a potential pneumocephalus. A delayed complication is meningitis, as nasopharyngeal organisms contaminate the CSF.

Postoperative Otolaryngologic Patient Figure 15.3. The typical tracheostomy tube is made The AE of patients after otolaryngologic pro- up of three parts: the outer sleeve (A), inner cannula cedures poses unique challenges in maintain- (B), and obturator used to place the tracheostomy ing the comfort and safety of these patients. tube (C). 15. Otorhinolaryngology Head and Neck Surgery Patients 209

To facilitate speech, the patient may use a removed only when the tracheostomy tube is custom tube that is cuffless and typically is of a first changed. The tracheostomy provides an smaller size, or is fenestrated. Fenestrated tubes excellent airway and should be kept free of have a hole on the outer curve (posterior) of secretions and crusts. Humidification should the tube to allow passage of air through the be provided due to the low relative humidity of mouth. A fenestrated inner cannula must be cabin air. used in conjunction with the fenestrated outer sleeve. The fenestrated tube has fallen into Tracheostomy Cuff some disfavor because of possible irritation Conventional teaching on tracheostomy tubes against the posterior trachea leading to sub- has been to replace the air in the cuff with water glottic stenosis. or saline prior to take-off to avoid problems of Foam-filled cuffs are available that have a changing cuff pressures in flight. The air-filled lower pressure against the tracheal mucosa. tracheostomy tube cuff pressure is normally The foam cuff is collapsed through an external between 20 to 60 torr, but in an unpressurized valve in the same fashion that air-filled cuffs aircraft at 35,000ft cuff pressure can reach 385 are. Also commonly seen are customized and torr.21 An excessively high pressure of this irregularly shaped tracheostomy tubes that may magnitude can damage the tracheal mucosa. have only a single lumen. Alternatively, inappropriately low pressures Several principles apply to the use of all upon descent can result in an inadequate seal, tracheostomy tubes.Tracheostomy tubes should increasing the risks of aspiration or air leaks if be frequently cleaned and inspected. Spares the patient is on a ventilator. should be available. Suction should also be The current recommendation, however, is to readily available. Either air or oxygen, if re- leave air in the tracheostomy tube cuff because quired, should be humidified and applied to the use of fluid causes difficulty in monitoring the tracheostomy tube rather than to the mouth cuff pressure and leakage. It could also cause or nose. damage to the cuff valve, requiring premature If a tracheostomy tube is dislodged, the inner changing of the tube, according to S. Derdak cannula should be removed and replaced by an (personal commonication, August 1998 and obturator that allows smooth reintroduction of March 2000). In practice, the pressure changes the outer cannula of the tracheostomy tube during flight are slow and of relatively small into the airway passage. The obturator is then magnitude because modern aircraft maintain a removed and the inner cannula is reinserted. cabin pressure equivalent to approximately The tracheostomy tube with obturator should 8000ft. It is a simple matter to check the cuff be lubricated or moistened prior to introduc- pressure with a cuffolator upon reaching cruis- tion and this should be done with the patient’s ing altitude, every 30 minutes during the flight, neck extended under good lighting. For this and again during descent. Self-regulating cuffs reason, the obturator should be secured in an are now also readily available. If the number obvious place prior to AE, such as on the front of aeromedical personnel available is not suf- of the patient’s chart or on the head of the bed. ficient to satisfactorily perform cuff pressure monitoring, replacement of the air with fluid Implications for AE remains a reasonable alternative. Patients who have tracheostomies are ready to fly as soon as they have recovered from their Specific Diagnoses operation and preferably have undergone their Tonsillectomy first tracheostomy tube change, usually after the fifth postoperative day. This period could be Patients who have undergone a tonsillec- compressed if surgical capability exists in the tomy, with or without adenoidectomy or uvu- AE transport and final destination. The tube lopalatopharyngoplasty, are at risk of hemor- should be sutured into position when the tra- rhage at two different times during the cheotomy is first performed and the sutures postoperative period. The time of greatest risk 210 D.G. Schall and J.R. Bennett

Table 15.2. Contraindications to AE for otorhino- gically. Endoscopic sinus surgery is used to laryngologic patients. enlarge natural sinus openings for patients with Absolute (contraindication to elective, urgent, and chronic infections, tenacious mucus, or congen- contingency AE) ital bony abnormalities and remove obstruct- Unstable airway ing pathology such as sinonasal polyps and Decompression sickness* tumors. Skull fracture with intracranial air* Aviators who have undergone this “func- Relative (contraindication to elective AE) Within 5d after tracheotomy tional endoscopic sinus surgery” have sig- Within 14d after tonsillectomy, tympanoplasty, or neck nificantly fewer or no episodes of sinus surgery barotrauma postoperatively. A study at Wilford Within 24h after rhinoplasty, septoplasty, or sinus Hall Medical Center of 54 aviators who had surgery undergone this procedure found that 98% 22 * Stabilized patients can be moved in aircraft capable of had returned to active flight duty. Aviators pressurization to the elevation of the departure site if the who have undergone endoscopic sinus surgery arrival site is not at a higher elevation. should be “preflight” tested in an altitude chamber prior to returning to flying status. is the first several hours after surgery. A post- In general,patients who have undergone such operative tonsillectomy hemorrhage that can surgery have few problems with air travel.23 be controlled in an emergency department or However, elective AE should be delayed for at operating room might be fatal in an aircraft. least 24 hours to allow resolution of any post- The second period of increased risk of hem- operative edema. Patients who require AE orrhage is approximately 7 to 14 days after sooner should be treated with nasal deconges- surgery, when the eschar separates from the tants and frequent Valsalva maneuvers to min- tonsillar fossa. For this reason, elective AE imize the risk of sinus block. Patients should be should be delayed until 2 weeks after tonsillec- cautioned that vigorous Valsalva maneuvers tomy or after the eschars in the tonsillar fossae after some types of ethmoid surgeries (eg, separate (Table 15.2). involving the lamina papyracea, cribriform If urgent or contingency AE is required plate, or fovea ethmoidalis) may result in orbital sooner than 2 weeks, the risk of bleeding may emphysema or pneumocephalus. be decreased by giving the patient humidified If a sinus block occurs during flight in a air and ensuring adequate fluid intake en route patient post-sinus surgery, the aircraft should to counteract the dry atmosphere. If significant climb back to the altitude where the sinus block bleeding occurs, diversion to the nearest med- developed, if at all possible. Decongestants ical facility is required. should be administered if available and descent Rhinoplasty and Septoplasty then can be resumed at a more gradual rate with regular Valsalva maneuvers. Analgesics Patients who have undergone rhinoplasty or may be administered if the patient is not in septoplasty are able to undergo AE after the control of the aircraft. Sinus barotrauma may nasal passage has been cleared of splints and result in an episode of epistaxis that is usually packing, usually 24 hours after surgery. Splints self-limiting and easily controlled. may be left in place as long as 1 week. The majority of patients will be able to breathe better Pressure Equalization Tubes through their nose after septoplasty. However, Patients with patent pressure equalization (PE) for several weeks after surgery residual edema tubes in their tympanic membranes should have of the turbinates and mucosa may predispose the no difficulty with ear blocks. These patients may patient to sinus blockage. Patients should be fly as soon as they are recovered from surgery. treated with a nasal decongestant spray before The patency of these tubes can usually be deter- and during flight if AE is required within the first mined with direct otoscopy and insufflation few weeks postoperatively. or, if patency cannot be determined by direct visualization, then this can be readily deter- Endoscopic Sinus Surgery mined by tympanography. A flat, high-volume Conditions that put patients at increased risk tympanogram indicates a patent pressure equal- for sinus barotrauma are often treated surization tube, whereas a flat, low-volume tym- 15. Otorhinolaryngology Head and Neck Surgery Patients 211 panogram indicates either a plugged PE tube vers. Movement of the tympanic membrane with middle-ear effusion or one that has flap during pressure changes may dislodge extruded and the tympanic membrane has since grafts or prostheses. Prior to taking a flight after sealed, with the development of serous otitis healing, these patients should begin performing media. A fluid-filled middle ear is not affected frequent Eustachian tube clearing maneuvers, by altitude change because fluid does not including gentle Valsalva maneuvers, chewing, expand and contract as gases do at altitude. if yawning, and swallowing.24 Placement of some types of ossicular prostheses creates a small but serious risk of peri- Stapedotomy lymphatic fistula, regardless of the time since Otosclerosis is a disease that causes fixation of surgery. A prosthesis such as a total ossicular the stapes to surrounding bone, causing a con- replacement prosthesis (TORP) lacks the ductive hearing loss. This can be treated with natural lever action of the ossicle that it re- hearing aids or surgically corrected by stape- places. Excessive tympanic membrane motion dotomy. This procedure involves removing the transmitted directly to the footplate of the stapes suprastructure over the stapes footplate, stapes may acutely create a perilymphatic drilling a small hole through the footplate, and fistula.25 This rarely can occur while the patient placing a piston-tike prosthesis into the hole, is trying to clear an earblock with forceful which is then directly connected to the incus. Valsalva maneuvers or during abrupt changes This restores ossicular mobility, resulting in in cabin pressure (ie, explosive decompression). improved hearing. A stapedectomy is a similar Symptoms can include sudden vertigo, nau- procedure; however, the entire footplate is sea, vomiting, and a sensorinerual hearing loss. removed and replaced with fascia/vein or peri- Treatment is supportive,with immediate follow- chondrium. Theoretically, these patients are up by a specialist after scheduled landing. at a higher risk of perilymph fistula. Patients who have undergone stapes surgery are al- Acoustic Neuroma and Cerebellar Pontine lowed to fly in commercial aircraft after they Angle Surgery have recovered from the anesthetic and are symptom free. Acoustic neuroma is the common name for a vestibular nerve schwannoma, a benign slow- growing lesion that causes compression of the Tympanoplasty contents of the internal auditory canal and ulti- Tympanoplasty encompasses a variety of mately grows into the cerebellopontine angle. operations that may involve the removal of These lesions can be treated with surgery, stero- middle-ear pathology, repair of ossicles, or tactic radiation, or observation. The surgical reconstruction of the eardrum. A variety of accesses most commonly used include the materials may be used to repair the tympanic translabyrinthine, retrosigmoid, and middle membrane and ossicles. A patient who has fossa approaches. Depending on the approach, undergone recent tympanoplasty or even a the patient has a 9% to 29% risk of developing tympanoplasty associated with some form of a CSF leak within the first few postoperative mastoid surgery should be able to fly as soon as days.26 recovered from the effects of the anesthetic and If a CSF leak develops after surgery, patients demonstrates no otologic complications. Typi- should not undergo elective AE for 2 weeks cally, after surgery the middle-ear space is filled after any leakage has resolved. In the past, it with fluid and absorbent surgical packing that was considered safe to fly immediately after a dissolves in about 3 weeks. Not every otologic CSF leak resolved. However, there are reports surgery involves middle-ear packing. In the of patients who flew immediately after the absence of packing, an ossicular reconstruction leakage resolved (following a translabyrinthine or tympanic membrane graft should be allowed approach) and developed bacterial meningitis to heal in place for at least 2 weeks before being within hours of landing.26 The hypothesis is subjected to barotrauma and Valsalva maneu- that, during descent, the relative negative 212 D.G. Schall and J.R. Bennett pressure that develops within the middle ear worn around the neck for the rapid release and Eustachian tube allows nasopharyngeal from fixation in the case of vomiting (Fig 15.4). pathogens to reflux back into the middle ear It is only necessary to cut and remove the wire and come into contact with CSF, resulting in loops spanning between the maxillary and meningitis. mandibular bars (Fig 15.5).

Laryngectomy Neck Dissection/Thyroidectomy/Free and Pedicled Flaps Patients who have undergone a total laryngectomy have had their larynx removed and the Patients who have undergone neck dissection, trachea brought out through the anterior neck. thyroidectomy, or free or pedicled flaps should They may have a short single lumen tube be able to be moved by elective AE after 2 similar to that of a tracheostomy tube that fits weeks and after all drains have been removed, within the trachea and helps prevent contrac- no fistula exists, and the flaps are viable. Earlier ture at the tracheastoma site. Patients who have undergone a total laryngectomy may have a small one-way valve inserted on the posterior wall of their trachea and into the pharynx (such as the Blom-Singer® valve, International Healthcare Technologies, Carpinteria, Calif) that allows oral speech when the tracheastoma opening is occluded with their thumb. There are no problems associated with this condition during flight other than excessive drying. One pilot was reported to fly even after his total laryngectomy.27

Mandible Fractures Patients with mandible fractures will usually require intermaxillary fixation (IMF, ie, their jaws are wired shut). For this type of fixation, arch bars are wired to the mandibular and maxillary teeth and then wired to each other, typically with four wire loops. Patients with IMF are at risk of aspiration if they vomit with the wire fixation in place. If patients have a tendency toward motion sickness, they should be given antiemetics and placed on their side with the head down. In high-risk patients, the fixation wires should be Figure 15.4. Patients with intermaxillary fixation removed and replaced with rubber bands.28 If should have wire cutters around their necks for rapid wires are left in place, wire cutters should be release from fixation in the case of vomiting. 15. Otorhinolaryngology Head and Neck Surgery Patients 213

Figure 15.5. Wire cut sites for emergency release of intermaxillary ﬁxation.

Table 15.3. AE checklist. movement may predispose patients to cuta- Hearing protection for all patients (ear plugs or muffs) neous emphysema or pneumopericardium. where required Patients at risk for hypoxia (eg, anemia <8.5g Hg, sickle cell anemia) Conclusion Oxygen supplementation given Tracheostomy patients Humidified air or oxygen used to avoid airway The field of otolaryngology—head and neck irritation surgery is strongly interwoven with the fields Obturator readily available of fight medicine and AE. Successful flying Spare tracheostomy tube requires the proper function of the middle-ear Unconscious patients spaces and sinuses. An intact and functioning Eyes protected (ophthalmic ointment and taped shut) Flashlight available to check pupils audiovestibular system is also highly desirable Intubated patients for passengers in aircraft and is required for Tube position and security confirmed those controlling aircraft. The transport of Steps taken to avoid cuff overpressure if using air postoperative, wounded, or ill patients by AE Monitor cuffs for incorrect pressure introduces another level of complexity in the Upon ascent until cruise altitude reached Every 30min during flight physical response to flight (Table 15.3). The On descent anatomy and physiology of the head and neck Or fill cuffs with saline is complex. When this anatomy is disrupted, the Spare tube and functioning laryngoscope, suction potential for troublesome or even disastrous available complications is significant. An understanding Appropriate ventilator and Ambu bag available Oxygen supply is adequate for the anticipated trip of normal anatomy and function, and how this length has been altered in the AE patient, is the key Patients with nasogastric or feeding tubes to safe and successful transport of these Anticipate a possible sinus block on tubed side patients. Trauma patients Wire cutters available if mandible wired Head-injured patients on litters are placed with head toward the front of the aircraft References Pneumocephalus ruled out with temporal bone, orbital, 1. DeHart RL, ed. Fundamentals of Aerospace or LeFort fractures Medicine. Philadelphia: Lea & Febiger; 1985:10, Air in globe ruled out with ophthalmic trauma 12. 214 D.G. Schall and J.R. Bennett

2. Randel HW, ed. Aerospace Medicine. 2nd ed. 16. Boyle MF, Hatton D, Sheets C. Surgical crico- Baltimore: Williams & Wilkins; 1971:2. thyrotomy performed by air ambulance flight 3. Farmer JC, Thomas WG. Ear and sinus pro- nurses: A 5-year experience. J Emerg Med 1993; blems in diving. In: Straus RM, ed. Diving 11:41–45. Medicine. New York: Grune and Stratton; 17. Xeropotamos NS, Coats TJ, Wilson AW. Prehos- 1976:109–133. pital surgical airway management: 1 year’s expe- 4. Stangerup SE, Tjernstrom O, Klokker M, rience from the helicopter emergency medical Harcourt J, Stockholm J. Point prevalence of service. Injury 1993;24:222–224. barotitis in children and adults after flight, and 18. Miklus RM, Elliott C, Snow N. Surgical cricothy- effect of autoinflation. Aviat Space Environ Med rotomy in the field: Experience of a helicopter 1998;69:45–49. transport team. J Trauma 1989;29:506–508. 5. Lundgren CEG, Malm LV. Alternobaric vertigo 19. Gluckman JL. Renewal of Certification Study among pilots. Aerosp Medi 1966;37:178. Guide in Otolaryngology—Head and Neck 6. Kozuka M, Nakashima T, Fukuta S, Yanagita M, Surgery. Dubuque: Kendall/Hunt; 1998:222. Inner ear disorders due to pressure change. Clin 20. Reddick EJ. Aeromedical evacuation. Am Fam Otolaryngol 1997;22:106–110. Physician 1977; 16:154–160. 7. Alberti PW, Ruben RJ, ed. Otologic Medicine. 21. Stoner JL, Cooke JP. Intratracheal cuffs and vol 2. New York: Churchill Livingstone; 1988: aeromedical evacuation. Anesthesiology 1974; 1794. 41:302–306. 8. Johnson A, Jr. Treatise on aeromedical eva- 22. Parsons DS, Chambers DW, Boyd EM. Long- cuation: II. Some surgical considerations. Aviat term follow-up of aviators after functional Space Environ Med 1977;48:550–554. endoscopic sinus surgery for sinus baro- 9. DeHart RL, ed. Fundamentals of Aerospace trauma. Aviat Space Environ Med 1997;68:1029– Medicine. Philadelphia: Lea & Febiger; 1985:546. 1034. 10. Rowe NL, Killey HC. Fractures of the Facial 23. Bolger WE, Parsons DS, Matson RE. Functional Skeleton. Edinburgh: E&S Livingstone Ltd; endoscopic sinus surgery in aviators with recur- 1955. rent sinus barotrauma. Aviat Space Environ Med 11. Andrews JL. Maxillofacial trauma in Vietnam. 1990;61:148–156. J Oral Surg 1968;26:457–462. 24. Syms CA III. Flying after otologic surgery. Am 12. Jevtic M, Petrovic M, Ignjatovic D, et al. Treat- J Otol 1991;12:162. ment of wounded in the combat zone. J Trauma 25. Moser M. Fitness of civil aviation passengers to 1996;40(suppl 3):S173–S176. fly after ear surgery. Aviat Space Environ Med 13. Linn S, Knoller N, Giligan CG, Dreifus U. The 1990;61:735–737. sky is the limit: Errors in prehospital diagnosis 26. Callanan V, O’Connor AF, King TT. Air travel by flight physicians. Am J Emerg Med 1997;15: induced meningitis following vestibular schwan- 316–320. noma (acoustic neuroma) surgery. J Laryngol 14. Tulloh BR. Diagnostic accuracy in head-injured Otol 1996;110:258–260. patients:An emergency department audit. Injury 27. Stoll W, Delank W. Fitness for flying despite 1994;25:231–234. laryngectomy. Laryngorhinootologie 1994;73: 15. O’Brien DJ, Danzl DF, Sowers MB, Hooker EA. 654–655. Airway management of aeromedically trans- 28. Sanger A, Stoner P. Air Force Flight Surgeon’s ported trauma patients. J Emerg Med 1988;6: Manual. chapter 19, U.S. Department of the Air 49–54. Force; 1976. 16 Ophthalmic Patients

Douglas Joseph Ivan

As the level of sophisticated weaponry has are trained and familiar with the nuances and increased, the mortality rates associated with medical/surgical management of this entire combat-related injuries in the field have spectrum of potential resultant ocular damage. decreased. This can be attributed to advances It is indeed likely, however, that high-speed bal- in medical and surgical capability, protective listic particles and their associated damage will equipment ensembles, forward deployment of tend to represent the bulk of military-related definitive medical treatment facilities, timely ocular injuries. In addition, wartime-related eye evacuation of wounded personnel from the injuries differ with respect to civilian situations field, and an extensive aeromedical evacuation in several other key areas: (1) longer time (AE) system. delays and restricted access to definitive oph- As overall mortality rates associated with thalmologic intervention; (2) risks associated combat have declined, combat-related ocular with intra- and extratheater evacuation, in injuries have paradoxically come to represent particular those involving AE; (3) laser-related an ever-increasing proportion of nonlethal ocular eye injuries; and (4) the sheer number of combat-related injuries. It may also be said that cases that will likely require intensive manage- the costs of prolonged medical care associated ment at virtually the same time. with ophthalmic injuries following cessation Unfortunately, an ophthalmologist is un- of hostilities represent an ever-increasing por- likely to be available at far-forward locations tion of postconflict expenditures. Some studies where ocular injuries may be most likely to have indicated that the cost of postconflict occur. Most of those ocular casualties will ophthalmic care related to the Vietnam Conflict depend on nonophthalmic medics for proper alone will likely exceed $4 billion.1 Nonlethal stabilization and movement to medical facil- weapon technologies and interventive thera- ities for definitive ophthalmologic treatment. pies of the future are certain to save lives but Depending on the intensity level of the military are almost equally as certain to increase these operation and the isolation of the area of oper- costs even further. Such statistics serve to em- ations, definitive ophthalmologic care will often phasize the necessity to assure that adequate be delayed. For this reason, it is important for eye protection is worn in the field. Sadly, even nonophthalmologic medical practitioners to during recent conflicts, the evidence shows eye have a basic working knowledge of the prin- protection is usually underutilized by troops in ciples of interim and emergency management the field. of common ocular injuries. They must also have Ocular injuries likely to be encountered an effective understanding of the indications during modern military operations run the full for AE, the potential modes of transport gamut of potential ocular damage scenarios available, and the appropriate return to duty experienced with similar peacetime occupa- criteria. This approach applies not only to tra- tional and vocational threats. Ophthalmologists ditional war-related ocular injuries but also to

215 216 D.J. Ivan laser injuries, as this threat increases on the vivability from other combat wounds. It should modern battlefield. also be stated that, will the exception of the This chapter will briefly discuss the history Gulf War, the threat of laser-based weapons of ocular casualties, the most common mecha- was previously nonexistent. Although proper nisms of injury, and some specific ocular ballistic and laser eye protection may signifi- diseases and injuries, together with their AE cantly reduce these ocular risks in the future, implications. compliance with such protective devices, especially under the rigors of combat, is unpredictable and certainly not universal. It is also History likely that the proliferation of laser-based weapons and the current focus on nonlethal Based on past military conflicts, medical man- weapon technologies may actually contribute agers and planners can anticipate that 8% to to an even greater number of disabling, albeit 10% of all combat-related injuries will likely nonlethal, eye injuries in the future. involve the eye (Table 16.1). A significant per- During the Vietnam Conflict, only about centage of these ocular injuries are likely to be 25% of combat-related ocular injuries were complicated and severe. Penetrating and per- ever returned to duty.3 Fortunately, timely evac- forating eye injuries will occur 20% to 50% of uation of ophthalmic causalities from the field the time. Of penetrating injuries, 30% to 85% has steadily improved, being reduced from an will be associated with one or more intraocular average of 36 to 48 hours from the time of foreign bodies, and 28% will involve both eyes.2 injury during World War II to about 4 hours In addition to battlefield trauma-related during the Gulf War.4–6 As the estimated costs injuries, other conditions that might require of medical care associated with ocular injuries AE from the theater are related to sports and rises, defensive and interventive strategies that systemic diseases. In most military opera- minimize the ocular risks and their sequelae tions, disease and nonbattle injuries (DNBIs) also have other ramifications on society that exceeded those related to combat by consider- go well beyond the immediate urgency of the able numbers. Fortunately, the majority of moment.1,7 patients with nontraumatic ophthalmic con- The risk for laser-related ocular injuries ditions will rarely require AE. Therefore, this remains high on the modern battlefield despite chapter will focus on trauma-related ophthal- an international treaty that bans the use of any mologic injuries, many of which are significantly laser weapon specifically designed to blind more likely to occur during combat. or damage the human eye. There are several The percentage of wartime-related ocular reasons why this treaty is not a panacea and will injuries has steadily increased and is perhaps a not eliminate laser eye injuries. These include: reflection of a parallel increase in overall sur- (1) Not all countries are signatories to this treaty; (2) The “Bad Guys” have a habit of breaking all the rules; and most importantly, (3) Table 16.1. Ocular casualty rates in military the current treaty does not ban military weapon conflicts. systems that employ lasers that will almost certainly cause injury when they accidentally Percentage Mortality rates Conflict of eye injuries (%) strike the human eye.

19th-Century wars <1 Unavailable World War I 1.5–2.1 12.0 World War II 2.0–3.4 4.5 Mechanism of Injury Korean War 2.8–8.1 2.4 Arab–Israeli wars 5.6–10.0 Unavailable The two most common mechanisms of ocular Vietnam Conﬂict 5.0–9.0 2.6 injury in combat will be ballistic and laser Gulf War 13.0 0.06 injuries. Ballistic injuries have been a part of Peacetime ocular injury rate: 1.7–2.4%. warfare from the beginning, but lasers have Source: Adapted with permission from Wong et al.2 only recently appeared on the battleﬁeld. This 16. Ophthalmic Patients 217

in this regard since World War I, when postconflict analyses indicated that 50% of all ocular injuries could have been avoided with proper eye protection.9 During the Yom Kippur War, only 27% of Israeli troops used their polycarbonate goggles and according to Heier et al only 3 of 92 US soldiers with field- related ocular complaints during the Gulf War acknowledged ever using goggles.9,10 The explanations for the inadequate use of eye protection are complex and multiple. In some cases, adequate eye protection may not be available. More often, the extreme range of environmental factors associated with the rigors of military operations discourages their use. Factors that tend to dissuade the individ- Figure 16.1. Anatomy of the eye. ual from using such equipment even when the threat is high include the presence of particu- lates, smoke, heat, sweat, fogging, movement of section will provide a summary of these dual the devices, glare, clarity, optical consequences, threats, followed by discussions of the specific and ease of integration with other personal injuries that occur as a result of each. A equipment. During the “heat of battle,” com- schematic diagram of the eye is included to pliance is further compromised by the over- facilitate the following discussion (Fig 16.1). powering drive to optimize all visual input. While ballistic injuries on the battlefield may Ballistic Injuries be of such magnitude that ocular damage will be the least of the concerns, properly worn The unprotected eye offers little innate tissue ballistic ocular protection will eliminate a con- resistance to flying battlefield projectiles and siderable number of unnecessary war-related concussive forces. This is true whether the pro- ocular injuries. Such protection undoubtedly jectile is kinetically enhanced by high speed avoids or mitigates many types of head trauma, and thus being of high energy or low speed, low perhaps even saving lives. Much the same can mass and, therefore, of lower energy. Although be said of current laser eye protection (LEP) the eye only represents a mere 0.27% of the devices, which consist most often of polycar- total body surface, the incidence of eye injuries bonate goggles or visors. is surprisingly 20 to 50 times higher than expected based on proportional surface area Laser Injuries representation.8 The inherent ballistic protection associated Accidental or deliberate laser-induced eye with wearing eye protection devices is well damage is becoming more likely with the appreciated in both the operational military proliferation of laser-based technology on and peacetime environments. In most cases, the modern battlefield. Essentially, any laser- any spectacle eyewear affords some degree of ranging weapon system can blind the human ocular protection for the eye. However, poly- eye, whether intended or designed for that carbonate lenses offer the greatest degree of purpose or not. Further, military history sup- protection to a wide range of projectiles ports the premise that, once at war, some adver- (including small-caliber bullets) when properly saries may choose to disregard international worn. treaty obligations or may not have been signa- Compelling troops to properly and consis- tories of such a treaty in the first place. Conse- tently wear eye protection remains a problem. quently, the likelihood of combat-related laser There has been only moderate progress made eye injuries on the battlefields of tomorrow will 218 D.J. Ivan continue to remain high.11 This means we will Table 16.2. Duration of cycloplegic agent effects. be faced with related dispositional decisions in Cycloplegic agent Percentage Duration of effect such cases to include management, evacuation, Tropicamide 0.5–1.0 4–6h and return to duty issues. Most laser-related eye Cyclopentolate 0.5–2.0 1d injuries will not compromise the integrity of the Scopolamine 0.25–0.50 2–3d ocular globe and will not usually involve any Homatropine 2.0–5.0 3–5d special medical AE criteria beyond routine Atropine 1.0–5.0 1–3wk ambulatory care. The spectrum of laser eye injuries will run the gamut from temporary reversible effect, such as lasers may result in an injury undistinguishable glare and flash blindness, to permanent damage from a corneal abrasion. In addition, exposure from outright ocular burns and hemorrhages. to laser energy not strong enough to directly Retinal damage can be caused by laser beams cause injury can result in reflex rubbing of the in both the visible and near infrared parts of the eyes, causing a secondary corneal abrasion. spectrum. These wavelengths are automatically Whenever a laser injury of the cornea is focused by the cornea and lens through to the suspected, a careful and comprehensive oph- retina. This focus significantly increases the thalmic examination, to include a dilated retinal energy density and, therefore, the potential to exam, must be accomplished to exclude other reach thresholds for damage in retinal tissues ocular tissue damage. increases dramatically. Corneal abrasions, although painful, are Many of these injuries will leave individuals relatively easy to manage clinically. Once more functionally disabled, either temporarily or per- serious injuries are excluded, corneal abrasions manently, thus presenting field commanders are treated with topical antibiotic drops and with additional casualty management consid- an appropriate cycloplegic agent. Cycloplegia erations and problems. In this chapter, laser- durations may vary depending on agent used induced eye injuries on the battlefield will (Table 16.2). Patching is appropriate, except for remain confined to those that affect the ocular corneal abrasions caused by soft contact lenses globe and surrounding ocular adnexa, although because such abrasions can be associated with powerful laser systems of today and tomorrow Pseudomonas infections. Patching or cyclople- are capable of causing even deeper and more gia may disrupt normal binocular function widespread tissue destruction (Fig 16.1). (stereopsis).

Corneal Lacerations Specific Ocular Injuries Tissue lacerations, such as in the cornea, are and Diseases described as either penetrating (partial) or perforating (through and through), if for example, Corneal Injuries the cornea is completely violated (Fig 16.2). Although most types of corneal lacerations Corneal Abrasions are treatable, perforating lacerations are more Corneal abrasions are caused by a wide variety serious because they are more likely to result of insults, including contact lenses, flying in permanent loss of vision. Further, perforat- projectiles, or direct contact by objects such as ing lacerations can introduce contaminated vegetation and fingers. Regardless of etiology, foreign material into the eye. Any resulting injuries to the cornea may vary from superficial intraocular infection, referred to as an endoph- epithelial defects to deeper corneal damage thalmitis, can be vision or life threatening. with the associated potential to develop a permanent corneal scar. Implications for AE A related corneal injury is laser burns. Although focused laser energy can result in Because virtually all corneal abrasions will heal serious burns or penetrating injuries, certain within a few days, such patients will usually not 16. Ophthalmic Patients 219

specialists feel that these eyes can travel safely at routine AE altitudes and that the most expedient AE methods should be selected that will deliver the patient to more deﬁnitive care as quickly as possible, thereby making altitude restrictions of lesser concern, especially if such a restriction would result in a signiﬁcant delay. However, the same cannot be said of intraocular gases in a closed eye, ie, following retinal detachment surgery, and will be discussed later in this chapter.

Lens Injuries Figure 16.2. Ocular injury terminology. Non- Isolated lens injuries are rare. Combat trauma intra–ocular injuries associated with an intact globe consist of (1) penetrating scleral injuries and or acute laser injury severe enough to cause a lacerations and (2) penetrating corneal injuries and lens injury is almost always associated with lacerations. Intraocular injuries resulting in rupture other more serious ocular damage. For this of the globe can involve single tissue injuries such as reason, all lens injuries need assessment by (3) perforating corneal injuries, or combinations an ophthalmologist as soon as possible, even of tissue injuries such as (4) perforating corneal, lens though not all such injuries will require im- and retinal injuries, (5) perforating corneal, iris, and mediate intervention. Ophthalmologic assess- lens injuries and, (6) double perforating injuries. ment, including baseline visual acuity and slit Intraocular injuries are also referred to as globe lamp examination, is required to determine the injuries. The lines in the figure indicate common extent of any associated lenticular damage. paths and corresponding solid circles indicate pos- Treatment for lens injuries will be necessary sible endpoints of potential ballistic particles that may involve the eye. whenever there is dislocation, formation of a cataract, or lens capsule rupture. Lens capsu- lar rupture often requires immediate surgical removal because exposure of the eye to lens require immediate AE. However, patients trav- proteins may result in a significant ocular eling in the AE system may have incidental inflammation. corneal abrasions so AE crews should know how to treat them. Implications for AE In most cases, urgent AE is required for serious corneal lacerations that occur in the Injury to the lens requires immediate ophthal- field because immediate evaluation by an oph- mologic evaluation for the reasons discussed thalmologist in a surgically capable facility is above, and the patient should thus be classified always required. Evacuation can be delayed for as urgent AE. If ophthalmologic evaluation a few days for less complicated nonpenetrating determines that the lens capsule is intact and no corneal lacerations, but contingency AE will other eye injury is present, such individuals can still be required for ophthalmologic evaluation usually return to duty. AE crews do not need to and treatment. accomplish any specific actions in the manage- Statistically, open eye injuries do better when ment of these patients. definitive ophthalmic care is not delayed. While some trapped air may be associated with pene- Globe Rupture trating lacerations, small amounts would not usually be expected to be a significant problem Globe rupture (ie, rupture of the eye) is a rela- in an open eye. While it is possible that an tively common combat-related ocular injury expanding bubble of trapped air in such an eye (Fig 16.2). The most common form of globe could cause additional ocular damage, many rupture is a perforating laceration, usually 220 D.J. Ivan of the cornea or sclera. Less commonly, Table 16.3. Field management for globe rupture. blunt trauma can cause rupture of the globe. Position the patient supine, with the head elevated Globe rupture must always be ruled out fol- Patch injured eye to eliminate light and contamination; lowing significant blunt trauma, especially if avoid direct pressure one eye is “soft” compared to the other eye or Shield the injured eye with a metal or plastic shield to there is obvious disruption of normal ocular prevent direct pressure and additional damage Minimize extraocular movements by also covering the architecture. good eye with a pinhole patch Any injury that perforates an entire layer or Prophylactic antibiotics should be administered coat of the eye carries with it a high potential intravenously to all patients with globe rupture for intraocular infection (endophthalmitis). Evacuation should be by urgent AE to the nearest Infection can be expected in 2% to 7% of all available ophthalmic care Altitude restriction: Usually none if the globe is open; perforating ocular injuries, with a slightly if closed and containing intraocular air or gas, see higher likelihood related to a perforating com- restrictions under retinal detachment section bat eye injury.12,13 Such injuries will require antibiotic intervention immediately. Intrave- nous fluoroquinolones would be an excellent first choice. Intravitreal antibiotics can also be With a ruptured globe, an appropriate field used, but an ophthalmologist must administer dressing can sometimes make a dramatic these. difference in final outcome. The injured eye The visual consequences of globe perforation should be covered with a patch to eliminate vary greatly, depending on the amount and light and protect the eye from contamination. It location of tissue disrupted as well as the is of critical importance that no direct pressure occurrence of any infection. However, today’s be applied to the globe. To prevent direct pres- modern ophthalmologic equipment and tech- sure and additional damage to the eye, a metal niques have dramatically improved our ability or plastic shield (eg, Foxx shield) should be to save the globe. properly secured over the patch for the injured eye. A Foxx shield is malleable and must be individually formed to the face so that its points Implications for AE of contact are clearly on the bony structures Regardless of etiology, a ruptured globe is an of the orbital rim and forehead and not on emergency that requires immediate surgical the patch or globe itself. To minimize extraocu- intervention by an ophthalmologist and should lar movements, the good eye should also be be classified as urgent AE. In most cases, the covered with a “pinhole” patch. A small hole prognosis for the eye will be guarded, but sta- in the center of the patch will give the patient tistically these eyes do better when definitive some vision while minimizing eye movement. ophthalmic care occurs quickly after the injury. In addition, intravenous prophylactic anti- Regardless, every attempt must be made to biotics (usually a fluoroquinolone) should be save the eye. given to all patients with a ruptured globe. Unfortunately, definitive care may be de- Unless full-service ophthalmic care is readily layed for hours or even days for casualties available at the site of injury, evacuation will be whose injuries occur in remote locations. In required for these patients. In general, this will these cases, appropriate field management and be in form of urgent AE because the failure to timely AE are of the utmost importance (Table receive timely specialized ophthalmic interven- 16.3) as discussed previously under corneal tion will increase the risk of both permanent lacerations. loss of vision and loss of the eye itself. There- Probably the most important issue for pa- fore, in an open globe rupture the benefits of tient transportation is position. Throughout expedient delivery of the patient to definitive the transportation process, the patient with a care usually outweighs most of the altitude- ruptured globe should remain reclined, with the induced effects. Thus, mandating an altitude head elevated and face up. In no instance restriction that significantly delays definitive should the patient be positioned head-down. care will prove problematic in most cases. 16. Ophthalmic Patients 221

Chorio-Vitreoretinal Injuries by an ophthalmologist as soon as possible. Patients should undergo evacuation as soon Chorioretinal injuries can be associated with as possible for ophthalmologic evaluation. any traumatic eye injury. They represent the However, these patients do not need to be clas- most likely type of laser injury to be encoun- siﬁed as urgent AE based on this type of injury tered. A complete ophthalmologic evaluation and require no speciﬁc treatment en route. of both eyes is required.

Vitreoretinal Hemorrhages Chorioretinal Burns Chorioretinal burns are the most likely and Traumatic hemorrhages from any cause will most serious laser-related eye injuries that will in general fall into four basic categories based occur on the modern battlefield. Management on location: subretinal, intraretinal, subvitreal, will depend on the site of the injury. A small and intravitreal (vitreal). Laser-induced hem- burn in the fovea can result in significant visual orrhage will vary in location and degree de- impairment, whereas burns in the retinal pending on the laser’s power, degree of focus periphery can be extensive and yet not affect (divergence), and wavelength, as well as which vision. These injuries require immediate oph- specific tissues are affected. thalmologic assessment to determine the etiol- Regardless of the etiology of hemorrhage, ogy, best management, and the potential for visual acuity may be affected as a direct con- return to duty. Laser eye experts should be sequence of the bleeding or because of the consulted immediately if a laser eye injury is primary location of the eye injury. Thus, a suspected. retinal hemorrhage may produce either an A laser injury of any significant degree in unrecognized and inconsequential small blink or near the macula will usually have serious spot if the damage is in the periphery, or a less permanent visual sequelae. Proper laser eye than best-corrected visual acuity, if central. protection remains the best defense against The treatment of vitreal hemorrhages is to laser eye injury. remove blood that does not spontaneously reabsorb after a suitable period of time. How- ever, treatment is required only when the Implications for AE remaining blood is functionally disabling. Immediate ophthalmologic evaluation is man- Although the emergency treatment of vitreo- datory, so these patients should be moved retinal hemorrhages is limited, several field by urgent AE if no ophthalmologist is avail- management principles should be followed to able locally. Unfortunately, little can be done minimize further damage (Table 16.4). Again, to restore vision after a serious macular position is an important issue for patient burn, making return to duty unlikely. These transportation. The patient with a vitreoretinal patients require no specific treatment en route hemorrhage should remain reclined with the other than pain relief or possibly systemic head elevated. Field evaluation should include steroids if recommended by the receiving ophthalmoscopic and x-ray evaluation for ophthalmologist. intraocular foreign bodies with reexamination Chorioretinal Tears

Table 16.4. Field management of vitreoretinal Chorioretinal tears represent a true emergency hemorrhages. and need immediate ophthalmologic evaluation and treatment. Consequently, patients with Position the patient supine, with the head elevated Field evaluation by ophthalmoscope and x-ray for this injury must be evacuated at the earliest intraocular foreign bodies, with re-examination by an possible moment and should be classiﬁed as ophthalmologist as soon as possible urgent AE. The treatment of chorioretinal tears Evacuation should be as soon as practicable to the is beyond the scope of this chapter and will nearest available ophthalmic care; neither urgent AE need to be addressed on a case-by-case basis by nor speciﬁc treatment en route is required ophthalmologists. 222 D.J. Ivan

Implications for AE Table 16.5. Intraocular gases. Weight Reabsorption These patients should remain as immobile as Types of gas (relative to air) time (1cc) possible during AE to minimize the risk of retinal detachment or vitreal hemorrhage. Field Air Same 7d and AE management is similar to those used Sulphur hexaﬂouride Heavier 10–14d Perﬂourocarbon gases Heavier 10–65d for globe rupture with the exception of the Xenon Heavier 1–2d requirement for antibiotics unless the tear is associated with a ruptured globe.

Retinal Detachment completely avoided in peacetime, in may be absolutely necessary in military situations. Retinal detachment should always be consid- Therefore, these issues must be totally con- ered following significant ocular trauma or sidered prior to planning and executing an AE when a patient complains of a loss of vision that mission. is usually described as “a shade being pulled over the visual field.” Field and AE manage- Implications for AE ment are the same as for chorioretinal tears. The details of specific diagnosis and treatment The reabsorption of these intraocular gases are beyond the scope of this text. However, its varies with the amount and type of gas involved treatment is significant to AE because of the (Table 16.5). Further, their effect on specific intraocular gases used during ophthalmologic patients at altitude has some individual vari- surgery. ability. Therefore, recommendations regarding Intraocular gases have been used to tampon- AE vary and are based on many different ade retinal tissue since Ohm introduced them considerations. The Aerospace Medical As- in 1911. It was not until 1973 that gases other sociation has published basic guidelines re- than air were used.14,15 Today, ophthalmologists garding routine air travel following intraocular use mixtures of air and other exotic gases surgery.19 Those guidelines state that flight is such as sulfur hexafluoride and perfluorocar- contraindicated until any injected gas bubble bon gases to help position or tamponade the decreases to less than 30% of the volume of the retina against the underlying ocular tissues vitreous. They further state that this will take to facilitate retinal reattachment and healing. approximately 2 weeks in the case of sulfur Exotic gas mixtures are used because of their hexafluoride and 6 weeks if perfluoropropane weight, ability to expand after injection, and was used.19,20 slower reabsorption times, all of which pro- In general, if patients with residual intrao- mote more prolonged positive effects in the eye cular gas must move for any reason cabin alti- compared to air alone. Nonetheless, all such tude should be limited to 2000ft or lower or no gases are subject to the same gaseous laws as higher than the altitude of the sending location, air and thus expand at altitude. However, the if higher than 2000ft. If other more urgent debate regarding the relationship between patients require movement on the same “safe and tolerable” amounts of intraocular gas mission as such “eye” patients, and an altitude and routine flight altitudes remains unresolved. restriction will significantly delay the mission While in general it is believed that a 10% and endanger lives, then the altitude restriction bubble should be safely tolerated at routine should not be requested. cabin altitudes, not all studies agree.16–18 The two major concerns are the impact an expanding gas bubble may have on retinal perfusion as In-Flight Issues the intraocular pressure increases in a closed globe and the tissue damage that may occur An eye problem may not always be readily due to delays while awaiting an AE aircraft apparent in an obtunded, unconscious, or capable of altitude restriction. While air travel heavily sedated patient, especially during con- following intraocular surgery may be easily and tingency AE. If an otherwise conscious patient 16. Ophthalmic Patients 223 suddenly complained of pain, decreased vision, available. Therefore, expedient delivery of the or increased drainage from the eye or orbit patient to definitive care typically overrides during aircraft ascent, this should draw imme- any altitude restrictions. One exception is for diate concern to the possibility of an expanding patients who have had surgical introduction of intraocular air bubble. Research has shown that intraocular gas in a closed globe. Further, there the expansion of as little as 0.25 to 0.50cc of are no absolute contraindications for moving air at altitude can significantly increase intraocular injuries, and a decision regarding AE ocular pressure to levels that threaten retinal profiles must take into consideration other perfusion.16 patients and factors related to the contingency In the event of the acute onset of eye pain situation. It is critical for medical triage per- during AE, an attempt should be made to sonnel in the field to make the proper clinical gently and carefully determine if gas is now and evacuation decisions early in the course of visible in the anterior chamber. A dire sign of the injury. potential intraocular air is prolapse of intra- Future providers will be challenged with new ocular contents. and expanding threats, such as the prolifera- If the presence of intraocular air creates tion of lasers on the battlefields of tomorrow. problems during an unrestricted altitude AE Telemedicine communication in the future may flight, the flight crew should be alerted im- facilitate field triage by extending ophthalmo- mediately and a request should be made to logic intervention and decisions directly to the descend the aircraft such that the cabin altitude scene. Certainly, every effort should be made to is 2000ft above ground level or lower. Such a prevent eye injuries. However, when injuries do luxury may not always be operationally pos- occur the modern combatant can take comfort sible, especially in hostile territory, but once that a modern AE system will help ensure free of immediate danger an appropriate lower that definitive medical care is obtained more flight level should be flown as expeditiously as quickly than before. possible. Resolution of the complaint upon descent References would be reassuring. Although damage may have already been done, lowering cabin altitude 1. Hornblas A. Ocular war injuries in South may prevent further damage and restore ade- Vietnam. Surg Forum 1973;24:500–502. quate retinal blood flow. However, no attempt 2. Wong TY, Seet B, Ang C. Eye injuries in should be made to replace any expulsed ocular twentieth century warfare: A historical perspec- contents back into the globe. tive. Surv Ophthalmol 1997;41:433–459. Finally, motion sickness associated with AE 3. Tredici T. Management ophthalmic casualties in Southeast Asia. Milit Med 1968;133:355– is a major concern with all open eye injuries or 362. recent intraocular surgery. Such motion sick- 4. Dausey-Browning GC. The value of ophthalmic ness may cause vomiting, leading to ocular or treatment in the field. Br J Ophthalmol 1994; suture rupture. Appropriate antiemetics should 28:87–97. be employed if evacuation and mental status 5. Scott GI, Michaelson IG. An analysis and follow- conditions allow their use, but only after con- up of 301 cases of battle casualty injury to the sideration of the potential impact on any other eyes. Br J Ophthalmol 1946;30:42–55. bodily injuries. 6. Leedham CS, Bood CG, Newland C. A descriptive analysis of wounds among US Marines treated at second-echelon facilities in the Kuwait Conclusion theater of operations. Milit Med 1993;158: 508–512. 7. Hornblas A. Eye injuries in the military. Int Rapid and appropriate AE of patients with Ophthalmol Clin 1981;21:121–138. serious eye injuries is an absolutely critical step 8. Treister G. Ocular casualties in the 6-Day War. in facilitating a favorable outcome when these Am J Ophthalmol 1969;68:669–675. injuries occur in locations where definitive oph- 9. Cruise RR. Protection of the eye in warfare. Br thalmologic evaluation and treatment is not J Ophthalmol 1917;1:489–492. 224 D.J. Ivan

10. Heier JS, et al. Ocular injuries and diseases at a den Glaskorper. Graefes Arch Klin Ophthalmol combat support hospital in support of Operation 1911;79:442–450. Desert Shield and Desert Storm. Arch Ophthal- 15. Norton EWD. Intraocular gas in the manage- mol 1993;111:795–798. ment of selected retinal detachments. Trans Am 11. Ivan DJ, et al. Laser induced acute visual and Acad Ophthalmol 1973;77:85–98. cognitive incapacitation of aircrew, protection, 16. Dieckert JP, et al. Air travel and intraocular gas. management, and cockpit integration. In: Ophthalmology 1986;93:642–645. Proceedings of the NATO Advisory Group on 17. Lincoff H, et al. Air travel and intraocular gas, Aeromedical Research and Development. 1998. I. The mechanisms for compensation. Arch AGARDOGRAPH AR-354, chapter 12, Ophthalmol 1989;107:902–906. AGARD, Neuilly sur-Seire, France. pp 87–90. 18. Mills MD, et al. An assessment of intraocular 12. Brinton GS, et al. Post-traumatic endophthal- pressure rise in patients with gas-ﬁlled eyes mitis. Arch Ophthalmol 1984;102:547–550. during simulated air ﬂight. Ophthalmology 13. David DB, et al. Bacillus endophthalimitis. Br J 2001;108:40–44. Ophthalmol 1994;78:577–580. 19. Bergan L, et al. Medical guidelines for air travel. 14. Ohm J. Uber die Behandlung der Netzhautablo- ASEM 1996;67(suppl):B14–B15. sung durch operative Entkeering der subreti- 20. Chang S. Retina. Mosby, Philadelphia, 1994. vol nalen Flussigkeit und Einspritzung von Luft in 3. chapter 131, pp 2115–2129. 17 Peripheral Vascular Casualties

David L. Dawson

Until the 20th century, the acute surgical documented an impressively low 5.1% lower- management of vascular injuries was solely limb amputation rate.3 Ninety-five percent of directed at the control of hemorrhage. By patients were admitted to the hospital within 30 the 1950s, a number of factors contributed to minutes of their injury and more than 80% had the successful application of vascular repair revascularization within 4 hours. In addition to techniques. In military medicine, rapid casualty rapid intervention, patch angioplasty arterial evacuation from the battlefield, using both heli- repair and the use of temporary shunts to main- copters and fixed-wing aircraft, often allowed tain flow during treatment of associated frac- surgical care to be rendered within 1 to 2 hours tures and soft-tissue injuries were felt to have following injury, thus improving outcomes. contributed to these results. In addition, better understanding of the im- In wars of the past century, vascular injuries portance of debridement, the use of delayed were reported in 0.07 to 2.4% of the combat primary wound closure, and the availability of wounded. The incidence is higher, up to 10%, antibiotics decreased the hazards of infectious when considering only those seriously injured complications. The broader use of arterial re- who are evacuated to a second- or third- pair preserved limb function and successfully echelon battlefield hospital. Vascular trauma lowered amputation rates following major can be expected to make up a significant vascular injury from approximately 50% in portion of the injuries sustained in the modern World War II to 13% during the Korean combat environment because wounding pat- conflict. Aeromedical evacuation (AE) and sur- terns of high-velocity missiles or fragments gical care further improved vascular outcomes often injure major vessels. In addition, the during the Vietnam War.1 In Vietnam, Rich and modern soldier’s body armor may protect colleagues reported an overall limb salvage rate him from otherwise fatal chest or abdominal of 86.5%.2 Repair of arterial injuries was the injuries. Therefore, extremity wounds, often norm by that time, and only 15 of 1000 cases with major vascular injuries, can be expected to were treated with primary ligation. In addition be a prominent part of the military surgeon’s to the availability of rapid casualty evacuation, experience in any future conflict. better surgical training and new techniques Vascular injuries can occur from multiple (including the use of the Fogarty embo- types of penetrating or blunt trauma. Blood lectomy catheter and external fixation of asso- vessels can also be injured by stretch, blast, ciated fractures) contributed to these improved or cavitation effects or by direct physical results. disruption.4 Direct injury can result not only Further insight into vascular trauma can be from penetrating trauma but also secondarily gained from the paramilitary and terrorist from fracture fragments lacerating the vessel. activities in Northern Ireland. In his report Minimal arterial injuries with nonocclusive on a decade of such trauma, Barros D’Sa intimal flaps may be asymptomatic and can

225 226 D.L. Dawson resolve over time without specific treatment.5 More extensive intimal disruption leads to thrombosis and occlusion. Injuries to major blood vessels can pose an immediate threat to lives and limbs. While acute problems often require management within hours of onset,7 casualties may require urgent AE for further intervention or management of associated injuries. Elective AE for convalescence and rehabilitation can usually be accomplished at an optimal time. Vascular disease alone may also necessitate AE. Patients with acute complications of peripheral vascular disease may need to be transferred to facilities with capabilities for complicated surgical procedures, angiography and endovascular therapy, and critical-care support. These patients are often elderly, have a history of tobacco use, may have diabetes, and frequently have concomitant cardiac, cerebrovascular, pulmonary, or renal disease. This chapter will discuss the specific injuries and diseases likely to require AE, the special postoperative considerations, and the general transportation considerations for these vascular patients. Figure 17.1. Emergency department arteriography following a motor vehicle accident demonstrates superficial femoral artery occlusion and femur Specific Vascular Diseases fracture. A short-segment thrombosis was due to an intimal tear. and Injuries

Significant physiological disturbances can re- severe distal ischemia with a single level of sult from vascular disease or injury, and these arterial occlusion. The result is a much higher disturbances can significantly effect a patient’s rate of amputation after acute vascular occlu- clinical status during AE. The most common sion in younger patients compared to older injuries and diseases will be discussed, includ- patients. ing the specific AE implications of each. The “five Ps” describe clinical findings associated with acute ischemia: pulselessness, Ischemia pallor,pain,paresthesia,and paralysis. Coolness, pallor, and the loss of palpable pulses distal Major arterial injuries interrupt distal blood to a site of injury usually indicate a significant flow (Figs 17.1 and 17.2). The severity of resul- arterial injury. These are not specific findings, tant ischemic injury depends on several factors, however, because cool extremities without pal- including the adequacy of collateral arterial cir- pable pulses may also be the consequence of culation, metabolic state, temperature, asso- hypovolemic shock with marked peripheral ciated venous injury, soft-tissue injury, and vasoconstriction. muscle type. Collateral circulation may be well Other signs of vascular injury include empty developed with chronic arterial occlusions in veins, decreased capillary refill, penetrating older patients with atherosclerosis, but healthy injury in proximity to major artery, or periph- adults (such as trauma victims) may have eral neurological deficit. 17. Peripheral Vascular Casualties 227

or proximal extremity vessels can cause exsanguination in minutes. Pulsatile bleeding or the presence of an expanding hematoma indicate arterial injury. Control of ongoing blood loss is always an immediate treatment priority that is accomplished using direct pressure or tourniquets. Direct manual pressure or pressure dressings can be applied to most extremity wounds but cannot be used for neck wounds and are of limited value for wounds to trunk vessels. There are few indications for tourniquet use, as this maneuver may result in permanent neurological injury and increase the likelihood of subsequent amputation. Extremity tourniquets should only be applied when other means fail to control bleeding and tourniquet application is necessary as a lifesaving measure in evacuating a casualty.Tourniquets, once applied, should be removed only when surgical means to arrest bleeding are available. Vasospasm and tamponade by surrounding tissues are physiological hemostatic mechanisms that help limit blood loss from vascular injuries. Bleeding may also slow as hypotension Figure 17.2. Preoperative arteriogram performed and hypovolemic shock intercede. A com- in a 14-year-old male who sustained a close- pletely divided vessel can retract and constrict, range shotgun wound to the right lower extremity. often with complete cessation of bleeding after Although there has been direct arterial injury, there an initial brisk hemorrhage. Blood loss can be was adequate collateral circulation to maintain via- more severe if the injured vessel is incompletely bility for several hours. Popliteal to posterior tibial transected, as the lacerated segment may artery bypass with a vein graft resulted in long-term remain open. Further, bleeding that has limb salvage. stopped in a patient with hypovolemic shock may resume after resuscitation restores perfu- Implications for AE sion pressure. Hemorrhage from an injured vein can actu- Patients with ischemic, or potentially ischemic, ally be greater than that from an arterial injury, injuries should be positioned so the medical despite the fact that the arterial pressure is con- crew has the ability to monitor distal blood flow siderably higher. Veins have larger diameters of the injured limb. Vasoconstriction due to and less capability for vasoconstriction because cooling can affect tissue perfusion, a consider- there is much less smooth muscle in the walls ation during transport in large military air- of veins. Although there is a difference between frames where significant hypothermic exposure the arterial and venous pressures, the two sides is a constant risk. of the circulation carry equal flow. Tears in vein walls can extend easily, and attempts to expose Hemorrhage the bleeding site can exacerbate blood loss. It is often difficult to accurately characterize The immediately life-threatening complication the amount of blood lost. External losses can from vascular injuries is hemorrhage. Notably, be deceptive, either appearing much greater or 80% percent of civilian trauma deaths are from less than actual loss. Internal losses are occult hemorrhage.6 Untreated major injuries to trunk and usually manifest only by the hemodynamic 228 D.L. Dawson consequences of the loss of intravascular (IV) Ischemia Reperfusion Injury volume. Nevertheless, some clinical findings are Prolonged interruption of a limb’s blood supply pathognomonic for major vascular injury. For results in cellular ischemia, which in turn leads example, a systolic blood pressure less than to severe biochemical derangements. These 90mmHg in a patient with a penetrating lower- derangements include energy loss from adeno- quadrant injury to the abdomen almost always sine triphosphate breakdown to hypoxanthine, indicates an iliac artery injury. Shock in a increased lactic acid production, and failure patient with trunk or extremity injuries, espe- of membrane ion pumps. Normal membrane cially in cases of blunt trauma, can be due to concentration gradients are lost, with increases blood loss unrelated to injury of a major vessel, in intracellular sodium (and water) and cal- eg, long bone or pelvis fractures. cium, as well as extracellular potassium. Analy- sis of venous blood from ischemic limbs

Implications for AE shows marked decreases in PO2 and pH, with increases in P and potassium. Patients must have hemorrhage under control CO2 Revascularization following prolonged limb prior to AE, whether urgent or elective. In ischemia does not completely prevent progres- extreme cases, the use of tourniquets might be sion of tissue damage because microcirculatory required to achieve hemostasis. Patients who failure and continued hypoxia are common. In have had significant blood loss should be placed addition, reoxygenation of previously ischemic in litter positions where the medical crew can tissue results in cytotoxic effects secondary readily assess their hemodynamic status and to the generation of reactive oxygen inter- assure that hemorrhage does not recur during mediates and proinflammatory substances transport. (including eicosanoids) and endothelial cell– polymorphonuclear leukocyte interactions. Shock Revascularization of a severely ischemic limb also leads to increased compartment pressures, Hypovolemia from acute blood loss is one of which causes muscle necrosis if not recognized the most common causes of shock; the state and treated with fasciotomy (see discussion is defined as inadequate perfusion to sustain below). the physiological needs of organ tissues. Drop Reperfusion injury can also have significant in blood pressure may reflect the onset and systemic effects. This is related to the high severity of shock, but significant shock may concentrations of lactic acid and potassium occur before systolic hypotension is noted. returning to the systemic circulation from a Physiological compensation mechanisms for revascularized ischemic limb. If muscle necrosis hemorrhage include peripheral and visceral has occurred, large amounts of myoglobin, vasoconstriction (thus shunting blood to the creatine phosphokinase, and other toxic central circulation) and progressive tachycar- compounds are released. The resultant “myone- dia. Age, concomitant illness or injury, medi- phropathic metabolic syndrome” is character- cations, and environmental factors all affect ized by metabolic acidosis and hyperkalemia, individual responses to hemorrhagic shock. kidney failure from myoglobin precipitation in the renal tubules, a reperfusion-induced Implications for AE renal medullary perfusion defect, pulmonary The single most important resources required failure caused by inflammatory mediators, and for AE of patients with hemorrhage are ade- depressed cardiac function. In severe cases, quate fluids and blood products to continue reperfusion injury can lead to limb loss or even resuscitation, should they be required. This death. is critical for missions longer than 5 hours, Ischemic reperfusion injury is diagnosed all overseas missions, and any other missions on the basis of systemic signs and symptoms. where emergency diversion may add hours to Metabolic acidosis, hyperkalemia, and fluid the transport time. sequestration can manifest as increased 17. Peripheral Vascular Casualties 229 postoperative fluid resuscitation requirements. be accomplished prior to AE when indicated Dark, tea-colored urine may indicate myoglo- (see below). binuria. Oliguria may indicate intravascular volume depletion or renal failure from acute tubular necrosis, which may ensue in the first Compartment Syndrome several days after injury or operation. Compartment syndrome occurs when inter- Management principles include complete stitial pressure within a confined anatomic early revascularization, anticoagulation, liberal compartment exceeds the capillary perfusion use of fasciotomies, and intensive medical pressure (30 to 50mmHg), thus resulting in support postoperatively. In trauma, early revas- microvascular compromise and ultimately cell cularization of an acutely ischemic limb should death. All four extremities, in particular the be given priority because the longer the dura- legs, contain osseofascial compartments that tion of limb ischemia the greater the chance are surrounded by a relatively inelastic fascial of reperfusion injury. If immediate, definitive covering. Important risk factors for compart- revascularization is precluded by orthopedic ment syndrome in the trauma victim include or soft-tissue injuries, a temporary in-dwelling crush injuries, severe closed fractures of shunt can be used. When systemic anticoagu- the extremities, combined arterial and venous lation with heparin is contraindicated, eg, injuries, prolonged ischemia with reperfusion, because of risks of increased bleeding from and circumferential full thickness burns. In associated injuries, regional heparin can be addition, iatrogenic compartment syndromes employed in the affected limb after vascular can be caused by extravasation of fluids control is obtained. Early fasciotomy (prior administered using pressure infusers and tight to revascularization) should be considered if dressings. ischemia has been prolonged or if severe soft- Unrecognized compartment syndrome con- tissue or combined arterial and venous injury is tinues to plague trauma victims.7 The diagnosis present. may not be obvious and can be excluded only Postoperatively, intensive medical support is in the presence of an open extremity wound. often required. To decrease the risk of myoglo- Palpable peripheral pulses do not rule out this bin precipitation in the renal tubules and ame- diagnosis because capillary perfusion can cease liorate the medullary perfusion defect, urine at pressures well below the systolic arterial can be alkalinized with bicarbonate infusions. pressure. An osmotic diuresis should also be established Signs and symptoms that suggest compart- by the administration of mannitol. Mannitol ment syndrome include pain (especially pain can also attenuate local and systemic effects of out of proportion to the injury or pain with free radical-mediated tissue damage by acting stretching or contraction of the muscles in the as an hydroxyl radical scavenger, although its compartment), swollen or tense compartments, effects are limited to the extracellular space. If and tenderness. Sensory loss and paresthesia available, hyperbaric oxygen therapy may also are early signs of compromised peripheral be useful in decreasing edema and muscle nerve function. Loss of motor function occurs necrosis after reperfusion. later and may be irreversible.

Implications for AE Measurement of Compartment Pressure It is crucial that AE medical crew members Compartment pressure can be measured if have an accurate history of which patients have invasive pressure monitoring capability is avail- undergone revascularization procedures. A dia- able. One of the simplest techniques is the gram from the surgeon can be a particularly “continuous infusion technique,” where a hypo- useful contribution to the medical record. dermic needle or intravenous catheter is in- Extra fluids must be available to assure a urine serted into the tissue and patency is maintained output large enough to preclude the kidney by the slow but continuous infusion of saline. damage described above. Fasciotomies should The pressure of the fluid within the needle or 230 D.L. Dawson catheter is continuously monitored with a swelling and mild discomfort. Increased tissue standard blood pressure transducer. Measured turgor, distension of superficial veins, and pro- compartment pressures <15mmHg reliably ex- minent venous collaterals may all be evident. clude the diagnosis of compartment syndrome. Examination with a hand-held continuous- wave Doppler ultrasound can screen for deep- Implications for AE venous thrombosis (Fig 17.3). In the exam, asymmetry of the limb compared to the con- The possibility of compartment syndrome tralateral limb, diminished spontaneous venous should be considered when examining any flow, and loss of the normal phasic variation patient after vascular surgery, even after fas- with ventilation are signs suggesting occlusive ciotomy. This is usually related to fasciotomies venous thrombosis. Small Doppler devices can that have been performed through limited inci- be used prior to transport in emergency depart- sions or have failed to release all potentially ment or field settings, but the fairly subtle find- effected compartments. ings of the extremity venous examination Development of a compartment syndrome may not be detectable in a noisy aircraft during transport can result in irreversible environment. nerve and muscle injury, leading to permanent The best noninvasive test to diagnose deep- disability or even limb loss. The cornerstone venous thrombosis is duplex venous ultra- of effective management of compartment sonography: 2D gray-scale B-mode imaging syndrome remains the preflight recognition of combined with pulsed-wave Doppler flow patients at risk. Extensive surgical fasciotomies evaluation. A venous thrombosis can be either to decompress compartmental hypertension directly visualized or inferred by the absence of are the best way to treat or prevent compart- vein wall collapse with extrinsic compression. ment syndrome and should be done prior to air Contrast venography is rarely, if ever, indicated. transport any time the condition is suspected.7,8 In high-risk patients, prophylactic fasciotomies are often appropriate prior to AE because monitoring for changes in the status of the limb is usually difficult during flight. If a Critical Care Air Transport (CCAT) Team is available, fasciotomies can be performed during flight for those patients who unexpectedly develop compartment syndrome.

Venous Thrombosis Patients with conditions that require AE often possess Virchow’s classic triad of factors predisposing to venous thrombosis, ie, local vessel wall injury, hypercoagulability, and stasis. Clinical conditions associated with these risk factors include: surgery (especially orthopedic, thoracic, abdominal, and genitourinary procedures), trauma (especially with pelvic, femur, or tibia fractures or with any neurologi- Figure 17.3. A Doppler ﬂow detector is essential for cal injury), malignancy, pregnancy, postpartum monitoring the status of limb perfusion. Several state, immobilization, and in-dwelling venous brands of hand-held portable continuous-wave catheter use. Doppler units are available. This unit has an optional Thrombosis of pelvic or lower-extremity strip chart recorder that can also be connected to deep veins (eg, iliac, femoral, or popliteal veins) a portable photoplethysmography device (photo most often presents with unilateral extremity courtesy of D.E. Hokanson Inc). 17. Peripheral Vascular Casualties 231

Complications affecting the limb associated established diagnosis of lower-extremity deep with venous thrombosis almost always develop vein thrombosis. Blood gas abnormalities may months or years later in the form of chronic be seen but are insufficient to diagnose pul- venous insufficiency of an extremity. However, monary embolism. acute limb-threatening complications can occur Electrocardiographic (ECG) abnormalities in rare cases. If there is concomitant obstruc- may be noted in field settings or during trans- tion of both the deep and superficial collateral port if multilead capabilities are available. veins, marked impairment of venous outflow of Associated ECG findings include: sinus tachy- the limb will occur. The result is a cyanotic hue cardia; atrial fibrillation or flutter; and an and dramatic swelling of the limb, termed S wave in lead I, a Q wave in lead V3, and an “phlegmasia cerulea dolens.” In severe cases, inverted T wave in lead V3. A rightward axis interstitial tissue pressure may exceed the shift and T wave inversion in lateral leads may capillary perfusion pressure, causing arterial indicate right ventricular strain. An initial man- hypoperfusion and ischemia, termed “phlegma- agement plan can be made before arrival at a sia alba dolens.” definitive care site with lung scintigraphy or pulmonary angiography capability. Pulmonary Thromboembolism Implications for AE Pulmonary thromboembolism is the most serious acute risk associated with lower-extremity Patients with known or suspected pulmonary or pelvic venous thrombosis. Although as thromboembolism should be stabilized and many as one half of patients with pelvic vein treated before transport whenever possible. thrombosis or proximal leg deep venous throm- If the patient has remained normotensive bosis have pulmonary embolism, most are with normal right ventricular function, pul- asymptomatic. In the presence of large or monary embolism is in general managed with multiple emboli, the acute signs and symptoms anticoagulation. IV heparin infusion (5000 are often dramatic and include9: to 10,000U heparin bolus, followed by an infusion of 1000 to 1500U/hour) remains the • Increased pulmonary vascular resistance. standard therapeutic choice in acute and • Impaired gas exchange. subacute settings. An activated partial throm- • Alveolar hyperventilation due to reflex boplastin time (PTT) twice the control value stimulation of irritant receptors. confirms therapeutic heparin dosing. Recent • Bronchoconstriction and increased airway studies suggest fixed-dose, subcutaneous low- resistance. molecular-weight heparin may be as effective • Loss of pulmonary compliance from lung and safe as adjusted-dose, IV unfractionated edema, lung hemorrhage, and loss of heparin for the initial management of pul- surfactant. monary embolism.10 • Circulatory collapse and death may result Adjunctive measures include pain relief and from acute right ventricular dysfunction. supplemental oxygen, especially during flights The clinical diagnosis of pulmonary embo- with cabin altitudes of approximately 8000ft. lism can be challenging. Dyspnea and tachyp- For patients with contraindications to anticoa- nea are frequent but nonspecific. Associated gulation, or those with recurrent pulmonary syncope, hypotension, or cyanosis may indicate embolism despite adequate anticoagulation, an a massive embolism. Small, distally lodged inferior vena cava filter should be placed.11,12 emboli may cause pleuritic pain, cough, or Caval filter placement, when available, should hemoptysis. Chest radiographs can help exclude be considered prior to elective transfer of other causes of acute pulmonary compromise patients with pulmonary embolism who cannot but rarely yield signs of pulmonary embolism. be maintained on heparin. The diagnosis of pulmonary embolism should Transthoracic echocardiography, if available, be suspected in the setting of any severe illness should be considered prior to interhospital or injury, especially if there is leg swelling or an transports to distinguish between different 232 D.L. Dawson

Table 17.1. Vascular contraindication to AE. blood pressure control, appropriate analgesia, Absolute (contraindications to elective, urgent, and supplemental oxygen, and consideration of contingency AE) beta-blocker use. Because concomitant dia- Pulmonary thromboembolism associated with betes is also common, blood glucose levels hypotension or acute right ventricular dysfunction should be checked regularly. Uncontrolled bleeding Acute ischemia if resources are locally available for revascularization Relative (contraindications to elective AE) Surgical Considerations Thrombolytic therapy Within 24h of hyperbaric oxygen therapy* Associated cardiac complications (myocardial ischemia Soft-Tissue Coverage or heart failure) All vessels, vascular repairs, and vascular grafts * Unless the cabin altitude pressure can be maintained at require adequate soft-tissue coverage to mini- the equivalent of sea level or the altitude (mean sea level) mize the risk of desiccation and infection. of the sending facility. Exposed vein grafts and arterial suture lines tend to break down, with resultant delayed hemorrhage. Although vessel coverage by skin etiologies of cardiovascular instability that may and subcutaneous tissue is important, coverage present with some features similar to pul- by fascia and/or muscles is critical. In some monary embolism. These include acute myocar- cases, muscle flaps may be employed and skin dial infarction, pericardial tamponade, thoracic left open. In cases of extensive soft-tissue injury aortic dissection, and right heart failure. (eg, high-velocity missile injuries), grafts may AE is contraindicated in those patients with be routed around the zone of injury. untreated pulmonary embolism associated with Nonanatomic positioning of grafts, either sub- hypotension or right ventricular hypokinesis cutaneous or deep to fascia, may be necessary. because the mortality risk is high (Table 17.1). When used, this positioning should be clearly Right heart failure and cardiogenic shock communicated to the accepting medical team. is treated with fluid restriction and the beta-adrenergic agonist dobutamine (a positive Shunts inotropic agent with pulmonary vasodilating effects). In cases of refractory hypotension, Placement of a temporary shunt to bridge a thrombolytic therapy may be required in segment of damaged artery can be used to addition to anticoagulation. In extreme cases, stabilize patients, thus allowing urgent AE to a catheter extraction or surgical embolectomy referral center for management by a vascular may be needed. specialist. Shunt placement is not technically demanding and can be rapidly performed (Fig Nontraumatic Vascular Disease 17.4). Shunt placement for management of limb ischemia is not prioritized above control of Patients with nontraumatic vascular disease are hemorrhage. It is unlikely to affect the outcome typically older and are likely to have many of patients who have an uncorrected source comorbid conditions. Detailed medical his- of hemorrhage or uncorrectable low cardiac tories should be obtained prior to transport output.13 Fasciotomies are required anytime a whenever possible. Peripheral arterial disease shunt is being used to maintain limb perfusion is frequently associated with atherosclerosis in during prolonged air transport. other vascular beds, including the coronary and Shunts can be left in place for hours but need carotid arteries. Patients with concomitant to be monitored. One case has been reported heart disease may experience perioperative that described the use of a shunt that was myocardial infarction, dysrhythmias, or heart inserted into the cut ends of a lacerated failure. superficial femoral artery prior to a 950-mile Risk of complications during AE in these air evacuation.14 The shunt functioned well patients is minimized by continuous monitor- for 16 hours. Animal models of traumatic ing, avoiding volume overload, attention to arterial injury have demonstrated that non- 17. Peripheral Vascular Casualties 233

Figure 17.4. A Sundt carotid endarterectomy shunt caliber rifle wound. The limb was successfully revascu- temporarily bridges the gap after the midportion of larized with an extra-anatomic bypass from the the superficial femoral artery was destroyed by a. 30- proximal superficial femoral to the popliteal artery. heparin-bonded shunts can provide adequate Arterial spasm is a greater problem in young limb blood flow to prevent acidosis, myocyte patients than in older patients with atheroscle- ischemic necrosis, or systemic complications, rotic arteries. Spasm can be treated with direct even when shunts are in place for up to 24 infusion of a vasodilator (eg, intra-arterial hours.15 Continued shunt patency can be nitroglycerin infusion or injection of 60 to assessed with a Doppler, either directly or by 120mg of intra-arterial papaverine) or post- serially assessing the distal arterial perfusion. operative treatment with a calcium channel In a contingency setting or in deployed blocker (eg, nifedipine 10 to 40mg orally every military operations, general and orthopedic 4 hours). Postoperative thrombosis is an indi- surgeons should consider shunt use and fas- cation for reoperation. ciotomy for initial surgical management of an ischemic limb if rapid AE with CCAT Teams Continuous-Wave Doppler are available. Continuous-wave Doppler is the most common method used to objectively monitor peripheral arterial circulation and is much more sensitive Postoperative Considerations than palpation of pulses. The only equipment Arterial Patency required is a pocket or portable continuous- wave Doppler flow detector (Fig 17.3), acoustic The result of the revascularization should gel, a sphygmomanometer, and pressure cuffs. be objectively demonstrated with continuous- A useful measure of perfusion of an injured wave Doppler or operative angiography. lower extremity can be obtained by determin- Reparable technical problems potentially ing the ratio of the Doppler-derived systolic compromising the success of revascularization arterial pressure of the arm to that measured at should be corrected before transport. Exam- the level of the ankle on the injured side. This ples include anastomotic narrowing from poor is the “ankle/brachial index” (ABI). For each suture technique, distal embolization or throm- lower extremity, the ankle pressure is deter- bosis, elevation of intimal flaps, graft twisting or mined as the highest measured systolic pressure entrapment, and spasm. obtained by comparing the anterior tibial, 234 D.L. Dawson posterior tibial, and in some cases the peroneal deployability of conventional radiology equip- arteries. The systemic pressure is determined ment, as does the need for darkrooms, fresh as the higher of the two brachial pressures. water, steady power, etc. While radiographic An analogous arterial pressure index can be assessment during transport is impractical, obtained for an injured upper extremity by there are commercially available portable comparing the pressure from the injured arm to ultrasound systems that can be used for vascu- that of the uninvolved arm. The use of ratios lar imaging. Compact, medium-resolution units corrects for some of the effects of systemic that weigh under 10lb can provide gray-scale pressure variations that occur over the course images adequate for a large number of ultra- of transport and allows comparison of perfu- sound exams, such as detecting the presence of sion measurements between individuals. an abdominal aortic aneurysm, venous throm- A measured pressure gradient (with an index bosis, or other vascular conditions. of <0.90) indicates the presence of arterial Duplex scanning combines real-time 2D obstruction secondary to occlusion or stenosis B-mode imaging of vessels and surrounding that narrows the lumen diameter by >50%. structures with pulsed Doppler ultrasound Serial assessments can detect changes in lower- evaluation of blood flow. Duplex scanning, by extremity arterial circulation and are used to combining sonographically derived imaging monitor the patency of arterial reconstructions. and hemodynamic information, takes advan- The normal ABI is 1.0. However, a value ≥0.9 tage of the strengths of each modality and after acute injury indicates a low likelihood of avoids many of the problems inherent with the a significant arterial injury requiring urgent use of imaging or flow studies alone. The two evaluation.16 The ABI may also be low due to greatest problems with duplex scanning are chronic arterial occlusive disease. This may be that it requires a skilled operator and advanced suspected in the elderly or in patients with a ultrasound capabilities are not in general avail- history of claudication or other peripheral arte- able in the smaller units. Newer capabilities rial disease manifestations. An ABI <0.30 indi- can be expected from future portable systems, cates severe ischemia. These patients will in including power Doppler, color flow Doppler, general have severe pain and face the threat spectral Doppler, and 3D volumetric rendering. of limb loss without revascularization. Absent The usefulness of technologies such as 3D ankle signals indicate severe acute or far ultrasound remains to be proven, but some advanced chronic occlusive disease. Differ- distinct advantages may be found in field envi- ences in serial ABI determinations of <0.10 in ronments where minimally trained users might general are not significant. be able to perform meaningful examinations Another helpful way to evaluate arterial flow that they otherwise would not be able to is by the audible characteristics of the Doppler accomplish. flow signal. Normal peripheral arterial flow is triphasic, with three distinct sounds or phases Anticoagulation and during each cardiac cycle. With decreased Antiplatelet Therapy peripheral resistance, the flow reversal will dis- appear and the arterial Doppler signal becomes Systemic anticoagulation is contraindicated in biphasic. Severe proximal stenosis or proximal those patients with multisystem trauma or occlusion with reconstitution via collateral other bleeding risks. Patients with thrombotic vessels will produce a low-velocity (low- or ischemic syndromes, however, may be trans- pitched), monophasic signal. ferred on heparin infusions, Pre- and in-flight monitoring of coagulation function and careful surveillance are critical to minimize bleeding Vascular Imaging in the Field risks. Heparin should be discontinued if there Until recently, diagnostic imaging capabilities is evidence of bleeding. In addition, protamine in environments encountered by deployed sulfate quickly reverses the anticoagulant personnel have been limited to large field effects of heparin. One milligram of protamine hospitals. Weight and volume constraints limit sulfate reverses 100U of heparin. 17. Peripheral Vascular Casualties 235

Patients who have undergone complex revas- ment. All patients with recent injuries or vas- cularizations may be on other antithrombotic cular repairs should have IV access. Patients or antiplatelet therapy. Recent administration with recent injuries should also receive in-flight of low-molecular-weight dextran may result in supplemental oxygen. volume expansion and risk for heart failure. Conventional antiplatelet regimens rarely Dressings and Drainage cause bleeding problems, but patients who have received combinations of antiplatelet therapies, All wounds should be evaluated and dressings especially GIIIb2a inhibitors, may be at in- replaced immediately prior to AE. The poten- creased risk for spontaneous bleeding or bleed- tial for limb swelling should be anticipated, and ing from recent puncture sites, injuries, or all circumferential dressings should be repeat- surgical wounds. edly checked to ensure they do not become constricting, especially if they overlay super- ficially routed grafts. Likewise, all casts must Secondary Infection be bivalved. After vascular compromise, the patient is at risk Dressings over open wounds, including for both local infection and systemic sepsis. fasciotomy incisions, need to be kept moist to Bacteria may be introduced by contamination avoid tissue desiccation, especially in the dry at the time of initial injury or may translocate AE environment. If dressings show evidence of from the intestinal tract after ischemic injury or continued blood loss, they should be removed shock. Tissues subjected to severe or prolonged and the wounds examined. ischemia are immunologically compromised Closed-suction drains are often used during and thus at higher risk for subsequent infection. vascular surgery. If such drains have been Patients who develop signs of systemic infec- placed, they will need venting during ascent to tion, such as fever, tachycardia, hyperemia, or avoid gas expansion in the wound. pain, may progress quickly to septic shock in the presence of ischemic or infarcted tissue. For Cabin Altitude this reason, early administration of antibiotics is indicated in the presence of open fractures, There are no cabin altitude restrictions for most grossly contaminated wounds, or an established vascular surgery patients. However, patients infection. might have undergone recent hyperbaric Because of the risk of infection, continuous oxygen therapy in the course of treatment for broad-spectrum antibiotics should be started associated conditions, such as acute crush infor all patients with significant vascular injuries juries, Clostridial gangrene, and chronic wound who require long-distance AE, eg, from Europe management. It is well appreciated that these back to the United States. patients are at risk for decompression sickness during air transport. Therefore, if such patients require AE <24 hours after a hyperbaric treat- Special AE Considerations ment, a cabin altitude restriction to sea level (or the altitude of the sending location) will be Aircraft Configuration required.

Movement of vascular patients by AE requires Medications and Treatment Supplies an aircraft configuration and patient positioning that assures the aeromedical crew can ade- Patients with recent vascular injuries or surgery quately evaluate the patient for both ischemia often require nonstandard items for in-flight and hemorrhage. For elective AE, a flight use. These can include heparin for infusions, crew comprised of flight nurses and technicians insulin and glucose, mannitol, antibiotics, blood is adequate. For urgent evacuations, a CCAT products and infusion sets, splints, and dressing Team should be considered, especially if any supplies. If patients are anticoagulated with patient has not yet had definitive surgical treat- heparin, protamine sulfate should be available 236 D.L. Dawson to reverse heparin anticoagulation in the event hematocrit, and blood gases. These values can of uncontrollable hemorrhage. help guide fluid administration and permit Early thrombolytic therapy is often used early detection of systemic effects of tissue for ischemic disease and can be continued ischemia and infarction, such as hyperkalemia during rotary-wing casualty medical evacua- and metabolic acidosis. Monitoring the PTT tion (MEDEVAC).11 However, thrombolytic should be considered if the transport team is therapy should not be used during long- responsible for managing heparin infusions for distance fixed-wing AE because of the difficul- more than 12 hours. ties and risks associated with its prolonged A simple urinalysis by dipstick is extremely use. important in the trauma patient to detect the presence of free myoglobin or hemoglobin Deployable Diagnostic Equipment in the urine. However, because the dipstick and Monitoring cannot differentiate myoglobin from hemoglobin both rhabdomyolysis and hemolysis will All patients with vascular diseases or injuries manifest on urine dipstick as positive for blood. should be evaluated during AE with routine In either case, the risk of subsequent renal hemodynamic and physiological monitoring. injury can be minimized by fluid loading with In addition, efforts to detect changes in limb Ringer’s lactate, urine alkalinization with IV perfusion should be made by serial evaluations bicarbonate, and perhaps mannitol use. of peripheral pulses, neurological function, and skin color and capillary return. Unfortunately, Specific Care Plans for Vascular aircraft noise, vibration, low lighting, and Casualty AE patient restraints may limit the accuracy of these evaluations. Unique aspects of care, criteria for urgent and elective AE, and checklists for major categories Continuous-Wave Doppler of vascular casualties are summarized in Tables 17.2, 17.3, and 17.4. Continuous-wave Doppler is useful in a field or Trauma patients are perhaps the most contingency setting to provide an objective frequent consideration for military AE (Table assessment of peripheral arterial circulation 17.2). Control of life-threatening hemorrhage is (see above). Many Doppler units can be used prioritized before limb salvage, but with limb with headsets, which can facilitate use in a noisy ischemia the best long-term functional out- aircraft environment. During AE of patients in comes result from rapid restoration of blood the first week after vascular surgery, vessel flow. patency should be documented by evaluating AE is less commonly required for non- the ABI preflight, postflight, and in-flight if traumatic acute ischemia or complications of there is any clinical indication of a change in chronic peripheral artery disease (PAD), but limb perfusion status. PAD is common in the elderly. PAD complications can be presenting problems or can result Laboratory Evaluation from iatrogenic injury (such as arterial cannu- The ability to perform basic blood and urine lation for cardiac catheterization or other tests immediately preflight or in-flight is extre- reasons). These patients often have multisys- mely useful when severely ill or injured patients tem problems (Table 17.3). are transferred over longer distances. Early Venous thromboembolism can be a compli- detection of adverse effects of tissue necrosis cation in trauma patients or a concomitant or ischemia reperfusion injury can permit process with acute or chronic illnesses. While immediate treatment. patients rarely require AE for venous throm- Hand-held portable clinical blood analyzers boembolic disease, the risk of pulmonary provide rapid, simultaneous quantitative deter- embolism may be significant in many AE mination of whole blood electrolytes, glucose, patients (Table 17.4). 17. Peripheral Vascular Casualties 237

Table 17.2. Extremity vascular trauma.

Related medical conditions Skeletal injury, bony instability, open fracture; soft-tissue injury, crush, compartment syndrome; peripheral nerve injury; multisystem trauma, shock Care and management prior to AE Assessment, resuscitation, stabilization (ABCs of trauma management); hemorrhage control; IV access; revascularization for ischemia (surgical, endovascular, or by placement of temporizing shunt) if surgical care available; fracture care (irrigation of open fractures, antibiotics, stabilization); soft-tissue injury management (irrigation, debridement of devitalized tissue) Preparation for AE Monitoring, including ECG, blood pressure, pulse oximeter, and Foley catheter; document perfusion status (careful pulse examination, ABI measurement); document neurological status (motor and sensory); evaluate for compartment syndrome (consider fasciotomies); evaluate dressings, wound check if appropriate Indications for return to medical Active bleeding; arterial, graft, or shunt occlusion (drop in ABI >0.15) or facility prior to evacuation evidence of critical ischemia; new sensory or motor deﬁcit

Urgent AE: Minimal conditions that must be met Airway protection; bleeding controlled; adequate immobilization of skeletal injuries; spinal and cervical immobilization if stability not demonstrated; wounds debrided and dressed Specific concerns, supplies, and needs Supplemental oxygen; Doppler flow detector; transport monitor; IV fluids of patients and infusion pumps; dressing supplies; consider blood products and infusion sets, heparin, intermittent pneumatic compression devices for prophylaxis of deep-vein thrombosis, mannitol, portable laboratory Possible in-flight emergencies Consequences and risks In-flight treatment

Recurrent bleeding Hypovolemic shock Direct digital or manual pressure; hemostatic dressings; tourniquet (only when all other measures fail); discontinue use of anticoagulants; IV lactated Ringer’s solution and/or transfusion; monitor vital signs and urine output Arterial, graft, or shunt Acute limb ischemia Consider diverting for immediate surgical care thrombosis Compartment syndrome Progressive loss of peripheral Compartment pressure measurement; compartment nerve function release (fasciotomy); consider diverting for immediate surgical care Metabolic complications Cardiac dysfunction or Monitor blood gases and chemistries (hyperkalemia, acidosis, dysrhythmia etc) Renal failure Adequate IV ﬂuid resuscitation (as needed) to augment resuscitation; correct electrolyte abnormalities

Elective AE: Usually dictated by associated conditions or injuries Ideal timing of AE Soft-tissue coverage of grafts and anastomoses; nonviable or infected tissue Conditions that should be met prior debrided, wounds dressed Antibiotics, as indicated to transportation Consequences and risks In-ﬂight treatment Possible in-ﬂight emergencies

Graft or arterial thrombosis Distal ischemia Heparin anticoagulation (if not contraindicated); consider diversion for progressive signs of acute ischemia or development of motor deﬁcit Pulmonary thromboembolism Hypoxemia; tachycardia; Heparin anticoagulation (see Table 17.4 for hypotension additional information) 238 D.L. Dawson

Table 17.3. Peripheral artery disease.

Related medical conditions Coronary artery disease; cerebrovascular disease; renal insufficiency Care and management prior to AE Supplemental oxygen; IV access; revascularization for ischemia if available (surgical, endovascular, or catheter-directed thrombolytic therapy); wound debridement and dressing care Preparation for AE Monitoring, including ECG, blood pressure, pulse oximeter, and Foley catheter; full heparin anticoagulation for acute ischemia if not revascularized; evaluate for significant systemic disease or acute problems (include baseline ECG); check laboratory tests, including hemoglobin, platelet count, serum electrolytes, coagulation status, and urinalysis; document perfusion status (careful pulse examination, ABI measurement); document neurological status (motor and sensory); evaluate for compartment syndrome if revascularized for acute ischemia (consider fasciotomies); evaluate dressings, wound check if appropriate Indications for return to medical Active bleeding; postprocedure arterial, graft, or shunt occlusion (drop in facility prior to evacuation ABI >0.15 or evidence of critical ischemia); new sensory or motor deficit

Urgent AE: Minimal conditions that must be met Hemodynamic stability; evaluate for myocardial ischemia; pain control Specific concerns, supplies, and needs Supplemental oxygen; Doppler flow detector; transport monitor; IV fluids of patients and infusion pumps; dressing supplies; Consider heparin, narcotics for ischemic pain, intermittent pneumatic compression devices for prophylaxis of deep-vein thrombosis, mannitol, portable laboratory Possible in-flight emergencies Consequences and risks In-flight treatment

Myocardial infarction Dysrhythmias Supplemental oxygen Heart failure Pain control; topical or IV nitrates; Advance Cardiac Life Support care (see Chapter 23); consider emergency divert Bleeding from arterial Hypovolemic shock Direct digital or manual pressure; hemostatic puncture sites or dressings; tourniquet (only when all other measures disruption of recent graft fail); discontinue use of anticoagulants; IV lactated or anastomosis Ringer’s solution and/or transfusion; monitor vital signs and urine output Arterial, graft, or shunt Acute limb ischemia Heparin anticoagulation (if not contraindicated); thrombosis consider diverting for immediate surgical care Compartment syndrome Progressive loss of peripheral Compartment pressure measurement; compartment nerve function release (fasciotomy); consider diverting for immediate surgical care Metabolic complications Cardiac dysfunction or Monitor blood gases and chemistries (hyperkalemia, acidosis, dysrhythmia etc) Renal failure Adequate IV ﬂuid resuscitation (as needed) to augment resuscitation; correct electrolyte abnormalities

Elective AE: Ideal timing of AE Usually dictated by associated medical conditions Conditions that should be met Soft-tissue coverage of grafts and anastomoses; nonviable or infected tissue prior to transportation debrided, wounds dressed; invasive monitoring and continuous infusions no longer required Possible in-ﬂight emergencies Consequences and risks In-ﬂight treatment

Same as above Pulmonary Hypoxemia; tachycardia; Heparin anticoagulation (see Table 17.4 for thromboembolism hypotension additional information) 17. Peripheral Vascular Casualties 239

Table 17.4. Venous thrombosis or thromboembolism.

Related medical conditions Recent surgery (especially orthopedic, thoracic, abdominal, and genitourinary procedures); trauma (especially with pelvic, femur, or tibia fractures or with any neurological injury); malignancy; pregnancy or postpartum state; immobilization; in-dwelling venous catheter use Care and management prior to AE Supplemental oxygen; anticoagulation, with documentation of coagulation test results; IV access; duplex ultrasound evaluation for lower-extremity venous thrombosis; consider transthoracic echocardiogram to evaluate right ventricular function; chest X-ray; arterial blood gas measurements Preparation for AE Monitoring, including ECG, blood pressure, pulse oximeter, and Foley catheter; elastic stockings; elevate affected limb to reduce swelling Indications for return to medical facility Hypotension; hypoxemia or ventilatory failure requiring intubation prior to evacuation

Urgent AE: Normal blood pressure; anticoagulation or, if contraindicated, inferior vena Minimal conditions that must be met cava filter placement Supplemental oxygen; Doppler flow detector; transport monitor; IV fluids Specific concerns, supplies, and and infusion pumps; heparin infusion; consider portable laboratory for needs of patients blood gases and coagulation testing; consider inferior vena cava filter placement

Possible in-ﬂight emergencies Consequences and risks In-ﬂight treatment

Bleeding Hypotension Stop anticoagulation Oliguria Reverse anticoagulation if bleeding continues; ﬂuid boluses Acute pulmonary Right heart failure Supplemental oxygen embolism Hypotension Dobutamine

Elective AE: Ideal timing of AE Usually dictated by associated medical conditions; easier if fully converted to oral anticoagulation (warfarin) or low-molecular-weight heparin Conditions that should be met Appropriate anticoagulation; consider placement of inferior vena cava filter prior to transportation if indicated Possible in-flight emergencies Consequences and risks In-flight treatment

Same as above

Conclusion 3. Barros D’Sa ABA. A decade of missile-induced vascular trauma. Ann Roy Coll Surg Engl 1982; 64:37–64. Speciﬁc considerations in the AE of peripheral 4. Bongard F, Wilson S, Perry M. Vascular Injuries vascular casualties include risks of both local in Surgical Practice. Norwalk, Conn: Appleton and systemic complications. Serial evaluation & Lange; 1991. of perfusion is indicated. Vascular injuries are 5. Hernandez-Maldonado JJ, Pedberg FT, Jr, often associated with skeletal or other injuries Teehan E, et al. Arterial intimal ﬂaps: A that must be considered. Concomitant medical comparison of primary repair, aspirin, and problems of patients with PAD may be primary endovascular excision in an experimental model. concerns during transport. J Trauma 1993;34:565–569. 6. Hoyt DB, Bulger EM, Knudson MM, et al. Death in the operating room: An analysis of a multi- References center experience. J Trauma 1994;37:426–432. 7. Gulli B, Templeman D. Compartment syndrome 1. Rich N, Spencer F. Vascular Trauma. Philadel- of the lower extremity. Orthop Clin North Am phia: W.B. Saunders; 1978. 1994;25:677–684. 2. Rich MM, Baugh JH, Hughes CW. Acute arter- 8. Mabee JR. Compartment syndrome: A compli- ial injuries in Vietnam: 1000 cases. J Trauma cation of acute extremity trauma. J Emerg Med 1970;10:359–369. 1994;12:651–656. 240 D.L. Dawson

9. Goldhaber S. Pulmonary Thromboembolism. 14. Johansen K, Hedges G. Successful limb reperfu- Harrison’s Online; 1999. sion by temporary arterial shunt during a 950- 10. Investigators C. Low-molecular weight heparin mile air transfer: Case report. J Trauma 1989; in the treatment of patients with venous throm- 29:1289–1291. boembolism. N Engl J Med 1997;337–657. 15. Dawson DL, Putnam AT, Light T, et al. Tempo- 11. Proctor MC, Greenﬁeld L. Pulmonary em- rary arterial shunts to maintain limb perfusion bolism: Diagnosis, incidence and implications. after arterial injury: An animal study. J Trauma Cardiovasc Surg 1997;5:77–81. 1999;47:64–71. 12. Greenﬁeld L, Proctor MC. Endovascular 16. Dawson DL, Johansen KH. Diagnosis of extre- methods for caval interruption. Sem Vasc Surg mity vascular injuries. Vasc Forum 1994;2:200– 1997;10:310–314. 205. 13. Ballard RB, Salomone P, Rozycki GS, et al. 17. Chalela A, Kasner SE, auch EC, Pancioli “Damage control” in vascular trauma: A new AM. Safety of air medical transportation after use for intravascular shunts. In: Proceedings tissue plasminogen activator administration in of Western Trauma Association 28th Annual acute ischemic stroke. Stroke 1999;30:2366– Meeting. Lake Louise, Alberta, Canada; 1998. 2368. 18 Aeromedical Evacuation of Cardiothoracic Casualties

Kenton E. Stephens, Jr.

Cardiothoracic casualties occurring during losses (ie,“third spacing”) and thereby increase armed combat, natural disaster, and peacetime the amount of fluid required for intravascular may have different mechanisms but the result- repletion. ing pathophysiology can be similar due to the Massive fluid resuscitation has detrimental effects of such injuries on the cardiopulmonary effects on many organ systems and thus it system. The distinct nature of each type of is not surprising that greater fluid resusci- injury will determine specific care require- tation volumes are associated both with ments. This, in turn, will dictate the expertise greater trauma and poorer prognosis. Common and equipment requirements of the aero- sequelae of massive fluid resuscitation in- medical evacuation (AE) transport team. This clude pulmonary edema, decreased pulmonary chapter will address common cardiothoracic compliance, decreased thoracic compliance, injuries, their sequelae, and management increased ventilator pressures, pulmonary during elective, urgent, and contingency AE. parenchymal barotrauma, pulmonary hypertension, right-sided heart failure, increased abdominal compartment pressures, and diaphragmatic elevation from visceral edema General Considerations (Fig 18.1). The volume of fluid required for resuscitation in the first 48 hours after injury is In both the civilian and military domains, severe a crude marker of the overall trauma to the thoracic injuries are particularly lethal, espe- patient and ultimate prognosis. cially when combined with head trauma.1 The Cardiothoracic injuries are often critical. mechanisms and resultant pathology of these However, the true severity of the injury is not injuries determine their physiological effects always initially apparent. The patient can tran- and clinical courses. The most important siently compensate for severe injuries with factors influencing the patient are blood loss, tachycardia, arterial and venous vasoconstric- direct destruction of organ tissue (such as tion, and anaerobic metabolism. Each of these myocardial contusion), secondary effects of compensatory mechanisms will eventually be tissue injury or sepsis on thoracic organ function exhausted, sometimes resulting in the rapid (such as adult respiratory distress syndrome deterioration of an apparently stable patient. [ARDS]), and tension effects (such as pericar- For this reason, safe AE requires that the dial tamponade). Blood loss obviously affects aeromedical crew have an accurate under- ultimate prognosis. Intravascular depletion standing of the injury, its variants, natural results in shock and decreased tissue perfusion, history, associated risk, and predictable compli- and the obligatory fluid resuscitation creates its cations.1 This is especially important when own complications. Local and remote tissue patients are transported early in the course of injury can cause significant interstitial fluid their recovery.

241 242 K.E. Stephens, Jr.

C 18. Aeromedical Evacuation of Cardiothoracic Casualties 243

Complications of process progresses, the rising intrathoracic pressure decreases venous return to the heart. Cardiothoracic Injuries Inadequate atrial filling renders the patient functionally hypovolemic and can lead to Pneumothorax cardiovascular collapse. Pneumothorax is defined as free air in the pleural space. In a combat or mass-casualty Chest Tube Management situation, this will be secondary to trauma to the lung, trachea, or chest wall. However, pneu- A chest tube is commonly required for patients mothorax may also occur spontaneously in tall, with cardiothoracic injuries. Medical providers thin, young men with pre-existing apical blebs taking care of these patients need a complete or patients with emphysema and parenchymal understanding of chest tube design, placement, degeneration. Pneumothorax can also occur management, and troubleshooting approaches. after relatively minor pulmonary barotrauma, A tube that is malpositioned, obstructed, too which creates alveolar overpressurization and small for the job, or not connected to suction rupture. Common causes of barotrauma properly can create a critical in-flight situation include a sudden blow to the chest during (Fig 18.2). breath-holding, uncontrolled depressurization Verification that the chest tube is adequately during flight or diving, severe bronchospasm, positioned is the foremost concern during place- and iatrogenic overpressurization of the ment. A misplaced chest tube (eg, in the sub- intubated patient. pulmonic space, lung fissure, or extrathoracic Traumatic pneumothorax can arise from location) will not drain an apical pneumothorax penetrating or blunt chest injuries. With pene- (Fig 18.3). Proper location is confirmed by chest trating injuries, air can be sucked into the radiograph immediately after placement and pleural space through the chest wall defect, whenever the tube is manipulated. forced from the lung into the pleural space Once placed, a chest tube must be connected through a puncture wound, or both. In blunt to a three-stage vacuum–collection system trauma, the air leak usually results from focal prior to AE (Fig 18.4). The first stage is a reser- rupture of the pulmonary parenchyma, punc- voir for the fluids that drain from the pleural ture of the lung by a fractured rib, or leak from cavity. The second stage is a one-way valve. This a large parenchymal tear. may be in the form of a Heimlich-type valve or Free air within the pleural space can create a water seal chamber that prevents the back- either simple or tension pneumothorax. Simple ward flow of air into the pleural space. A water pneumothorax occurs when a relatively stable seal chamber has the added advantage of dis- amount of intrapleural air compromises lung playing an active air leak as the continuous expansion in the affected hemithorax. Tension passage of bubbles. The final stage is a regula- pneumothorax occurs when a lung defect acts tor or relief valve to prevent excessive suction as a one-way valve and air entering the pleural from being applied to the pleural space and space during inspiration cannot escape during potentially injuring the lung by sucking it into expiration. This creates an expanding pocket of the chest tube. Although newer designs replace intrapleural air that can completely collapse the some of these components with water-free ipsilateral lung and shift the mediastinal con- mechanical devices, these three essential func- tents toward the opposite hemithorax. As this tions of the device remain the same.

᭣ Figure 18.1. Abdominal compartment syndrome. elevated diaphragms, low lung volumes, and Initial clinical presentation was identical to cardiac pulmonary edema. After decompressive laparotomy tamponade post blunt abdominal trauma, with pro- (B), all radiographic (C) and cardiac ﬁndings nor- found hypotension and hypoxia despite a central malized. Decompressive laparotomy should be con- venous pressure of 25mmHg and good cardiac sidered for any patient showing signs of abdominal contractility. A chest radiograph (A) revealed the compartment syndrome prior to urgent AE. 244 K.E. Stephens, Jr.

Figure 18.2. A diligent aeromedical crew prepared with the appropriate skills and equipment is necessary for safe AE of intubated patients.

Chest tube management includes wound and anaerobic environment that can encourage dressing care to prevent wound infection. Dry wound infection. Intravenous (IV) antibiotic dressings are preferable, as salves and oint- administration is optional but favored in ments do not seal the air leak around an in- trauma to help prevent wound infection or adequately secured tube but do create a slimy empyema via ascending wound colonization. A ﬁrst-generation cephalosporin is adequate for this task. If Gram-negative colonization or fecal contamination is possible, a second- or third- generation drug with anaerobic coverage should be added. Careful monitoring to assure continued tube function is mandatory. The chest tube system may malfunction due to chest tube occlusion (eg, kinks in the tubes, external occlusion, internal clots), detached or leaky connections, or malfunction of the suction sources. Each of the three-system stages must be methodically monitored and restored to working order as required.

Implications for AE An untreated pneumothorax is a contraindication to AE (Table 18.1). Left untreated, a pneumothorax can severely compromise patient oxygenation and circulation during AE by three methods: (1) The pneumothorax may Figure 18.3. Potential misplacement of chest tubes. enlarge due to ongoing air leak from the 18. Aeromedical Evacuation of Cardiothoracic Casualties 245

Figure 18.4. Three-stage vacuum–collection system for chest tube drainage during AE. injured lung or bronchus; (2) the decreased oxygenation must be adequate, in general cabin pressure associated with flight may cause defined as above 90% in a patient without sig- the volume of a stable pneumothorax to nificant cerebrovascular or coronary vascular increase; and (3) the partially collapsed lung on disease. the side of the pneumothorax may cause arter- All chest tubes must be connected at a ial desaturation from shunting, in addition to minimum to a one-way valve system (eg, altitude-related hypoxia.2,3 Heimlich valve), and preferably a three-stage Elective AE should be delayed until there is suction–collection apparatus, prior to AE. radiographic evidence that the pneumothorax Additional aspects of in-flight manage- has spontaneously resolved or until a chest tube ment include connection of the chest tube to has been inserted. The pneumothorax prefer- continuous suction, administration of supple- ably will have completely resolved, although a mental oxygen and first-generation cephalo- small residual pneumothorax is both common sporin prophylactic antibiotics, and verification and tolerable (eg, a <1-cm apical pneumotho- of adequate oxygenation by pulse oximetry rax). Patients with a residual pneumothorax (Table 18.2). may be transported by urgent or contingency Prophylactic chest tube placement in patients AE after a chest tube has been placed and is at high risk of developing a pneumothorax (eg, verified to be functioning properly. Patient

Table 18.2. AE checklist for chest tube management. Table 18.1. Contraindications to AE. Preflight Within 48h of cardiothoracic surgery if cardiac Proper placement has been verified radiographically tamponade is a risk Tube is connected to a one-way valve or drainage Within 24h of repair of ruptured diaphragm apparatus Untreated pneumothorax Adequate oxygenation verified Untreated pneumomediastinum or pneumopericardium Tube insertion site inspected for air leaks and secure Ruptured diaphragm with herniation into the chest tube anchor Active endobronchial bleeding Need for suction and suction capability of airframe New or unstable arrhythmias assessed Deteriorating hemodynamics Supplies for emergent tube replacement verified Deteriorating respiratory status Pain control plan prepared and drugs available Relative (contraindication to elective AE) In-flight Within 14d of most cardiothoracic surgery Tube connected to continuous suction or one-way valve Within 7d of repair of ruptured diaphragm Prophylactic antibiotics Within 48h of significant chest wall trauma Supplemental oxygen Hemothorax with continued chest tube bleeding Pulse oximetry 246 K.E. Stephens, Jr. patients with existing blebs or bullous disease) less common in the acute trauma patient and is rarely indicated. The risk of bleb rupture are usually due to pre-existing heart failure, during a flight in a pressurized aircraft is low, cirrhosis, or accumulated third-space fluid and tube placement itself may injure the lung, losses. resulting in an air leak. Because pneumothorax Exudative effusions have a wide variety of can occur suddenly in any patient, the aero- causes (eg, pneumonia, malignancy, mediastinal medical crew should be prepared to treat a or subphrenic abscesses) or injuries to adjacent tension pneumothorax during any AE flight. organs (eg, pancreas, esophagus, chest wall). In most cases, a needle thoracostomy will be Conditions that mimic pleural effusion include adequate, with results comparable to placement collections of blood (hemothorax) or lymph of a tube thoracostomy.4 If the patient has (chylothorax), and these can be differentiated an active air leak into the pleural space, the by diagnostic thoracentesis. chest tube or needle thoracostomy must be Therapy consists of placement of a chest tube connected to suction. for diagnosis and drainage. Coexisting injuries must be treated as appropriate. Otherwise, Pleural Effusion AE management of a chest tube placed for a pleural effusion is identical to that for A pleural effusion is any collection of fluid pneumothorax. other than blood, chyle, or pus in the pleural space and is common in trauma patients. Effu- Hemothorax sions are designated as either transudative or exudative based on the relative concentrations Hemothorax is a potentially life-threatening of protein and lactate dehydrogenase in the complication of a pulmonary parenchymal, fluid. Exudative effusions usually have a pleural chest wall, mediastinal, or thoracic vascular fluid to serum protein ratio >0.5 and a lactate injury (Fig 18.5). Hemothorax may also occur dehydrogenase ratio >0.6.5 Transudates are postoperatively as a complication of thoracic

Figure 18.5. Blast wound to the chest. Prior to wall and lung, laceration and contusion of the AE, the patient must be evaluated and treated for lung, hemothorax, pneumothorax, and hemorrhagic multiple injuries, including laceration of the chest shock. 18. Aeromedical Evacuation of Cardiothoracic Casualties 247 surgery (eg, thoracotomy or lung resection). <100cc/hour. Greater rates of blood loss put Hemothoraces must be assiduously sought and the patient at considerable risk of progressive vigilantly monitored because of several unique anemia, hypotension, hypoxia, and dilutional characteristics that create the potential for coagulopathy during flight. Urgent AE of these rapid deterioration. First, a significant amount precarious patients will require a Critical of concealed bleeding can occur with minimal Care Air Transport (CCAT) team equipped symptoms. Each pleural cavity can hold several with appropriate blood products, transfusion liters of blood, collapsing the lung as the chest supplies, and autotranfusion equipment. fills with blood. Second, in contrast to internal For all patients, the amount and type of chest bleeding in confined locations, tamponade tube output must be closely monitored during occurs relatively late. Finally, the volume of AE. Routine chest tube management, as blood in the pleural cavity causes a corre- described for pneumothorax, will also be sponding decrease in functional lung tissue. required (Table 18.2). This combination of pulmonary parenchymal loss with major blood loss contributes to the In-Flight Complications high mortality of this condition. The cornerstone of diagnosis and treatment Patients with hemothorax and continued bleed- for hemothorax is chest tube drainage. A chest ing are at risk for chest tube obstruction by tube alone will be adequate therapy for the vast clotted blood. Signs of hemodynamic instabil- majority of intrapleural bleeding. However, if ity with ineffective chest tube drainage should the initial amount of blood drained by the chest make the aeromedical crew suspicious of un- tube is >1000 to 1500cc, or if the continued detected intrapleural bleeding or an occluded blood loss is >500cc/hour, emergency thoraco- tube. In this situation, every effort should be tomy is indicated to stop the bleeding. The made to clear the tube or replace it if necessary. objective of therapy is to stop the bleeding and Disconnecting the chest tube and sterilely decrease the chance of empyema or fibrothorax sucking out the obstructing clot with an endo- developing from undrained blood. No rigid cri- tracheal tube suction catheter or extracting teria exist, but when the fluid drainage becomes the clot with a Fogarty balloon embolectomy serosanguineous and is less then 200 to 300cc catheter are simple and effective techniques. per day it is reasonable to consider removing These can be successfully accomplished even in the chest tube. If the chest radiograph reveals the most austere AE environment. Resuscita- a residual clotted hemothorax, it must be tion with fluids and blood products should be evacuated, either surgically or by instilling instituted until diversion to the nearest medical fibrinolytic agents into the pleural space. facility is possible.

Implications for AE Pneumomediastinum Active bleeding from a hemothorax placement A bronchial air leak can sometimes result in air is a contraindication to elective AE. A residual leakage proximally into the mediastinal space clotted hemothorax is temporarily acceptable instead of peripherally into the pleural space. as long as bleeding has been stopped for 48 The result is pneumomediastinum or pneu- hours (ie, residual drainage is serosanguineous) mopericardium (Fig 18.6). There is frequently and the patient has adequate respiratory associated subcutaneous emphysema, and if reserve. The patient’s hemoglobin should be the air dissects across the diaphragm via the 10g/dL or greater and the chest tube should mediastinum or retroperitoneum pneumoperi- be managed as described above. toneum will develop. During armed conﬂict or mass-casualty In the trauma patient, the presence of pneu- situations, urgent or contingency AE may be momediastinum or related conditions should required despite continued intrapleural bleed- prompt a search for a central airway rupture or ing. Patients can be moved with a reasonable esophageal injury. A large central airway injury degree of safety if the chest tube blood loss is will require surgical repair. Otherwise, no 248 K.E. Stephens, Jr.

Figure 18.6. Tension pneumopericardium is demonstrated by chest radiograph (A) despite bilateral chest tubes. Clinical signs of cardiac tamponade and the abnormally enlarged cardiac silhouette (B) resolved after emergency placement of a subxiphoid pericardial drainage tube.

specific treatment is necessary for stable present, it is safest to place bilateral chest tubes patients who do not require air transportation. before evacuating the patient. Rarely, place- However, the patient should be observed for ment of a chest tube via the subxiphoid route the development of pneumothorax because into the pericardial space is necessary for even a small leak could extend into the pleural decompression of tension pneumopericardium. space. Similarly,although subcutaneous emphysema may create an alarming appearance, it Implications for AE poses no immediate threat to the patient so long as the pleural cavity is decompressed. If it Untreated pneumomediastinum and related is unclear whether a pneumothorax is or is not conditions are a contraindication to AE 18. Aeromedical Evacuation of Cardiothoracic Casualties 249 because of the risk of subsequent pneumotho- Implications for AE rax in these patients (Table 18.1). Prior to AE, Endobronchial bleeding is always a con- these patients should have prophylactic chest traindication to AE. Medical evacuation tubes placed. (MEDEVAC) to the nearest appropriate Untreated pneumopericardium is a con- medical facility should be undertaken only traindication to AE because expansion of air after the bleeding has been controlled by in the pericardium during flight can result mainstem bronchus intubation and any coagu- in cardiac tamponade. Although tension pneu- lopathy has been corrected. mopericardium is rare, the results can be disastrous. For this reason, these patients must have adequate pericardial drainage prior to Air Embolism AE, using either a subxiphoid pericardial drainage tube or a pericardial window (Fig 18.6). Lung injury is a major risk factor for air embolism. Air can pass from injured alveoli Tracheobronchial Bleeding into the pulmonary venous circulation, where it is transported to the left atrium and quickly Airway bleeding may be the result of a pene- ejected by the left ventricle into the aortic root. trating lung injury, massive blunt chest trau- Air naturally rises to the highest spot, which in ma, inflammation, burns, infection, pulmonary the supine patient is the anterior aortic root, hypertension, foreign bodies, or malignancy. near the ostium of the right coronary artery. Significant endobronchial bleeding is asso- The bubbles pass down the right coronary ciated with a high mortality rate. Emergency artery until they eventually lodge in the small treatment consists of endotracheal intubation vessels or myocardium. This creates ischemia of to secure the airway. The patient should be the right ventricle, inferior left ventricle, and positioned with the bleeding side (if this is septum, which quickly become dysfunctional. known) down. Oxygen should be administered The result is rapid, profound hypotension, right and aggressive respiratory care implemented to ventricular failure, bradycardia, and cardiac clear the airway of blood. Coagulopathy should arrest. (If the patient is in the 10% to 15% of be identified and corrected. If the airway the population with strongly left-dominant cannot be cleared due to voluminous bleeding, coronary circulation, the ventricular depression proceed with advancement of the tube into the will be limited to the right ventricle and thus be mainstem bronchus contralateral to the site of better tolerated.) bleeding. This temporizing maneuver permits The most important treatment approach is “one-lung” ventilation and prevents entry of increasing coronary perfusion pressure by blood into the ventilated lung. Definitive non- administration of epinephrine or other alpha- surgical treatment involves placement of a adrenergic agonists and fluids in an effort to double-lumen endotracheal tube. Angiographic flush the bubbles out of the coronary circula- embolization can be helpful if available, as tion and restore coronary capillary perfusion the bleeding source is frequently a bronchial pressure. Further measures include changing branch of the aorta. Bronchoscopic occlusion of the patient’s position to the left lateral decubi- the bleeding bronchial orifice with a balloon tus,Trendelenburg position to direct aortic root catheter (eg, a Fogarty or small Foley catheter) air away from the coronary arteries and allow is on occasion successful. the air to aggregate in the ventricular apex. Uncontrolled tracheobronchial bleeding will Halting further entrance of air into the circula- usually necessitate emergency thoracotomy tion requires an emergency thoracotomy for with resection of the bleeding lung segment or pulmonary hilar control, repair or resection of the entire affected lung (ie, pneumonectomy). the injured lung, and aspiration of the air These procedures have a significant mortality pockets in the ventricles and great vessels. rate, even in a fully equipped operating room. The most effective approach to air embolism Radiographic selective embolization of the is prevention. In high-risk patients with bronchial or pulmonary artery may be reason- parenchymal pulmonary injuries, prophylactic able options in selected situations. measures include maintenance of low airway 250 K.E. Stephens, Jr. pressures and relatively high atrial filling pres- in the diagnosis and treatment of postoperative sures as reflected by central venous pressure complications in these high-risk patients. Post- and pulmonary capillary wedge pressure. operative problems associated with various Air entering the circulation through IV lines conditions are discussed below. can also be dangerous because right-sided air embolization can be fatal. A massive amount of air (tens to hundreds of ccs of air) can cause General Considerations for AE right ventricular cavitation and immediate cardiogenic shock. Less commonly, air bubbles Safe AE of the cardiothoracic patient depends in the venous circulation can pass through a on an adequate understanding of the unique patent foramen ovale or atrial septal defect, aspects of their injuries and the associated thereby becoming a left-sided air embolus. postoperative risks. Although pain control, These latter two entities are more likely in respiratory hygiene, and fluid management are conditions that increase right-sided cardiac required for all postoperative patients, post- chamber pressures, such as hypoxia, volume thoracotomy patients have special concerns overload, acidosis, pulmonary hypertension, or that must be recognized. tamponade. Emergency management of venous air em- Pain Control bolism includes halting the ingress of air, fluid resuscitation, inotropic support, and reposition- Effective pain management is essential for ing the patient in the left lateral decubitus, optimizing respiratory function in the post- Trendelenburg position to allow the air to thoracotomy patient. Intermittent morphine accumulate in the apex of the right ventricle. is effective but has the disadvantage of being A pulmonary artery balloon catheter (eg, a respiratory depressant. Ketorolac (given Swan–Ganz) can be floated into the right ven- by either intramuscular or IV injection) is an tricular outflow tract to aspirate the bubbles extremely effective adjunct but should not and foam creating the obstruction. be used for patients with renal insufficiency, coagulopathy, or a history of gastrointestinal Postoperative Cardiothoracic Patients bleeding. When available, a thoracic epidural catheter is an excellent method for providing Early postoperative complications in cardio- pain relief without depressing the sensorium. thoracic patients can provoke rapid deteriora- However, they do place additional monitoring tion due to compromise of the circulatory and burdens on the AE crew and can be somewhat respiratory systems. For these reasons, elective variable in their efficacy. Periodic intercostal AE should be delayed until patients are in the blocks are an effective adjunct that can help convalescent phase of their recovery from tide the patient over during critical intervals. thoracotomy. This is usually 7 to 14 days after surgery, when patients have had chest tubes Respiratory Hygiene removed, are tolerating regular diets, and are ambulatory. For comparison, in the civilian It is critical to minimize atelectasis in post- environment such patients will be at home, thoracotomy patients. The cornerstone of this self-sufficient in their activities of daily effort is effective pain management to allow living, accomplishing their own pulmonary deep inspiration. Other methods include incen- hygiene, and ready to begin cardiopulmonary tive spirometry, chest physiotherapy, and bron- rehabilitation. chodilators to loosen secretions. All of these Urgent or contingency AE may be required methods must be continued throughout the AE much sooner after surgery. However, the process. Aggressive baseline therapy when the patient should be allowed to stabilize for at patient appears to be stable can prevent the least 12 hours after thoracotomy prior to AE. sudden hypoxia and respiratory distress that This will almost always require the assistance occur when occult atelectasis or mucous reten- of a well-equipped CCAT team experienced tion reaches a critical level. 18. Aeromedical Evacuation of Cardiothoracic Casualties 251

Fluid Management Specific Injuries Cardiothoracic trauma is often associated with massive blood loss, which creates a need for Flail Chest and Pulmonary Contusion disproportionate fluid resuscitation to restore Flail chest refers to chest wall trauma in which equilibrium. In addition, pulmonary injury one or more ribs is fractured in at least two and cardiac failure are both associated with places, mobilizing a plate of chest wall from the “third spacing” of fluids, but for different remainder of the thorax. It can be the result of reasons. The complex relationship between blunt trauma, projectile, or blast shock wave. intravascular fluid balance and both increased The paroxysmal, painful inward movement of and decreased cardiac output makes appropri- this plate limits respiratory excursion and effi- ate fluid management critical in the postthora- ciency. Flail chest is almost universally accom- cotomy patient. Further, in the presence of panied by pulmonary contusion and commonly cardiac dysfunction it is critical to discriminate by pleural effusion or hemothorax as well. between left- and right-sided heart failure. Pulmonary contusion is characterized by Central venous and capillary wedge pressure interstitial and alveolar hemorrhage with archi- monitoring is invaluable in managing critically tectural disruption resulting in decreased gas ill patients. exchange across capillary–alveolar interfaces. Severe cases may develop regions of lung necrosis and hemoptysis. Radiographically, pul- Venous Thrombosis Prophylaxis monary contusion is usually evident at the time Postthoracotomy patients are at increased risk of injury as an area of consolidation and will of pulmonary embolus due to immobility and often progress in size over the next 24 to 96 hypercoagulability. In addition, their com- hours. The lung injury can be aggravated by the promised respiratory physiology increases the massive fluid administration often required for physiological impact of subsequent pulmonary trauma resuscitation. thromboembolism. For this reason, all such Respiratory insufficiency after significant patients should be treated on the ground chest wall trauma has several potential causes, with sequential compression devices on their including pulmonary contusion, splinting sec- lower extremities. During flight, these must be ondary to rib fractures, hemothorax, atelectasis, replaced with elastic compression hose because pneumonia, and deranged respiratory mechan- sequential compression devices are not ap- ics due to flail chest. These complications are proved for use in the hypobaric AE environ- most likely to manifest in the first 48 hours ment. In addition, all postoperative patients postinjury. During this time, the patient should who have not achieved full ambulation and be treated with pain medications, bronchodila- do not have active bleeding or risk thereof tors, and active pulmonary hygiene (eg, incen- should be treated with heparin prophylaxis. The tive spirometry, chest percussive therapy) and advent of low-molecular-weight heparin pro- observed closely for signs of deterioration. phylaxis has increased the safety and reliability Although these steps will maximize chest wall of this therapy. compliance and respiratory function, endotracheal intubation will often be required in patients with significant pulmonary contusions. Chest Tubes Implications for AE Chest tubes are a ubiquitous component of postoperative thoracic surgical management. The first 48 hours after significant chest wall Details of chest tube placement, design, trauma is the critical period during which dete- and management have been discussed above. rioration of pulmonary function may occur. For The design and essential components of this reason, patients with fractured ribs and pul- the standard three-chamber suction–collection monary contusion should not be transported by apparatus are shown diagrammatically in elective AE for the first 48 hours postinjury Figure 18.2. (Table 18.1). Patients transported by AE within 252 K.E. Stephens, Jr.

7 days of pulmonary contusion should be given In an emergency situation, urgent or contin- supplemental oxygen. gency AE should be delayed for 12 hours During a military operation or mass-casualty after definitive surgery to observe for early situations, or if appropriate medical care is not operative complications (anastomotic disrup- available locally, movement of these patients tion or pneumothorax) and fluid resuscitation. by urgent or contingency AE may be required These patients will be relatively unstable and after little more than medical stabilization. The require the special expertise of a CCAT team presence of a pneumothorax will require place- for safe transport so soon after surgery. Prior to ment of a chest tube with a one-way valve, as AE, the patient should be afebrile and the chest discussed above. The presence of hemothorax tube output should be <50cc/hour. Thoracic air is especially dangerous, as discussed above. leaks often continue for the first 2 to 5 days Pain relief can be provided with parenteral nar- postoperatively, and thus AE prior to this time cotic and nonnarcotic drugs, local injection (ie, will require effective drainage with chest tubes intercostal block), or regional anesthesia (ie, connected to continuous suction. Muscular epidural block). If the patient continues to have paralysis may be required to prevent bucking a severely abnormal PaO2 on room air (ie, and maximize thoracic compliance. 50mmHg or 88% SaO2), endotracheal intuba- Patients who have undergone emergency tion should be considered prior to AE. lung resections must be observed for postoperative air leaks. These patients may undergo Tracheobronchial Injuries urgent or contingency AE 12 hours postoperatively if the air leaks are adequately treated Intrathoracic tracheobronchial injuries are by a chest tube connected to continuous usually the result of penetrating chest injuries, suction. although they can result from severe decelera- Patients with profound injury to one lung tion or crush mechanism. They are associated will have asymmetrical pulmonary compliance. with significant morbidity and mortality. These If this is severe enough to cause hypoxia and injuries affect multiple critical systems, and hypoventilation from shunting through the can simultaneously create airway obstruction, injured lung and overventilation of the com- pneumothorax or pneumomediastinum, and pliant lung, two ventilators will be needed significant blood loss. Emergency care is to provide differential lung ventilation during primarily supportive, and immediate surgery transport. In addition to pulse oximetry, the is usually required. The surgery itself can be patient will usually require central venous and technically challenging for both the surgeon arterial pressure monitoring. and anesthetist. Associated injuries can cause substantial blood loss and a fatality rate approaching 25% at tertiary-care centers. In-Flight Emergencies Surgical tracheobronchial repair leaves an Anastomotic dehiscence, although uncommon, anastomotic suture line that is delicate, slow to can be fatal unless the condition is quickly rec- heal, and vulnerable to barotrauma, tension ognized and lung isolation achieved. The cardi- ischemia, and infection. Postoperatively, early nal signs are massive air leak through one or extubation is indicated to minimize airway both chest tubes (depending on the level of pressure and avoid anastomotic erosion from anastomosis), sudden intractable hypoxia, and airway catheters. pneumothorax. Lung isolation is achieved with a single-lumen endotracheal tube by advancing Implications for AE the tube beyond a tracheal anastomosis or into Elective AE should be deferred until the con- the mainstem bronchus contralateral to the valescent period, usually at least 14 days after lung with a bronchial anastomosis. If the exper- surgery. The patient should no longer require tise and equipment is available, a double-lumen chest tubes and be substantially recovered from endotracheal tube can be placed and positioned coexisting injuries. to isolate the leaking lung. If a CCAT team or 18. Aeromedical Evacuation of Cardiothoracic Casualties 253 an appropriately trained specialist accompanies cardiac tamponade, a potentially fatal com- the patient, ancillary equipment should include plication requiring emergency re-exploration. a flexible bronchoscope in addition to endo- In-flight care should include monitoring of bronchial suction catheters, a light source, and central venous and arterial pressure, as well as endotracheal tubes of a variety of sizes and pulse oximetry. Blood pressure must be rigor- styles. ously controlled because excessive hypertension can result in the failure of an otherwise Cardiac Trauma secure arterial or cardiac suture line. Complications are common in the first 72 Cardiac trauma may be either blunt or pene- hours after surgery and require immediate treat- trating. Cardiac contusions clinically resemble ment. Inotropic, vasoregulatory, and anti- acute myocardial infarctions in many ways. arrhythmic drugs should be available. Because However, the area of tissue damage is more cardiac arrhythmias are common postopera- likely to conform to regions of impact than tively, a defibrillator with internal and external anatomic boundaries of coronary perfusion. paddles and a pacing device compatible with These patients usually will not require specific both surgically placed and transvenous wires medical intervention unless they develop should be available. An open-chest instrument arrhythmias or heart failure. Implications for tray and skilled personnel should be present for AE after such an injury are covered in more the emergency treatment of cardiac tamponade, depth in chapter 24. should it occur. Blood and clotting factors Penetrating cardiac injuries must be treated should be available if significant bleeding is a surgically. Unfortunately, military trauma pa- problem. Warming devices are mandatory if the tients with penetrating cardiac injuries rarely patient is hypothermic. survive to the point of requiring AE unless the injuries are trivially small or they are injured very near a surgical unit. Patients with more Blunt Aortic Trauma limited injuries may survive their injury after Blunt aortic trauma resulting in transection is surgical repair via sternotomy, thoracotomy, or highly lethal. In peacetime, almost 90% die at clamshell incision. Their postoperative course the accident site and many more die before will be similar to that of the postthoracotomy diagnostic studies are completed.6 The diagno- patient, as described below. sis should be suspected in any patient in Implications for AE hemorrhagic shock after significant blunt chest trauma, especially after sudden deceleration. Like most postoperative cardiothoracic pa- Emergency care is limited to airway man- tients, elective AE should be delayed until agement and vascular volume expansion with well into the convalescent phase of recovery, fluids and blood products. In surviving patients, approximately 14 days after surgery. The diffi- exsanguination is usually prevented by the culties encountered when attempting to per- formation of an adventitial hematoma. The form emergency surgery in-flight are enormous, single most important aspect of care is to and thus every effort should be made to delay prevent hypertension, which could disrupt this AE until the patient is stable. hematoma. Hypertension can be minimized by Urgent and contingency AE can be per- the adequate treatment of pain and hypoxia, formed 12 hours after surgery but will require avoidance of fluid overload, pharmacological the assistance of a fully equipped CCAT team. muscular paralysis, and beta-adrenergic antag- The patient must be hemodynamically stable onist therapy. with coagulation parameters in the normal range. It is imperative that mediastinal chest Implications for AE tube output is <100 to 150cc/hour because patients with greater rates of output are at Patients with aortic trauma who are still alive significant risk of anemia, coagulopathy, and when they reach a medical facility will often 254 K.E. Stephens, Jr. require further MEDEVAC to a higher level of usually fatal. Penetrating injury to the cervical care because cardiopulmonary bypass is com- esophagus should be suspected with any deep monly required for surgical repair of this injury. neck injury, especially in the presence of sub- Although the injury can be repaired without cutaneous air. Treatment of associated vascular cardiopulmonary bypass, the surgeon is without or tracheal injuries must take precedence over resort if the lesion extends into the proximal esophageal repair. aortic arch or ascending aorta, and protection Barotrauma to the esophagus usually results of the spinal cord and viscera during the cross- from violent emesis (Boerhaave’s syndrome). clamp interval is suboptimal. The referring The most common site of perforation is near surgeon must decide if the urgency of the the hiatus at the left lateral wall, where the situation warrants undertaking these risks. esophagus lies adjacent to the negative pres- Like all postoperative cardiothoracic pati- sure of the pleural space. ents, elective AE should be delayed approxi- The primary risk of esophageal rupture is mately 14 days, until the patient is well into pleural or mediastinal contamination with the convalescent phase of their recovery and oral or gastric contents and secondary sepsis. complications are unlikely. Pleural or mediastinal contamination will re- Urgent or contingency AE will require the quire surgical drainage, repair of the primary assistance of a well-equipped CCAT team and injury, generous chest tube drainage, and anti- may be initiated approximately 12 hours after biotic therapy. surgery, when the patient is hemodynamically stable and coagulation parameters have re- Implications for AE turned to the normal range. A distinctive problem related to aortic dis- Time from injury to surgical repair is critical for ruption is visceral ischemia secondary to intra- esophageal perforation because necrotizing operative aortic cross-clamping. Within the mediastinitis may force esophageal diversion or first 72 hours after surgery, bowel edema and esophagectomy, a morbid and potentially fatal massive third-space fluid loss will often increase intervention under these circumstances. Urgent intra-abdominal pressure. If abdominal AE should be undertaken as soon as the diag- compartment syndrome is suspected in-flight, nosis of esophageal perforation is made, assum- diversion to a medical facility for decompres- ing the patient is stable in respect to other sive laparotomy is indicated. Measurement concurrent injuries. Prior to AE, these patients of a decompressed bladder pressure of greater should have nasoesophageal or nasogastric than 40cm H2O is suggestive of this diagnosis. drains placed and receive continuous broad- Delayed spinal cord ischemia can also occur spectrum antibiotics. after aortic cross-clamping and aortic surgery. Postoperative patients should be allowed If this occurs, intrathecal decompression by to recover for 14 days prior to elective AE. lumbar drainage of cerebrospinal fluid can be After esophageal repair, oral alimentation is in beneficial. Although the patient stable enough general withheld for 7 days, until a swallowing for AE will be outside of the usual time window study verifies the integrity of the repair site. for this complication, the well-prepared AE Prior to elective AE, the patient should be able crew will have the necessary supplies to react if to swallow normally and be adequately recov- it does develop. ered from any coexisting injuries. Urgent or contingency AE can be carried out Esophageal Perforation after the patient has been allowed to recover for 12 hours postoperatively, assuming the Esophageal perforation may result from pene- patient is stable in respect to other injuries. The trating trauma, blunt trauma, caustic ingestion, patient will usually require up to three large barotrauma, or impaction of sharp objects, chest tubes (eg, >32 to 36 French) and neck food, or pills. Penetrating injury to the thoracic drainage with Penrose drains. Broad-spectrum esophagus is seen less often because the accom- antibiotics with good anaerobic coverage are panying injuries to the great vessels or heart are mandatory. 18. Aeromedical Evacuation of Cardiothoracic Casualties 255

Diaphragmatic Rupture massive blood loss are common. As a result, these patients have many unique aspects to Diaphragmatic rupture is common in trauma their care, both before and after surgery. For patients and can be difficult to diagnose, espe- this reason, elective AE should be delayed until cially if the defect is small. At surgery, 19% of the patient is well into the convalescent phase patients with penetrating lower thoracic of recovery. Urgent or contingency AE can be trauma, but without preoperative evidence of done within hours of most thoracotomies, but visceral herniation, can be found to have 7 the expertise and equipment of a CCAT team diaphragmatic perforation. In blunt trauma, will usually be required. the left hemidiaphragm is more likely to be injured, apparently because of a protective effect of the liver on the right. This is the pre- References sumed explanation for why 85% of diaphragmatic injuries involve the left hemidiaphragm 1. Pape HC, Remmers D, Rice J, Ebisch M, Krettek C, Tscherne H. Appraisal of early evaluation of and fewer than 15% involve exclusively the 8 blunt chest trauma: Development of a stan- right. dardized scoring system for initial clinical Implications for AE decision making. J Trauma 2000;49:496–504. 2. Bendrick GA, Nicolas DK, Krause BA, Castillo A ruptured diaphragm with herniation of CY. Inflight oxygen desaturation decrements in abdominal contents into the chest is a aeromedical evacuation patients. Aviat Space contraindication to AE (Table 18.1). Visceral Environ Med 1995;66:40–44. ischemia and respiratory compromise may 3. Henry JN, Krenis LJ, Cutting RT. Hypoxemia during aeromedical evacuation. Surg Gynecol worsen as the intestinal gas expands during Obstet 1973;136:49–53. flight. Rupture of the stomach, colon, or small 4. Baron ED, Epperson M, Hoyt DB, Fortlage D, intestine into the pleural space can lead to Rosen P. Prehospital needle aspiration and tube sepsis and death. Surgical repair of the hernia thoracostomy in trauma victims: A six year expe- and nasogastric decompression is mandatory rience with aeromedical crews. J Emerg Med before transport. 1995;13:155–163. Elective AE implications for patients after 5. Heffner JE, Brown LK, Barbieri CA. Diagnostic surgical repair of a ruptured diaphragm should value of tests that discriminate between exudative be delayed for 7 days to minimize the risk of in- and transudative pleural effusions. Chest 1997; flight complications. Urgent or contingency AE 111:970–980. may be undertaken as soon as 6 hours post- 6. Cowley RA, Turney SZ, Hankins JR, Rodriguez A, Attar S, Shankar BS. Rupture of the thoracic operatively if hemodynamic and respiratory aorta caused by blunt trauma. A fifteen year stability have been demonstrated. experience. J Thorac Cardiovasc Surg 1990;100: 652–661. 7. Madden M, Paull D, Shires GT, et al. Occult Conclusion diaphragmatic injury from stab wounds to the lower chest and abdomen. J Trauma 1989;29: Cardiothoracic trauma carries a high mortality 292–296. rate and often requires emergency surgery for 8. Brooks JW. Blunt traumatic rupture of the survival. Injuries to the lungs and heart and diaphragm. Br J Surg 1978;26:199–204. 19 Patients Requiring Mechanical Ventilation

Steven L. Chambers and Thomas G. Ferry

In the modern era of technology-dependent pressurized to an altitude of approximately medicine and sophisticated methods for high- 8000ft above sea level. This decreased baro- speed transportation, it has become increas- metric pressure reduces the inspired partial ingly necessary to move relatively ill patients pressure of oxygen. Using standard tables for from areas with insufficient medical care to atmospheric pressure, it can be determined that medical centers with a full range of specialty a PaO2 on room air at sea level of 60mmHg care. Aeromedical evacuation (AE) of pul- can be expected to decrease to approximately monary patients can be safely accomplished, 41mmHg at an altitude of 8000ft. For this but having an appropriate medical team, equip- reason, patients with diseases that affect oxy- ment, and supplies is essential.1 Inherent in this genation at sea level will often decompensate concept are a high level of clinical competency at altitude. and a thorough understanding of the effects of A dramatic example of the effect of altitude altitude and flight on the pathophysiology of on hypoxia was illustrated by a study examin- disease. This chapter will begin with a review ing the arterial blood gases of military patients of the most important aspects of AE for pul- without pulmonary conditions who were trans- monary patients. It will also describe the indi- ported by air from Vietnam to Japan.2 Those cations for and operations of flight ventilators, flown at low cabin altitude (3000 to 3800ft including the potential complications caused by above sea level) rarely had a PaO2 <60mmHg. them. In contrast, patients transported at higher cabin altitudes (6700 to 7500ft above sea level) had a

PaO2 in the 34 to 50-mmHg range 48% of the Effects of Altitude on time. Pulmonary Patients It comes as no surprise that any patients with evidence of hypoxia at sea level will experience 3 Changes in altitude can dramatically affect a worsening in their PaO2 with altitude. There patients with pulmonary disease secondary to are elaborate equations to predict FiO2 require- changes in oxygenation, atmospheric moisture, ments at altitude. Practically speaking, most and changes in the partial pressure and volume patients require an additional oxygen supple- of gases within the lung. Changes in airway mentation of at least 2L per minute more than moisture may induce airway irritation and their requirements at sea level. It is in general bronchospasm and changes in gas volumes may recommended that if a patient has an underly- result in barotrauma within the lung or other ing respiratory condition they should undergo organ systems. arterial blood gas testing and appropriate Probably the most dramatic effect of altitude oxygen supplementation should be added is on gas exchange, potentially resulting in both before they are entered into the aeromedical hypoxia and hypercapnia. Most aircraft are system (Table 19.1). This is true for all pul-

256 19. Patients Requiring Mechanical Ventilation 257

Table 19.1. Comparison of different oxygen delivery systems. System Liter ﬂow Oxygen delivered Advantages Disadvantages

Low ﬂow Nasal cannula 1–8L/min 25–50% Allows talking and eating For each liter of ﬂow, expect

O2 saturation to increase by 2–3% Nasal catheter 1–8L/min 25–50% Same as cannula Clogs easily

Simple mask 5–8L/min 40–50% Less comfortable, FiO2% may not be low

confining, not easy to enough for CO2 retainers eat/talk Partial 6–10L/min 55–70% High oxygen delivery Rebreathing mask Non-re–breathing 6–10L/min 70–100% High oxygen delivery mask High flow Venturi mask Variable 24–50% Allows exact concentrations of oxygen delivery monary diseases regardless of the pathophysi- piratory fatigue associated with overwhelming ology of their disease. metabolic acidosis that occurs with an acute The effect of altitude on hypercapnia has myocardial infarction or sepsis. The latter is been less well studied. It is known that sup- much akin to running a marathon without the plemented oxygen can be dangerous for a pa- required prerequisite training. tient with chronic CO2 retention and must be Rapid identification and treatment is critical used judiciously. However, it is unlikely that a to minimize mortality, which has been reported 4 patient with chronic CO2 retention will experi- to be as high as 40% in some series. Subtle ence increased respiratory distress at altitude clinical signs of impending respiratory failure due to worsening hypercapnia if the PaO2 is include confusion (suggestive of hypoxemia), kept in the range of 60 to 75mmHg. If cabin somnolence (common with hypercapnia), and pressure cannot be maintained at or near sea increased work of breathing. The definitive level, an oxygen saturation of 90% to 95% by diagnosis is determined by arterial blood gas pulse oximeter should be maintained with results showing a PaO2 < 60mmHg and/or supplemental oxygen to avoid both oxygena- PaCO2 > 50mmHg. tion and ventilation problems. Pulse oximeters When evidence of increasing respiratory are standard pieces of equipment in most compromise is noted, an immediate search for aeromedical inventories and are included in the reversible causes of acute respiratory failure equipment carried by USAF Critical Care Air should be initiated. Early treatment of altitude- Transport (CCAT) Teams. induced exacerbations of chronic pulmonary conditions (eg, obstructive lung disease) may avoid acute pulmonary arrest (Table 19.2). Acute Respiratory Failure Early recognition and treatment of acute conditions (eg, anaphylactic shock, drug overdose Acute respiratory failure is especially dan- with altered mental status, acute pulmonary gerous when it occurs unexpectedly in-flight. edema) may avoid the need for mechanic ven- Respiratory failure is typically classified as tilation in these situations as well. being one of three types: (1) hypoxic, (2) hyper- capneic, or (3) mechanical failure. Most com- Emergency Treatment of monly,respiratory failure is due to intrinsic lung Acute Respiratory Failure disease resulting in inadequate gas exchange. However, respiratory failure can also result Treatment of acute respiratory failure re- from the increased work of breathing and res- quires a two-pronged approach: (1) support of 258 S.L. Chambers and T.G. Ferry

Table 19.2. Common medications used in the management of obstructive lung diseases. Type Method of administration Examples

Bronchodilators Beta-agonists Fast-acting Primarily inhaled Albuterol, terbutaline, metaproterenol Long-acting Primarily inhaled Salmeterol Anticholinergics Primarily inhaled Ipratroprium bromide Methylxanthines Oral Theophylline Anti-inflammatories Corticosteroids Inhaled, PO, IV Beclomethasone, triamcinolone, flunisolide, fluticasone, budesonide, prednisone, methylprednisolone Nonsteroidal Inhaled Cromolyn, nedocromil Leukotriene modifiers Oral Zafirlukast, montelukast Expectorants/mucolytics Oral Guanefesin, acetylcysteine (not FDA approved)

Abbreviations: PO, by month; IV, intravenous. ventilation and (2) identification and treatment oximeter is the ideal way to verify adequate of the underlying cause. Initial support of ven- oxygenation in an austere AE environment. In tilation can be as simple as airway stabilization the absence of sophisticated monitoring equip- and supplemental oxygen. However, most ment, the patient must be carefully observed patients with acute respiratory failure will for clinical signs of inadequate oxygenation, ultimately require a combination of intubation eg, using accessory muscles or exhibiting para- and mechanical ventilatory support. doxical respiratory efforts. In these cases, a rapid survey should be accomplished to iden- Basic Life Support tify treatable conditions such as right mainstem bronchus intubation or pulmonary edema When one encounters a patient with acute resulting from fluid overload. respiratory failure, the first steps are to stabilize the airway, ensure that the airway is patent, and summon help. If the patient has stopped Patients on Mechanical breathing, ventilatory support should be provided with a bag–valve–mask apparatus and Ventilators supplemental FlO2 when available. The next Principles of Mechanical Ventilation step is to determine if the patient has a pulse and initiate cardiopulmonary resuscitation if Mechanical ventilation is a method of sup- required. Once the proper equipment is avail- porting patients during illness and is never cura- able, endotracheal intubation should be per- tive or therapeutic.5 A primary physiological formed as soon as possible to minimize the risk objective is to normalize alveolar ventilation, of both inadequate ventilation and aspiration. thus achieving and maintaining an acceptable It is imperative that an experienced physician arterial blood oxygenation level using an Ossass the patient’s respiratory status before acceptable inspired oxygen concentration. A placing that patient on AE and makes the secondary physiological objective is to reduce appropriate interventions before flight. the patient’s work of breathing until specific When acute respiratory failure occurs during therapies can reverse the condition leading to AE, it is unlikely that a mechanical ventilator the increased workload. will be available, Fortunately, manual assistance The clinical objectives of mechanical ventila- with a bag–valve–mask apparatus will usually tion are to relieve potentially life-threatening be effective in maintaining adequate oxygena- hypoxia, correct life-threatening respiratory tion until an emergency landing can be made. acidosis, and relieve respiratory distress and However, it is often difficult to monitor the patient discomfort while the primary disease patient during flight because of increased noise process reverses or improves. In some cases (eg, and suboptimal lighting, limited equipment, flail chest), the primary objective is to stabilize and space constraints. When available, a pulse the chest wall to provide adequate ventilation 19. Patients Requiring Mechanical Ventilation 259 and lung expansion. In all cases, an equally patient breathing to occur at an elevated pres- important clinical objective must be to avoid sure baseline that decreases atelectasis in the iatrogenic lung injury and other complications. airway. Ventilators operate almost exclusively on Each ventilation mode has relative advan- one of five modes (Table 19.3). Assist-control tages and disadvantages. For this reason, the ventilation is a volume-cycled mode where the mode of ventilation should not be changed tidal volume and minimum ventilatory rate are immediately prior to AE unless some signifi- preset. Each time the patient initiates a breath, cant problem has rendered the original mode the preset tidal volume is delivered. This mode unsafe for the patient. is the best way to allow the patient to rest by Although there are many ventilators in the significantly decreasing the work of breathing commercial market, only three are at present for the patient. approved for use in the USAF AE system. Synchronized intermittent mandatory These are the Bear 33 (Fig 19.1) and the Impact ventilation is another volume-cycled mode 750 and 754. The Impact Uni-Vent Eagle Model where there is a preset tidal volume and a 754 is the ventilator currently used by the set number of breaths delivered per minute. USAF CCAT Teams (Fig 19.2). It is important Any breaths over the preset number will to note that, at present, these approved venti- have a tidal volume delivered based on the lators have only three modes: assist-control, patient’s ability to generate that tidal vol- synchronized intermittent, and continuous ume and not the preset volume. Patients who positive airway pressure. When possible, the are “more awake” can tolerate this mode ideal ventilation mode for long-distance AE better. will be assist-control ventilation. Pressure-support ventilation has a preset pressure for each breath that helps overcome the resistance in the system but may have a Steps to Institute Mechanical variable tidal volume with each breath. The Ventilation patient controls respiratory rate, duration of inspiration, gas flow rate, and tidal volume. This There are several important steps involved for mode is often coupled with synchronized inter- instituting mechanical ventilation prior to AE mittent mandatory ventilation. (Table 19.4). The first is to select the ventilation Pressure-controlled ventilation is a time- mode, depending on the patient’s condition and cycled mode that limits the peak inspiratory the experience of the clinician. In our experi- pressures set by the clinician. This theoretically ence, assist-control ventilation, when practica- limits both barotrauma and volutrauma. It has ble, is ideal for AE. For burn patients, pressure been found to be especially useful in patients control ventilation is often required.6 A second with pulmonary burn.6 This mode requires standard step is to begin ventilation with a considerable experience because there is no set 100% fraction of inspired oxygen (FiO2). The tidal volume and minute ventilation will vary. patient is then weaned to the lowest possible For this reason, it may be the least commonly oxygen level required to maintain adequate used mode of ventilation for aeromedical oxygenation (to avoid oxygen toxicity). transport. The third step is to set the initial tidal Finally, continuous positive airway pressure volumes at 5 to 8cc/kg. Historically, tidal is not a true mode of ventilation but allows volumes of 10 to 15cc/kg were used. However, recent data from the National Institutes of Health and others have suggested that lower Table 19.3. Modes of mechanical ventilator tidal volumes in the range of 5 to 8cc/kg may operation. significantly lessen the risk of volutrauma.7 Assist-control ventilation Patients with neuromuscular disorders will be Synchronized intermittent mandatory ventilation more comfortable with an even larger tidal Pressure-support ventilation volume (10 to 12cc/kg). Pressure-controlled ventilation The fourth step is to evaluate arterial blood Continuous positive airway pressure gas pH to determine the ideal tidal volume and 260 S.L. Chambers and T.G. Ferry

Figure 19.1. The Bear 33 Volume Ventilator (Bear Medical Systems, Palm Springs, Calif) is a digital portable ventilator that operates on 120-VAC, external 12-VDC power source, or an internal 12-VDC battery. Its external dimensions are 19.2 (height) ¥ 35.8 (width) ¥ 33.0cm (depth), and it weights 17.2kg (37.9lb).

respiratory rate. Although some medical con- and restrained to protect the airway and pre- ditions warrant the use of permissive hyper- vent the patient “fighting the ventilator.” The capnea, this situation should be avoided while loss of the airway in air travel is catastrophic in-flight if possible. The fifth step is to add a and resecuring the airway can be difficult minimal amount of positive end-expiratory in-flight. pressure (PEEP) to assist oxygenation. PEEP The final step is to allow the patient to stabi- is usually started at 5cm H2O and increased by lize on the ventilator for hours or days to allow increments of 2 to 3cm H2O as needed. It is fine adjustments of PEEP,respiratory rate, tidal uncommon for patients to require more than volume, and oxygen. A steady state should be

15cm H2O of PEEP. achieved prior to transport. There are portable, The sixth step prior to AE is to verify that the miniaturized devices that can perform arterial patient is adequately sedated (using paralysis blood gas analysis in-flight, but they are not yet if necessary) to assure adequate patient– widely available. Even with the benefit of pulse ventilator synchrony (Table 19.5). It is impera- oximeters and CO2 monitors, adjusting ventila- tive that the patient be appropriately sedated tion can be difficult during flight.

Figure 19.2. The Impact Uni-Vent Eagle Model 754 Positive Pressure Ventilator (Impact Instrumentation Inc, West Caldwell,NJ) is a portable ventilator designed for use with neonatal, pediatric, and adult patients. It has a typical battery operating time of 3h when using its compressor and 12h when external gas is used. External dimensions are 29.2 (height) ¥ 22.6 (width) ¥ 11.4 cm (depth), and it weighs 8.4kg with the battery. 19. Patients Requiring Mechanical Ventilation 261

Table 19.4. Important steps for instituting mechan- needs, a skilled pediatric critical-care team ical ventilation prior to AE. is essential to guarantee appropriate care of 1. Select the ventilation mode infants and children with pulmonary disease 2. Begin ventilation with 100% fraction of inspired during transport. It is not unusual for these oxygen (FiO2) patients to develop conditions during AE that 3. Set the initial tidal volumes at 5–8cc/kg will require the team to intervene. 4. Evaluate arterial blood gas pH The key to success in pediatric patients is 5. Add a minimal amount of PEEP 6. Verify that the patient is adequately sedated (including careful assessment for impending or existing paralysis, if necessary) respiratory failure, with obvious attention to 7. Allow the patient to stabilize on the ventilator and stabilization of the patient’s airway, breathing, and circulation. The airway must be stabilized and secured, with appropriate tube When dealing with a patient requiring high placement conﬁrmed. The size of the endotra-

PEEP pressures (20cm H2O PEEP or greater), cheal tube must be based on the age of the child strong consideration should be given to the use (Table 19.6). The depth of the tube is three of bilateral chest tubes for prophylaxis. This is times the tube size. If the tube is cuffed (not necessary because barotrauma can result in the recommended for very young children), only sudden and unpredictable development of uni- minimal air should be inﬂated in the cuff with lateral or bilateral pneumothoraces. A second frequent reassessment as the cabin altitude reason for considering prophylactic chest tubes increases (Boyle’s law). This holds true for all is the fact that both bronchospasm and pneu- cuffed tubes, adult or child. mothorax are extremely difﬁcult to detect in Even in the controlled environment of an the noisy AE environment. ICU, up to 14% of intubated pediatric patients will have an accidental extubation.9 Therefore, Pediatric Issues sedation and/or paralysis may be crucial to prevent this catastrophe during AE. Dosages Pediatric patients frequently require trans- of commonly used medications must be portation in the AE system.8 To meet their adjusted as indicated in pediatric references

Table 19.5. Medications commonly used for adult patients on mechanical ventilation. Drug Route Onset Peak effect Starting dose* Indications

Haloperidol IV, IM 5–20min 15–45min 0.5–2.0mg Agitation PO 30–60min 120–240min 5–10mg Droperidol IV, IM 3–10min 15–45min 2.5–10mg Agitation Chlorpromazine IM 5–40min 10–30min 25mg Agitation PO 30–60min 120–240min Diazepam IV 2–5min 2–30min 2–5mg Sedation, agitation PO 10–60min 30–180min Lorazepam IV, IM 2–20min 60–120min 1–2mg Sedation, agitation SL 2–20min 20–60min 0.5–1.0mg PO 20–60min 20–120min 0.5–1.0mg Morphine sulfate IV 1–2min 20min 4–10mg Analgesia IM 10mg Propofol IV 40s Continuous 10–80mg/kg per min Sedation Midazolam IV 2–3min Continuous 2–8mg/h Sedation Pancuronium IV LD 0.1mg/kg Paralysis MD 0.05–0.1mg/kg per h Vecuronium IV LD 0.1mg/kg Paralysis MD 0.05–0.1mg/kg per h Atracurium IV LD 0.5mg/kg Paralysis MD 0.5–1.0mg/kg per h

Abbreviations: IV,intravenous; IM, intramuscular; PO, by month; SL, sublingual; LD, loading dose; MD, maintenance dose. * Dosages need to be individualized for each patient taking into account routes of elimination and other potential drug interactions that may exist. 262 S.L. Chambers and T.G. Ferry

Table 19.6. Size of the endotracheal tube for school-aged or older children. Rates may need pediatric patients. to be higher than the rates used for adults to Age Size maintain a normal pH, and a PEEP of 2 to 4cm 10 Newborn to 6mo 3–3.5 French H2O is usually adequate. 6–12mo 3.5–4.0 French >18mo (age + 16)/4 Complications of Mechanical Ventilation 8 (Table 19.7). Because of the inherent risks Pulmonary Barotrauma associated with the use of paralytics, only clinicians familiar with their use should use these Pulmonary barotrauma most commonly drugs. manifests as the triad of acute pneumothorax, Infants less than 5kg are usually placed on interstitial emphysema (pneumomediastinum), time-cycled pressure-limited ventilation with and subcutaneous emphysema. Of these condi- peak inspiratory pressures started at low levels tions, only pneumothorax requires immediate of 18 to 20cm H2O and then adjusted clinically attention because it can progress rapidly to based on adequate chest movement and pH tension pneumothorax and death. Immediate stabilization (Fig 19.3). A tidal volume of 10 to treatment is needle decompression until a 15cc/kg is usually achieved in this manner. chest tube can be placed for definitive treat- In children, synchronous intermittent man- ment. Neither interstitial nor subcutaneous datory ventilation is the most frequent mode emphysema require any specific therapy. used. Suggested settings are a tidal volume However, any patient who develops these con- 10cc/kg, with a flow rate resulting in an inspi- ditions while on a mechanical ventilator must ratory time of 0.6 to 0.7 seconds for babies, 0.8 be closely monitored for development of a seconds for toddlers, and 0.9 to 1.0 seconds for pneumothorax.

Table 19.7. Medications commonly used for pediatric patients on mechanical ventilation. Drug Dose Route Effect Notes

Midazolam 0.15–0.40mg/kg IV or IM Sedation, amnesia Avoid if already hypotensive Diazepam 0.1–0.6mg/kg IV Sedation, amnesia Lorazepam 50–100mg/kg IV Sedation, amnesia Morphine 50–200mg/kg IV Analgesia, sedation May cause histamine release; avoid if hypotensive Fentanyl 1.0–5.0mg/kg IV Analgesia or sedation Ketamine 0.5–1.5mg/kg IV Analgesia or amnesia May increase intracranial pressure; hallucinations Etomidate 0.2–0.4mg/kg IV Amnesia May activate seizure foci Flumezanil 2.0–4.0mg/kg IV over 15–30s Reverses benzodiazepines Naloxone 10mg/kg IV Opioid antagonist (maximum total dose of 100mg/kg) Succinylcholine 1–2mg/kg IV Paralysis (for initial Associated with dysrrythymia, intubation) hyperkalemia, myoglobinuria, and malignant hyperthermia Pancuronium 0.1mg/kg IV Paralysis Vagolytic and sympathomimetic; may cause tachycardia Vecuronium 0.1–0.3mg/kg IV Paralysis Rapid, stable cardiovascular effect

Abbreviations: IV, intravenous; IM, intramuscular. 19. Patients Requiring Mechanical Ventilation 263

Figure 19.3. A premature infant is usually transported on a time-cycled pressure-limited ventilator (USAF photo).

Endotracheal Intubation and supplemental oxygen until adequate help Complications and equipment for reintubation becomes available. The patient should then be adequately Common complications related to endotra- sedated, restrained, and reintubated as quickly cheal intubation include the risk of right as possible. mainstem intubation and inadvertent self- If the patient develops signs of inadequate extubation. Right mainstem intubation can ventilation despite proper placement of a result in hypoventilation, atelectasis, and pneu- patent endotracheal tube, the cuff balloon mothorax. It is imperative to verify bilateral should be reinflated and checked for leaking. It breath sound immediately after intubation and the leaking continues, it can be managed either at regular intervals thereafter. by intermittently instilling additional air into Inadvertent self-extubation can be cata- the cuff or replacing the endotracheal tube. strophic during AE because of the increased If the endotracheal tube requires changing, difficulty that may be encountered when it should be changed using either a tube attempting to reintubate the patient. Therefore, exchanger technique or direct larnygoscopy. airway security must be reassessed immediately prior to AE and all patients on mechanical Cardiac Complications of ventilation must be adequately sedated and Mechanic Ventilation restrained. Despite appropriate care and monitoring Cardiac complications of mechanic ventilation of mechanically ventilated patients, airway can be the result of either positive pres- problems can occur during AE. When they do, sure within the chest or inadequate oxygena- the situation should be calmly and methodically tion. Both of these may result in hypotension, assessed and treated. If the patient has self- decreased cardiac output, and arrhythmias. extubated, the patient should first be reassessed Arrhythmias may be the result of inadequate to determine if mechanical ventilation is still oxygenation secondary to intrinsic pulmonary necessary. If so, the patient should be ventilated disease or as a result of inadequate ventilation. manually with a bag–valve–mask apparatus In the case of arrhythmias, always re-evaluate 264 S.L. Chambers and T.G. Ferry the adequacy of your ventilatory support and altitude on pulmonary patients, especially those treat the arrhythmia as outlined by Advanced requiring ventilatory support. Cardiac Life Support clinical guidelines.11 Auto-PEEP is a phenomenon in which not all References of a volume of air or oxygen is exhaled with each breath. The volume that is not exhaled 1. Farmer JC. Respiratory issues in aeromedical may continue to increase until it causes patient transport. Respir Care Clin North Am extra pressure within the alveoli. When there 1996;2:391–400. is enough pressure, increasing intrathoracic 2. Henry JN, Krenis LJ, Cutting RT. Hypoxia pressure can cause barotrauma or significant during aeromedical evacuation. Surg Gynecol hypotension by impeding venous return. Obstet 1973;136:49–53. 3. Bendrick GA. In flight oxygen saturation decre- Auto-PEEP can be due to either suboptimal ments in aeromedical evacuation patients. Aviat ventilator settings or the patient’s disease Space Environ Med 1995;66:40–44. process. Another cause is patient–ventilator 4. Weiss SM, Hudson LD. Outcome from respira- dysynchrony, ie, when an inadequately sedated tory failure. Crit Care Clin 1994;10:197–215. patient fights the ventilator. 5. Slutsky AS. Mechanical ventilation, American Once auto-PEEP is recognized, it can be College of Chest Physicians’ Consensus Confer- treated by allowing a longer exhalation time ence. Chest 1993;104:1833–1859. (by adjusting the inspiratory to expiratory 6. Barillo DJ. Pressure control ventilation for the ratio) or adding PEEP to maintain the integ- long range aeromedical transport of patients rity of the airways so less gas is trapped. If with burns. J Burn Rehabil 1997;18:200–205. patient–ventilator dysynchrony appears to be 7. The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal values as the cause, the patient can either be removed compared with traditional tidal volumes for from the ventilator or more effectively sedated. acute lung injury and acute respiratory distress syndrome. N Engl J Med 2000;342:1301– 1380. Conclusion 8. Brink LW, Neuman B, Wynn J. Air transport. Pediatr Clin North Am 1993;40:449–456. The need to transport critically ill patients by 9. McDonald TB, Berkowitz RA. Airway manage- air has dramatically increased in the last 20 ment and sedation for pediatric transport. Trans- years, and many patients requiring such transport Med 1993;40:381–406. port are ventilator-dependent. In response to 10. The Harriet Lane Handbook. 14th ed., Barone, this need for critical-care air transport, a better Mass; 444–458. understanding of the implications of flight on 11. The American Heart Association in collabora- tion with the International Liaison Committee pulmonary patients has developed, and both on Resuscitation. Guidelines 2000 for cardio- the personnel and equipment have progressed pulmonary resuscitation and emergency cardio- to the point that an AE airframe can now be vascular care. Part 6: Advanced cardiovascular converted into a mobile intensive-care unit. life support: 7C: A guide to the International Central to the modern AE mission is a thor- ACLS algorithms. Circulation 2000; 102:1142– ough understanding of the effects of flight and 1157. 20 Orthopedic Patients

Steven L. Oreck

Orthopedic trauma comprises a significant Pathophysiology of percentage of all injuries, either by themselves or in combination with other injuries. This holds Orthopedic Injuries for both the civilian world and during military operations. The use of modern protective Bone fractures result in three immediate and equipment by both civilians and military distinctive pathologic responses that can have members reduces the overall rate of injury or grave sequella: pain, bleeding, and the release wounding yet paradoxically increases the per- of “injury amines.” Pain is related to both the centage of orthopedic injuries.1–4 This is because interruption of the sensitive periosteum and both civilian restraints (eg, airbags and safety the damage the jagged edge of a compound harnesses) and military body armor protect fracture can inflict on adjacent nerves, vessels, vital central nervous system and visceral struc- and soft tissue. Pain can be adequately treated tures but do little to protect the extremities, only with a combination of immobilization of which remain exposed. the fracture, elevation of the limb, and pain Orthopedic injuries include not only fractures medication, as discussed below. and dislocations but also soft-tissue injuries, Likewise, potentially massive bleeding origi- including tendon and nerve injuries, loss of nates from both the fracture itself and the tissue, and vascular injuries. This constellation associated soft-tissue and vessel injuries. The of trauma can be treated by several different formation of a fracture hematoma usually surgeons including orthopedic, trauma, general, controls the bleeding. If left undisturbed, the and plastic surgeons or a team of surgeons. hematoma will become fibrous and stable. The exact composition of the surgical team Limb movement related to inadequate splin- depends upon several factors including the tage can result in hematoma disruption and setting of the injury, the training of the individ- renewed bleeding. This has obvious implica- uals involved, and the inclination of the medical tions for AE both in terms of movement tech- system where they are treated. This chapter will niques and patient monitoring. cover these multitissue injuries as well as frac- The final pathologic response to fracture is tures and dislocations. the local release of injury amines and other This chapter will begin with a brief descrip- substances. These include histamine, bradyki- tion of the pathophysiology of orthopedic nin, various prostaglandins, and others—with injuries followed by a discussion of treatment more substances being elucidated on a regular and implications for the aeromedical evacua- basis. The predictable consequence is sub- tion (AE) of these patients. It will end with stantial tissue edema that results from local a discussion of the preparation for and con- changes in capillary permeability. This can be traindications of AE. minimized by both elevation and splintage of

265 266 S.L. Oreck the fractured limb. Unfortunately, edema can lacerating soft-tissue structures. In addition, worsen during an AE flight (ie, “flight edema”) splintage reduces bleeding by allowing clotting because of fluid shift caused by reduced cabin to occur and the fracture hematoma to stabilize. pressure.5–9 Given the significant bleeding that can occur from long-bone and pelvic fractures, this is an Fat Embolism Syndrome important consideration. Splintage can be anything from a rifle A unique and potentially fatal condition that strapped around a leg to a complex internal can occur after any significant fraction is fat fixation device. It also includes casts, traction, embolism syndrome. It has long been attrib- and external fixators. For medical evacuation uted to the release of marrow fat into the (MEDEVAC), orthopedic injuries with frac- circulation but may actually result from the ture or dislocation need to be splinted using release of injury amines into the systemic cir- whatever is available, including the soldier’s culation, which then induce changes in systemic rifle. Although the details of splintage are fat metabolism. As the fracture hematoma beyond the scope of this chapter, it is important forms, the risk of fat embolism decreases, but to realize that many orthopedic devices that can occur if the fracture hematoma is disrupted work well in a hospital setting are incompatible as a result of either surgical manipulation or with AE, as discussed below. inadequate splintage. Elevation of the Injured Limbs The Danger Zone An important aspect of care of the orthopedic The “danger zone” for immediate orthopedic casualty is elevation of the injured limb. This complications is the first 72 hours after fracture deceptively simple maneuver decreases, pain, or any major bone surgeries, especially long- bleeding, and edema, probably as a result of bone manipulation. During this period, injury- decreasing venous capillary pressure. Main- related edema becomes maximal. In addition, taining elevation during transportation is well during this period patients are at greatest risk worth the small effort required. for fat embolism syndrome, manifesting most commonly by acute respiratory distress.3,10 Monitoring of Vital Signs Once the fracture is reduced and the patient’s Treatment of pain is well controlled, the risk of serious com- Orthopedic Casualties plications appears to be decreased. However, the risk of complications remains significant for There are several important considerations for the first 72 hours. Many of the most serious the care of orthopedic casualties and recogni- complications discussed below start with subtle tion of complications in a timely fashion as they signs and symptoms. Because effective treat- occur. Key among these are adequate splintage ment depends on early recognition, careful and elevation of the injured limb, monitoring monitoring of vital signs in the apparently of general vital signs, and frequent checks stable orthopedic casualty is essential. of the neurovascular status of the affected limb. Neurovascular Status Checks

Splintage Continued reassessment of limb status is vital during the 72-hours danger zone after fracture, Splintage is the single most crucial aspect of when patients are at the greatest risk of limb orthopedic casualty treatment.1,11–15 Adequate edema and other causes of neurovascular com- splintage of orthopedic injuries reduces pain promise. The standard of care requires thor- and edema and prevents further damage to ough documentation of normal neurovascular the limb by preventing sharp bone ends from function before, during, and after AE. 20. Orthopedic Patients 267

Implications for AE tant if the patient is anticoagulated. Patients with compartment syndrome should be treated Orthopedic casualties possess both positive and prior to AE because the occurrence of any negative characteristics that influence AE. On flight edema will only worsen the problem. the positive side, orthopedic injuries are rarely Finally, elective AE should be avoided when life-threatening and, after initial stabilization, possible for patients with gas gangrene because complications are uncommon. Notable excep- any reduction in oxygen tension will worsen tions to this are patients with significant pelvic this condition. fractures (especially posterior) or multiple If urgent or contingency AE is required re- long-bone fractures. On the negative side, the latively soon after major orthopedic injury or most common complications that may develop surgery, several important precautions should in orthopedic casualties during AE are in be taken. First, the aeromedical crew should general beyond the capability of the aeromedi- be advised of the increased risk patients are cal crew to treat and usually require expedient at during the 72-hour danger zone following surgical treatment. An understanding of the orthopedic injury or surgery. For any patient potential complications and when they might who has undergone microvascular reattach- occur will help avoid elective AE of orthopedic ment of a limb or digit, or who is suspected casualties during the periods when they are at or known to have gas gangrene, the flight highest risk for devastating complications. altitude should be restricted to maintain sea- Appropriate planning is crucial to achieve an level cabin pressure. There are no altitude or ideal outcome for all patients. cabin pressure restrictions for patients with compartment syndrome, but reasonable attempts should be made to maintain the cabin Orthopedic Contraindications for pressure as close as possible to sea level to min- Elective AE imize additional edema. The greatest possible care must be taken when moving patients with There are several orthopedic conditions that unreduced or unstable fractures to minimize are contraindications to elective AE (Table damage to surrounding tissue and the associ- 20.1). After major orthopedic trauma or ated pain (Fig 20.1). Careful monitoring of the surgery, elective AE should be delayed for 3 neurovascular status of the affected limb is days (72 hours) to avoid the danger zone. If the required for early detection of developing injury required microvascular reattachment problems. of a limb or digit, AE should be delayed until 7 days after surgery. Because of the risk of further damage to surrounding tissue, AE should be delayed until fractures are reduced and, if necessary, fixed. This is especially impor- Preparation of the Orthopedic Patient for AE Splintage Table 20.1. Contraindications to elective AE. The most important consideration for AE is Less than 72h following major orthopedic trauma or selection and preparation of splintage. Some surgery splints are difficult or impossible to use during Less than 7d following microvascular reattachment of a AE and others have potential complications. limb or digit Free weight traction should not be used during Unreduced long-bone fractures or major joint dislocations AE, even in a sophisticated air ambulance, Unstable long-bone or pelvic fractures because of the adverse affect of movement An anticoagulated patient prior to definitive fracture and G-forces on these systems. Both US fixation and NATO doctrines specifically forbid free Untreated compartment syndrome weight traction. MAST trousers, a type of splin- Gas gangrene tage sometimes used for pelvic fractures, is 268 S.L. Oreck

Figure 20.1. Unstable pelvic/ acetabular fracture. Patients with unstable symphysis diastasis and acetabular injuries must at least have provisional external ﬁxa- tion prior to AE to avoid signiﬁ- cant problems.

also inappropriate for AE.12,15 The amount of Preflight Checklists pressure exerted by these inflatable trousers will vary with cabin pressure. The resultant There are several steps that should be taken excess pressure on the lower extremities can be prior to AE to minimized the chance of dangerous when MAST trousers are used for complications during flight (Table 20.2). Above prolonged periods during an AE flight. Like- all, it should be ensured that the medical wise, air splints are relatively contraindicated records are complete and appropriate radio- for AE because splint expansion related to graphs accompany the patient. If possible, the reduced cabin pressure can constrict circulation fracture should be drawn on the cast, as well as to the limb.5,11,15,16 Air splints are acceptable a list of any procedure done. This will guaran- for MEDEVAC, as the altitudes flown will tee that this important information is available not induce significant expansion of a properly to both the caregivers during the flight and the inflated air splint. All splints, whether inflat- accepting physicians. If AE is required within able or attached with elastic bandages, must the 72-hour danger zone following injury or be checked to ensure they are not too tight surgery, the aeromedical crew must be made before and during any MEDEVAC or AE aware of higher risks for this patient. A flow flight. sheet should be provided to record continuing Casts present several unique challenges to neurovascular monitoring of the patient during AE. A rigid cast that fit well on the ground may flight. If the patient has undergone micro- become dangerously tight during flight because vascular reattachment of a limb or digit within of flight edema or other changes in the patient’s 7 days or has gas gangrene, flight altitude condition. For this reason, all casts must be should be restricted to maintain sea-level cabin bivalved down both sides prior to AE (Fig pressure. 20.2). The underlying cast padding should be Clinically, the most important preparation divided as well, and the cast held together with for AE involves careful examination of any an elastic bandage. In some cases, windows cast or traction devices (Table 20.3). First, it must be cut to allow adequate monitoring of must be verified that no free weight traction, neurovascular status. These windows must have MAST trousers, or air splints are being used. plaster covers that can be replaced after every Next, all casts should be examined to ensure check. If a windowed area is left uncovered, they are in good condition and both the plaster soft-tissue swelling can result in an artificial and underlying cast padding have been com- “hernia.” pletely bivalved. The entire cast should be held 20. Orthopedic Patients 269 together with an elastic bandage. All windowed to assure that normal neurovascular status of areas that have been cut in the cast should any fractured limb is present and has been have corresponding plaster covers in place to clearly documented. avoid localized soft-tissue swelling. Finally, all spring traction device settings should be In-Flight Care checked. Prior to take-off, it should be confirmed that General nursing care for orthopedic patients all required equipment is on-board. This should during AE is straightforward. Adequate patient include a spare blanket or pillow to elevate the monitoring and documenting of vital signs and injured limb during flight, a large paramedic- limb neurovascular status should be carried out type scissors capable of cutting cast padding, a at regular intervals. This interval may vary from cast saw, extra elastic bandages, and standard every 1 to 4 hours, and needs to be specified by dressings. The final clinical step prior to AE is the referring physician in the preflight orders.

Figure 20.2. Properly bivalved cast. A bivalved cast (A) should also have the padding split and be partially wrapped with an elastic bandage. The cast is removed (B) to illustrate the complete split down both sides. A sketch of the injury and other data should be written on the cast with a marker. B 270 S.L. Oreck

Table 20.2. Administrative preflight checklist. Each of these complications is considered Ensure complete medical records and radiographs below. accompany the patient If urgent or contingency AE is required during the 72-h Neurovascular Compromise danger zone following injury or surgery, alert the aeromedical crew to increased risk Neurovascular compromise is always at the top Restrict the flight altitude to maintain sea-level cabin of the list of problems associated with orthope- pressure for any patient who has undergone dic injuries. Injuries to nerves or blood vessels microvascular reattachment of a limb or digit within 7d can be on the same basis as the fracture (eg, or who has gas gangrene Provide a neurovascular monitoring flow sheet for the projectile or crushing injury). A partial vessel patient injury, such as an intimal tear, can be com- Draw on the cast the patient’s fracture and a list of any pletely asymptomatic immediately after injury procedures done; in the event that paperwork becomes but progress to complete vessel occlusion unavailable, this information will be invaluable to both during transport. The jagged end of unstable the in-flight caregivers and the receiving physician fractures can create new nerve or vessel injuries as a result of inadequate splintage. Partially impeded circulation can become further compromised due to edema or the pressure of com- If a cast or dressings impedes the caregiver’s partment syndrome. ability to palpate distal pulses, capillary refill Vascular compromise from any cause of fingernails/toenails should be evaluated to (including compartment syndrome, discussed verify adequate limb perfusion. If motor testing below) present with acute loss of distal pulses, of distal extremities is difficult to evaluate a cold extremity, or bleeding through dressings because of pain, the response to touch can be or casts due to the failure of a vascular repair. used as a simple guide. The results of each Management of acute vascular compromise of exam should be recorded with the dates and a limb is limited to supportive measures such as times.

Potential In-Flight Emergencies Table 20.3. Clinical preﬂight checklist.

Patients with orthopedic injuries may suffer Verify that no free weight traction, MAST trousers, or air from all of the problems common to other splints are being used trauma patients, including infection and exter- Ensure all casts have been completely bivalved (not just nal hemorrhage. However, there are several split down one side); even the underlying cast complications that are relatively unique to padding should be cut, and the entire cast held together with an elastic bandage orthopedic injuries, many of which are often Ensure all windowed areas cut in the cast have “hidden.” Vascular and neurological complica- corresponding plaster covers; an uncovered window tions, especially common with military ortho- area will result in localized soft-tissue swelling pedic injuries, can be obvious and thus repaired forming a hernia prior to entrance to the AE system. Alterna- Ensure all casts are in good condition; soft, or soggy, or otherwise “beat-up” casts should be replaced or tively, more subtle neurovascular compromise reinforced can subsequently occur as a result of progressive Ensure the availability of a spare blanket or pillow to intimal tears or the failure of a vascular repair. elevate the injured limb during flight Concealed hemorrhage, significant enough to Check all spring traction device settings result in shock, is a risk for any patient with Ensure that normal neurovascular status of any fractured limb has been clearly documented long-bone or pelvic fractures. Two complica- Ensure the following supplies are available on the aircraft tions relatively unique to orthopedic injuries Extra elastic bandages are compartment syndrome and fat embolism Large paramedic-type scissors capable of cutting cast syndrome. Two other complications for which padding a patient is at increased risk after orthopedic Cast saw Standard dressings injuries are gangrene and crush syndrome. 20. Orthopedic Patients 271 oxygen supplementation and diversion to an permanent damage, including limb loss, is likely appropriate medical facility. to occur.10,15,17,18 Swelling of a limb inside an improperly bivalved cast over a prolonged flight Shock has necessitated subsequent amputation.15 During flight, the diagnosis of possible com- Shock is both an acute and delayed risk in an partment syndrome is made on clinical grounds apparently stable orthopedic casualty. Absence in patients at high risk. Both increasing limb of external bleeding can lead to a false sense of pain and pain upon passive stretch of the security in a patient with long-bone or pelvic compartment (elicited by extending the fingers fractures. The risk of continued bleeding is or toes) indicates compartment syndrome until especially great in patients with unreduced or proven otherwise. Loss of distal pulses or neu- unstable fractures. These casualties can lose sig- rological changes can be late signs. nificant amounts of blood into a thigh or pelvis For patients with diminished capacity to with none of the dramatic distension associated respond to a clinical exam for compartment with intra-abdominal bleeding. Transfusion syndrome (eg, decreased consciousness due to coagulopathy also becomes a risk if large central nervous system injury), direct measure- amounts of blood replacement are required. ment of compartment pressure may be necessary. However, only experienced personnel Compartment Syndrome should place in-dwelling monitoring devices. A compartment is an anatomic area of the body Commercially available compartment measur- that is incapable of significant expansion due to ing devices not much larger than a hypodermic rigid bony or fascial boundaries. With increas- syringe can be utilized, even in the noisiest ing edema or bleeding in a rigid compartment, AE environment. On the ground or in the rela- the pressure in the compartment rises. Once tively quiet environment of modern dedicated the pressure in the compartment exceeds AE aircraft, compartment pressure can also be capillary perfusion pressure, approximately 30 measured with a simple in-dwelling catheter to 35mmHg, blood flow at the cellular level to hooked to an arterial pressure monitor. the tissues in the compartment ceases. This is The first step in the treatment of evolving most important to the skeletal muscle because compartment syndrome is loosening of a it is the most metabolically active tissue.10,17,18 properly bivalved cast. However, continued The resultant ischemic muscle swells further symptoms will require diversion to the nearest and becomes extremely painful in what is medical facility because definitive treatment, known as compartment syndrome. surgical fasciotomy, should be performed Compartments most at risk for this syndrome within 4 hours.10,17,19 with an orthopedic injury are the anterior, posterior, and lateral leg compartments and the Fat Embolism Syndrome volar compartment of the forearm. An artificial “compartment” is created whenever a rigid cast Another complication unique to orthopedic is place around an extremity. If a cast is not injuries is fat embolism syndrome. This is most bivalved properly so that it does not allow ade- typically seen in long-bone fractures, such as quate room for edema, iatrogenic compartment femur fractures, but can be seen in patients syndrome can result. with pelvic fractures or multiple fractures of It is important to note that the compartment smaller bones. This complication is most com- pressure at which capillary perfusion of the mon in the 12 to 72 hours after orthopedic muscle ceases is well below mean arterial injury or surgery. Probably the highest-risk pressure. Therefore, full-blown compartment surgery for this complication is the placement syndrome can occur even in the presence of an of an intramedullary rod into the femur with excellent palpable distal pulse. Once compart- reaming. Postmortem examination of patients ment syndrome develops, the problem must who die from this syndrome reveals widespread be treated (ie, fasciotomy) within 4 hours or fat emboli in alveolar blood vessels of the lung. 272 S.L. Oreck

The clinical presentation of fat embolism syn- Crush Syndrome drome is the rapid development of progressive One final complication that is seen in orthope- respiratory distress syndrome in a patient at dic casualties is “crush syndrome.” Casualties risk. Severity ranges from a mild hypoxia with who have crushing injuries of an extremity a mild tachypnea to a profound respiratory associated with a significant period of limb distress requiring intubation and mechanical hypoxia may develop crush syndrome. The ventilatory support. Other clinical signs include etiology of this syndrome is muscle ischemia progressive tachypnea, confusion secondary resulting in necrosis. The elements of crush to hypoxia, and a distinctive petechial rash on syndrome include compartment syndrome the chest and neck, which is pathognomonic symptoms (which may be delayed) and myo- when present.3,10 In-flight treatment of fat globinuria, sometimes severe enough to result embolism syndrome consists of supplemental in renal failure. Casualties who have been oxygen and diversion to a medical facility if pinned for any length of time in a structure or symptoms warrant. Intubation and assisted vehicle are at risk for this syndrome, even in the ventilation assistance may be required in severe face of a relatively benign looking limb. If cases. symptoms of crush syndrome develop during Pulmonary Thromboembolism AE, the treatment is limited to supplemental oxygen, hydration to treat the myoglobinuria, The one relatively common complication of and diversion for emergency surgical treatment orthopedic injury which is not limited to the of compartment syndrome. first few days following injury, is thromboembolism.10 The symptoms, while respiratory in nature, differ from those of fat embolism in two Conclusion key ways. First, pulmonary thromboembolism Orthopedic casualties present specific chal- usually presents with acute onset, as opposed to lenges to both the civilian and military AE the frequently more insidious onset of fat system. While usually not critically ill from their embolism. This can vary from moderate re- orthopedic injuries, these patients frequently spiratory distress and pleuritic chest pain to represent a difficult nursing and transport chal- cardiac arrest. Second, jugular venous disten- lenge due to lack of mobility and potentially sion is commonly noted. bulky and heavy splintage and traction devices. In-flight treatment of pulmonary throm- While orthopedic emergencies that threaten boembolism consists of supplementary oxygen life or limb are rare during AE, there is rela- and ventilatory support as needed. Depending tively little the aeromedical crew can do to treat on the severity of symptoms, diversion to a them in-flight. For this reason, the cornerstone facility that can initiate immediate anticoagula- of the safe AE of orthopedic casualties is ade- tion, thrombectomy, and/or insertion of a vena quate preparation and stabilization, together cava filter may be necessary. with delaying AE until 72 hours after injury or Gas Gangrene surgery if possible. A particular complication of a dirty extremity References injury, especially with delayed or inadequate debridement, is clostridial (gas) gangrene. 1. Demartines N, Scheidigger D, Harder F. Patients with gas gangrene may require urgent Helikopter und Notarzt an der Unfallstelle. AE to a facility with a hyperbaric chamber Helvet Chirurg Acta 1991;58:223–227. 2. Oreck SL. Orthopaedics in the combat zone. to assist in the treatment of this condition. The Milit Med 1996;161:458–461. single most important AE-specific management 3. De Tullio A. Problemi aeromedici nel polifrat- action for these patients is altitude restriction to turato. Minerva Med 1977;68:4101–4108. maintain the aircraft at sea-level air pressure 4. White MS, Chubb RM, Rossing RG, et al. because any reduction in oxygen tension will Results of early aeromedical evacuation of result in a worsening of this condition.9,15 Vietnam csualties. Aerosp Med 1971;43:780–784. 20. Orthopedic Patients 273

5. Charbanne JP, Sourd JC. Les evacuations sani- 14. Johnson A, Jr. Treatise on aeromedical taires aeriennes. SOINS 1984;432:35–41. evacuation: II. Some surgical considerations. 6. Evard E. Le transport aerienne de maladies et Aviat Space Environ Med 1977;48:550– blesses. Bruxell Med 1970;50:339–359. 554. 7. Pats B. Le transport aerien sanitaire collectif des 15. Parsons CJ, Bobechko WP. Aeromedical trans- blesses de guerre. Cahiers Anesthesiol 1991;39: port: Its hidden problems. CMA J 1982;126: 337–344. 337–344. 8. Pensiton-Feliciano H. Aeromedical transport. 16. Hansen PJ. Safe practice for our aeromendical Del Med J 1995;67:340–345. evacuation patients. Milit Med 1987;152:281– 9. Unsworth IP. Gas gangrene and air evacuation. 283. Med J Austr 1974;1:240–241. 17. Matsen FA III. Compartmental Syndromes. 10. Epps CH, Jr, ed. Complications in Orthopedic New York: Grune & Stratton; 1980. Surgery. 3rd ed. Philadelphia: J.B. Lippincott; 18. Yamaguchi S, Viegas SF. Causes of upper 1994. extremity compartment syndrome. Hand Clin 11. Andersen CA. Preparing patients for aeromedi- North Am 1998;14:365–370. cal transport. J Emerg Nurs 1987;13:229–231. 19. Garlin SR, Mubarak SJ, Evans KL, et al. 12. Bowen TE, Bellamy RF, eds. NATO Handbook: Quantiﬁcation of intracompartmental pressure Emergency War Surgery. Washington, DC: US and volume under plaster casts. J Bone Joint Government Printing Ofﬁce; 1988. Surg 1981;63A:449–453. 13. Hansen PJ. Air transport of the man who needs 20. White MS. Tactical intratheater aeromedical everything. Aviat Space Environ Med 1980; evacuation of SEA casualties. Milit Med 1968; 51:725–728. 133:921–924. 21 Burn Patients

David J. Barillo and James E. Craigie

An estimated 1.4 to 2 million people are burned rary munitions. Based upon the Vietnam War every year in the United States, resulting in experience, the Wound Data and Munitions 500,000 emergency department visits, 75,000 Effectiveness Team suggests that, for planning hospital admissions (including 20,000 admis- purposes, thermal injury or other major soft- sions to burn centers), and 6500 deaths.1,2 In the tissue injury requiring operative debridement civilian sector, burn care is delivered in 138 will be present in 10% of combat casualties.3 self-designated burn treatment centers in the In actual conflict, thermal injury was seen United States and in 21 centers in Canada for in 8.1% of casualties from the Yom Kippur a total of 1951 specialty-care beds.1 In the mili- War and 18% of British casualties from the tary health care system, the USA Burn Center Falklands War.4,5 Conflicts involving chemical (USA Institute of Surgical Research) functions weapons (blister agents) or tank warfare may as the international burn center for all branches be expected to produce even greater numbers of the US military, retirees, and dependents and of burn casualties. as the national burn center for the Department Full-thickness burn injury requires surgical of Veterans Affairs. The Institute of Surgical excision and grafting, with attendant blood loss. Research/Army Burn Center is a tenant agency The average burn patient may require trans- at Brooke Army Medical Center, Fort Sam fusion of up to 19.7U of blood products dur- Houston, Tex, and has a normal capacity of ing acute hospitalization,6 making in-theater 40 burn beds, all of which are configured to burn surgery impractical. For this reason, provide intensive care. By utilizing other wards the aeromedical evacuation (AE) system will at Brooke Army Medical Center, the burn have significant exposure to burn victims center is capable of expansion to an 80-bed unit during future conflicts, as definitive care will on short notice or a 200-bed unit in time of war. likely be provided in the communication zone Military service poses unique burn risks. (COMMZ) or the continental United States Sailors live and work in close proximity to (CONUS). superheated steam, aviation fuel, and munitions. Soldiers handle demolition devices, tank rounds, and artillery shells and depend upon Overview of Military gasoline-fueled cooking stoves and tent heaters Burn Casualties while in the field. Aviators operate rotary-wing and fixed-wing aircraft at design extremes and Burn injury may be caused by contact with under adverse weather conditions. steam or hot liquids, flame, electrical current, or Historically, burn injury has comprised 3% chemicals. Patients injured in closed spaces of all battle casualties. In recent conflicts, the such as buildings or vehicles may have smoke incidence of burn injury is higher, possibly inhalation injury to the lungs, which signi- related to increased lethality of contempo- ficantly complicates management. Combat-

274 21. Burn Patients 275 related burns may be complicated by blast >20% and <70% body surface area (BSA).3,9 injury, open fractures, or other trauma. The For triage purposes, burn size is increased by presence of associated traumatic injury must 10% for the presence of inhalation injury or always be considered and visceral injury ruled other major trauma.3,9 When medical assets are out prior to long-range transfer. The preflight unable to accommodate patients within this work-up and preparation of burn patients in range, the maximum burn size to receive treat- general is presented below. Subsequent sec- ment may be decreased in 10% increments tions present information specific to chemical until assets are adequate.3 or electrical injuries. Transport guidelines for civilian practice recommend the use of ground ambulances for transport distances less than 30 miles, rotary- Acute Thermal Burn Injury wing aircraft for distances of 30 to 150 miles, and fixed-wing aircraft for distances over (With or Without 150 miles. In battle, rotary-wing aircraft would Smoke Inhalation) be used for tactical distances and fixed-wing aircraft used for strategic transfer. General Considerations Determining who Should Be Transferred Determining the Optimal Time and How Transfer Should Be Carried Out for Transfer The American Burn Association has estab- Two factors, hemodynamic stability and pul- lished criteria for the referral of patients with monary insufficiency from smoke inhala- thermal injury to special-care facilities (Table tion injury, determine the optimal time for 21.1). These criteria, endorsed by the Advanced aeromedical transfer. Burn injury has profound Trauma Life Support and Advanced Burn Life effects on the circulation. Capillary permeabil- 7,8 Support programs, represent a national civil- ity is increased both at the site of the burn and ian standard of care and are the criteria utilized throughout the systemic circulation, resulting in by the USA Burn Center for accepting patients. hypovolemia, shock, and the need for fluid In combat, triage may become necessary when resuscitation. With resuscitation, capillary per- treatment or evacuation assets are limited. meability is restored at 24 hours postinjury. In such situations, transfer priority is given to Cardiac output is depressed in the first hours victims with second- and third-degree burns of following thermal injury and then becomes elevated to levels of 2 to 2.5 times normal in the second 24 hours postinjury.10 This hyper- Table 21.1. American Burn Association criteria for metabolism persists until the burn wounds burn center referral. are healed or surgically closed. Patients with Second- and third-degree burns limited cardiac reserve may suffer myocardial Greater than 10% BSA infarction, usually at the peak of hypermeta- Full thickness (third-degree) burns of any size BSA Of the hands, face, feet, perineum, genitalia, or over a bolic response approximately 1 week post- 10 major joint burn. If sepsis occurs, the hypermetabolic Circumferential burns of the chest or extremities response may be further exaggerated. From In patients with preexisting medical conditions a hemodynamic standpoint, the ideal time to In patients with coexisting trauma transfer a patient is after a patient begins to By mechanism of injury Electrical or lightning injury respond to resuscitation but before sepsis Chemical burn injury occurs or hypermetabolism becomes severe. Smoke inhalation injury Smoke inhalation injury may be present when fires occur indoors or within a vehicle. *The burn surface area calculation considers only second- Approximately 400 toxic compounds can be and third-degree burns and does not include first-degree burns or sunburn. identified in smoke from an ordinary house 11 Source: Adapted with permission from Advanced Burn fire. Pulmonary insufficiency may result from Life Support course.8 a number of mechanisms including asphyxia, 276 D.J. Barillo and J.E. Craigie carbon monoxide poisoning, thermal burns to the optimum time to send the burn flight team the upper airway from breathing superheated for transfer. air, tracheal injury, or parenchyma injury. Because the heat-carrying capacity of air is Determining Who and What Should minimal, true thermal injury below the epiglot- Accompany the Patient tis is unusual; rather, such injuries represent tracheitis or pneumonitis from chemical irrita- Optimal transport of the burn patient considers tion. An exception is the inhalation of steam, that the patient is being moved from one which can produce a true thermal pulmonary intensive-care area (emergency department or injury. The presence of smoke inhalation ICU) to another intensive-care area (burn increases the mortality associated with a given center). Transport should not be attempted sized burn by up to 20%. If pneumonia devel- unless an ICU level of care can be maintained 11 ops as a complication of inhalation injury, in-flight. mortality is increased by up to 60%.12 For urgent evacuation, our preference is to Airway loss or pulmonary failure can rapidly send a burn flight team to stabilize and accom- occur in previously asymptotic patients with pany the patient. The Army Burn Flight Team, smoke inhalation injury. Initial physical exami- operational since the 1950s, consists of a general nation, chest radiograph, and arterial blood surgeon or burn center general medical officer, gas determination are usually normal. Carbon a burn ICU nurse, a licensed vocational nurse monoxide, present in all fires, binds to hem- (MOS 91C), and a respiratory therapist (MOS oglobin and produces carboxyhemoglobin, 91V). In a recent 16-year period, the burn which rapidly decreases oxygen carrying capa- flight team managed the care of 1196 patients city. Carboxyhemoglobin produces false eleva- over a distance of approximately 850,000 miles 11 tion of oxygen saturation values on both blood without in-flight fatality or major mishap. gas analysis and on pulse oximetry. Unless The flight team carries sufficient supplies the carboxyhemoglobin level is known, high to stabilize and transport burn patients independent of the referring facility (Table 21.2), PO2 or saturation values upon arterial blood gas analysis cannot be relied on to indicate including a transport ventilator designed for proper oxygenation. military use (TXP ventilator, Percussionaire 14 The diagnosis of smoke inhalation is best sug- Corp, Sandpoint, Idaho). The transport venti- gested by the combined history of loss of con- lator is oxygen powered, weighs 1.5lb (0.68kg), sciousness and exposure to fire in enclosed and can accommodate tidal volumes between spaces. Signs such as the presence of soot in the 5 and 1500cc and respiratory rates between 6 oropharynx,facial burns,or singed nasal hairs are and 250 breaths per minute (Fig 21.1). The ven- nonspecific. Diagnosis is confirmed by laryngo- tilator system operates for several hours on scopic evaluation of the upper airway, followed a composite Kevlar/aluminum oxygen cylinder by fiber optic bronchoscopy.As these maneuvers weighing 7.3kg, which is carried on the back of are impractical on the battlefield, elective endo- the respiratory therapist. tracheal intubation is indicated in situations where inhalation injury is likely. The mainstay of treatment is oxygen ministration and mechanical Care and Management Immediately ventilation. Neither steroid nor antibiotics are Prior to AE indicated in smoke inhalation injury.13 Preparation for AE Our criteria for safe transfer of patients with inhalation injury is the presence of a secure Where possible, the patient should be evaluated airway, a minute ventilation of 25L or less, at the referring medical facility rather than on and an adequate arterial blood gas measured the flight line or in the aircraft. We follow the at ground level on a FiO2 of 0.5 or less. When sequence advocated by the Advanced Trauma patients do not meet these criteria, fre- Life Support and Advanced Burn Life Support quent communication between the referring curricula,7,8 including primary and secondary physician and the burn center determines surveys. 21. Burn Patients 277

Table 21.2. Equipment carried by the USA Burn Flight Team.

Monitoring capability Medical capability ECG Resuscitation fluids Pulse oximetry ACLS drugs Core temperature Pain and anxiety control Automated blood pressure Stress ulcer prophylaxis Pressures: CVP, arterial line, Swan–Ganz catheter Burn care End-tidal carbon dioxide Nasogastric tubes Portable arterial blood gas analyzer Foley catheters Defibrillator Topical agents Surgical capability Burn dressings Tracheostomy Sheets, blankets, and Mylar rescue blankets Venous access—central or cutdown Communications Tube thoracostomy Cellular/digital telephones (within the CONUS) Transvenous pacing Satellite communications (extended missions outside Respiratory support the CONUS) Endotracheal intubation/tracheostomy supplies Secure, portable FM radios Transport ventilator/oxygen supply Battery-operated suction Battery-operated fiber optic bronchoscope Adapters/connectors

Figure 21.1. Portable pressure-controlled time-cycled high-frequency ventilation. The controller for the transport ventilators used for the long-range aero- TXP system (B; photo courtesy of Percussionaire medical transport of patients with burns. The Duotron Corp, Sandpoint, Idaho) provides pressure-cycled System (A; the black cylinder apparatus) utilizes ventilation alone.14 two controllers to provide pressure-cycled and 278 D.J. Barillo and J.E. Craigie

The primary survey is a 1-minute, head-to-toe auscultation. Circulation is assessed by capil- survey for life-threatening conditions, following lary refill and palpation of pulses in each the algorithm of ABCDEF (Airway, Breathing, extremity. Disability evaluation documents Circulation, Disability, Exposure, and Fluid level of consciousness and ability to move resuscitation).7,8 The airway should be secured extremities to command or noxious stimuli. by nasotracheal intubation if there is any ques- Any suspected spinal trauma is immobilized at tion of inadequate patency, smoke inhalation this point if not already done. The patient is injury, or if the massive resuscitation necessary then exposed and examined to determine extent for a large BSA burn would cause facial and of burn injury. Clothing is removed from any airway edema. Nasotracheal intubation is pre- area where burn injury is a possibility and any ferred over the orotracheal route, as a naso- rings, watches, or jewelry are removed to avoid tracheal tube can be easily secured by using constriction as edema forms during resuscita- multiple tracheostomy ties around the patient’s tion. Posterior skin surfaces are evaluated by head. Facial burns preclude the use of adhesive logrolling if other traumatic injury is suspected. tape to secure an orotracheal tube, which, in The burn surface area is then estimated using any case, is easier to dislodge in-flight than a “the rule of 9s” (Fig 21.2). In the adult, the nasotracheal tube. Anticipating the need for surface area of the head, each extremity, and fiber optic bronchoscopy, the nasotracheal tube the anterior and posterior trunk can be di- should be at least 7.0 to 7.5mm inner diameter. vided by nine, providing a convenient estimate. Breathing is next assessed by observation and Children have a similar system except that

Figure 21.2. The rule of 9s for determining the total surface area of a burn. 21. Burn Patients 279

Figure 21.3. Typical second- degree (partial thickness) burn.

the head is proportionally larger and each placed through burned skin if necessary. The IV lower extremity is 14% BSA. The palm of the catheters are easily dislodged and should be patient represents 1% BSA and can be used to sewn in place prior to flight. estimate irregular surfaces. Only second- and Rarely, peripheral access is unobtainable and third-degree burns are included in calculations. central venous access must be performed. We Second-degree burns (partial thickness injury) prefer to cannulate the femoral vein using are typically supple, red or pink in color, the Seldinger wire technique rather than the weeping, painful to the touch, and may have subclavian vessels, as a delayed pneumothorax blister formation (Fig 21.3). Third-degree burns following chest line placement would be diffi- (full-thickness injury) are cold, inelastic, leath- cult to later detect in-flight. ery,pale, brown or charred, and insensate, as the For the first 24 hours, estimated fluid needs cutaneous nerve endings have been damaged in milliliters are two times the percentage BSA (Fig 21.4). Once the burn size is known, intra- of second- and third-degree burn times the venous (IV) lines are placed and fluid resusci- patient’s weight in kilograms (2cc/kg per tation is started according to the Modified percent burn). Children (under 30kg body Brooke formula. At least two large-bore (16 weight) should receive lactated Ringer’s solu- gauge or bigger) peripheral IV cannula should tion at 3cc/kg per percent burn, in addition to be placed. The upper extremities are preferred maintenance fluids of 5% dextrose in half- over the lower extremities. IV lines may be normal saline.15 One half of the calculated fluids

Figure 21.4. Third-degree (full thickness) burn. 280 D.J. Barillo and J.E. Craigie should be infused in the first 8 hours postburn, blood flow is restored, delayed bleeding may with the remainder given over the next 16 occur, which may go undiagnosed if the extrem- hours. Infusion should be calculated from the ity is wrapped in bulky dressings. Hypotension time that the burn occurred: If treatment is during flight should prompt removal of dress- delayed, it is necessary to attempt to “make up” ings over escharotomy sites to rule out bleed- initial fluid requirements within the first 8 ing. To avoid this complication, we recommend hours. Resuscitation formulae provide only an serial examination of escharotomy sites for 30 estimate of fluid need, and IV fluid rates should to 60 minutes following performance of the be adjusted hourly to obtain 30 to 50cc of urine procedure or reexamination of the sites prior to per hour in the adult and 1cc/kg body weight in leaving the medical facility for the flight line. infants under 30kg body weight. When urine Adjuncts to resuscitation include placement output is inadequate or excessive, rate of fluid of a nasogastric tube, a Foley catheter, and administration should be changed in 20% to monitoring of pulse oximetry and electrocar- 30% increments. Inadequate urine output in diogram. Patients with burns over 20% BSA the first 24 hours is nearly always hypovolemia often develop gastric atony, making nasogastric rather than renal failure.9 In the second decompression essential. 24 hours postburn, capillary permeability is Following initial stabilization, a complete restored and resuscitation fluids are changed to history is taken and a secondary survey per- colloid and free water. Albumin, 5%, is given at formed to rule out associated injury. Tetanus a rate of 0.3mL/kg/% burn for burns between immunization should be given if the patient 30% and 50% BSA, at 0.4mL/kg/% burn for has not been immunized within the last 5 years. burns between 50% and 70% BSA, and at Hyperimmune globulin is also given if the 0.5mL/kg/% burn for burns >70% BSA. Free history of tetanus immunization cannot be water as D5W is given to maintain adequate obtained or if adult patients have had less than urine output.3 Beyond the second postburn day, three tetanus immunizations in their lifetime.7 albumin is discontinued and fluids adjusted to The burn wound should be washed with a gradually return the patient to preburn weight surgical disinfectant and loose necrotic mater- by postburn day 10. ial should be debrided. Blisters that would Circumferential burns of the chest or extre- burst in-transit should be unroofed and mities may restrict breathing or circulation as debrided. Whether or not to apply a topical resuscitation proceeds and the patient becomes antimicrobial cream will depend on the cir- edematous. The treatment is escharotomy or cumstances of transport. In civilian practice, use incision through the burn eschar. Escharotomy of topical antimicrobial agents are discouraged is a bedside procedure performed with a knife prior to burn center arrival, as these creams will or electrocautery. Incision is made only to the have to be removed by the burn team to assess level of the dermis–fat interface: Once the the wounds. Instead, covering the burn surface dermis is completely divided, there is no advan- with a clean (nonsterile), dry sheet is advo- tage to cutting deeper into fat. Escharotomy of cated. When the Army Burn Flight team trans- the chest is performed in the shape of a shield ports a patient, the wounds are placed in silver (Fig 21.5). Escharotomy of an extremity is per- sulfadiazine cream prior to transport with the formed along the midmedial or midlateral line rationale that the burn physician and nurse on (Fig 21.6). The incision should extend along the flight team have already performed wound the entire length of the full thickness burn. If assessment. In battle, wound care is deferred escharotomy on one side of an extremity does until the patient arrives at the level of a combat not restore circulation, then a second escharo- support hospital, at which time silver sulfa- tomy on the second side should be performed. diazine is applied after wound debridement.9 Because the tissue being divided is insensate In combat situations, penicillin may be given third-degree burn, general anesthesia is both for the first 5 days postinjury to prevent beta- unnecessary and undesirable. hemolytic streptococcal burn wound infection, Bleeding at escharotomy sites is controlled the onset of which may be missed during with electrocautery or absorbable suture. As evacuation.3 Systemic antibiotics are otherwise the compression is relieved and extremity not indicated in the acute phase of burn care. 21. Burn Patients 281

common reasons for return to the medical facility preﬂight are hemodynamic instability, loss of the airway, loss of peripheral pulses, or continued bleeding from escharotomy sites.

Urgent AE Minimal Conditions That Must Be Met Contraindications to aeromedical transfer of burn patients are listed in Table 21.4. In the absence of these conditions, a burn patient is ready for urgent AE when the airway is patent, successful resuscitation is underway or completed, appropriate lines are in place (see checklist), adequate arterial blood gases have been obtained on the transport ventilator, the chest radiograph has been reviewed, and wounds are dressed.

Specific Concerns, Supplies, and Needs of Patients The noise and vibration present during flight make auscultation difficult and changes in airway or breathing status are easily missed. Assurance of adequate airway and breathing preflight is important. In-flight, adequacy of airway and breathing are assessed with continuous pulse oximetry and, if available, end-tidal Figure 21.5. Incision lines for escharotomies. capnography. In rotary-wing aircraft, vibration-induced motion artifact often precludes use of a contin- In all circumstances, the patient must be uous electrocardiogram (ECG) monitor. When protected from heat loss and tight dressings this happens, heart rate can be monitored by must be avoided. The burn wound should be using the pulse oximetry waveform displayed inspected at least daily during the transport on a multifunction monitor such as the ProPaq process. Encore system. The transport team should obtain records of Patients with large BSA burns are unable to treatment performed, IV fluids given, urine regulate body temperature and can rapidly output, and results of any laboratory studies to become hypothermic at normal ambient tem- carry with the patient. The chest radiograph peratures. The cold associated with increasing should be reviewed and a copy obtained. altitude accentuates this problem. Preflight, we normally wrap the patient in a clean sheet, Indications for Return to Medical Facilities covered with a wool blanket, followed by a Mylar rescue blanket. Core temperature should Prior to Evacuation be frequently assessed with rectal probe or ear Immediately prior to the flight, a preflight tympanic membrane thermometer. In fixed- checklist should be used to verify that the wing aircraft, the cabin temperature should be patient is ready for AE (Table 21.3). The most raised. 282 D.J. Barillo and J.E. Craigie

Figure 21.6. Escharotomy of an extremity performed along the midmedial or midlateral line of the full thickness burn.

Burn patients require repeated administra- to facilitate mechanical ventilation. All pain tion of IV narcotics and anxiolytics at doses and antianxiety medications should be given in much higher than used for other patients. small, frequent, IV doses. Flight planning must Chemical paralysis may also become necessary consider this increased need for analgesic and anxiolytic drugs.

Table 21.3. Preﬂight checklist: Items that should be reassessed before leaving the medical treatment In-ﬂight Emergencies facility. Restlessness or anxiety are signs of hypovo- Airway lemia or hypoxia. When present, the adequacy Airway is patient of oxygenation, ventilation, and resuscitation Endotracheal or tracheostomy tubes are secured Breathing Presence of bilateral breath sounds Chest radiograph has been examined Table 21.4. Contraindications to the aeromedical Adequate arterial blood gas after 20–30min on the transfer of burn patients. transport ventilator Pulse oximeter is functioning Marginal respiratory reserve

Circulation Inadequate arterial blood gas at ground level on FiO2 IV lines are functioning and sewn in place of 0.5 Peripheral pulses are present Minute ventilation >25L Foley catheter functional/urine output is adequate Uncontrolled bleeding, GI or otherwise ECG is functioning Body temperature >39.5°C not controllable with Escharotomy sites are not bleeding antipyretics Other Uncontrolled cardiac dysrhythmia Nasogastric tube functional Intraocular or intracranial air or recent intraocular or Wound dressings are not constrictive intracranial surgical procedure Transport team has copy of hospital chart, results of Relative contraindication any tests performed, and intake and output records Intra-abdominal or intrathoracic surgical procedure Patient protected against heat loss within 24–48h of flight 21. Burn Patients 283 should be reassessed. Hemodynamic instability BSA. Patients with burns outside of this range may result if escharotomy sites start to bleed. would then be selectively transported as space With bulky dressings, this blood loss may not be becomes available. readily apparent and removal of dressings and direct inspection of the wound is necessary. Electrocauterization and blood transfusion are Electrical Injury impractical in-flight. When bleeding sites are identified, the best treatment is to oversew Electrical injury, including lightning contact, the bleeding vessels with absorbable suture meets American Burn Association criteria for (3-0 chromic or Vicryl). treatment in a burn center. While overall man- Physiological consequences of change in agement is similar to thermal injury, pathology barometric pressure during ascent or descent and complications specific to electrical injury are familiar to the aeromedical team. Burn- must be identified and addressed prior to specific problems include the need to monitor evacuation. endotracheal tube cuff pressure (or the use of Electrical injury may be caused by contact saline to inflate the cuff), the need to monitor with alternating or direct current. Alternating inflation of air splints if used to stabilize concurrent produces more severe injury and is current trauma, and the need to ensure that more likely to cause muscle tetany or cardiac burn dressings do not become constrictive. arrhythmias. Tetany may prevent the victim Change or loss of peripheral pulses should first from releasing hold of a current source. On be treated by elevation of the extremity and occasion, tetany of paraspinal muscles produces loosening of the dressings. Any possible need compression fractures of the thoracic or lumbar for escharotomy or fasciotomy should be antici- vertebrae. pated preflight, as in-flight surgical procedures Cardiac arrhythmias are seen in up to 37% are difficult. of patients with electrical injury.16 Cardiac arrest may be present at the time that the victim is removed from the current source. Other Elective AE arrhythmias include ventricular fibrillation, ventricular tachycardia, sinus tachycardia, or A number of patients will meet American Burn nonspecific ST-T changes. Arrhythmias, when Association criteria for burn center care, but do present, usually occur prehospital or in the not require urgent evacuation. This group emergency department and rarely present after would include patients with small BSA burns the first postburn day. Selective ECG monitor- being transferred for functional or cosmetic ing of electrical injury patients for 24 to 48 considerations (burns of the hands, feet, and hours is advocated when current may have face), small full thickness burns, or small chem- passed across the chest and in patients with ical burns. A second group considered for elec- cardiac symptoms or a history of cardiac risk tive AE are patients nearing the conclusion of factors.16 It would be prudent to monitor the acute care that are being transferred for reha- ECG of electrical patients while in-flight, in bilitation. The need for urgent rather than elec- particular within the first 24 to 48 hours of tive AE cannot be determined on burn size injury. alone and should consider the patency of the As current passes through the extremities, airway, the need for mechanical ventilation in- blood vessels and nerves may be injured. flight, and the presence of preexisting medical Muscle and bone resist current flow and, like conditions or associated traumatic injury. Con- resistance wires in a toaster, become heated. sultation with the receiving burn facility is This heat continues to radiate internally after useful when the need for urgent versus elective the current is stopped, resulting in muscle transport is unclear. necrosis, edema, and compartment syndromes. During armed conflict, triage decisions in Skin may be spared from thermal injury general afford the highest transport priority to because the external location allows heat dis- patients with burns between 20% and 70% sipation. It cannot be overemphasized that 284 D.J. Barillo and J.E. Craigie necrotic muscle may be present underneath sis of the skin and are less severe than alkali intact skin and that the absence of burned skin burn, which produce liquefaction necrosis with does not rule out deep injury from electricity. disruption of tissue planes. Organic compounds Lysis of myocytes or erythrocytes may re- such as gasoline produce burn injury by skin lease myoglobin, hemoglobin, or potassium. contact and, in addition, may be absorbed, Life-threatening hyperkalemia may result, re- causing systemic toxicity. Renal or hepatic quiring treatment with bicarbonate, insulin, and insufficiency or failure may result. The fumes of glucose infusion or binding resins. Radical organic compounds may cause unconsciousness excision of dead tissue is on occasion required or pulmonary injury. to control hyperkalemia. Free myoglobin or Chemical burns meet American Burn Asso- hemoglobin are excreted in the urine as dark ciation criteria for treatment in a burn center. pigment and can precipitate in renal tubules, Compared to thermal injury, chemical burns causing renal failure when the urine is acidic. are usually of a smaller surface area but more When dark pigment is present in urine, resusci- likely to be full thickness or third-degree injury. tation fluids should be increased to provide Full thickness chemical burns may initially urine outputs in the 75 to 100mL/hour range mimic second-degree or partial thickness burns, and 50mEq of sodium bicarbonate should be presenting as erythematous areas of blister added to each liter of resuscitation fluid. As formation. The true depth becomes apparent urine color returns to normal, fluids should be in the next few days as the burn becomes readjusted to provide 30 to 50cc/hour of urine blanched and leathery. output. If urine pigments fail to clear, mannitol The treatment of all types of chemical injury can be given with the understanding that this is to flush the burned area with water until the osmotic diuretic will render urine output inac- pain significantly decreases or stops. Chemicals curate as a resuscitation indicator. that are dry powders should be brushed off Frequent neurovascular assessment of extre- of the wound prior to irrigation. Acid burns mities is indicated in electrical injury. Change typically require 30 minutes to 1 hour of irriga- in pulse or neurovascular status indicates the tion. Alkali burns may require several hours need for escharotomy of circumferential ex- of irrigation. Irrigation has the added advantage tremity burns. If the skin is not burned, or if of providing some decontamination of hazar- escharotomy does not restore pulses, formal dous chemical exposure by dilution. Many surgical exploration and fasciotomy or even am- hazardous chemicals, including chemical war- putation is required. Patients should not be fare agents, require specific decontamination accepted for flight until neurovascular status methods that are beyond the scope of this has been determined and surgery performed or chapter. the need for surgery ruled out. Change of neu- For evacuation purposes, chemical burns are rovascular status or loss of pulse is an indication treated identically to thermal injuries with to return to the medical facility prior to flight. several exceptions. The smaller size of the Associated trauma should be ruled out prior injury usually places these patients into a rou- to transportation. A history of electrical contact tine rather than an urgent transport status and on a power pole should prompt consideration simplifies in-flight management, as patients are of a fall with possible cervical spine or internal usually ambulatory. The transport team must organ injury. We routinely obtain radiographs verify that wound irrigation and decontamina- of the thoracic and LS spine in cases where tion has been performed prior to arrival of compression fractures are a possibility. the team. Transportation of a patient prior to decontamination will place the flight crew at risk and will remove the aircraft from service Chemical Burn Injury until aircraft decontamination has been performed. In civilian practice, we likewise ad- Chemical burn injury can be caused by skin vise against the use of rotary-wing aircraft to contact with acids, alkalis, or organic com- transport patients from the scene of hazardous pounds. Acid burns produce coagulation necro- materials incidents. The prop wash generated at 21. Burn Patients 285 take-off and landing will spread chemical con- percent BSA second- and third-degree burn tamination, and any accidental contamination during the first 24 hours. In practice, such of the aircraft by an incompletely decontami- formulae are only guidelines and fluid adminis- nated patient will place an expensive asset out tration is adjusted hourly based upon urine of service.11 output. Certain situations, such as inhalation injury, delayed resuscitation, associated traumatic injuries, or very large burn size increase Contingency AE the need for resuscitative fluids. Twenty-four hour IV fluid requirements of 6 to 8cc/kg per The complex pathophysiology of acute burn percent burn are not uncommon. To provide injury superimposed upon the physiological a margin of safety, sufficient Ringer’s lactate stresses associated with flight make the aero- to provide flow rates of at least 10cc/kg per medical transport of burn patients difficult. percent BSA burn for the duration of the Specialized burn transport teams have been flight should be available for each burn patient available in peacetime and in war since the transported. Vietnam War era and are likely to play a Burn patients normally require narcotic significant role in the next armed conflict. In medications for pain control and usually benefit nearly all situations, the long-range transport of from simultaneous administration of benzo- burn patients should be performed by burn or diazepines. Neuromuscular blockade may be critical-care specialty teams. required to facilitate mechanical ventilation. To In some wartime situations, transport of avoid hypotension, these medications should burn patients without a specialized team may be started in small doses and given intra- become necessary. While it is not possible to venously at frequent intervals. If hypotension cover all contingencies in a textbook chapter, occurs with administration of 2 to 5mg of general planning guidelines should include con- morphine, the adequacy of resuscitation should sideration of triage and the increased needs for be reassessed. IV fluids and other medications unique to the After the initial administration of small doses burn patient. of narcotics, benzodiazepines, and paralytics, it As previously mentioned, wartime triage usually becomes apparent that the need for all may require restriction of transportation to three classes of medication in burn patients far patients with burns between 20% and 70% exceeds dosages normally encountered in total BSA. In theory, patients with burns in the critical-care practice. The authors have treated 10% to 20% BSA range can be resuscitated burn patients who have required the simulta- with oral fluids and transported as “walking neous administration of 15 to 20mg of mor- wounded.” In practice, the gastric atony associ- phine, 15 to 20mg of benzodiazepine, and 10 ated with burn injury, coupled with distension to 15mg of vecuronium per hour for several and contraction of hollow organs secondary to days at a time. When expedient transfer of burn changes in barometric pressure, may make oral patients is attempted, the need for very large resuscitation impractical. For this patient pop- doses of narcotics, benzodiazepines, and neuro- ulation, IV fluids must be available in-flight if muscular blocking agents must be anticipated. vomiting precludes oral resuscitation. Alterna- A final point to consider is that the present tively, evacuation can be delayed 24 to 48 hours standard of care permits the morbidity and until oral resuscitation is completed. mortality-free transport of seriously burned For planning purposes, the availability of patients over long distances when a properly sufficient quantities of IV fluid, narcotics, seda- trained and equipped team is available. The tives, and paralytics must be anticipated. In expedient transfer of burn patients without the contemporary civilian practice, burn patients benefit of specialized assets will be expected to are resuscitated on the Modified Brooke increase in-flight mortality and morbidity. In formula (2cc) or on the Parkland formula wartime, the possibility of death in-flight must (4cc), and should require between 2 to 4cc of be balanced against other possibilities, includ- Ringer’s lactate per kilogram body weight per ing death on-scene for lack of medical assets or 286 D.J. Barillo and J.E. Craigie tactical considerations such as the possibility 5. Eldad I, Torem M. Burns in the Lebanon War that a forward medical facility will be captured 1982: “The blow and the cure.” Milit Med or overrun by aggressor forces. 1990;155:130–132. 6. Graves TA, Cioffi WG, Mason AD, Jr, McManus WF, Pruitt BA, Jr. Relationship of transfusion and infection in a burn population. J Trauma Conclusion 1989;29:948–954. 7. Committee on Trauma, American College of Thermal injury will be a likely consequence of Surgeons. Advanced Trauma Life Support Pro- the next armed conflict. Surgical management gram for Doctors. Chicago: American College of thermal injury is resource intensive and of Surgeons; 1993. impractical in the far-forward arena; rather, 8. Nebraska Burn Institute. Advanced Burn Life burn casualties will require evacuation out of Support. Lincoln, Neb: Nebraska Burn Institute; theater for definitive care. The experience of 1992. the USA Burn Flight Team over the past 40 9. Cioffi WG, Rue LW, Buescher TM, Pruitt BA, Jr. years demonstrates that long-range aeromedi- The management of burn injuries. In: Zajtchuk cal transport of the massively injured can be R, ed. Textbook of Military Medicine Part 1. vol 5. Washington, DC: US Government Printing safely performed when the patient is properly Office; 1990. stabilized and the transport team is both expe- 10. Barillo DJ, McManus AT. Infection in burn pa- rienced and well equipped. tients. In: Armstrong D, Cohen J, eds. Infectious Diseases. London: Mosby International; 1999. References 11. Jordan B, Barillo DJ. Prehospital care and transport. In: Carrougher GJ, ed. Burn Care and 1. Pruitt BA, Jr, Mason AD, Jr. Epidemiological, Therapy. St Louis, Mo: Mosby; 1998. demographic and outcome characteristics of 12. Shirani KZ, Pruitt BA, Jr, Mason AD, Jr. The burn injury. In: Herndon, DN, ed. Total Burn influence of inhalation injury and pneumonia on Care. Philadelphia: W.B. Saunders; 1996. burn mortality. Ann Surg 1987;205:82–87. 2. Pruitt BA, Jr, Goodwin CW, Mason AD, Jr. 13. Pruitt BA, Jr, Goodwin CW, Cioffi WG, Jr. Epidemiology of burn injury and demography Thermal injuries. In: David JH, Sheldon GF, eds. of burn care facilities. Prob Gen Surg 1990; Surgery, A Problem-Solving Approach. 2nd ed. 7:235–251. St Louis, Mo: Mosby-Yearbook; 1995. 3. Bowen TE, Bellamy RF. Emergency War 14. Barillo DJ, Dickerson EE, Cioffi WG, Mozingo Surgery, Second United States Revision of DM, Pruitt BA, Jr. Pressure-controlled ventila- the Emergency War Surgery NATO Handbook. tion for the long-range aeromedical transport of Washington, DC: US Government Printing burn patients. J Burn Care Rehabil 1997;18: Office; 1988:v. 200–205. 4. Cioffi WG, Rue LW, Buescher TM, Pruitt BA, Jr. 15. Graves TA, Cioffi WG, McManus WF,et al. Fluid A brief history and the pathophysiology of resuscitation of infants and children with mas- burns. In: Zajtchuk R, ed. Textbook of Military sive thermal injury. J Trauma 1988;28:1656–1659. Medicine Part 1. vol 5. Washington, DC: US 16. Winfree J, Barillo DJ. Nonthermal injuries. Nurs Government Printing Office; 1990. Clin North Am 1997;32:275–296. 22 Aeromedical Evacuation of Obstetric and Gynecological Patients

William W. Hurd, Jeffrey M. Rothenberg, and Robert E. Rogers

It is noteworthy that obstetric and gynecologi- Although active-duty dependents are no longer cal diagnoses are the most common reasons for a major consideration, many of the medical hospital admissions in the United States.1 This problems experienced by women living under is related in part to the fact that childbirth field conditions are gynecological in nature. A occurs almost exclusively in a hospital setting. recent example is the Persian Gulf War.2 Prior In addition, problems related to the female to and during the offensive actions in Kuwait reproductive tract are relatively common in and Iraq, more than 600,000 US military per- women of all ages, but especially in women of sonnel were billeted under field conditions, reproductive age. Together, childbirth and many for more than 6 months. Women made up hysterectomy account for more than 30% of 7% of the active-duty personnel in the theater. all surgical procedures performed annually However, more than 17% of the sick call in the United States.1 The implications for long- visits were by women, and more than 25% of distance civilian aeromedical evacuation (AE) these visits were for gynecological problems.4 are obvious. Although most problems were treated locally, Obstetrics and gynecology has taken on many gynecological patients eventually required increased importance in military medicine as AE for medical or administrative reasons. well. The active-duty military population is now One unanticipated result of billeting a large made up of more than 15% women, who are number of men and women together under almost exclusively of reproductive age.2 In ad- field conditions for an extended period was dition, the majority of active-duty and retired inadvertent pregnancy. Because pregnancy is men have wives who often utilize the military an administrative indication for reassignment medical care system. This is especially true outside of the theater of operations, pregnancy overseas, where civilian medical care might not became the single most common reason for AE be available or adequate. With more than 200,000 of women during Operations Desert Shield and active-duty troops and 400,000 dependents Desert Storm.5 stationed overseas, large portions of the per- This chapter will explore both the obstetric sonnel who utilize overseas the military medi- and gynecological implications for AE. Un- cal system are female.3 The AE implications complicated and complicated pregnancies will related to the significant number of obstetric be examined at all stages, including the first, and gynecological patients treated in military second, and third trimesters and the postpar- medical facilities should not be underesti- tum period. Information on emergency delivery mated, and contingency plans should be imme- is also included. Chronic and acute gynecolog- diately available. ical conditions and considerations for AE of Even during armed conflict, gynecological the postoperative gynecological patient will be considerations remain surprisingly important. discussed.

287 288 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

Ob/Gyn Emergency Equipment Obstetric menstrual pads are included for both for gynecological vaginal bleeding and normal An important consideration for AE of the ob- postpartum bleeding. In addition, specific med- stetric and gynecological patient is the avail- ication might be required when transport- ability of equipment specific to these problems. ing high-risk pregnant patients (see specific Because many specialized instruments are not diagnoses below). routinely available without preplanning, an ob/gyn emergency kit should be made available. This is composed of instruments that are Obstetric Patients commonly used for both obstetric and gynecological problems. In addition, the kit should Uncomplicated Pregnancy include instruments specific to emergency va- Flight imposes little risk to the healthy preg- ginal delivery (Table 22.1). nant woman or her fetus. Pregnant women have The kit should include instruments for eval- flown millions of hours in commercial aircraft uation and prepared for vaginal lacerations or at all stages of gestation without a documented vaginal bleeding including speculums, suturing increased in the risk of any pathologic or phys- instruments and materials, and scissors. Instru- iological events associated with pregnancy. This ments and equipment specific for delivery of is not to say that say that there are no medical infants include cord clamps, suction bulbs, and implications related to flying during pregnancy. towels. A relatively important piece of equip- Sudden, potentially catastrophic events might ment for an emergency vaginal delivery in a occur at any time in pregnancy and are more confined area is a bedpan. This is used to common near term. The space constraints and elevate the buttocks during emergency deliv- the relative isolation from immediate medical ery, as described below. Various types of gauze care that often occurs during flight must be and padding are also essential. This includes taken into account both by potential pregnant gauze for packing a vaginal laceration or the passengers and the flight crew. vagina in the event of uterine hemorrhage. Effects of Altitude During routine commercial flights, the maxi- Table 22.1. Emergency ob/gyn kit. mum cabin pressure is equal to an altitude of Sterile preassembled ob/gyn kit approximately 8000ft. This results in a 25% Instruments decrease in PO2 in a healthy pregnant adult Vaginal speculum (Graves & Pederson) breathing ambient air from 80mmHg to Needle holder 60mmHg.6 Fortunately, this drop has no appre- Suture scissors Thumb forceps ciable effect on a healthy pregnant woman or Large (Russian) her fetus. However, in pathologic conditions Small (Allis) where the fetus might suffer from decreased Ring forceps (2) oxygenation supplemental oxygen should be Single-tooth tenaculum given as a matter of course. Vascular clamps Large (Kelly) hemostat (2) Small (Crile) hemostat (2) Immobilization Bandage scissors Cord clamp Prolonged immobilization is probably the most Suction bulb significant medical consideration for the pre- Towels Gauze, 4 ¥ 4≤ (40) gnant patient during a long flight. Pregnant Gauze 2≤ tape, 10ft (for packing) women have increased coagulability for hor- Sterile gloves monal reasons, leading to an increase risk Thermal absorbent blanket and head cover (for newborn of venous thrombosis.7 In late pregnancy, infant) increased intra-abdominal pressure from the Bedpan (to elevate buttocks) pregnancy decreases venous return from the 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 289 lower extremities, thus increasing the risk of 35th week for overseas flights) to minimize the venous thrombosis further. The risk of lower- risk of such an event occurring during flight.10 extremity venous stasis might be increased USAF regulations recommend against routine even further in a sitting position with the knees air transfer of patients beyond the 34th week of flexed. For these reasons, it is recommended pregnancy (including AE) for the same reason.9 that women flying late in pregnancy in a seated Fortunately, there are usually a matter of position should ambulate at frequent intervals hours between the onset of labor and delivery throughout the flight.8 A semirecumbent of the infant in most women. At term, labor position afforded by reclining the seat back lasts an average of 8 to 12 hours.7 However, might also help with venous return. High-risk some women deliver less then 2 hours after the pregnant women should be transported in onset of painful contractions. For this reason, a lateral recumbent position by litter, pre- the onset of obvious labor during a commercial ferably keeping the patient on the left side. flight is best treated by diversion to the nearest large airport and evaluation of the laboring Effects of G-Forces patient in a hospital setting. If AE is required during the last month of an uncomplicated Pregnant patients might be more susceptible to pregnancy, the availability of obstetric emer- the effects of increased G-force. During take- gency supplies and an attendant who is trained off and landing, both commercial and military in emergency vaginal delivery is a wise passengers experience a slight increase in G- precaution. forces. For most people, this G-force effect is A related concern is that the risk of sponta- virtually undetectable. However, there is an neous ruptured membranes might be increased increased susceptibility to orthostatic hypoten- by the changes in pressure associated with sion during the second half of pregnancy as a flight. It has long been suspected that subtle result of increased venous pooling in the lower changes in atmospheric pressure might in- extremities. This might also explain an appar- crease the risk of spontaneous rupture of ent increased sensitivity to G-forces in late membranes.11 Anecdotal evidence suggests pregnancy. In one study, two of three patients that the rapid increase in pressure associated transported by military AE after 34 weeks with landing of commercially pressurized air- experienced “dizziness and shadowing of craft might increase the risk of membrane vision” during descent that responded to sup- rupture near term.9 plemental oxygen.9 Although the exact mechanism of these symptoms remains uncertain, orthostatic hypotension related to a combina- Problems During the First Half tion of venous pooling and increased G-forces of Pregnancy is a likely explanation. First-Trimester Bleeding: Miscarriages Onset of Labor During Flight The first trimester is defined as the first 13 A potentially more pressing concern in late weeks of pregnancy after the last menstrual pregnancy is the onset of labor or any one of period. During this time, bleeding is extremely the normal or pathologic processes associated common. It has been estimated that more than with labor during a prolonged flight. Each year, one third of pregnant women experience some the sudden onset of labor, rupture of the am- bleeding in early pregnancy. At least 20% of niotic membranes, or bleeding in pregnancy all clinical pregnancies will end in spontane- during flight requires emergency diversion of ous abortion, commonly referred to as a commercial airlines. Because of the significant “miscarriage.” implications of this, the International Air Trans- In any case of bleeding in the first trimester, portation Association has recommend that consideration should always be given to the pregnant women should not fly on commercial possibility that the patient actually has an aircraft after the 36th week of pregnancy (the ectopic pregnancy, discussed in more detail 290 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

Table 22.2. Contraindications for AE of obstetric sequelae of illegal abortions. The implications and gynecological patients. of a septic abortion for AE are similar to a Obstetric patients uterine infection related to other causes, and First trimester are discussed below. Another uncommon con- Uterine bleeding (especially with cramping) dition is a “missed” abortion, defined as a preg- Suspected ruptured ectopic pregnancy nancy in which the fetus is no longer viable but Second and third trimesters no bleeding or cramping has occurred. This Active labor Uterine bleeding condition can be treated the same as a threat- Cervix >4cm dilated ened abortion for the purposes of AE. Incompetent cervix, untreated Severe preeclampsia Implications for AE Postpartum Heavy vaginal bleeding Active bleeding in the first trimester of preg- Gynecological patients nancy is a contraindication to elective AE PID with peritonitis (Table 22.2). Emergency transportation to the Ruptured tubo-ovarian abscess Heavy vaginal bleeding nearest appropriate medical facility (ie, medical evacuation [MEDEVAC]) should be considered only if the facilities for definitive treatment are not available locally. Patients with below. The importance of making this diagno- minimal spotting might be moved short dis- sis lies in the fact that minimal external vaginal tances relatively safely if there is no significant bleeding can be associated with life-threatening cramping and the cervix is closed (eg, an early intra-abdominal hemorrhage from an ectopic threatened abortion) (Table 22.3). Fortunately, pregnancy. For this reason, ultrasound should few patients will experience heavy bleeding be used to verify that the pregnancy is in- within the first week after the onset of trauterine in any patient with first-trimester spotting.12 bleeding.12 During contingency operations (eg, natural Once an ectopic pregnancy has been ruled disaster or armed conflict), it might be neces- out, the spontaneous abortion can be further sary to move pregnant patients who are expe- classified according to stage of progression. A riencing more than minimal spotting by AE. “threatened” abortion describes a pregnancy in Before AE is considered, several conditions which any spotting or bleeding is occurring. should be met to minimize the chance that Fortunately, the first sign of a spontaneous a threatened abortion will progress to heavy abortion, relatively light bleeding, almost al- bleeding. The most valuable tool is ultrasound. ways occurs days to weeks before progression In a patient with bleeding, the presence of to the heavy bleeding and cramping.12 The most cardiac activity indicates that the chance of critical stages of a spontaneous abortion are accompanied by heavy bleeding and are termed “inevitable” abortion if the cervix is open but no tissue has been passed or “incomplete abor- Table 22.3. Criteria for AE: First-trimester tion” if some, but not all, tissue has been passed bleeding. vaginally. In some cases, the bleeding can be Elective AE heavy enough to constitute a medical emer- No bleeding for 48h with ultrasound evidence of a gency. The final stage of most spontaneous viable fetus abortions, termed “complete” abortion, is when After fetal nonviability is verified by ultrasound, all tissue has been passed and is usually associ- perform D&C prior to transport Convalescent period: 24h after D&C ated with minimal residual bleeding. This Urgent AE diagnosis is usually verified by ultrasound. Bleeding 48 hours, AE is relatively safe. In together), a vaginal speculum and concentrated contrast, the absence of cardiac activity with an light source are used to inspect the cervix. If intrauterine sac >10mm in diameter 7 or more tissue is seen protruding through the cervical weeks from the last menstrual period is associ- os, the tissue should be removed by gentle ated with an increased risk of miscarriage and traction with ring forceps. This might result heavy bleeding.12 in completion of the spontaneous abortion Regardless of the ultrasound findings, the process and decrease bleeding. However, if most important clinical consideration is the significant bleeding continues emergency treat- amount of bleeding and uterine cramping. If ment consists of tightly packing the vagina with the bleeding is less than a menstrual period and gauze and diversion of the flight to an airfield there is minimal or no uterine cramping, then near a medical facility. urgent AE is reasonable in a contingency situ- Another, less common, complication of spon- ation. However, if the patient is bleeding more taneous abortion is intrauterine infection, than a normal menstrual period or having sig- termed septic abortion. If a patient with a diag- nificant cramping she should not undergo AE nosis of spontaneous abortion develops a fever, (Table 22.3). In these emergency situations, with or without chills, emergency therapy MEDEVAC to the nearest medical facility for consists of IV hydration and broad-spectrum cervical dilation and curettage (D&C) might be antibiotics. In most cases, definitive surgical lifesaving. treatment (D&C) can be delayed for several hours with little risk to the patient. Preparation for AE If AE is required for a patient with a threatened Ectopic Pregnancy abortion, certain steps should be taken to min- An ectopic pregnancy, usually located in the imize the risk to the patient during flight. First, fallopian tube rather than the uterus, occurs in it should be verified that the patient’s hemo- approximately 1% to 2% of all pregnancies. In globin is >12g/dL so that she will have an ade- patients at increased risk of tubal pregnancies quate reserve should heavy bleeding occur. If because of previous pelvic infection or tubal the patient is found to be anemic, transfusion surgery, the ectopic rate can be as high as 15% prior to transportation might be needed to to 25% of pregnancies. increase the margin for safety. A patient with an ectopic pregnancy most In any pregnant patient who is bleeding, an commonly presents with vaginal bleeding and intravenous (IV) catheter should be placed unilateral pain 6 to 8 weeks after her last men- prior to flight because placing it during flight strual period. However, this presentation is might be difficult. The amount of bleeding will neither specific nor sensitive for ectopic preg- determine whether the patient will require nancy. A threatened spontaneous abortion ongoing IV hydration or only a heparin lock. can often present with these symptoms. Alter- However, in all cases, the ability to quickly start natively, some patients present with atypical IV fluids is imperative. In addition, the patient symptoms that can range from painless bleed- needs an adequate supply of obstetric pads to ing to severe abdominal pain with hemorrhagic last throughout the flight or longer, should a shock. delay occur. With modern ultrasound and serum beta- human chorionic gonadotropin (hCG) deter- Potential In-Flight Emergencies mination, the diagnosis of ectopic pregnancy is The vaginal bleeding that can be associated often made well before tubal rupture and with a spontaneous abortion can be massive, intrauterine hemorrhage. The result is that resulting in hypovolemic shock. The first step of many ectopic pregnancies might be diagnosed in-flight treatment of heavy bleeding is a pelvic days or weeks prior to the need for definitive 292 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers surgery. In some patients, the tubal pregnancy Because sudden rupture is always a possibil- resolves spontaneously or can be treated med- ity, IV access should be established prior to ically and surgery avoided. flight. This can be either a functioning IV line or a heparin lock. Transportation as a litter Implications for AE patient is imperative. A diagnosis of ectopic pregnancy is a contraindication for elective AE. Although the In-Flight Emergencies chance of sudden tubal rupture and intra- Sudden rupture of an ectopic pregnancy is abdominal hemorrhage is small, the inability to uncommon prior to 6 weeks’ gestation as deter- treat this emergency by means other than mined by the last menstrual period. However, immediate surgery makes AE relatively risky. the patient might have already been pregnant Once the ectopic pregnancy has been surgically at the time of the apparent “last menses,” removed, AE is delayed until the patient has making the gestational age 2 to 4 weeks greater recovered from surgery, as discussed below for than calculated using this “menses.” For this the postoperative gynecology patient. reason, the onset of severe unilateral pain in a A nonsurgical approach for the treatment of patient with a tentative diagnosis of ectopic ectopic pregnancies has become more popular pregnancy constitutes a medical emergency, in the last few years. This involves the use of with or without signs of peritoneal irritation methotrexate, a chemotherapeutic agent that and hemodynamic instability. destroys placental tissue and results in resorp- Emergency in-flight treatments include IV 13 tion of the ectopic pregnancy. Although this hydration and Trendelenburg position. Trans- approach is safe in selected patients, there is fusion with type-specific packed red cells or an approximately 5% risk of tubal rupture whole blood is indicated for signs of hypo- requiring emergency surgery. For this reason, volemic shock. Because the only definitive patients being treated nonsurgically for ectopic treatment for a ruptured ectopic pregnancy is pregnancy should not be transported by elec- surgical, any sudden changes in the patient’s tive AE until their serum beta-hCG levels are condition is an indication for emergency flight undetectable. diversion to an airfield with a nearby medical In contingency operations, or when definitive facility. treatment is not available locally, it might be Lesser degrees of unilateral pelvic pain are necessary to transport patients with an ectopic common with an ectopic pregnancy. However, it pregnancy. If required, patients with a diagno- is difficult to differentiate pain related to tubal sis of an unruptured ectopic pregnancy should distension from catastrophic tubal rupture. For be transported at the earliest opportunity. this reason, any change in the nature or degree of pelvic pain in a patient with an ectopic pre- Preparation for AE gnancy should be treated as a likely “ruptured When AE is required, certain criteria should be ectopic” and considered life-threatening. met prior to transportation. First, the patient Vaginal bleeding is a common occurrence in should be hemodynamically stable. Second, patients with ectopic pregnancies. For this there should be no evidence of intra-abdominal reason, several days’ supply of menstrual pads bleeding such as peritoneal signs or free should be sent with the patient. Heavy vaginal intraperitoneal fluid on ultrasound. Finally, the bleeding with a diagnosis of ectopic pregnancy patient should have a sufficient hematologic suggests that the patient might actually be reserve (Hgb >12g/dL) in case of rupture having a spontaneous abortion (see above). during transport. An important point to remember is that a vigorous pelvic exam should Hyperemesis of Pregnancy be avoided in patients suspected of having an ectopic pregnancy to avoid iatrogenic tubal Another common problem encountered in the rupture. first trimester is hyperemesis. This excessive 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 293 nausea and vomiting can lead to dehydration earliest sign of this is usually a cessation of fetal and electrolyte imbalances. Treatment consists movement noticed by the patient. The diagnosis of supportive measures including IV hydration can be suspected by absence of fetal heart tones with electrolyte replacement and antiemetic by auscultation but is verified by ultrasound. therapy. No other special considerations are After fetal demise, the patient will usually re- needed for AE. main asymptomatic for days to weeks. Some patients will experience bleeding, resulting in a second-trimester spontaneous abortion. Later Problems During the Second in pregnancy, premature labor might occur. In Half of Pregnancy extreme cases, the patient can experience a disseminated intravascular coagulation. However, With the exception of spontaneous abortion, this complication is rare in a patient in whom the the incidence and implications of problems fetus has been dead for less than 4 weeks.7 continues to increase until term. Because of this, any pregnant patient considering long- distance flight, including AE, should first have Premature Labor a thorough obstetric evaluation (Table 22.4). The single most common complication of the This should include verification of fetal viabil- third trimester is premature labor, which oc- ity by auscultation of fetal heart activity (by curs in approximately 20% of all pregnancies.7 fetoscope, Doppler, or ultrasound) and a pelvic Premature labor is defined as painful, regular examination to verify that the cervix is closed contractions associated with progressive dilata- and accurately estimate the gestational age. tion before 37 weeks’ gestation. In some cases, underlying causes can be determined, such as Incompetent Cervix abruptio placenta (see below) or intrauterine infection. However, the vast majority of cases Approximately 5% of pregnancies are compli- are idiopathic. cated by painless dilation of the cervix, almost The initial treatment for premature labor exclusively in the middle third of pregnancy. is bedrest, IV hydration, and medications The treatment for an incompetent cervix is to decrease uterine contractility, referred to as strict bedrest until a suture (cerclage) can be tocolytics. Intramuscular (IM) steroids are placed around the cervix. These patients are at commonly given to accelerate fetal lung matu- risk for premature rupture of membranes and rity. In many cases, prolonged treatment with premature labor and delivery. subcutaneous or oral tocolytics is required to decrease the chance of premature delivery. Fetal Demise Intrauterine fetal demise might occur at any Premature Rupture of Membranes time. During the second or third trimester, the Premature rupture of membranes is another relatively common condition. In general, the Table 22.4. Criteria for AE: Second and third fetal membranes rupture during labor as a trimesters. part of the normal delivery process. However, Elective AE in approximately 5% of patients ruptured £34wk pregnant membranes occur prior to the onset of labor No labor for 48h and often prior to term. The latency period Cervical dilation <4cm Amniotic membranes intact is defined as the time interval between the No vaginal bleeding for 7d rupture of membranes and the initiation of Urgent AE labor. The length of this period is inversely Premature labor effectively stopped for 24h proportional to the gestational age at the time < Cervical dilation 4cm of rupture. In over half of these patients at No vaginal bleeding for 24h term, spontaneous labor begins within 12 to 294 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

48 hours. If membranes rupture prior to labor, sion, or preeclampsia, which occurs in approx- these patients are at increasing risk of in- imately 5% of all pregnancies.7 The hyperten- trauterine infections as the interval between sion of preeclampsia is usually accompanied by membrane rupture and delivery increases. proteinuria and edema of the hands and face. Care should be taken to avoid unnecessary This condition puts the fetus at risk for abrup- digital examination of the cervix after rupture tio placenta and intrauterine demise and the of membranes. mother at risk for grand mal seizures, referred to as eclampsia. The ultimate treatment is delivery of the Third-Trimester Uterine Bleeding fetus. However, if the woman is remote from Bleeding from the uterus in the third trimester delivery the treatment often consists of bedrest is a potentially life-threatening problem for for mild cases. More serious cases are treated both the fetus and mother. These patients can with IV magnesium sulfate to prevent seizures, be divided into two major categories: abruptio antihypertensive medication, and induction of placenta and placenta previa. labor, regardless of gestational age.

Abruptio Placenta The most common serious cause of bleeding in Implications for AE the third trimester is abruptio placenta, which Women with the complications listed above in occurs in 1% to 2% of all deliveries. In this the second and third trimesters of pregnancy situation, the placenta partially or completely constitute a group of extremely high-risk pa- detaches prematurely. The result is vaginal tients for AE. Contraindications to AE include bleeding associated with premature labor. This untreated incompetent cervix, labor (prema- can also result in massive hemorrhage, which ture or term) that cannot be stopped with can be fatal to the unborn child and potentially tocolytics, any degree of uterine bleeding, and to the mother as well. In extreme cases, this can severe preeclampsia (Table 22.2). If facilities also be associated with disseminated intravas- are not available locally to treat these con- cular coagulopathy. Most often in these cases, ditions, the patient should be transported to there will not be enough time to transport the the nearest appropriate medical facility by patient before delivery except by short-distance MEDEVAC. MEDEVAC to the nearest medical facility. Patients with intrauterine fetal demise can undergo AE as long as their clotting factors (as Placenta Previa reflected by prothrombin time, partial throm- The painless bleeding associated with placenta boplastin time, fibrinogen, and platelets) are previa occurs in approximately 1% of all pre- within the normal range. Because disseminated gnancies.7 In this condition, the placenta is intravascular coagulation is uncommon and implanted abnormally low in the uterus, such usually occurs after the fetus has been dead for more than 4 weeks, transportation as soon as that it partially or completely covers the cer- 7 vical opening. As uterine contractile actively possible is advisable. becomes more common near term, the risk of Patients with the remainder of these com- bleeding increases. Digital cervical examination plications can be transported by AE if their is contraindicated because this might incite condition can be stabilized. A patient with a bleeding. This condition can result in massive history of premature labor can be transported hemorrhage that can be fatal for both the if she has been without uterine contractions for > mother and fetus. 48 hours. The fetal position should be verified to be vertex (head down) because unexpected delivery from a breech position can be danger- Pregnancy-Induced Hypertension ous for the infant. Tocolytic therapy should be Another relatively common complication in the continued throughout the flight to minimize the third trimester is pregnancy-induced hyperten- risk of recurrent labor. Finally, an individual 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 295 trained to perform a vaginal delivery and the mild preeclampsia should be treated with necessary equipment should accompany the antiseizure medicine as well. patient. Patients with premature rupture of mem- Potential In-Flight Emergencies branes are at significant risk for premature labor. If labor has not started within 12 hours In the third trimester, most in-flight emergen- of rupture, AE might be considered. However, cies can be treated only with supportive mea- tocolytic therapy should be available in case sures inflight, whereas definitive treatment will labor starts during the flight. As with premature require emergency flight diversion to an airfield labor patients, the fetus should be vertex and near a medical facility with obstetric capabili- both trained personnel and equipment for ties. Because emergency delivery is a significant delivery should be available. risk for many of these patients, they should Patients with a diagnosis of placenta previa be accompanied by medical personnel trained or chronic abruptio placenta should be free of in emergency vaginal delivery and an ob/gyn bleeding for at least 24 hours prior to AE equipment kit (Table 22.1). and should remain at bedrest throughout transport. Patients with the other conditions listed Hemorrhage can be moved by AE but should be accom- Treatment of obstetric hemorrhage during flight panied by a physician trained in the manage- is limited to supportive measures, including ment of spontaneous vaginal delivery and IV fluids, transfusion of whole blood or packed obstetric complications that might occur. In red blood cells, Trendelenburg and left-lateral most cases, urgent AE should be carried out as decubitus position, and supplemental oxygen soon as practical after the diagnosis and the (4L/minute by nasal prongs). Emergency flight need for transportation is determined and the diversion with immediate transfer to a medical patient’s medical condition is determined to facility equipped with an operating room might be stable. be lifesaving for the mother and child. Patients with mild preeclampsia can be After emergency delivery, postpartum hem- transported by AE but should be treated in- orrhage can be a problem in as many as 5% of flight with antiseizure medicine as a precau- cases. The treatment of this is discussed below tionary measure. The most common of these is in the section on emergency delivery. magnesium sulfate given as a continuous IV infusion (Table 22.3). Seizure

Preparation for AE Eclampsia is the most common cause of seizure during pregnancy and is usually associated with Prior to AE, the patient should be ascertained hypertension and proteinuria, as described to have (1) cervical dilation <4cm (by visual above. Emergency treatment consists of main- inspection only in patients with placenta taining the maternal airway, control of convul- previa), (2) no bleeding or premature labor sions, and lowering of the blood pressure if the for 24 hours prior to transportation, and (3) diastolic blood pressure is >100mmHg.7 adequate hematologic reserve (Hgb >12g/dL). Seizures are most commonly treated with

All patients should be transported by litter in parenteral magnesium sulfate (MgSO4). An the left lateral decubitus position and must initial bolus of 4g MgSO4 is given intravenously have a functioning IV line in place. Supple- as a 20% solution at a rate of 1g/minute. Main- mental oxygen (4L/minute by nasal prongs) tenance MgSO4 should be given until delivery, should also be routinely administered. Contin- usually at a dose of 2g/hour. The patient must uous fetal monitoring is not required because be observed closely for respiratory depression all conservative treatment for fetal distress related to MgSO4 toxicity. The treatment is (position, hydration, and oxygen) are already calcium gluconate (1g intravenously adminis- in place and deﬁnitive treatment (operative tered slowly), which should always be readily delivery) is not possible in-ﬂight. Patients with available when MgSO4 is used. 296 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

If the patient was diagnosed as having pre- Emergency Vaginal Delivery eclampsia prior to AE, she might be already receiving MgSO4. If she is having a seizure In-flight vaginal delivery is fortunately an un- despite MgSO4 therapy, the emergency treat- common event. This might be because women ment is IV diazepam (10mg). Although this in late pregnancy avoid prolonged flights. In is an expedient way to treat seizures, there is addition, there is normally a matter of hours a risk of respiratory depression that might between the onset of labor and the actual deli- require respiratory support. In addition, the very in most patients. However, AE flight infant will show signs of respiratory depression crews, especially on long overseas flights, should if born within 1 hour of this treatment. be familiar with the signs of labor and know how to best assist a woman during delivery Fever should this become necessary. When transporting a patient with premature labor or premature rupture of membranes, Signs of Labor the development of an elevated temperature is most likely a sign of intrauterine infection In general, labor is a relatively prolonged (chorioamnionitis). Another common source of course of events that beings with regular infection is pyelonephritis. The fetal heart rate painful contractions and/or a spontaneous will almost always be elevated with maternal rupture of membranes and ends with vaginal fever. In all cases of maternal fever, treatment delivery. Labor is usually a long process, aver- aging 12 hours for the first child and 8 hours for consists of IV antibiotics and acetaminophen 7 as an antipyretic. Aspirin and nonsteroidal subsequent deliveries. However, labor can be anti-inflammatory drugs should be avoided in unexpectedly quick in some cases, especially late pregnancy. If the patient is not already on with premature labor and women who have oxygen supplementation, this also should be had several previous children. Once the patient started (4L/minute by nasal cannula). Trans- has an urge to push, delivery usually occurs in fer to a medical facility within 1 to 2 hours is less than 2 hours and sometimes in a matter of important. minutes, especially in multiparous women. Because of this, an emergency ob/gyn kit and Labor personnel trained to assist with a vaginal delivery should be available any time a pregnant Regular, painful contractions can occur in any patient is transported in the late second or third pregnant patient during flight but is most likely trimester of pregnancy. to occur in patients previously diagnosed with premature labor or premature rupture of the Stages of Labor membranes. The initial treatment is bedrest in a left lateral recumbent position and Labor progresses in a predictable manner IV hydration (lactated Ringer’s solution at divided into three stages. The first stage is the 175cc/hour). If the patient is being given a regular painful contractions that result in tocolytic agent, the dose can be increased. gradual dilation of the cervix. After an average Careful monitoring must be done for signs of 8 to 10 hours, the complete dilation of the and symptoms of toxicity. Flight diversion and cervix is coupled with an often irresistible urge transfer to an obstetric unit will be required to push. The second stage of labor is the descent if the labor cannot be stopped. In the absence of the presenting part through the open cervix of placenta previa, cervical examination by and ends with delivery of the infant.This usually someone with obstetric experience can give the takes 1 to 2 hours of active pushing, although crew an estimation of how imminent delivery it can take less than 10 minutes in some cases. might be. Should the patient experience the The third stage of labor is the delivery of the urge to push, preparation for vaginal delivery placenta, which can be the most dangerous should be made. stage for the mother if hemorrhage occurs. 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 297

Vaginal Delivery with a to deliver the shoulders (shoulder dystocia) is Vertex Presentation discussed below. Once the anterior shoulder is delivered, general upward traction will assist in In approximately 96% of all deliveries, the fetus the delivery of the posterior shoulder. The descends through the birth canal with the top remainder of the infant’s delivery proceeds of the head proceeding first.7 This vertex pre- relatively quickly because the largest part is sentation is the simplest and safest mode of the head and the shoulders. delivery. Several steps are involved in assisting The umbilical cord is clamped twice and cut a vertex vaginal delivery (Fig 22.1). between the clamps. The infant is then rubbed When the perineum begins to bulge, or the briskly and dried to stimulate breathing and presenting part becomes visible, the patient minimize loss of core temperature. The infant should be placed in an appropriate position for should be wrapped in a warm blanket. A full- delivery. This is usually in a semirecumbent term infant might be left in the mother’s arms position, with the back elevated approximately or on her bare chest, then covered during the 45° from horizontal. Adequate lateral room remainder of the delivery as long as the infant should be made to allow the patient to abduct is breathing without difficult. If the infant is her thighs such that the angle between her making inadequate respiratory efforts, neonatal thighs is at or near 90°. In this position, the resuscitation might be required. patient’s buttocks must be elevated at the time of delivery to allow for the delivery of the ante- Delivery of the Placenta rior shoulder of the infant (see below). A padded, inverted bedpan under the buttocks The third stage of labor is delivery of the pla- works well for this propose. centa. After delivery of the infant, the cord The delivery process itself involves assisting protrudes from the vagina. If there is minimal the patient and minimizing the risk of vaginal bleeding, the vagina and perineum can be eval- and peritoneal trauma. Having the patient uated for lacerations while waiting for the pla- grasp her knees or behind her knees and pull centa to separate. Usually,placentas will deliver backward often assists in delivery.As the vertex spontaneously within 30 minutes. If significant is seen bulging from the vaginal opening, vaginal bleeding occurs prior to the placental general pressure is placed on the head so as to delivery, gentle downward traction on the avoid explosive delivery. A gentle, slow deliv- umbilical cord and uterine massage might expe- ery will minimize the risk of trauma to the per- dite this. Every effort must be made to avoid ineum, whereas explosive delivery often results excessive traction on the umbilical cord, which in significant vulvar and vaginal lacerations. can result in inversion of the uterus. The hemorrhage associated with severe vulvar Once the placenta is delivered, the uterus and vaginal lacerations can be life-threatening. should be massaged and the patient adminis- Once the infant’s face is within view, the head tered oxytocin 20IU/L intravenously at a rate should be gently turned either facing to the of 200mL/hour until the uterus remains con- right or left thigh and both mouth and nose suc- tracted and vaginal bleeding slows. Maternal tioned with bulb suction. During this time, breast-feeding might also help expedite deliv- the mother can be instructed to try to avoid ery of the placenta or decrease postpartum pushing, although this is often not possible for bleeding. her to do. Once uterine contracture and hemostasis is The next step is delivery of the infant’s shoul- assured, any resulting vaginal or perineal lacer- ders. As the mother pushes, gentle downward ations should be repaired with suture under traction on the infant’s head will aid in delivery local anesthesia. If no other individual trained of the anterior shoulder. Significant traction in this procedure is available, then closure of should be avoided because this can injure the lacerations that are not actively bleeding can brachial nerves that extend from the infant’s be delayed until transportation to a medical neck vertebrae to the upper arm. The inability facility. However, if hemorrhage from the 298 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

Figure 22.1. Emergency vaginal delivery,vertex pre- shoulder is delivered by maternal pushing and gentle sentation. (a) The perineum is supported as the head downward traction on the head. (e) The posterior emerges. (b) A nuchal cord is reduced (if present) by shoulder is delivered by continued maternal pushing lifting it from the posterior neck over the head. (c) and gentle upward traction on the head. (f) The The mouth and nose are suctioned. (d) The anterior infant’s body is delivered by gentle outward traction. 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 299 lacerations is a significant problem temporary This changes the angle of the pelvis and often hemostatic control can usually be achieved by results in delivery of the anterior shoulder with direct pressure. In extreme cases, tight vaginal gentle downward traction on the infant. packing might be required. The risk of hemor- Another effective approach is suprapubic rhage from vaginal and cervical lacerations pressure (Fig 22.3b). An assistant pushes firmly should not be underestimated because they downward with the heel of their hand immedi- can potentially lead to hemorrhagic shock in ately above the symphysis pubis. This will often untreated cases. The perineum should be rou- push the anterior shoulder beneath the sym- tinely examined in the immediate postpartum physis pubis and allow delivery to proceed. period to evaluate for excessive blood loss. If a medical attendant experienced in obstetrics is available, cutting a large episiotomy will also aid in delivery of the shoulders. However, Delivery Complications because of the risk of hemorrhage and injury to Breech Presentation the infant or mother in inexperienced hands, an episiotomy should only be used by someone Approximately 4% of infants are delivered with obstetric expertise. from a breech presentation. Ideally, the pre- A final procedure, which takes a significant sentation of the infant should be determined by amount of obstetric skill, is delivery of the pos- ultrasound prior to AE. However, in many terior arm of the infant (Figs 22.3c and 22.3d). cases ultrasound is not available or the infant This involves reaching into the vagina, finding changes position between the ultrasound and the posterior arm, which is pinned against the the flight. For this reason, patients at high risk infant’s body, and delivering the entire arm. for delivery should be accompanied by a me- Once the posterior arm and shoulder are deliv- dical attendant who is experienced in assisting ered, a hand is placed on the infant’s back and in delivery regardless of the presentation. The on the abdomen and the infant is then rotated steps for assisting a vaginal breech delivery are such that the previously anterior is shoulder is listed in Figure 22.2. now posterior and this arm is likewise delivered. This difficult maneuver might result in sig- Other Abnormal Presentations nificant vaginal lacerations and might fracture Rather than a presentation of a head or breech, the arm of the infant. However, if all other an arm or a shoulder might present. This situa- methods for delivering the shoulders have tion is often associated with rupture of mem- failed this maneuver can be lifesaving for the branes and is more common prior to term. In a infant. medical facility, this complication is an indication for cesarean delivery. In any other situa- Cord Prolapse tion, immediate transportation to a medical facility with an obstetrician and surgical capa- In some patients, spontaneous rupture of the bilities is the only acceptable approach. membranes results in prolapse of the cord prior to the delivery of the infant. This is much more common in infants who are not presenting in Shoulder Dystocia the vertex (head-down) position. If cord pro- Difficulty in delivering the shoulders after the lapse occurs during the late first stage or early head has been delivered occurs in <1% of all second stage, voluntary maternal pushing by vaginal deliveries. If the shoulders do not someone who has had children before can deliver with the expulsive efforts of the mother result in the delivery of the baby quickly coupled with gentle downward traction on the enough to avoid problems. However, if the head, several simple techniques might assist in cervix is not completely open, or if this is the this delivery (Fig 22.3). An extremely effective patient’s first child, pushing usually takes 1 hour procedure is McRobert’s maneuver. Two assis- or more. The situation can be temporarily tants help the mother press her thighs back mediated by placing a hand in the vagina to against her abdomen, while continuing to push. keep the presenting part from compressing the 300 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

Figure 22.2. Emergency vaginal delivery, breech arm is delivered with a single finger. (e) The presentation. (a) The feet are guided out during infant is rotated 180° and the opposite arm is deli- maternal pushing. (b) The infant is delivered to vered with a single finger. (f) The infant’s head is the level of the umbilicus by maternal pushing delivered using maternal expulsion and suprapubic alone and rotated such that the back is upward. pressure. A finger should be placed over the maxil- (c) The infant is rotated 90° to visualize the left arm lary process and the body kept parallel to the (or alternatively the right arm). (d) The anterior floor. 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 301

Figure 22.3. Procedures to deliver the shoulders in so that the shoulders are near vertical and a hand a difficult vaginal delivery. (a) McRobert’s maneuver is reached in posterior to the head. The posterior involves flexing the hips such that the thighs are arm is delivered by sweeping it across the chest almost touching the abdomen. (b) Suprapubic pres- and grasping the hand. The infant is then rotated sure applied by an assistant may also be helpful. In 180° and the process repeated for the opposite the most difficult cases (c and d), the infant is rotated arm. cord and cutting off the circulation to the amount of bleeding often occurs, usually in the infant. However, unless an emergency cesarean range of several hundred milliliters of blood. At section is carried out in a matter of minutes this point, the placenta must be delivered so prolapse of the cord is usually fatal to the that the uterus can fully contract because the infant. only way the uterus can achieve hemostasis after delivery is by significant uterine contraction. For this reason, the next step after deliv- Postpartum Hemorrhage ery of the placenta is vigorous transabdominal Life-threatening hemorrhage after delivery uterine massage. An experienced operator will of the infant occurs in approximately 5% of often place a hand in the vagina below the all vaginal deliveries.7 For this reason, those uterus to assist in the massage. The patient involved in caring for women who deliver should be given IM or IV oxytocin at this time outside of a hospital setting must be familiar to expedite uterine contractions. The natural with the treatment of postpartum hemorrhage. way to release oxytocin is by breast stimulation Once the infant is delivered, there is usually associated with breast-feeding. A combination a period of time when little bleeding occurs of natural or exogenous oxytocin and uterine prior to delivery of the placenta (see above). As massage will result in adequate hemostasis in the placenta begins to separate, a significant most cases. However, it should be kept in mind 302 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers that the average blood loss for a vaginal deliv- episiotomy associated with delivery. In addi- ery is approximately 500mL and thus what tion, most normal newborn infants will also be might appear to a nonobstetrician to be exces- ready for transportation 1 week after delivery. sive hemorrhage during and immediately after If either the mother or infant is not ready for delivery of the placenta is to be expected. transportation, AE should be delayed so that they can be transported together. An exception Uterine Inversion to this would be if the infant were extremely An uncommon but important complication of premature or will require prolonged hospita- a normal vaginal delivery is uterine inversion. lization related to another medical condition. This is usually a result of too aggressive trac- After cesarean delivery, elective AE should tion on the umbilical cord. If the placenta is be delayed for at least 2 weeks. This is usually implanted in the top of the uterus (fundus), more than enough time for the mother to excess traction on the cord can result in the become medically stable from a postpartum uterus turning inside out. In this configuration, perspective, as described above. However, she the uterus can no longer achieve hemostasis by needs to recover from major abdominal surgery contraction. In this situation, the fundus of the as well. Prior to elective AE, she should be uterus must be pushed back up to return the tolerating a regular diet and be fully ambula- uterus to its natural configuration. This should tory so that she can travel in a seat rather be done with the placenta still in place. The final than a litter. By this time, most women will be step is vigorous bimanual massage and oxytocin able to perform all activities other than heavy therapy. If replacement of the uterine fundus is lifting. not possible, then the patient should be aggres- In a contingency situation, the earliest time sively hydrated as she is transported as quickly the patient should be transported by AE is 24 as possible to a medical facility. hours after delivery. The mother and child need this period of physiological adjustment immediately after delivery. In addition, postpartum The Postpartum Patient hemorrhage is most likely to occur in the first day after delivery. During this time, many The immediate postpartum period is a time patients will receive IV hydration and a dilute of dramatic change in the physiology for both solution of oxytocin until uterine contraction the mother and newborn infant. This is more and adequate hemostasis is assured. obvious for the newborn child than for the Likewise, the newborn infant is carefully mother, but these changes have significant observed during the first 24 hours for early implications for AE for both. After either signs of circulatory or breathing problems. If vaginal delivery or cesarean section, the patient the infant develops signs of decompensation has to deal with significant physiological during AE, this might be difficult to recognize changes. After cesarean section, the patient in the flight environment. In addition, expert must also deal with the expected sequela of pediatric care is unlikely to be available. major abdominal surgery. The mother and newborn infant should be transported together, with rare exception. Thus, Implications for AE if one is taking more time to stabilize after birth transportation of the other should be delayed. Elective AE of the postpartum patient and her One possible exception would be when the newborn infant should be delayed for at least infant has serious medical problems or is 1 week after vaginal delivery. This assures extremely premature. If the infant will need to adequate uterine involution, such that post- remain hospitalized for weeks to months, the partum hemorrhage is unlikely to occur. This mother might need to be transported sepa- 1-week recovery time also allows for the rately. If expedient AE of the premature infant complete physiological readjustment and the is absolutely required, a Critical Care Air Trans- almost complete healing of any laceration or port Team will need to be involved. 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 303

Prerequisites for AE AE transportation of a newborn infant will take special arrangements. Because a litter After either vaginal delivery or cesarean is too narrow to accommodate both mother section, the most important requirement for and infant, a separate temperature-controlled AE is that the patient’s postpartum bleeding isolet will be required (see chapter 24). The (lochia) has slowed sufficiently. The bleeding infant will need frequent feedings, and many < should be 1 obstetric pad per hour with no mothers will be breast-feeding. In general, the episodes of “flooding,” and the uterus should most appropriate position for infant feeding remain firmly contracted. Continued heavy by the mother will be in a sitting position. For postpartum bleeding might be due to inade- this reason, the mother will need to be in a quate uterine contracture, retained intrauterine stretcher low enough to the deck that she will placenta, or infection and is a contraindication be able to get up to attend to the infant. She to AE. Because of the risk of sudden bleeding will also need a seat in which to feed or nurse after delivery, the patient should have adequate the baby. If the mother is unable to feed and > hematologic reserve with a Hgb 10g/mL. care for the infant, a separate attendant will be Appropriate wound healing should be as- required. sured prior to AE. After a vaginal delivery, any vaginal lacerations or episiotomy should also be healing appropriately. After cesarean sec- Potential In-Flight Complications tion, the abdominal incision should be healing normally. Hemorrhage By far, the greatest risk in the immediate post- Preparation for AE partum period (24 to 72 hours after delivery) is postpartum hemorrhage. Heavy bleeding The length of time since delivery and any com- can occur any time within the first month after plications the patient had with her pregnancy delivery but is much less frequent after the first will dictate preflight preparation. If AE is week. Later bleeding may be due to subinvolu- required in the immediate postpartum period, tion, which is often associated with subclinical appropriate pain and nausea medicines should infection. Another cause of postpartum hemor- be available. In all cases, the patient should rhage is the undiagnosed presence of retained be given a several days’ supply of obstetric placenta. pads for vaginal bleeding. If the patient devel- The treatment of postpartum hemorrhage oped a uterine infection (endometritis) during during flight is primarily supprortive with IV or after delivery, continuation of IV antibiotics hydration. If the patient is within 72 hours of is usually required until the patient has been delivery, lack of uterine contracture might be afebrile for 4 hours. If the patient remains the cause. In these cases, treatment consists of hypertensive after delivery, antihypertensive uterine massage and IV oxytocin (10U over 2 medication might be required. minutes) or increasing circulating endogenous All patients, both vaginal delivery and cesa- oxytocin by breast-feeding. If an obstetrician is rean section, who are transported within 1 week available, uterine packing might be attempted. of delivery should be transported in the supine Emergency flight diversion to a facility with position as litter patients because prolonged obstetric care is required for definitive treat- sitting might increase the risk of deep-vein ment of postpartum hemorrhage. thrombosis (DVT). Women who have had cesa- A less common source of serious postpartum rean sections will sometimes require continued bleeding is a vaginal laceration or episiotomy. IV hydration for up to 3 days after delivery until Should moderate vaginal bleeding occur in bowel function has returned. Women within a patient with vaginal lacerations, evaluation 72 hours of vaginal delivery should be trans- of the perineum and vagina is important to ported with a heparin lock in place in the event determine if the bleeding is from this area. This that unexpected hemorrhage should occur. type of bleeding will usually stop with direct 304 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers pressure over the bleeding site. If the laceration Infection is higher in the vagina, vaginal packing should Infection is a relatively common postpartum be attempted whenever the bleeding does not complication. In most cases, this will follow abate with the above-mentioned methods. an infection during pregnancy. However, even Abdominal Pain in some patients without intrapartum infection endometritis will manifest within the first 4 Patients might experience severe abdominal weeks after delivery. The primary symptom pain within the first week after delivery as a of endometritis is uterine tenderness with in- result of nonmechanical (paralytic ileus) or creased vaginal bleeding. A more advanced mechanical bowel obstruction. Paralytic ileus infection usually presents with fevers, chills, and is usually caused by bowel irritation related to purulent vaginal discharge. the intra-abdominal blood or infection associ- The primary treatment is IV hydration and ated with cesarean section. The risk is greatest oral antipyretics. If antibiotics are available, a within the first 48 hours of surgery and is broad-spectrum antibiotic can be started intra- uncommon after vaginal delivery. Decreased venously or orally as a first line of therapy until pressure associated with altitude can result in a medical facility can be reached. Flight diver- expansion of trapped gas in the gastrointesti- sion will rarely be necessary unless the patient nal tract and exacerbate postoperative pain, appears to be getting septic. nausea, and vomiting. Mild symptoms might be treated with par- Breast Engorgement enteral pain medication and antiemetics. More serious nausea or vomiting is an indication to Although engorgement is not truly a medical pass a nasogastric tube. In extreme cases of emergency, this common postpartum problem pain, a decrease in altitude might be helpful. can be distressing to the patient. Breast engorgement commonly occurs 2 or 3 days after Postpartum Seizure delivery and is usually less dramatic in women who are breast-feeding. However, it can occur Patients who had preeclampsia during preg- both in those patients who choose breast- nancy are at a small risk for a grand mal seizure feeding and those who do not. for the first week after delivery. The risk is The treatment for breast-feeding patients is highest for the first 24 hours after delivery and to increase the frequency of nursing the infant. decreases after this time. For this reason, most The treatment for non-breast–feeding patient patients with a diagnosis of moderate to severe is exactly the opposite. Breast stimulation preeclampsia are treated with IV magne- should be minimized. Breast binding, by wrap- sium sulfate for 24 hours after delivery. A full ping the upper thorax with an elastic bandage, 25% of eclamptic seizures occurs in the post- will decrease engorgement and the discom- partum period, and therefore any woman with fort. Engorgement can sometimes be associ- a seizure after delivery should be treated as an ated with significant temperature elevation. eclamptic. Antipyretics and analgesics will help with both The treatment for seizures is IV or IM the discomfort and the fever associated with antiseizure medication. This can be diazepam engorgement. (10mg) given every 30 minutes for a total of 30mg until the seizures have stopped. Follow- ing the cessation of seizure, the treatment is The Gynecological Patient supportive and includes IV hydration, a lateral position to avoid aspiration, oxygen supple- Chronic Gynecological Conditions mentation (4L/minute by nasal prongs), and close observation for signs of respiratory Patients with chronic gynecological conditions suppression. Should this patient have problems might require AE (Table 22.5). These condi- with respiration, temporary bag–mask venti- tions include such diverse conditions such as latory assistance might be required. endometriosis, gynecological malignancies, and 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 305

Table 22.5. Criteria for AE: High-risk gynecological place for hydration. Significant vomiting and conditions. abdominal distension might require a nasogas- Elective AE tric tube. Finally, abdominal pain might require Pelvic infections treatment with parenteral pain medications Afebrile for 48h after cessation of parenteral or antiemetics. The onset of severe colicky antibiotics abdominal pain at altitude suggests expanding Abnormal uterine bleeding trapped intestinal gas. If the pain does not Bleeding etiology has been diagnosed and treated Bleeding < normal menstrual flow respond to standard doses of pain medication Postoperative or gastric intubation, decreasing altitude might 1wk after minor surgery or laparoscopy help. 4wk after major surgery Urgent AE Pelvic infections Genital Trauma, Including No evidence of abscess rupture Sexual Assault Abnormal uterine bleeding No heavy vaginal bleeding for 12h Trauma to the external female genitalia can be Hgb >12g/dL significant enough to impair functionality for Postoperative days or weeks. These injuries are most com- 12h after minor surgery or laparoscopy 24h after major surgery monly straddle-type injuries where the patient has fallen forcefully on an object such as a beam or cross-bar of a bicycle. These types of blunt traumas to the external genitalia might result in nothing more than bruising. However, intractable menstrual abnormalities. The symp- significant vulvar and vulvo–vaginal hemato- toms vary with the diagnosis. However, the mas are possible. three most common gynecological symptoms When a patient is found to have significant these patients might have are vaginal bleeding, genital trauma, the possibility of rape should nausea, and lower abdominal pain. be considered. In these cases, psychological considerations are important because many Implications for AE rape victims might suffer from significant post- The risk of in-flight problems for patients traumatic distress. Even with minimal physical with chronic gynecological conditions is low. trauma, rape victims might have to be evacu- Asymptomatic patients might be transported at ated from the theater if they are unable to carry any time. The risk of symptoms with gyneco- out their military function. logical malignancies increases over time, so Medical treatment of blunt genital trauma these patients should be transported as soon as most commonly involves observation with de- possible after the diagnosis is made. creased activity until the signs and symptoms Patients with advanced gynecological malig- resolve. Symptomatic pain relief includes ice nancies are at risk for vaginal bleeding, anemia, packs acutely, followed by heat and oral pain and gastrointestinal symptoms. A supply of medication. gynecological pads should always be available. Lacerations, even those that are relatively If the patient has experienced any abnormal superficial, might bleed significantly because vaginal bleeding, preparations should be made this is a relatively vascular area. Direct pressure for the possibility of vaginal hemorrhage during is usually all that is required to stop the bleed- flight. Significant hemorrhage is treated with ing. In severe cases, vaginal packing might IV fluid expansion and flight diversion. In ex- be required. Surgical repair might be required treme cases, tight packing of the vagina might to stop arterial bleeding or close clean, deep be required to slow the bleeding until transfer lacerations. Prophylactic antibiotic coverage is to a medical facility can be arranged. Patients recommended because vulvar and vaginal lace- with significant gastrointestinal symptoms, in- rations are prone to infection. cluding nausea, vomiting, and abdominal pain, Penetrating peritoneal injuries might involve should be transported with an IV line in not only the vagina and external genitalia but 306 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers also the rectum and bladder. In extreme cases, Gynecological Pelvic Infections surgical exploration might be required to rule out injury to the intra-abdominal organs. Pelvic infections, most commonly in the form of pelvic inflammatory disease (PID), are relatively frequent in the reproductive-aged popu- Implications for AE lation. The most common presenting symptoms Patients with serious genital injuries should are the triad of pelvic pain, vaginal discharge, be allowed to recover for 7 days after defini- and fever. However, PID can have an indolent tive surgical treatment before elective AE. onset and might be confused with gastroenteri- This will decrease the risk of bleeding or infec- tis or appendicitis. Gynecological examination tion developing during the flight and dramati- usually reveals a purulent cervical discharge cally reduce the amount of pain the patient will and tenderness of the cervix, uterine fundus, experience. In contingency situations, urgent and adnexa. Leukocytosis is common. The AE might be carried out as soon as 12 hours differential diagnosis includes appendicitis, after vulvo–vaginal surgery if the patient is ectopic pregnancy, ruptured ovarian cyst, and otherwise medically stable. However, the risk ovarian torsion. of in-flight complications will subsequently be When a diagnosis of PID is made early in the increased. course of the disease, the patient can be treated As with any condition with a possibility of as an outpatient with a combination of IM and significant blood loss, the patient should have oral antibiotics (eg, ceftriaxone 150mg IM plus ¥ an adequate hematologic reserve (Hgb >12g/ doxycycline 100mg PO bid 10 days). For more mL) in case of hemorrhage during transport. If serious cases of PID, indicated by fever, leuko- the patient has significant vulvar edema, or is cytosis, significant nausea, peritoneal signs, or a transported by litter, a bladder catheter is also pelvic mass, the patient should be treated as an required. In addition to any required anti- inpatient. biotics, the patient should have an adequate The most serious sequelae of PID are pelvic supply of menstrual pads. abscesses, which occur in 5% to 10% of pati- Psychological support prior to and during ents. Pelvic abscesses are suggested by palp- AE is especially important in the case of sexual able adnexal masses. Once PID has advanced assault. The relatively prolonged periods of to this stage, effective treatment consists of isolation and removal from normal psychoso- prolonged bedrest and high-dose antibiotics. cial support inherent in long-distance AE will Surgical drainage is frequently required. Rup- increase the stress on the patient. Agitated ture of a pelvic abscess is a medical emergency patients might benefit from the short-term use that has a presentation similar to a ruptured of a sedative or hypnotic during the flight (eg, appendix. Immediate laparotomy is indicated zolpidem 10mg PO). and might be lifesaving. The mode of AE will depend on the severity Implications for AE of the injury and the length of recovery before AE. If the injury makes prolonged sitting A ruptured tubo-ovarian abscess is a con- uncomfortable, the patient should be trans- traindication to AE. For this reason, patients ported by litter. Patients transported in a seated with PID and signs of peritoneal irritation, position might require analgesics during flight. such as rebound tenderness, decreased bowel Potential in-flight complications include in- sounds, shoulder pain, or nausea and vomiting, creased vaginal bleeding and infection. These should not be transported by AE. Although problems are discussed below under post- these signs could be the result of PID alone, operative gynecological care. The sexual assault they might also be the result of a ruptured or victim might suffer from a panic attack as part leaking pelvic abscess. A ruptured tubo-ovarian of a posttraumatic stress syndrome. This will abscess has a significant mortality rate, even usually respond to the acute administration of with immediate surgical treatment.14 an anxiolytic (eg, diazepam 5 to 10mg PO, IM, Patients with mild PID (no leukocytosis, or IV). fever, or abscess) might be transported by AE 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 307 at any time. Elective AE of patients with more changes in cabin pressure during AE increase serious cases of PID should be delayed until this risk. the convalescent phase of their illness. These The primary symptom of a ruptured tubo- patients should be treated as inpatients with ovarian abscess is an acute increase in abdomi- parenteral and oral antibiotics. AE should be nal pain with signs of peritonitis. This might delayed until the patient has been afebrile for be accompanied by signs of sepsis and progress at least 24 hours and is able to tolerate oral to shock if untreated. In-flight treatment is hydration and feeding. She should be ambula- supportive and consists of IV hydration and tory with minimal or no pelvic pain. supplemental oxygen. If the patient is no longer During a contingency situation, urgent AE taking IV antibiotics, coverage with a broad- might be required prior to this point. If the spectrum antibiotic (eg, a second- or third- patient has a pelvic abscess, it should be sur- generation cephalosporin) is appropriate. Any gically drained prior to AE when possible. rapid deterioration of a patient’s condition with Vaginal drainage might be possible if the ab- a known tubo-ovarian abscess is an indication scess is bulging into the posterior cul-de-sac. to divert to the nearest airfield with a nearby Alternatively, the abscess can be drained using medical facility. an ultrasound-guided needle transvaginally or A less serious complication is the recurrence using a laparoscopic approach. If drainage is of fever and/or pelvic pain in a patient recov- not possible, the patient can be transported by ering from PID. If the patient has no history of air after she has remained afebrile for 48 hours, a pelvic abscess, and otherwise appears stable, but only if there is no sign of peritoneal irrita- treatment should consist of recumbence, oral tion suggestive of a leaking abscess. Forceful pain medication, antipyretics, and antibiotics. pelvic exams should be avoided because this If possible, the patient should be given IV might increase the risk of abscess rupture. fluids and antibiotics. Flight diversion might be These patients should be transported on a litter required if the patient becomes unstable. with continuous IV hydration and parenteral antibiotics. Abnormal Uterine Bleeding Preparation for AE Excessively heavy or frequent bleeding is a common occurrence among reproductive- For elective AE, the patient should be recov- aged women. The differential diagnosis in- ered to the point that she is fully ambulatory, cludes pregnancy (see spontaneous abortion tolerating a regular diet, and taking only oral and ectopic pregnancy, above), anovulatory antibiotics. She might be transported in a sit- bleeding, infection, and malignancies. In post- ting position. If she is known to have a resolv- menopausal–aged women (usually >51 years ing tubo-ovarian abscess, establishment of a of age), any uterine bleeding is abnormal heparin lock is a reasonable precaution in case and uterine cancer is more common. Clinical of in-flight abscess rupture. evaluation includes a pregnancy test (in pre- When urgent AE is required during the acute menopausal women), complete blood count, phase of more serious PID, the patient will Pap smear, and physical examination. Endome- require continuous IV hydration and IV anti- trial biopsy is commonly performed in women biotics. These patients might not yet be tolerat- >40 years of age with abnormal bleeding. ing a regular diet and should be transported The treatment for gynecological bleeding by litter. Many patients will require pain and depends on the diagnosis. Anovulatory bleed- antinausea medication during flight. ing is usually treated with hormones, whereas infection is treated with antibiotics. D&C Potential In-Flight Complications might be required for definitive diagnosis and The most serious complication that can occur treatment. with PID is the sudden rupture of a tubo- In cases of cervical or endometrial malig- ovarian abscess. The movement required for nancy, hemorrhage is usually related to neovas- AE might increase this risk. It is unknown if cularity of the tumor itself. Lesser degrees of 308 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers bleeding might be treated with vaginal pack- be available. An ob/gyn emergency kit should ing until definitive treatment with surgery or be available (Table 22.1). radiation can be carried out. Extreme cases of After definitive treatment, patients need no bleeding might require emergency hysterec- special preparation and might be transported as tomy. If the necessary expertise is available, ambulatory. If a patient is at high risk for recur- radiographic selective cauterization and embo- rent heavy bleeding during flight, she should lization of the bleeding vessel might be used. have a functioning IV line in place, type-specific blood products available, and must be a litter Implications for AE patient. Uncontrolled, heavy vaginal bleeding from any cause is a contraindication to AE. Definitive Potential In-Flight Complications diagnosis and treatment (most commonly by The obvious risk is recurrent heavy vaginal D&C) is required prior to AE. bleeding. This risk is not increased by cabin Patients with limited bleeding resulting from pressure changes but might be increased by anovulation or endometritis might be safely patient movement, in particular in cases of transported by elective AE. Likewise, those gynecological malignancy. Vaginal bleeding of with light bleeding after definitive treatment any etiology might be massive enough to result with D&C can safely undergo AE. If abnor- in hypovolemic shock. mal bleeding is treated nonsurgically with The in-flight treatment of vaginal bleeding hormones or antibiotics, elective AE should includes IV hydration and supplemental oxy- be delayed until 1 week after the last episode gen. Vaginal inspection with a speculum, fol- of heavy bleeding to minimize the risk of recur- lowed by tight vaginal packing with gauze, rent hemorrhage during flight. might temporarily slow the bleeding. Diversion Patient with significant vaginal bleeding of the flight to the nearest airfield and emer- resulting from endometrial or cervical cancer gency transportation to the nearest medical should be definitively treated prior to elective facility will usually be required. AE. After radiation therapy or selective embolization, the patient should be observed for at least 1 week to minimize the risk of recur- Postoperative Gynecological rent hemorrhage. If the definitive treatment Patients includes hysterectomy, AE should be delayed as discussed below for postoperative gyneco- Many gynecological conditions require surgery logical patients. for definitive therapy. Because gynecological In a contingency situation, urgent AE might procedures are some of the most common be required for patients with continuous or major operations performed, an understanding recent episodes of heavy vaginal bleeding. of these patients is important for AE. The only appropriate approach is transporta- Gynecological procedures are often divided tion of these unstable patients to the nearest into three general categories: major, minor, and appropriate medical facility (ie, MEDEVAC). laparoscopic. The majority of laparoscopic pro- The patient will require a functioning large- cedures are minor in nature. However, because bore IV line and readily available blood the peritoneal cavity is entered, and because products. there is a <1% incidence of major complications, postlaparoscopy patients should be con- Preparation for AE sidered separately from those undergoing other Evaluation prior to AE includes a pregnancy minor surgery.15 test (for women of reproductive age), complete The most common nonlaparoscopic minor blood cell count, and physical examination. The procedure is cervical D&C. This procedure is patient’s Hgb should be >12g/dL so she will often performed in conjunction with hystero- have an adequate reserve should she begin scopy. Another common minor procedure is hemorrhaging during AE. An adequate supply a cone biopsy of the cervix, where a relatively of menstrual pads to last several days should large center portion of the cervix is removed 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 309 using a scalpel, laser, or electrocautery. The a 1-week recovery time. After uncomplicated latter of these techniques is referred to as a major surgery, elective AE should be delayed “loop electrosurgical excision procedure (LEEP).” for 3 or 4 weeks, depending on the patient’s rate Mini-laparotomy (<6cm) for tubal ligation or of recovery. removal of an ovarian cyst is also considered If earlier urgent AE is required during a minor surgery. Vulvar and vaginal biopsies also contingency situation, the risk to the patient fit into this category. increases. The sooner a patient undergoes The most common major gynecological pro- transportation after surgery, the greater the risk cedure is hysterectomy. This is most often per- of in-flight complications. For this reason, AE formed through an abdominal incision (total should be delayed for a minimum of 24 hours abdominal hysterectomy; TAH) but is some- after major gynecological surgery or 12 hours times performed exclusively through a vaginal after minor gynecological surgery. This will incision (total vaginal hysterectomy; TVH). allow the healing process to begin and reduc- Either might be performed with or without the tion of the surgical hemorrhage risk. In addi- removal of the ovaries (bilateral salpingo- tion, it will allow the patient to recover from the oophorectomy; BS&O). A recent innovation is effects of anesthesia. Finally, the measured Hgb termed “laparoscopically assisted vaginal hys- level will more accurately reflect the patient’s terectomy” (LAVH).This carries all the risks of hemodynamic state because equilibration takes both TVH and laparoscopy. Other major gyne- several hours after the acute blood loss associ- cological procedures include vaginal surgical ated with surgery. repairs, bladder suspensions, and laparotomy for removal of pelvic masses. Preparation for AE Laparoscopy (other than LAVH) was first used almost exclusively to diagnose pelvic Patients who are almost completely recovered pathology or perform a tubal ligation. In the from gynecological surgery need little prepara- last decade, the types of laparoscopic proce- tion. They should ready for transportion in a dures have increased dramatically. It is now sitting position but might still require oral pain common for more intricate or involved proce- medication. Some patients might still be expe- dures to be performed laparoscopically, includ- riencing vaginal bleeding and thus will need ing removal of ectopic pregnancies, ovaries, and menstrual pads. uterine fibroids. If the patient is transported within 1 week of Laparoscopic complications are most often major surgery, probably the most important related to introduction of sharp instruments consideration is the Hgb level. Postoperative through small incisions, and include injury to patients should have a Hgb ≥12mg/dL prior to intestines, bladder, and blood vessels. These AE. Most patients will need to be transported most often are discovered at the time of sur- by litter. Adequate medication for pain and gery, but the diagnosis might be delayed for nausea should be available. several days after surgery. Later complica- If AE is required within 72 hours of major tions of laparoscopy include infection, delayed gynecological surgery, the patient should have bleeding, and occult injury of the bowel or a functioning IV line. Patients without return urinary tract. of normal bowel function should be actively hydrated. These patients should be transported Implications for AE by litter and have parenteral pain and antinausea medications available. Patients should Prior to elective AE, the postoperative gyneco- be routinely fitted with elastic stockings for leg logical patient should be allowed to recover compression to decrease the risk of deep-vein to the point that she is ambulatory, tolerating thrombosis. regular diets, and her pain has decreased to the point that she is able to tolerate the rigors of Potential In-Flight Complications long-distance flight in a sitting position. After minor or laparoscopic gynecological surgery, The risk of postoperative complications de- the patient will usually be ready for AE after creases with time after surgery. For this reason, 310 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers complications will be relatively uncommon matic devices cannot be used during AE but during elective AE in the convalescent period. elastic stockings should be continued. If AE is required prior to recovery, complica- Patients at high risk for DVT are also treated tions that rarely occur outside the hospital with prophylactic heparin in the perioperative setting might occur during flight. period. A standard approach is subcutaneous unfractionated heparin (5000U/12 hours) or Intra-Abdominal Hemorrhage low-molecular-weight heparin (30mg/12 hours) until the patient is ambulatory. For patients Perhaps the most common early postoperative being transported by AE with 72 hours of complication is intra-abdominal hemorrhage. surgery, the use of either elastic stockings or This complication almost always occurs within heparin is important. the first 24 hours of surgery and thus will Emergency in-flight management of pul- be unlikely to occur in patients transported monary embolism is limited to supportive after this initial recovery period. However, the therapy, including IV hydration and oxygen. movement to which the patient is subjected If the symptoms warrant, flight diversion and during AE might result in hemorrhage in the transportation to the closest medical facility days immediately following surgery. might be required. Modern management of The signs of intra-abdominal hemorrhage pulmonary embolism consists of full anticoagu- include increased abdominal discomfort and lation. In severe cases, clot lysis with streptoki- hemodynamic instability. Late signs are abdo- nase or urokinase might be required. Surgery minal distention and hypovolemic shock. If might be required for recurrent emboli and intra-abdominal hemorrhage is suspected massive emboli resulting in cardiovascular in flight, supportive measures include intra- collapse. vascular volume expansion and supplemental oxygen. Emergency diversion of the flight to an airfield near a medical facility might be Abdominal Pain lifesaving. Some postoperative patients might experience increased abdominal pain during AE. If the Pulmonary Embolism pain is acute, intra-abdominal hemorrhage A potential early complication of major gyne- should be considered, as discussed above. cological surgery is pulmonary embolism, However, a more common cause of postopera- which accounts for almost half of all deaths tive abdominal pain is related to gas trapped in after gynecological surgery.16 It is also the the bowel. It is not uncommon for postopera- second most common cause of death after non- tive patients to have a temporary obstruc- medical abortion and the most frequent cause tion related to bowel irritation, referred to of postoperative death in patients with uterine as paralytic ileus. It usually spontaneously or cervical cancer. The risk is increased in resolves within 1 week of surgery. Bowel ob- patients who are over 40 years of age, obese, or struction that does not resolve is more likely have a history of DVT.17 to be mechanical in nature, related to intra- The clinical presentation of pulmonary em- abdominal adhesions, or an errant suture. bolism is sudden onset of shortness of breath, Even in the hospital, bowel obstruction chest pain, tachypnea, and tachycardia. The condition can lead to abdominal distension patient might have symptoms of DVT of the leg, and colicky pain usually associated with nausea such as unilateral leg edema, pain, or erythema. and vomiting. The pain might be worsened As with many postoperative complications, by expansion of bowel gas associated with the primary approach is preventive. After decreased cabin pressure in-flight. Treatment major gynecological surgery, most patients are is gastric decompression with a naso- or oro- treated with leg compression devices (elastic gastric tube, IV hydration, and supportive stockings or intermittent pneumatic compres- therapy with pain and antinausea medicine. sion devices) until fully ambulatory. Because of It is unlikely for this complication to require decreased cabin pressure at altitude, the pneu- emergency flight diversion. However, complete 22. Aeromedical Evacuation of Obstetric and Gynecological Patients 311 medical reevaluation of the patient at the next will remain intact and a pressure dressing will scheduled stopover is mandatory. minimize further bleeding. Uncontrollable bleeding will require further evaluation at a Postoperative Infection medical facility. Heavy vaginal bleeding in the postoperative One of the most common postoperative com- patient is a more difficult problem. If a physi- plications in the first week after surgery is in- cian with gynecological experience is available, fection. Even with the use of prophylactic the vaginal cuff can be evaluated using a specu- antibiotics, clinically significant infection occurs lum and focused light source. A discrete bleed- in 5% of hysterectomies.18 One of the most ing site might be selectively clamped and common sites of postoperative infection is ligated. Vaginal packing might be most helpful the abdominal incision. The clinical presenta- in controlling postoperative bleeding. tion is redness and induration around the incision, with or without purulent discharge. Other sources of infection in a postoperative patient Dehiscence with a fever or signs of sepsis might be more A serious, but fortunately uncommon, wound difficult to determine. Infection at the vaginal complication is dehiscence. This is defined as cuff after hysterectomy or infections of the disruption of all layers of the abdominal inci- urinary or pulmonary tract are difficult to diag- sion, including skin, subcutaneous, fascia, nose during flight. muscle, and peritoneum. The most serious If a postoperative patient develops fever or variant of wound dehiscence is evisceration, signs of sepsis in-flight, the primary treatment where peritoneal cavity contents spill out. consists of IV hydration and oral antipyretics. Dehiscence is usually related to sudden If available, broad-spectrum antibiotics can be increases in abdominal pressure from coughing instituted. Flight diversion is necessary if the or patient movement. Obesity, wound infec- patient exhibits signs of advanced sepsis, such tions, diabetes, and malignancies increase the as tachycardia or hypotension. risk of wound dehiscence. The treatment for wound dehiscence in-flight Wound Complications is support of the wound with a pressure dress- Other Than Infection ing and an abdominal binder. A binder can be made by wrapping an elastic bandage around Bleeding the abdomen over a thick dressing. If eviscera- A relatively common postoperative complication occurs, the bowel should be covered with tion is bleeding from the operative site. a moist, sterile towel or dressing. If available, Although hemostasis in the subcutaneous this dressing should be covered with a layer of tissue is achieved prior to enclosure, patient plastic (eg, trash bag) to limit loss of body heat movement and the normal healing process can and moisture. Every effort should be made to sometimes result in significant bleeding. In avoid compromising the blood supply to the general, this will occur in the first 48 hours after bowel because bowel hypoxia might cause surgery. Later bleeding from the wound might necrosis and necessitate bowel resection. represent infection. After most gynecological Emergency flight diversion for emergency procedures, the bleeding will come from an medical care is mandatory. abdominal incision. After hysterectomy and vaginal procedures, the bleeding might come from the vaginal incision. Conclusion Treatment for in-flight bleeding from an abdominal incision consists of direct pressure Long-distance AE of obstetric and gynecologi- over the bleeding site and placement of an cal patients present many unique challenges. overdressing over the original dressing. When An understanding of the common diagnoses possible, the dressing should be removed to and their related complications might help evaluate the wound. In most cases, the wound minimize the risk of these complications during 312 W.W. Hurd, J.M. Rothenberg, and R.E. Rogers

AE. This knowledge might also help the 8. Barry M, Bia F. Pregnancy and travel. JAMA medical flight crew develop a rational approach 1989;26:728–731. to emergency in-flight treatment. 9. Connor SB, Lyons TJ. US Air Force aeromedical evacuation of obstetric patients in Europe. Aviat Space Environ Med 1995;66:1090–1093. References 10. Breen JL, Gregori CA, Neilson RN. Travel by airplane during pregnancy. NJ Med 1986;82: 1. Graves EJ, Kozak LJ. Detailed diagnosis and 2979. procedures, National Hospital Discharge Survey, 11. Polansky GH, Varner MW, O’Gorman T. Prema- 1996. Vital Health Stat 1998;138:1–155. ture rupture of the membranes and barometric 2. Murphy F, Browne D, Mather S, Scheele H, pressure changes. J Reprod Med 1985;30:189– Hyams KC. Women in the Persian Gulf War: 191. Health care implications for active duty troops 12. Hurd WW, Whitfield RR, Randolph JF, Kercher and veterans. Milit Med 1997;162:656–660. M. Expectant management vs elective curettage 3. Government Accounting Office. Overseas pre- for the treatment of spontaneous abortion. Fertil sence: More data and analysis needed to deter- Steril 1997;68:601–606. mine whether cost-effective alternatives exist. 13. Stovall TG, Ling FW. Single-dose methotrexate: NSIAD 1997;97:133. An expanded clinical trial. Am J Obstet Gynecol 4. Hines JF. A comparison of clinical diagnoses 1993;168:1759–1762. among male and female soldiers deployed 14. Landers DV, Sweet RL. Current trends in the during the Persian Gulf War. Milit Med 1993; diagnosis and treatment of tuboovarian abscess. 158:99–101. Am J Obstet Gynecol 1985;151:1098–1110. 5. Hanna JH. An analysis of gynecological prob- 15. Hurd WW,Pearl ML, DeLancey JOL, Quint EH, lems presenting to an evacuation hospital during Garnett B, Bude RO. Laparoscopic injury of Operation Desert Storm. Milit Med 1992;157: abdominal wall blood vessels: A report of three 222–224. cases. Obstet Gynecol 1993;82:673–676. 6. Huch R, Baumann H, Fallenstein F, Schneider 16. Thompson JD, Rock JA. TeLinde’s Opera- KTM, Holdener F, Huch A. Physiologic changes tive Gynecology. 7th ed. Philadelphia: J.B. in pregnant women and their fetuses during jet Lippencott; 1992. air travel. Am J Obstet Gynecol 1986;154:996– 17. Clagett GP,Anderson FA Jr, Heit J, Levine MN, 1000. Wheeler HB. Prevention of venous thromboem- 7. Cunningham FG, MacDonald PC, Gant NF. bolism. Chest 1995;108:312S–334S. Williams Obstetrics. 18th ed. Norwalk, Conn: 18. Olive DL, Berek JS, eds. Novak’s Gynecology. Appleton & Lange; 1989. 12th ed. Baltimore: Williams & Wilkins; 1996. 23 Medical Casualties

Thomas J. McLaughlin, J. Christopher Farmer, and Robert A. Klocke

The transport of critically ill patients from medical facility or between relatively nearby one location to another is inherently perilous. medical facilities.1 This includes both ground Although this is true even for in-hospital con- transportation and air transportation, most veyances (eg, down the hall to accomplish a commonly by rotary-wing aircraft. In the civil- computed tomography scan), the risk is ian sphere, MEDEVAC is the majority of air considerably greater during long-distance transportation, and the most common scenario aeromedical evacuation (AE) because the only is transportation of trauma patients from expertise and medical equipment available is the site of a motor vehicle accident to an that which was enplaned with the patient. For emergency department. In the military, the this reason,AE of medical casualties (especially MEDEVAC system is designed to transport those needing intensive care) requires exten- combat and noncombat casualties to the closest sive preplanning and careful preparation for field medical facility or between medical facili- both predictable and unanticipated problems. ties within the theater. Unfortunately, the ability to prepare for AE On the other end of the spectrum, AE is is limited by the amount of personnel, equip- defined as the long-distance (usually >300 ment, and supplies that will fit on a rotary- miles) air transportation of casualties between wing or fixed-wing aircraft. Therefore, success- medical facilities. In the civilian sphere, this is ful transport of medical casualties depends on likely to be a shorter distance between an emer- (1) an accurate understanding of the diseases gency department and an ICU to a higher level that afflict the patient; (2) knowledge of poten- of care at another facility. It is usually per- tial or likely complications; and (3) a clear formed using rotary-wing aircraft. However, it appreciation of how the AE process can aggra- has also been clearly demonstrated that trans- vate disease. Simply put, you can take only what portation of patients over distances greater is necessary but you must ensure you have what than 800 miles is safe.2 For military AE, the you need! distance of transport is often measured in thousands of miles and fixed-wing aircraft Definition of Terms are almost exclusively used. The similarities between AE and MEDEVAC are obvious, Medical Evacuation vs AE especially when transporting critically ill patients by air. The first important distinction to be made is between medical evacuation (MEDEVAC) and Elective vs Urgent or Contingency AE AE, two clearly different processes that are Elective AE often confused because they have much in common. MEDEVAC is defined as transporta- Elective AE is characterized by virtually unlim- tion of casualties from the site of injury to a ited time for planning prior to transportation.

313 314 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke

In most cases, elective AE takes place well after environment where the culture, language, and definitive therapy, when the rigors of air travel medical capabilities are significantly different. are unlikely to result in medical decompensa- In every case, the decision to transfer a patient tion. Although these patients are stable and should be made with consideration of (1) the convalescing, some may be critically ill and risks to the patient of not being transferred; (2) require high levels of in-flight medical care the risks inherent to AE; and (3) the expected and support requirements. In addition, even the benefits of the transfer. Regardless of the most stable patients may experience complica- reason, elective AE patients should be stable tions and become unstable when exposed to the with a secure airway and have demonstrated an sometimes-rigorous AE environment. appropriate response to therapy, including For the critically ill patient, the goal of elec- stable vital signs prior to transport. tive AE is seamless critical care from the point of transfer through arrival at the accepting facility. The most significant determination of Urgent and Contingency AE the quality of transport care is the training and Medical casualties may sometimes have to be expertise of the medical attendants. To this end, transported by AE after having received only medical attendants should be knowledgeable in enough therapy to “stabilize” their disease the environment of flight as well as the provi- process (Fig 23.1). Common reasons for urgent sion of critical care. or contingency AE include: Elective AE of a medical casualty is most commonly performed to transport a patient to 1. Transportation to a facility capable of a a facility capable of a higher level of care. It is higher level of care when appropriate care is also used to transport a patient from a foreign not available locally.

Figure 23.1. A recently stabilized patient being carried up the ramp of a C-141 Starlifter during a contingency AE exercise. 23. Medical Casualties 315

Table 23.1. Medical conditions that often require Description of Patient Condition urgent AE to a higher level of care. Another important area to consider is the use Respiratory conitions of precise terms to describe a patient’s medical ARDS Acute respiratory failure requiring mechanical condition. A patient who is described as “criti- ventilation cally ill” by one provider may be depicted as Pulmonary embolism, with or without shock “stable” by another. For example, a patient with Toxic gas inhalation with respiratory injury primary respiratory failure on a mechanical Respiratory failure secondary to sepsis or cardiac ventilator requiring adjustment once or twice causes Cardiovascular conditions daily is critically ill, but is also stable. This is in MI contrast to a patient with respiratory failure Unstable angina secondary to evolving adult respiratory distress Congestive heart failure syndrome (ARDS), who is both critically ill and Recurrent ventricular tachycardia unstable. The relative risk involved in moving Septic shock these two patients on ventilators is drastically different and is influenced by the patient’s medical condition, the equipment available, 2. Removal from a military theater of and the experience level of the providers caring operations. for the patient. 3. Removal from a disaster area where local Safe AE is dependant on reliable com- medical facilities are saturated. munication between all involved physicians to There are a number of medical diseases and ensure that the right personnel and equipment conditions that commonly require urgent AE to are available. Using the same terminology to a higher level of care (Table 23.1). These seem- express the difference in acuity of illness is ingly disparate conditions are similar in that one of the most fundamental requirements of they all possess an increased risk for en route critical-care–related casualty transport. While deterioration. Aggregate experience from the this is vital for critically ill patients, it is also true USAF Critical Care Air Transport (CCAT) for medical casualties of lesser acuity. Teams suggest that a preponderance of these Stable vs Stabilized vs Unstable Patients risks relate to acute airway compromise. In some patients, rapid airway deterioration can Patients who require AE can be divided into require immediate recognition and definitive three basic groups: stable, stabilized, and unsta- intervention to avoid loss of life. Continu- ble. Stable patients are those patients who are ous and comprehensive physiological monitor- extremely unlikely to medically decompensate ing is essential in these patients to recognize during a prolonged flight either because their impending disasters and permit preemptive medical condition is not life-threatening or intervention. because they are in the convalescent stage of A surprisingly large number of previ- their illness or injury. For the purposes of this ously healthy patients develop life-threatening book, these are the patients transported by cardiac syndromes (eg, infarction, pump fail- elective AE and are classified as “routine” using ure, or uncontrolled hypertension) in rela- the standard AE patient nomenclature (see tively austere locations, necessitating transfer to chapter 7). higher levels of care. Because of lack of appro- The second group are stabilized patients: priate medical facilities locally, these patients those who have received just enough medical often require transfer during the most unstable care to allow them to be transported by AE but phases of their diseases.3 Complete evaluation are at significant risk of becoming unstable and definitive treatment is often unfeasible during the flight. These include patients trans- prior to AE. This results in reliance on state-of- ported by urgent AE (when a patient’s serious the-art monitoring throughout AE for timely condition cannot be adequately treated locally) detection of complications that may develop and what we termed in this book contingency during the natural progression of the disease. AE (when patients are moved for nonmedical 316 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke reasons, including armed combat or natural dis- of flight on a patient. These stressors can be aster). These patients are termed “special” by considered in three broad categories: (1) phys- standard AE patient classification because they ical, (2) mechanical, and (3) environmental. require special equipment or expertise for AE. The most important physical stressors are the The final AE group is made up of unsta- consequence of altitude-induced changes in ble patients. These patients require continued cabin pressure on the patient and the adjunc- intensive care throughout AE for survival. tive medical devices used en route. The physio- These patients are also classified as both urgent logical implications of these effects will be and special and may be more common during discussed in the respiratory and cardiovascular contingency AE. In response to US military sections below. doctrinal changes, AE of both stabilized and Mechanical stressors include aircraft-specific unstable patients is becoming increasingly factors, such as vibration, noise saturation, and common. For this reason, the AE system now poor lighting. Noise and vibration render audi- includes CCAT Teams made up of inten- tory diagnostic assessment difficult or impossi- sive-care providers trained to use sophisticated ble. For this reason, medical equipment must air-transportable intensive-care equipment (see provide ample visual cues, especially for alarms chapter 9). on devices such as mechanical ventilators and cardiac monitors. In a contingency situation, this problem may be compounded by Variables Influencing a high patient-to-provider ratio (Fig 23.2). In Long-Distance AE this potentially low-light environment, visual alarms must reliably attract the caregivers’ Stressors of Flight attention (eg, by blinking incessantly). Finally, the most important environmental Successful AE of medical casualties requires a stressors include those related to extremes clear understanding and insight of the stressors of temperature and low humidity. Failure to

Figure 23.2. A C-17 Globemaster conﬁgured to transport 36 littered patients and 48 ambulatory patients using a three-tier litter system (USAF photo). 23. Medical Casualties 317 account for these variables can signiﬁcantly Table 23.2. Barometric pressure at indicated alti- complicate patient management. tude and standard temperature. Barometric Barometric Altitude pressure pressure - 47 Temperature Decreased Pressure (ft) (mmHg) (mmHg) (°C)

At the altitude flown during routine fixed-wing 0 760 713 15.0 AE, the cabin pressure in a pressurized aircraft 1000 733 686 13.0 is equivalent to an altitude of approximately 2000 706 659 11.0 3000 681 634 9.1 8000ft. This lower pressure significantly de- 4000 656 609 7.1 creases the amount and rate of oxygen that 5000 632 585 5.1 diffuses across alveolar–capillary membrane 6000 609 562 3.1 surfaces. For this reason, the flight altitude 8000 564 517 -0.8 - must be restricted for patients with severe 9000 542 495 2.8 10,000 523 476 -4.8 lung disease and unresolvable hypoxemia at the 11,000 503 456 -6.8 normal cabin altitude. Even with a partial alti- 12,000 483 436 -8.8 tude restriction (ie, 3000 to 7500ft) during 14,000 446 399 -12.7 - fixed-wing AE, the PaO2 in a majority of casu- 16,000 412 365 16.7 - alties may be compromised to <60mmHg.4 18,000 379 332 20.7 20,000 349 302 -24.6 Altitude restriction for AE aircraft creates a 22,000 321 274 -28.6 significant cost in terms of speed and fuel effi- 24,000 294 247 -32.5 ciency; thus, it should only be used when essen- 26,000 270 223 -36.5 tial. The obvious result is increased duration of the flight, related both to decreased air speed and increased refueling stops. This, in turn, increases the overall risk to the patient trans- lower barometric pressure can be calculated as port and must be carefully accounted for during follows: the AE planning phase. ()() Required FiO221=- FiO PB47 PB 2- 47

Oxygen Therapy where FiO2 is the current FiO2,PB1 the current barometric pressure and PB the barometric All AE patients should receive the same 2 pressure at the new altitude (Table 23.2). amount of oxygen equal to that received For example, if a patient is located in a city prior to transport to minimize complications of 1000 feet above sea level and is receiving an hypoxia. This requires maintenance of the same FiO of 0.50, but will be transported at a cabin inspired oxygen partial pressure (PiO ). Even 2 2 altitude of 8000 feet to a hospital located 4000 though the inspired fraction of oxygen is con- feet above sea level, the following calculations stant at all altitudes, the reduction of baromet- illustrate the required FiO during transport ric pressure with ascent to altitude decreases 2 and after arrival: the ambient PiO2 according to the following () formula: In-ﬂight required FiO2 = 050686..= 066 () ()517 PiO22=- PB PH O FiO2 () Destination required FiO2 = 050686..= 056 where PB is ambient barometric pressure and ()609 PH2O is the partial pressure of water vapor that is dependent on the patient’s temperature. At If a patient requires substantial oxygen supple-

37°C, body temperature, PH2O is 47mmHg. mentation, it may not be possible to deliver suf- Although PH2O will vary with patient temper- ﬁcient oxygen to correct hypoxia. For example, ature, for practical purposes it can be assumed if 75% or greater FiO2 is required at sea level, to be constant over the range of temperatures it is not possible to deliver the same PiO2 at a present in patients. Thus, the required FiO2 to cabin altitude of 8000 feet even if the FO2 is 5 maintain PiO2 constant during exposure to a raised to 1.0. 318 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke

Pneumothorax chapped lips, hoarseness, or sore throat among crew members and patients. An unrecognized pneumothorax can have a Long flights with such low humidity may devastating effect on respiratory system func- complicate patients’ underlying medical condition during AE. Even a small pneumothorax tions. Patients with respiratory problems on the ground may develop life-threatening will begin to be uncomfortable if the humi- tension pneumothorax because gas trapped dity drops much below 5% to 10%. Respira- in this closed space expands as the aircraft tory secretions may become thick, resulting in ascends. For this reason, special efforts should impaired gas exchange and thus contribute to be made to diagnose a simple pneumothorax hypoxia. Humidified oxygen should be used for prior to flight in high-risk patients, such as patients requiring oxygen therapy. Warmed, trauma or mechanically ventilated patients. humidified air should be supplied to trache- In general, a chest tube should be placed ostomy patients, even if supplemental oxygen in all patients with a pneumothorax prior is not given. to AE, even in the absence of symptoms. Low ambient humidity increases insensible Once inserted, the chest tube should never be fluid losses in all patients but especially those clamped during transport but must instead be who are flown >4 hours, have large surface- vented using a one-way (eg, Heimlich) valve, a area open wounds, or require mechanical ven- water seal, or a continuous suction device. tilation. For patients with large open wounds, insensible fluid losses can be limited by cover- Effects on Equipment ing the wound or affected extremity with a non- permeable plastic sheet. In high-risk patients, The risk of altitude-related gas expansion this increased insensible fluid loss may increase is also a concern for air-containing medical the risk of hypovolemia, and thus two large- devices, such as a Foley catheter or endo- bore intravenous (IV) catheters should be tracheal tube. On the ground, air in an endo- placed prior to take-off. In the event of cardio- tracheal tube cuff is extremely unlikely to vascular deterioration, fluid resuscitation needs expand to the point of causing tracheal injury. to be increased accordingly. However, during ascent the cuff can expand to a sufficient diameter to rupture the trachea and/or obstruct the endotracheal tube, especially in the event of cabin decompression. For Temperature Changes this reason, the USAF AE system insists that all As altitude increases, the temperature outside patients with endotracheal and tracheostomy the aircraft decreases an average of 2°C (3.4°F) tubes have the cuffs filled with sterile saline for every 1000ft. These temperature changes rather than air prior to take-off. If air is left may not be adequately ameliorated by the in the cuff, pressures must be measured and aircraft climate control system, potentially documented frequently during AE. exposing a patient to a significant variation in temperature. In addition, during long-distance Low Humidity AE significant temperature variation commonly develops in different locations of the air- The fresh air supply of the aircraft, obtained craft cabin. from the surrounding atmosphere, becomes Exposure to temperature extremes for an progressively drier as altitude increases. As a extended period may result in motion sickness, flight progresses, moist air is continuously headache, disorientation, fatigue, discomfort, replaced by drier air, resulting in a decreasing and irritability. It will also increase metabolic humidity within the aircraft. The cabin humid- rates, resulting in increased oxygen consump- ity may drop as low as 5% after 2 hours and as tion. For patients with borderline pulmonary low as 1% after 4 hours of flight. This low reserve, significant physiological compromise humidity may result in symptoms of dry mouth, can result. 23. Medical Casualties 319

Table 23.3. Medical equipment approved for use pressure monitor, arterial line monitor, pulse during aeromedical transport. oximetry, end-tidal CO2 monitor, in-line O2 Monitoring devices analyzer, Wright spirometer, and cuffolator

Pulse oximetry (SpO2) (endotracheal tube cuff pressure measurement External blood pressure measuring device device) (Table 23.3).6 Cardiac monitor Arterial line monitor

End-tidal CO2 monitor Defibrillators Pulmonary Conditions Paddle Model “Hands-off” model Respiratory considerations are paramount for Ventilators successful AE. The effects of altitude, while Adult/child inconsequential to a healthy individual, may be Infant Portable laboratory instruments devastating to the compromised patient. There- Arterial blood gases fore, a crucial AE concern is identification Hemoglobin and hematocrit of patients susceptible to hypoxia so that the Electrolytes effects of altitude can be prevented or recog- Miscellaneous nized early. Suction pump and tubing Resuscitation bag Pneumothorax An untreated pneumothorax is a contraindica- Technology Required for tion to AE (Table 23.4). A pneumothorax of Transportation any size must be treated prior to flight because expansion of intrapleural air with aircraft Medical equipment commonly used for critical ascent can compress functioning lung tissue and care in fixed medical facilities may not function compromise oxygenation. Tension pneumo- properly in an aircraft, primarily because of the thorax can develop as continued expansion of changes in cabin pressure. For this reason, a trapped air shifts the mediastinal contents number of devices have been modified and, toward the opposite hemithorax. The resultant after extensive testing, approved for AE by the compression of the vena cava decreases venous Armstrong Research Site of the Air Force return, resulting in decreased cardiac out- Research Lab. All AE aircraft must be capable put and potential cardiopulmonary collapse. of providing electrical power for medical equipment, and this is often accomplished by using an inverter. The inverter transforms aircraft Table 23.4. Contraindications to AE of medical power to 110V/60Hz, the wall source power patients. almost exclusively used in US hospitals. In a dedicated ambulance aircraft, this is never Absolute* Untreated pneumothorax an issue. However, contingency AE may be Chest tube without one-way valve, water seal, or suction accomplished in any available aircraft. If a non- Uncorrected severe arterial oxygen desaturation AE–dedicated aircraft is used, the aeromedical Uncorrected respiratory acidosis crew must make sure that the appropriate Life-threatening hypotension power source is available for any necessary Uncontrolled cardiac arrythmia Relative† medical equipment. MI within one week Unstable angina Congestive heart failure Monitoring Devices Severe anemia (hemoglobin <7mg/dL) The most commonly used devices during Alcoholism without a prior 3–5 day observation period AE are electronic monitoring devices. These * Contraindication to Elective, Urgent or Contingency AE. include a cardiac monitor, external blood † Contraindication only to Elective AE. 320 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke

Tension pneumothoraces must be treated im- oxygenation for “borderline” ARDS patients. mediately with a needle thoracostomy in the Unfortunately, increasing the inspired oxygen second or third anterior rib interspace, followed concentration alone may not improve oxygena- by the insertion of a chest tube. The chest tube tion because these patients have a marked should be connected to a Heimlich valve or degree of pulmonary shunting. The most effec- other one-way valve system to prevent further tive way to improve oxygenation is to re- expansion of the pneumothorax. Lack of a expand collapsed alveoli, thereby increasing one-way valve on a chest tube is another functional residual lung capacity (FRC). This contraindication to AE. is accomplished with a combination of positive pressure ventilation and positive end- expiratory pressure (PEEP). Recent work has Acute Respiratory Failure demonstrated the value of PEEP in correcting Acute respiratory failure is classified as either altitude-associated hypoxia in an animal model 7 primary or secondary. Primary respiratory of ARDS. Changes in cabin pressure make failure refers to the inability of the lungs to adjustment of respirator settings extremely maintain adequate gas exchange (oxygena- difficult. This, plus the nature of ARDS, puts tion and carbon dioxide removal) because of a the patient at increased risk of pulmonary severe pulmonary condition such as pneumonia barotrauma during AE. or pulmonary embolism. In contrast, secondary respiratory failure refers to inadequate pulmonary gas exchange due to extrapulmonary Chronic Obstructive causes such as cardiac failure or the hyperme- Pulmonary Disease tabolism associated with sepsis. Chronic obstructive pulmonary disease (COPD) refers to the triad of asthma, emphy- Implications for AE sema, and chronic bronchitis. Each of these diseases involves airway obstruction in some The AE transportation of patients with acute manner and predisposes a patient to complica- respiratory failure requires meticulous plan- tions associated with the flight environment. ning, special equipment (ie, respirator, pulse Both acute and subacute aggravating factors oximeter, et.), and, in almost every case, accom- can predispose these patients to complications paniment by a respiratory therapist or critical- both at sea level and during flight.8 Acute care physician. factors that can result in immediate respira- The patient’s precarious medical condition tory deterioration include pneumothorax, pul- may be made worse by altitude-associated monary embolism, and lobar atelectasis. hypoxia, requiring careful adjustment of the Subacute factors that can result in a slower respirator. In addition, equipment and incom- deterioration include acute bronchitis, pneu- patibility of supplies such as connectors are monia, small pulmonary emboli, segmental often a problem, especially at interface points atelectasis, minor trauma such as rib fractures where the responsibility for care of a patient is or small pulmonary contusions, and meta- transferred from one group of clinicians to bolic factors. In addition, gastric distention another. Patients may quickly deteriorate while secondary to decreased cabin pressure may clinicians try to fix these problems. For this limit diaphragmatic excursion and reduce vital reason, the respiratory therapist is an irre- capacity. placeable resource for troubleshooting and improvising. A well-prepared respiratory ther- Implications for AE apist will bring a supply of the most common fittings and the necessary tools to connect them. During AE, the COPD patient should be The most difficult types of respiratory failure observed for early signs and symptoms of patients to transport by AE are those with hypoxia, including tachycardia, tachypnea, dys- ARDS. As the aircraft ascends, the altitude- pnea, hypertension, confusion, restlessness, related hypoxia will often result in decreased and headache. Pulse oximetry should be used 23. Medical Casualties 321 during AE to continuously monitor the oxy- with saline, which will not expand with ascent genation of COPD patients. to altitude. The expansion of gas at altitude also Arterial oxygen saturation is ≥95% in nor- requires that the tidal volume of ventilators be mal healthy patients at sea level. Patients recalibrated at altitude to avoid barotrauma. with COPD frequently have lower readings Patients should be closely monitored with (90–94%) which appear to be tolerated chron- cross-reference to the patient, cardiac monitor, ically and do not require oxygen supplementa- and ventilator. In cases where the patient’s res- tion. However, any drop in a patient’s oxygen piratory status is in unclear, an arterial blood saturation requires immediate evaluation of gas may be able to provide guidance. Finally, a ventilation and initiation of oxygen therapy to high index of suspicion should be maintained restore oxygenation to an acceptable value for development of a pneumothorax in patients (≥90%). who demonstrate respiratory distress or The use of high levels of supplemental cardiopulmonary decomposition. oxygen therapy in patients with COPD can be relatively dangerous since increased oxygen may decrease the patient’s hypoxic drive to Cardiovascular Conditions breathe, resulting in acute respiratory acidosis. This usually occurs in unstable patients with an Myocardial Infarction and acute exacerbation rather than in patients with Unstable Angina compensated respiratory acidosis. Although a patient’s arterial PCO2 may rise somewhat with A diseased and recently injured heart has a judicious use of supplemental oxygen, in most limited ability to compensate for the additional cases marked respiratory acidosis is avoided. cardiovascular stresses imposed by AE. One However, an unstable patient with an acute of the greatest threats to a diseased heart is exacerbation of COPD cannot be transported hypoxia. Patients with ischemic heart dis- without significant risk unless personnel and ease demonstrate decreased oxygen saturation facilities are available for inflight endotracheal during AE, with a reported oxygen saturation intubation and mechanical ventilation. Obvi- of <90% in approximately 20% of patients.9 ously, such patients are not candidates for This drop in oxygen saturation increases both elective AE. myocardial workload and oxygen demand and In patients requiring mechanical ventilation, can result in clinical deterioration of patients several factors need to be considered. Ventila- with little cardiac reserve. tors should be plugged into an external power There are other cardiovascular stresses source if possible to conserve battery power imposed by AE related to the physiology and sufficient battery reserve should be present of flight. These include acceleration during to operate the ventilator for 1.5 times the take-off, which can decrease cardiac output by expected flight duration. Expected oxygen uti- decreasing venous return, especially if litter lization should be carefully calculated using the patients are transported with their head posi- patient’s minute ventilation. At least 1.5 times tioned forward. The low humidity associated the expected oxygen utilization should be avail- with flight may cause mild dehydration, thus able on board the aircraft. increasing cardiac workload. Finally, the stress As gases expand with ascent to altitude in of flight can result in the increased release of accordance with Boyle’s law, air in an endotra- catecholamines and autonomically induced cheal tube cuff will expand as well, although dysrhythmias.10 usually not enough to cause injury to the trachea. Rapid decompression, however, could Implications for AE result in tracheal rupture or obstruction of the distal outlet of the endotracheal tube. Endo- Because of the increased risk of complications tracheal cuff pressures may be monitored with immediately after a myocardial infarction (MI), use of a cuffolator pressure monitor. Alterna- elective AE is contraindicated until at least 1 tively, the endotracheal tube cuff can be filled week after the acute event. 322 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke

A study of 196 patients who traveled on com- fered a myocardial infarction during AE. Of the mercial aircraft after an MI found that while 31 patients with available in-flight data, there complications occurred in <5% of patients the were no reported arrhythmias. It is not clear if majority of these occurred in patients trans- this data is applicable to all cases of unstable ported <14 days following the event.11 Addi- angina considering the relatively benign out- tional time for recovery before elective AE comes in all 59 patients (five with congestive may be indicated based on factors that could heart failure, two with eventual myocardial predispose the patient to complications in- infarction and one death). Patient selection for flight. These factors include extensive coronary AE may have been responsible for the gener- disease, a difficult postinfarction course, limited ally favorable outcomes reported. Unfor- cardiovascular reserve, and a substantial need tunately there are no prospective controlled for medications. studies published in the literature regarding In contrast to commercial transport of AE of patients with severe cardiovascular patients post-myocardial infarction, AE utiliz- problems. ing dedicated air ambulances and experi- Several basic principles should be applied enced medical personnel may be achieved when AE is required for patients with severe earlier. Essebag and colleagues12 retrospec- coronary disease or recent MI. These patients tively reviewed transport of 109 patients with should be transported by litter and receive serious cardiovascular disease by commercial continuous supplemental oxygen to minimize and dedicated air ambulance flights as long as cardiac stress. Pulse oximetry should be used to 10 hours duration. Of these patients, 51 who make certain that the patient’s oxygen satura- were transported by air ambulance had suf- tion remains >95%. Appropriate cardiac drugs fered myocardial infarctions, and one half of must be available, including antiarrhythmic and these were complicated (Killip class II, III or vasoactive drugs, sedatives, and analgesics. IV IV). In 16 patients transported >7 days post access is important for fluid therapy and the infarction, there were no in-flight complica- administration of cardiac drugs. Cardiac moni- tions. Five of 35 patients transferred 0–7 days toring should be used in any patient at risk post infarction suffered complications during of dysrhythmia. Central venous and/or arte- AE. Four patients had chest pain and one rial monitoring may be necessary in unstable exhibited arterial desaturation. All patients patients. A cardioversion unit should be readily responded to conventional measures and had available. In all cases, the patient should be no sequelae. These data underscore the impor- accompanied by critical-care specialists trained tance of experienced teams in successful in the treatment of acute complications of coro- Urgent or Contingency AE. Although data in nary artery disease. the literature is sparse, it is clear that the closer in time to the myocardial infarction, the more likely serious events will occur. AE of patients Congestive Heart Failure with MI during the initial phases of their ill- Heart failure occurs when the pumping action nesses should be carried out only after careful of the heart is inadequate to meet the circula- planning and in the presence of experienced tory requirements of the body. Common critical-care personnel. precipitating factors include cardiac tachy- AE of patients with unstable angina should arrhythmias and acute myocardial ischemia. be attempted only when absolutely necessary The primary treatment of congestive heart because of their tenuous medical condition. failure includes oxygen administration and the 13 Castillo and Lyons reported outcome data on pharmacological reduction of preload and 59 patients with unstable angina who under- afterload. went transoceanic AE. Unfortunately, in-flight data were only available on 31 of the patients. Implications for AE Of these, six patients had in-flight events (three with chest pain, one each with arterial desatu- The stresses of flight may significantly worsen ration, headache and hypertension). None suf- the cardiovascular state of a patient with con- 23. Medical Casualties 323 gestive heart failure, and thus this condition is a prolonged tachycardic rate. The increased a relative contraindication to elective AE, espe- rate is easily correctable by placing a magnet cially in class 3 and 4 congestive heart failure. over the pacemaker and converting it to a non- The hypoxia associated with ascent to altitude inhibited unsynchronized paced rythm. may worsen the patient’s condition by predisposing to tachyarrhythmias and acute myocardial ischemia. Hypoxia also increases right Dysrhythmias ventricular afterload by an increase in pul- The early recognition and treatment of dys- monary arterial pressure. Unfortunately, even rhythmias is essential in the safe aeromedical a small increase in afterload can result in transport of patients. Dysrhythmias should be cardiovascular decompensation and cardio- treated the same as would be treated at ground genic shock in those patients with significant level. When at altitude, however, special atten- right ventricular failure. Oxygen supplementation should be given to ensuring the patient is tion to prevent hypoxia and monitoring arter- receiving adequate oxygenation and ventila- ial saturation by pulse oximetry are indicated. tion. Defibrillation and cardioversion can be Decreases in preload may also result in performed during flight provided standard cardiac decompensation in these patients. safety precautions are observed to ensure the During flight, decreased cabin pressure may safety of medical attendants, crew members, predispose to loss of intravascular volume into and other patients. Although defibrillation the interstitial space (ie, third spacing). Some has demonstrated no adverse effect upon an patients might have inadequate cardiac reserve aircraft’s instruments, navigation, or electrical to compensate for the increased myocardial supply, aircrew members should be notified workload resulting from the compensatory prior to use of this intervention. increased heart rate and contractility. The resulting interstitial edema often will manifest clinically as a dry cough, while progression to alveolar Other Medical Conditions edema will appear as pink, frothy sputum. If urgent or contingency AE is required, Anemia critical-care specialists prepared to detect and treat deterioration in the patient’s condition Hemoglobin functions as a carrier of oxygen must be available. A patient with congestive from the lungs to the tissues. A reduced level of heart failure should be positioned with the hemoglobin (actual or functional) reduces the head oriented toward the front of the aircraft oxygen-carrying capacity and subsequently so that the acceleration during take-off will not tissue oxygenation. One gram of hemoglobin transiently exacerbate the congestive failure. will carry approximately 1.4ml of oxygen. With an average hemoglobin concentration of 15g of oxygen per 100ml of blood (dl), the average Pacemakers male will have an O2 concentration of approx- Modern cardiac pacemakers have advanced to imately 21ml/dl (ie, 1.4 ¥ 15) at 100% oxygen the point that they can emulate the heart’s saturation. natural response to the demands of exercise Anemia seriously reduces tolerance to a by increasing heart rate during periods of hypoxic environment. At 100% oxygen satura- increased physical activity. Pacemakers accom- tion, the maximum O2 concentration for a plish this by sensing vibration and interpreting patient with a hemoglobin reduced to 7g/dl this as increased physical activity. will be only 9.8ml/dl. To compensate for this The vibration of flight, in particular in rotary- decreased oxygen-carrying capacity, cardiac wing aircraft, may actuate pacemakers with output must increase. If a patient’s compen- activity-sensing functions and increase the satory mechanisms are compromised, slight pacemaker rate.14 This may have significant reductions in arterial oxygenation may produce implications for patients with severe cardiovas- hypoxic symptoms. Alternatively, increased cular disease as they may be unable to tolerate cardiac stress in a patient with borderline 324 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke

cardiac reserve may result in angina, MI, or arterial PO2 at which this occurs is <60mmHg. heart failure. Fortunately, during flight in individuals without pulmonary disease this level is reached at a Implications for AE cabin altitude of approximately 10,000ft, and modern aircraft are pressured to maintain a < Severe anemia ( 7mg/dl) is a relative con- cabin altitude of <8000ft. However, in patients traindication to AE. At this level, even healthy with pulmonary abnormalities, sickling can be individuals are at risk. Patients should be induced at a cabin altitude as low as 4000ft. For transfused with whole blood or packed red this reason, patients with sickle cell disease blood cells until the hemoglobin concentration should receive supplemental oxygen during > is 10mg/dl. If transfusion is unavailable, AE. either altitude restriction should be imposed Patients who are heterozygous for the sickle to maintain a cabin pressure equal to sea level cell gene (ie, sickle cell trait) do not appear or sufficient supplemental oxygen should be to be at risk for altitude-related symptoms in administered to ensure maximum possible which aircraft are pressurized to about 8000ft oxygen saturation. or lower, the level of commercial aircraft pres- Mild anemia (hemoglobin 10 to 15mg/dl) is surization.15 When transporting patients with usually well tolerated by healthy individuals sickle cell trait, however, the patients’ overall during AE. However, supplemental oxygen medical condition must be considered including should be administered. This is especially the pulmonary, vascular, and hematologic important during pregnancy, when most status. patients have physiological anemia and the stresses imposed by pregnancy make them more likely to become symptomatic (see chapter 22). Patients who have or are at risk of cardiac Gastrointestinal Diseases disease are at special risk of hypoxia-related The gastrointestinal (GI) tract normally con- complications with any degree of anemia. If tains a small amount of gas that will expand transfusion is not practicable, pulse oxymetry upon ascent. In healthy individuals, gas expan- and supplemental oxygen to maintain a satura- sion is rarely problematic at cabin pressures > tion of 90% is the mainstay of treatment. at or below 8000ft equivalent because of the Patients must be closely monitored for decom- resilience of the intestinal walls and the ability pensation. Symptoms that do not respond to to relieve the increased pressure through belch- increased oxygen may require altitude restric- ing or flatulence. On occasion, intraluminal gas tion or diversion to the nearest appropriate expansion during flight may cause abdominal medical facility. discomfort because of tight clothing or restraining devices. Also, gas expansion in the splenic Sickle Cell Disease flexure of the colon can cause upper-left quadrant fullness and a pressure radiating to the left Sickle cell disease is a hereditary chronic side of the chest that can be confused with the hemolytic anemia due to the presence of an pain of cardiac ischemia. abnormal hemoglobin molecule, hemoglobin S. In contrast, patients with GI disorders (eg, The disease is present in individuals homo- bowel obstruction, ileus, or motility problems) zygous for the sickle cell gene (SS) or in het- may have significant difficulties during flight. erozygous states when hemoglobin S is paired Excessive gas production and the inability for with other abnormal hemoglobins. gas to be normally transported through the Sickle cell crisis is characterized by severe intestines place patients at risk of significant joint and abdominal pain related to sludging of problems related to gas expansion during flight. crescent-like “sickle cell” erythrocytes, which In addition to abdominal discomfort and pain, occurs when hemoglobin S polymerizes into the patient may suffer from nausea, vomiting, tube-like fibers. By far the important cause of shortness of breath, and, in extreme cases, vagal this sickling is deoxygenation, and the critical symptoms. 23. Medical Casualties 325

Implications for AE the supine position and 1 hour in the prone position. All patients known to have GI disorders should Some patients may have increased intra- have a nasogastric tube placement prior to cranial pressure as a result of trauma, cranial flight. During flight, the tube should normally surgery, or infection such as bacterial meningi- be attached to a low-flow suction device. If tis. For these patients, steps should be taken to suction is not available, an open nasogastric prevent factors that are known to increase tube may be of some use whereas a clamped intracranial pressure further, such as vomiting, tube will not. hypoxia, and seizure activity. Patients with colostomies may have an Patients with a seizure disorder may be at increased amount of bowel elimination during increased risk during AE because hypoxia flight due to the increased peristaltic motion lowers the convulsive threshold. For this stimulated by intraluminal gas expansion. All reason, a therapeutic level of an anticonvulsant such patients should have their colostomy bag medication should be documented prior to replaced immediately prior to AE, and extra flight and supplemental oxygenation should be bags should be available. Excess flatus and provided. The treatment of seizures during gas expansion in the bag may require careful flight begins by ensuring that the patient’s release in some cases. oxygenation and ventilation are adequate, followed by administration of anticonvulsive Airsickness medication. General treatment of the obtunded or Airsickness occurs in some people as a result of comatose patient includes an in-dwelling abnormal labyrinthine stimulation from unac- urinary catheter and IV fluid administration. customed pitching, rolling, yawing, accelerating, These patients must be observed closely and decelerating forces experienced during throughout flight because they are at increased flight. The result is a predictable sequence of risk of airway compromise and aspiration of symptoms that progress from lethargy, apathy, gastric contents.16 and stomach awareness to nausea, pallor, and cold eccrine perspiration, and finally to retch- ing and vomiting and total prostration. Renal Failure Motion sickness can complicate the care of Patients with acute renal failure should patients and their attendants and on occasion undergo dialysis immediately prior to all long- incapacitate an AE crew member. Interven- distance AE flights. The normal interval tions should be initiated promptly following between dialysis treatments is usually 1 to 2 the onset of early signs and symptoms, and days; thus, the need for dialysis during AE will include the administration of oxygen, placing be unlikely if the flight is point to point. the patient in a supine position with restricted However, during overseas AE the aeromedical head motion and a cross-cabin orientation if crew should be aware of when the next dialysis possible, cooling of the environment, and the treatment is required so that arrangements can administration of antiemetic medications. be made en route if required. Serum electrolytes should be routinely reassessed every 3 Neurological Disorders days for patients with acute renal failure, even if they are not yet dialysis dependent. The care of the nontraumatic neurological patient entails the prevention of complications Alcoholism associated with their underlying medical condition. In the case of paralyzed patients, special The importance of considering the special need attention should be paid to ensuring insensitive of the alcoholic patient is made clear by the areas of the body are protected from injury. special AE categories used to designate these Those patients on Stryker frames should be patients (see chapter 7, Table 7.2). Alcoholism turned on a prescribed basis, usually 2 hours in may be the primary reason for AE or an 326 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke undiagnosed disease process in a patient being amine to prevent the precipitation of Wernike’s transported for another condition. The major encephalopathy. risk in either case is acute alcohol withdrawal, which can be fatal if unrecognized or untreated. Septic Shock Alcohol withdrawal symptoms develop within 8 to 24 hours after the reduction of The use of aircraft for the transportation of ethanol intake and peaks between 24 and 36 severely ill and injured patients is becoming hours. These symptoms range from mild with- increasingly more common. As a result, it is drawal characterized by insomnia and irritabil- inevitable that a patient thought to be stable ity to major withdrawal typified by autonomic will deteriorate in flight. One diagnosis that hyperactivity resulting in tachycardia, fever, must be considered in these patients, especially diaphoresis, and disorientation. those who are immunocompromised, have experienced recent surgery, sustained signifi- Implications for AE cant trauma, or have in-dwelling catheters, is the development of sepsis. To minimize the risk of alcohol withdrawal Sepsis may present in a spectrum of signs and during AE, patients known to be alcoholic symptoms that may range from extremely should be hospitalized for 3 to 5 days of ob- subtle in the early phases of the disease to com- servation prior to flight. Alcohol withdrawal plete cardiovascular collapse. This later phase, symptoms that present unexpectedly in-flight sepsis with hypotension and inadequate tissue require the prompt recognition and treatment perfusion, is defined as septic shock. The of symptoms. A high index of suspicion is constellation of signs and symptoms of sepsis required in patients who are not known to be include fever, chills, tachycardia, tachypnea alcoholic. with respiratory alkalosis, dermatologic Mild alcohol withdrawal symptoms may be changes, widened pulse pressures, and altered effectively treated with supportive care alone, mentation. Although fever is common in sepsis, such as reassurance, personal attention, and patients may present with hypothermia, general nursing care (Table 23.5). If the symp- especially neonates or elderly patients. With toms progress, moderate to severe withdrawal decreased perfusion of tissues in septic shock, should be treated with pharmacological severe metabolic acidosis is a common addi- doses of benzodiazepines. Withdrawal symp- tional complication. toms unresponsive to benzodiazipines may The goal of the treatment of sepsis should be benefit from haloperidol. If IV hydration is the eradication of the infecting organism prior given with glucose-containing fluids, these to the onset of the cascade of cellular, microvas- patients should first receive magnesium and thi- cular, and cardiovascular events that lead to septic shock. Therefore, treatment is usually Table 23.5. Patient care plan: Alcohol withdrawal initiated prior to the identification of a specific syndrome infecting organism. Empirical treatment is recommended using broad spectrum antibiotics 1. Administer medications as appropriate chosen to cover the organisms most likely to be Sedatives to counteract the depressant withdrawal syndrome responsible for the sepsis. The patient’s history Thiamine to prevent Wernicke’s encephalopathy of illness of trauma is especially helpful in Vitamin replacement for malnourishment determining the choice of antibiotics. Antacids to reduce potential gastritis symptoms Supportive therapy is essential in main- 2. Monitor vital signs taining adequate oxygenation and hydration. 3. Follow patient safety protocols because major brain functions may be impaired Adequate ventilation with supplemental 4. Keep environmental stimuli at a low level as excessive oxygen will correct hypoxia and its associated stimulation leads to hallucinations and agitation symptoms. IV fluid therapy will enhance tissue 5. Provide adequate hydration and caloric intake perfusion and oxygen delivery. In those cases 6. Observe for signs of increasing tremors or confusion where septic shock does not respond to fluid indicating impending delirium tremens therapy, treatment with vasoactive pharmaco- 23. Medical Casualties 327 logical agents such as dopamine may result in with Lassa fever who have been transported by increased cardiac output and improved tissue commercial and AE flights.17 For the purposes perfusion. of AE, all patients exposed to a biologic agent should be considered infected, regardless of symptoms. Although the infectious risk to Implications for AE medical personnel depends on the agent Monitoring for signs and symptoms attribut- involved, it may be impossible to determine the able to early sepsis is essential in patients who exact agent prior to AE. have conditions that are predisposed to this development and subsequent progression to Biologic and Chemical Casualties septic shock. Initial evaluation of the patient’s oxygenation and tissue perfusion is a priority Patients contaminated with chemical or bio- because the aeromedical environment may pre- logic agents as a result of occupational expo- dispose a patient to hypoxia and dehydration, sure or terrorist event may sometimes need AE compounding the effects of sepsis upon the transportation. External decontamination is respiratory and cardiovascular systems. Early the first important consideration and must be intubation and mechanical ventilation may be performed prior to AE for all patients exposed required in these patients. IV fluid administra- to chemical or biologic agents. Once patients tion is important in maintaining appropriate are decontaminated, the degree of further pre- blood pressure and tissue perfusion. Anemia cautions needed during AE will be determined may be extremely detrimental in patients by the actual or suspected agent involved with sepsis. Although healthy individuals in the and the patient’s medical condition. To protect aeromedical environment may tolerate mild medical personnel and other patients, precau- anemia, septic patients who are anemic are at tions should be used when transporting any increased risk and may require transfusion to patient exposed to chemical or biologic agents, maintain oxygenation of tissues. as outlined in Chapter 11 and the excellent 17 Precautions required to prevent secondary review of Withers and Christopher. infection during AE depends upon the Both the incubation period prior to sympto- minimum infective dose to produce illness and matic disease and the time of greatest infectiv- the mode of transmission of the disease. Air- ity vary greatly for different biologic agents. borne precautions are designed to reduce risk Diseases that are transmissible during the incu- of infection transmitted by airborne particles bation period present the greatest challenge. £5mm in diameter. These particles remain Because the infected individual cannot be suspended in air indefinitely. Diseases com- identified on the bases of clinical findings, municated by larger (>5mm) particles are less the chance of secondary infection of other transmissible and require droplet precautions. personnel is increased and preventive measures Less stringent respiratory precautions are cannot be applied selectively. required since large droplets remain suspended Isolation During AE in air for short periods of time. Contact precautions are used to prevent illnesses spread by Patients confirmed or suspected to have a highly direct contact with skin, contaminated surfaces infectious or contagious disease can be isolated and body fluids. Standard infection control pro- during AE using the Vickers aircraft transport cedures are sufficient for diseases spread by the isolator (VATI) (see chapter 11, Fig. 11.2) an air contact or droplet modes and only airborne dis- transport isolator. A stretcher isolator is a eases require additional special techniques such lightweight unit for initial patient retrieval, as high efficiency particle filtration (HEPA) where the patient is then transferred to the air masks.17 The prototype of this class of agents transport isolator in or near the aircraft. This is the smallpox virus. The viral hemorrhagic allows for full nursing capability provided by an fevers have been considered to be in this class isolation team from the USA Medical Research in the past, but uncertainty has developed in Institute of Infectious Diseases to care for this position based on observations of patients patients in-transit. All air passing in and out 328 T.J. McLaughlin, J.C. Farmer, and R.A. Klocke of the unit travels through a high-efficiency 5. Saltzman, AR, Grant BJB, Aquilina AT, particulate air filter. If the unit is accidentally Ackerman NB Jr, Land P,Coulter V,Klocke RA. punctured, negative pressure within the unit Ventilatory criteria for aeromedical evacuation. prevents potentially contaminated air from con- Aviat Space Environ Med 1987;58:958–963. taminating the cabin air. Gloved sleeves within 6. American College of Critical Care Medicine, Society of Critical Care Medicine, and American the unit facilitate care of the patient. Because of Association of Critical-Care Nurses. Trans- its size, the use of this unit is limited to large porting critically ill patients. Health Devices transport aircraft such as the C-130 and C-141. 1993;22:590–591.

For shorter distances, the CH47 Chinook heli- 7. Lawless N, Tobias S, Mayorga MA. FiO2 and copter may transport patients. positive end-expiratory pressure as a compensa- A few diseases are considered by the World tion for altitude-induced hypoxemia in an acute Health Organization to be internationally quar- respiratory distress syndrome model: implica- antinable and are thus a contraindication to tions for air transportation of critically ill elective AE. Authorization by both command, patients. Crit Care Med 2001;29:2149–2155. if military, and diplomatic authorities must be 8. Mandavia DP, Daily RH. Chronic obstructive obtained prior to AE across international pulmonary disease. In: Rosen P, Barkin R, et al, eds. Emergency Medicine, Concepts and Clinical borders. Practice. St Louis, Mo: Mosby; 1998:1494–1511. In both the civilian or military spheres, the 9. Bendrick GA, Nicolas DK, Krause BA, Castillo possibility exists of chemical contamination as CY. Inflight oxygenation saturation decrements a result of either occupational exposure or in aeromedical evacuation patients. Aviat Space terrorist activities. Onset of symptoms is usually Environ Med 1995;66;40–44. rapid after exposure to most chemical agents, 10. Tyson AA, Jr, Sundberg DK, Sayers DG, Ober although symptoms may be delayed for several KP, Snow RE. Plasma catecholamine levels hours after exposure to some agents. in patients transported by helicopter for acute Patients exposed to chemical agents must be myocardial infarction and unstable angina thoroughly decontaminated prior to AE. Treat- pectoris. Am J Emerg Med 1988;6:435–438. ment may be required throughout the AE 11. Cox GR, Peterson J, Bouchel L, Delmass JJ. Safety of commercial air travel following myo- flight. Medical attendants must be familiar cardial infarction. Aviat Space Environ Med with appropriate therapies for various chemical 1996;67:976–982. agent exposures. 12. Essebag V, Lutchmedial S, Churchill-Smith M. Safety of long distance aeromedical transport of References the cardiac patient: a retrospective study. Aviat Space Environ Med 2001;72:182–187. 1. Department of the Army. Medical Evacuation in 13. Castillo CY, Lyons TJ, The transoceanic air a Theater of Operations: Tactics, Techniques, and evacuation of unstable angina patients. Aviat Procedures. Washington, DC: US Government Space Environ Med 1999;70:103–106. Printing Office; 1991. FM 8-10-6. 14. Gordon RS, O’ Dell KB, Low RB, Blumen IJ. 2. Valenzuela TD, Criss EA, Copass MK, et al. Activity-sensing permanent internal pacemaker Critical care air transportation of the severely dysfunction during helicopter aeromedical trans- injured: Does long distance transport adversely port. Ann Emerg Med 1990;19:1260–1263. affect survival? Ann Emerg Med 1990;19:169– 15. Sears DA. Sickle cell trait. In: Embury SH, 172. Hebbel RP, Mohandas N, Steinberg MH, eds. 3. Fromm RE, Haiden E, Schlieter P, Cronin LA. Sickle Cell Disease, Basic Principles and Clinical Utilization of special services by air transported Practice. New York: Raven Press; 1994. cardiac patients: an indication of appropriate 16. Kalisch BJ. Intrahospital transport of neuro ICU use. Aviat Space Environ Med 1992;63:52– patients. J Neurosci Nurs 1995;27:69–77. 55. 17. Withers MR, Christopher GW. Aeromedical 4. Henry JN, Krenis LJ, Cutting RT. Hypoxemia evacuation of biological warfare casualties: during aeromedical evacuation. Surg Gynecol a treatise on infectious diseases on aircraft. Obstet 1973;136:49–53. Military Med 2000;165(suppl 3):1–21. 24 Pediatric Casualties

Robert J. Wells, Howard S. Heiman, and William W. Hurd

The specialty of pediatrics was one of the ear- regional centers for trauma, dialysis, and trans- liest to recognize the benefit of moving pati- plantation further increased the need for ents between medical treatment facilities. The interhospital transport of pediatric patients. In impetus for this was to both maximize patient response, the American Academy of Pediatrics outcomes and conserve medical resources. By published guidelines for both air and ground 1900, the Chicago Lying-In Hospital had transport in 1986, with subsequent revisions in developed specific equipment for transporting 1993 and 2000.4 In addition, many pediatric sub- newborn infants. By 1950, the New York City specialty textbooks in neonatology, pediatric Department of Health had set up a newborn intensive care, and pediatric emergency medi- transportation system to serve a network of cine now contain chapters on ground and air hospitals, complete with specific transportation transport of pediatric patients.5–7 equipment and teams and a central dispatcher. This chapter will first cover pediatric trans- During 1950 to 1952, this system moved more port goals and the composition, training, and than 1200 patients between hospitals.1 equipment of pediatric transport teams. Next, Many areas of the United States developed the most common general pediatric conditions regional neonatal ICUs during the 1960s and moved via AE and the AE implications will be 1970s as a result of both the significant medical described. Finally, common neonatal conditions progress in this area and the increasing diffi- requiring AE will be discussed. culty of supporting such units. This regionaliza- tion further increased the number of infants Pediatric Transportation being transported. As the size of the regions increased, the Transportation Goals potential benefits of aeromedical evacuation (AE) compared to traditional ground transport The ultimate goal of pediatric AE is to rapidly became obvious. Early reports of this mode of bring the patient to a higher level of care. To do transport were encouraging and included 53 this successfully, three tasks must be accom- infants transported by large fixed-wing military plished. First, the transport team must assess aircraft (Operation Baby Lift, 1969 to 1970) the patient’s needs with the assistance of the and 101 infants moved by both rotary-wing referring medical care providers. A key deter- and small fixed-wing aircraft by St. Anthony’s mination at this point is which personnel are Air Transport Service (Denver) from 1972 to necessary for the transport team. The second 1973.2,3 task is to determine that the patient is stable The advantages of transporting neonates to enough to transport. This determination is a regional ICUs quickly became apparent to joint responsibility of the referring medical other pediatric subspecialists. The subsequent care providers and the transport team after development of regional pediatric ICUs and they have arrived on-scene. The final task is to

329 330 R.J. Wells, H.S. Heiman, and W.W. Hurd maintain stability of the patient throughout the In reality, it is sometimes difficult for regional course of movement between medical treat- planners to construct expert pediatric emer- ment facilities, counteracting the stresses asso- gency teams. When expert pediatricians are un- ciated with AE as well as potential progression available, various levels of technicians, nurses, of the underlying medical problem. and physicians in training can be utilized to maximize the pediatric skills of the team.8 Transport Team Composition Regional planners are encouraged to orga- nize the base of their transport system at a The composition of the transport team utilized pediatric center of excellence. This allows for for a particular mission will vary based on the accomplishment of two important objec- patient needs and the potential for compli- tives. First, the primary team members located cations. A transport team is most commonly at these centers can establish and maintain their composed of some combination of the follow- clinical skills. Second, other pediatric specialists ing personnel: pediatric nurses with special available at these centers serve as a large pool expertise in the appropriate subspecialty to draw from in the event their special skills (eg, neonatal intensive-care nurses or nurse are required for a specific pediatric transport. practitioners), emergency medical technicians When a team is augmented by a specialist with with pediatric experience, respiratory thera- little background in pediatric transport, good pists with pediatric experience, pediatricians in communication between the expert and the training (ie, residents and fellows), general transport team is essential to assure that patient pediatricians, and subspecialty trained pediatri- care is not fragmented. cians. The exact combination depends on the diagnosis, condition, and age of the patient to Team Training be transported. Not all teams require physicians and in some locales physicians participate All aeromedical transport team members must in only a few selected transports. be trained in flight preparations, flight physiol- The Children’s Hospital Medical Center ogy, and safety. The specific content and cur- transport team (Cincinnati) always includes rency requirements for transport team training a pediatric nurse with additional skills in the are outlined in the Air Medical Crew National patient’s disease (eg, neonatology) and a res- Standard Curriculum, which is based on both piratory therapist with pediatric experience. Federal Aviation Administration regulations Physicians participate in 22% of the neonatal and the Commission on Accreditation of Air transports and 38% of the pediatric transports. Medical Services standards. Recently, all ground transport teams have Transport teams may be combined neonatal/ been augmented with emergency medical tech- pediatric teams or separate teams for neonatal nicians for technical and logistical assistance and other pediatric transports. Members of (Shelton G. 2000. Unpublished data). both combined and separate neonatal/pediatric Ideally, all pediatric transport service direc- transport teams require further specialized tors should be physicians with expertise in the training in pediatric and/or neonatal resusci- evaluation and treatment of pediatric disease tation, stabilization of infants and children and injury. These expert pediatricians include for transport, and in the frequently encoun- board-certified specialists and subspecialists tered diseases in each respective age group. in neonatalogy, pediatric emergency medicine, Well-organized educational programs on these and pediatric intensive care. Although they per- topics are offered by the American Heart sonally participate in only a minimal portion of Association, the American Academy of Pedi- the patient movements, they are responsible for atrics, the American College of Emergency administrative, technical, and medical decision Physicians, and the University of Virginia making as well as education of transport teams. Medical Center. Advanced training for team Actual transport team members must have members may sometimes be required, depend- pediatric skills that support the anticipated ing on team composition and required trans- needs of the patient transported. port missions. 24. Pediatric Casualties 331

Continuing education for all team members In addition to the previously mentioned attri- is crucial to the maintenance of knowledge and butes, this electrical equipment must have an skills. Those efforts should include not only extended battery capability because a long operational and medical aspects of transport time can easily elapse between leaving the but also strategies for enhancing team commu- sending medical facility and enplaning. How- nication skills and stress management. ever, equally important considerations are the effects of flight on equipment performance and the effects of the equipment on the aircraft. Transport Team Supplies Performance of pediatric transport equip- and Equipment ment should be thoroughly tested for the Supplies stresses of flight, including: altitude-related changes in pressure, temperature, and humid- Neonatal/pediatric transport supplies should ity; acceleration–deceleration forces; vibration; be maintained separately from adult supplies. and the airframes’ electromagnetic environ- Although this will result in some duplication of ment. In addition to adversely affecting the supplies carried by adult transport teams, it is performance characteristics, these stresses may necessary to avoid the potential danger that can significantly shorten the useful life of the equip- result from confusion of medicine doses and ment. Because of these environmental stresses, concentrations. an effective biomedical maintenance program is critical. Equipment In addition, the effects of pediatric transport Pediatric and neonatal transport equipment equipment on the aircraft must be thoroughly must be lightweight, compact, durable, and tested to verify that the electromagnetic emis- easily secured to function well in the AE envi- sions of the equipment does not interfere with ronment (Table 24.1). Some basic equipment the performance of aircraft avionics, including for pediatric transportation, such as cervical communications and navigational devices. collars and backboards, are part of the standard Extensive safety and performance evalua- emergency medical service inventory and us- tion of equipment for AE has been carried out ually do not need to be duplicated by the pedia- by both the USAF Medical Equipment and tric transport team. the USA Aeromedical Research Laboratory.9,10 Electrical equipment represents a special Civilian testing labs and transport organiza- challenge for pediatric aeromedical transport. tions have only recently begun to develop comprehensive testing programs for avionics and pediatric aeromedical equipment. Unfortu- nately, the majority of the transportation equip- Table 24.1. Neonatal transport equipment. ment that has been tested and approved for use Transport Incubator or Litter on aircraft (eg, infusion pumps and ventilators) Monitors was designed for treatment of adult patients. In Pulse/respiratory rate many cases, it may not be appropriate for use Pulse oximetry in pediatric patients if it lacks accuracy at the Temperature (skin, core +/- air) Blood pressure (invasive, non-invasive) small volumes that must be delivered for pedi- ECG: Digital and waveform displays. atric and especially neonatal patients. Ventilator with humidification device Oxygen blender with flow meter up to 15 LPM Portable suction unit Incubators Infusion pumps Portable compressed gas with oxygen +/- air at 50psi The incubator is the focal point of the neonatal Auxiliary equipment transport system because it provides for two of Defibrillator-cardioverter the most critical aspects of transport, thermal Intracranial pressure monitor support and patient monitoring. It is also the Point of care blood analyzer largest and heaviest piece of equipment used Nitric oxide delivery system in neonatal transport (Fig 24.1). Thus, it has a 332 R.J. Wells, H.S. Heiman, and W.W. Hurd

Figure 24.1. An incubator aboard a Beech King Air 200 aircraft flown by Intermountain Health Care Life (Salt Lake City) (photo used with permission from Spectrum Aeromed Inc, Wheaton, Minn). significant impact on the final configuration tion Inc, West Caldwell, NJ), which is described and composition of the entire transport system. in chapter 19. Prior to using an incubator for the first time in a particular aircraft, it must be verified that the Extracorporeal Membrane Oxygenation incubator fits through the aircraft door and can Extracorporeal membrane oxygenation be fixed firmly in place. In rotary-wing and (ECMO; also known as extracorporeal life smaller fixed-wing aircraft, the chief pilot must support) is the use of a modified heart–lung carefully review any impact on weight and machine for days or weeks to support life and balance calculations because an incubator and permit treatment and recovery during severe cart can weigh as much as 285lb. cardiac or pulmonary failure in neonates, children, and adults.11 Neonatal ECMO is indicated Ventilators in acute severe reversible respiratory failure The choice of ventilator for air medical trans- when the risk of dying from the primary disease port, although limited, is based on power source despite optimal conventional treatment is high requirements, gas consumption, and the age (>50%). The most common neonatal indica- of the patient because different ventilators are tions include meconium aspiration syndrome, required for neonates and infants. The delivery congenital diaphragmatic hernia, persistent volumes, pressures, and rates must be carefully pulmonary hypertension, respiratory distress/ evaluated to ensure that the ventilator meets hyaline membrane disease, and neonatal the respiratory management philosophy of the pneumonia/sepsis. The current overall survival regional neonatal care team. Critical evaluation rate for neonatal respiratory failure is 80%. by the respiratory care department will identify ECMO machines are now routinely being potential needs and problems. The respirator flown in both rotary-wing and fixed-wing air- most commonly used by the USAF AE system craft (Figs 24.2 and 24.3). Because of the size it the Impact Uni-Vent Eagle Model 754 Posi- and weight of these units, the USAF primarily tive Pressure Ventilator (Impact Instrumenta- uses its larger aircraft (eg, C-9, C-17) to move 24. Pediatric Casualties 333

Figure 24.2. USAF doctors and AE crew members monitor a baby being supported with an ECMO machine aboard a C-9A Nightingale (USAF photo by Captain John Sheets). infants on the ECMO. Because of the com- rated, even if one or more family member plexity of the equipment and treatment, spe- accompanies the patient as a nonmedical atten- cialized “ECMO teams” are required for all dant. Separation of a child from loved ones or such transports. parents from their normal support network may adversely affect the psychological health of both the child and family. Transportation Risks The Harsh Aeromedical Environment Transportation of neonatal and pediatric patients, either by ground or air, represents a The simple act of patient movement can put the real risk for many reasons. In one study, inter- patient at increased risk of displacing airways facility transport of premature neonates was or intravascular lines. Movement, plus the associated with a slightly increased risk of vibration associate with ﬂight, can further advanced intraventricular hemorrhage.12 In all loosen dressings and disrupt healing wounds. cases, the risks of transport must be weighed The noise in most AE environments exceeds against the patient’s need for advanced care the recommended levels for children and com- and the ability of the referring medical facility pletely precludes the use of auscultation by to provide this care. Simultaneously, the added medical personnel.13 The variation in lighting risk of air transport must be measured in light often diminishes visual assessment skills as of the availability, duration, and utility of well. ground transport. Thermal Stress Psychological One of the most important aspects of neonatal When patients are moved between medical AE is the maintenance of an optimal thermal treatment facilities, families are usually sepa- environment. Cold or heat stress signiﬁcantly 334 R.J. Wells, H.S. Heiman, and W.W. Hurd

Figure 24.3. Same infant in Figure 24.2 being center aboard a C-17 Globemaster III (USAF photo transported on the second leg of her journey from an by Captain John Sheets). overseas hospital to a stateside USAF medical increases both the caloric and oxygen needs Effects of Altitude of an already compromised infant. Unlike the adult, the neonate is severely limited in his or In contrast to rotary-wing aircraft, which fly at her capabilities to compensate. Heat loss can relatively low altitudes, pressurized fixed-wing occur through evaporation, radiation, convec- aircraft usually fly with a cabin altitude equiv- tion, or conduction. Both radiation and evapo- alent to approximately 8000ft. The more fragile ration are responsible for significant heat loss physiology of an ill infant or child is especially because of the neonate’s large body surface sensitive to the three-fold problems associated area. Evaporative heat loss that results from with altitude, which include gas expansion, the administration of dry medical gases con- decreased oxygen concentration, and decreased tributes to the thermal imbalance. air humidity. The effects of these problems are The exposure to thermal stress is not well tol- discussed in depth in Chapter 9. erated by pediatric patients even when specific Isolation from Comprehensive measures (eg, incubators) are used to counter- Medical Care act this stress. Although the purpose of an incubator is to maintain a stable environment in The time the patient spends between medical terms of temperature and humidity, each time treatment facilities during long-distance AE the incubator is opened this advantage is lost can range from a few hours to 10 or more hours. until the system re-equilibrates. The time is determined not only by flying time Continuous temperature monitoring of the but also the two ground transport legs from neonate and of his or her environment is the referring hospital to the aircraft and from crucial. Monitoring the infant’s axillary tem- the aircraft to the special-care unit/hospital. perature alone does not assure that the thermal Weather and mechanical difficulties with the environment is appropriate. A table of age and aircraft or ground transport vehicle may in- weight should be used to determine the proper crease the time further. neutral thermal air temperature, which is in the This time away from comprehensive medical range of 32 to 36°C. care presents multiple problems. Probably the 24. Pediatric Casualties 335 most significant problem occurs when the For neonatal transportation, by far the most patient’s condition worsens. Adjustments in common indication was respiratory insuffi- care are severely limited because of limited ciency, related primarily to respiratory distress supplies and equipment and the lack of both of the newborn and meconium aspiration syn- diagnostic imaging and all but the most rudi- drome. Gastrointestinal (GI) conditions (eg, mentary laboratory tests. esophageal atresia) were the second most com- Another significant problem related to isola- mon, followed by congenital cardiac anomalies tion is equipment failure. Most AE equipment and infections, such as sepsis. is powered by batteries or self-contained pres- Conditions requiring pediatric transport were surized gas. Prolonged transportation times, more varied. The most common were respira- especially if unexpected, may exceed the tory conditions, such as severe asthma and reserve of the equipment power source. Even croup. The next most common conditions on relatively short flights, equipment failure can were various types of traumas most commonly adversely affect patient status because repair- related to motor vehicle accidents,serious infec- ing or replacing equipment en route may not be tions such as meningitis and pneumonia, and feasible. neurological conditions most commonly with seizure activity. Conditions Requiring Transport for Tertiary Care Specific Pediatric Conditions

The scope and nature of pediatric transport is Asthma wide ranging. However, some of the most Asthma (ie, reactive airway disease) affects common problems encountered can be ascer- more than 4.8 million children under the age of tained by examining the types of patients who 18, and of these more than 150,000 are hospi- required emergency transport to a large, ter- talized each year.14 Including adults with this tiary-care pediatric medical center. From July 1, condition, there are more than 5000 deaths 1999, through June 30, 2000, almost 800 children from asthma annually.15 From these statistics were transported to the Children’s Hospital the implications for the AE system are obvious. Medical Center at the University of Cincinnati, including 462 neonatal and 334 pediatric trans- Implications for AE ports.13 A series of 100 consecutive patients from this group is presented in Table 24.2. Children with severe asthma are at risk during AE for acute exacerbations, probably because of the dry cabin air and the other stresses Table 24.2. Conditions requiring transport to related to flight. An acute asthma attack is the Children’s Hospital Medical Center in 100 con- characterized clinically by increased wheezing, secutive patients. respiratory rate, and inspiratory–expiratory Neonatal ratio and the increased use of accessory 16 Respiratory insufficiency 21 muscles. Pulse oximetry will reveal decreased GI problems 16 oxygen saturation, which can be <70% on room Cardiac anomalies 8 air in severe cases. Spirometry, when available, Infection 6 will reveal a peak expiratory flow rate of 35% Pediatric Respiratory conditions 12 to 75% of predicted values. Trauma 9 Serious infections 9 Treatment of Acute Asthma Neurological conditions 8 Cardiac disease 5 The initial approach to an acute exacerbation GI conditions 4 of asthma in children is administration of the Diabetes 1 beta-2 agonist terbutaline. This can be given Other 1 either by nebulization (0.5mL of a 1-mg/mL 336 R.J. Wells, H.S. Heiman, and W.W. Hurd respiratory solution in 2mL of 0.9% saline) nor auscultation can be used to confirm tube or by one puff of a 0.5-mg/dose terbutaline placement. In addition, anesthesia support dur- turbohaler. ing transport is in general not available and If symptoms do not resolve, the patient vibration and vehicle movement complicate the should receive either prednisolone tablets mechanics of any procedure attempted. 2mg/kg (maximum dose, 60mg) or a single dose An artificial airway will be required in almost of budesonide turbohaler 1600mg (four puffs 70% of children and more than 20% of adults of budesonide, 400mg/puff). For those who with acute epiglottitis.17 Those who present with responded well, steroids should be continued severe respiratory distress or actual airway while en route in the AE system, with either obstruction will require oropharyngeal intuba- prednisolone tablets four times daily (2mg/kg tion or surgical intervention (eg, cricothyro- per day) or budesonide turbohaler 200mg. tomy) as part of the initial treatment.A partially Long-term therapy will be determined by the open airway can be converted to complete receiving physician, but may include a mainte- airway obstruction with injudicious maneuvers nance course of corticosteroids for several (eg, foreign bodies, stable epiglottitis). weeks. An artificial airway should be established prior to AE for any patient who has significant Acute Epiglottitis and interference of airway function, most com- Upper-Airway Obstruction monly manifested by respiratory discomfort present even in the upright position, stridor, Acute epiglottitis is a potentially fatal cause of or drooling, Patients at high risk of airway airway obstruction in both young children and obstruction are those whose symptoms are of adults. In recent years, there has been a marked short duration (<24 hours) or rapidly progress- decline in the number of pediatric cases, most ing, those with significant enlargement of the likely due to the introduction of efficacious epiglottis, and children under 5 years of age. vaccines against H. influenzae type b. These factors may be suggestive of an influenza infection. Clinical Presentation If a patient meeting this criteria does not have an artificial airway established prior to The most common symptoms for children are AE, they must be closely observed during flight difficulty breathing, stridor, fever, and sore and monitored by pulse oximetry. Adminis- throat. In contrast, the most common symp- tration of humidified oxygen (2L/minute by toms in adults are sore throat, difficulty swal- nasal prongs) is advisable. If acute respiratory lowing, and difficulty breathing.17 obstruction occurs during flight, facemask ventilation might be attempted prior to intubation. Implications for AE However, a two-handed facemask seal must be Children with acute epiglottitis but without res- made and high enough oxygen flow and pres- piratory difficulty, stridor, or drooling and who sures used to overcome the resistance of the have only mild swelling upon laryngoscopy can severely narrowed airway. Adequate ventila- often be managed without an artificial airway. tion should be determined by adequate chest

The parents should be encouraged to keep wall movement and O2 saturation of >90% by the child calm during flight. Sedation that may pulse oximetry. Placement of an endotracheal weaken muscle tone or depress respiratory tube is often extremely difficult. If intubation effort should be avoided. Preparations for in- is not possible and equipment for surgical flight establishment of an emergency airway cricothyrotomy is not available, a needle (emergency intubation or cricothyroidotomy) cricothyroidotomy may be lifesaving. are mandatory. In “borderline” situations with regard to intubation of patients to be trans- Seizure Disorders ported,“semielective” intubation prior to transport may be preferred to emergent intubation A generalized tonic–clonic (grand mal) seizure during transport, where neither radiographs during flight is a disturbing and potentially 24. Pediatric Casualties 337 serious occurrence. Any seizure that lasts >10 three major physiological derangement; dimin- minutes becomes a life-threatening emergency ished cardiac output, poor vascular tone, or low and should be treated aggressively. Status blood volume. In combination or individually, epilepticus refers to an epileptic seizure lasting these derangements result in poor delivery >30 minutes or when there is not full recovery of nutrients and oxygen to end-organ systems of consciousness between seizures. and the poor removal of the waste products of Seizure etiologies include febrile convulsions metabolism. If allowed to persist, a downward (a cause rarely found in adults), acute central cycle of hypoglycemia, hypoxia, acidosis, and nervous system (CNS) injury (eg, trauma, infec- hypercarbia can cause serious morbidity or tion, mass/vascular lesion, metabolic disorder, mortality. Systolic blood pressure should be or anticonvulsant withdrawal/noncompliance), maintained at normal levels. If there is no chronic CNS injury (eg, previous trauma, evidence of shock, intravenous (IV) isotonic stroke, infection, encephalopathy), and intoxi- fluids should be given at minimal flow rates cant induced (eg, cocaine, tricyclic antidepres- (2 to 3ml/kg per hour). sants). Many seizures are idiopathic. Maintain Normal Glucose Treatment of Seizures Hypoglycemia is a rare cause of prolonged sei- In the convulsing patient, initial supportive, zures in children. However, all patients should therapeutic, and diagnostic measures need to have prompt measurement of blood glucose. be conducted simultaneously.18 The goal of anti- If hypoglycemia (blood glucose <40mg/dL) convulsant treatment is the rapid termination is documented or if it is impossible to obtain of clinical and electrical seizure activity by the the measurement, IV glucose (5mL/kg) should prompt administration of appropriate drugs in be administered as 10% glucose. adequate doses. Attention must be given to the possibility of complicating apnea, hypoventila- Administer Antiseizure Medications tion, and other metabolic abnormalities. The efficacy of diazepam for the treatment of status epilepticus is well recognized, with Assure Adequate Oxygenation termination of episodes in 80% of cases. Hypoxemia can be both the cause and conse- Diazepam, administered either intravenously quence of a seizure. In severe episodes, hypox- 0.2mg/kg) or rectally (0.2 to 0.5mg/kg), can sig- emia can lead to bradycardia and hypotension. nificantly shorten the duration of status epilepticus and reduce the likelihood of recurrent Initial treatment is airway maintenance by 19 proper positioning of the head and neck and seizures. Although IV diazepam may be more suctioning of the mouth and oropharynx. readily available, the possibility of respiratory An oral airway should be inserted if this can depression must be considered and adequate be done without trauma to the mouth and support for breathing must be assured. teeth. Oxygen should be administered by nasal If available, rectal diazepam should be used cannula or ventilation with a bag–valve–mask instead because respiratory depression from apparatus. In prolonged seizures, endotracheal rectal diazepam is rare among children. This is intubation should be considered. However, probably related to the slower rise in serum diazepam concentrations compared with that administering an anticonvulsant is a top prior- 19 ity because managing the airway and assisting achieved after IV administration. The clinical respiration are much easier after the convulsion effect from rectal diazepam occurs in approxi- has stopped. mately 5 minutes and peak serum concentrations are achieved 6 to 10 minutes after administration. Even with rectal diazepam, Maintain Normal Blood Pressure patients with serious comorbidity, those on Hypotension can exacerbate any already regular anticonvulsants, or those with chronic existing malfunction of cerebral physiology CNS abnormalities are at increased risk of and function. Hypotension can result from respiratory depression and thus should be 338 R.J. Wells, H.S. Heiman, and W.W. Hurd treated with a lower rectal dose of diazepam dose and route of administration. Some author- (0.25mg/kg). ities advise using 0.5cc to start, then giving the other 0.5cc about 20 minutes later if needed. Diabetes Mellitus Diabetic Ketoacidosis Diabetes mellitus is one of the most common chronic diseases diagnosed among pediatric Diabetic ketoacidosis (DKA) is the most com- populations. The two most significant problems mon cause of hospitalization of children with 22 associated with diabetes are hypoglycemia and diabetes and has a fatality rate of 1% to 2%. diabetic ketoacidosis, both of which are poten- DKA is preceded by hyperglycemia second- tially severe problems during AE. ary to insulin deficiency. The resulting decrease in glucose uptake induces hyperketonemia. Both the hyperglycemia and hyperketonemia Hypoglycemia cause an osmotic diuresis that manifests clini- All possible measures should be taken to cally as dehydration and increased thirst. The avert severe hypoglycemia in diabetic children. dehydration is often worsened by hyperventi- These may include regular monitoring of blood lation and vomiting that can be either a part of glucose, decreasing insulin dosages, altering in- the primary precipitating illness or resulting sulin regimens for patients with prior severe from the ketosis. Eventually, the hyperosmolal- hypoglycemia, or administering slowly released ity associated with untreated DKA can progress carbohydrate (eg, uncooked cornstarch).20 to coma and even death as a result of intra- Mild to moderate hypoglycemia (blood glu- cerebral crises. cose <100mg/dL) is treated with oral glucose- Diabetic children should be evaluated for containing solutions followed by complex ketonuria if they have either persistent hyper- carbohydrate. Self-treatment is usually in the glycemia (blood glucose >240mg/dL) or a ser- form of 4oz of juice or soft drink followed by ious intercurrent illness. The primary goals of a cookie or candy. Blood glucose testing should treatment are to restore perfusion to reverse be repeated within 30 minutes to ensure resolu- the progressive acidosis and stop ketogenesis tion of hypoglycemia. by normalizing blood glucose concentration Severe hypoglycemia cannot be identified with insulin therapy.22 by a fixed blood glucose value but rather by For fluid therapy with DKA, it is safe to noticing a hypoglycemic child who requires assume dehydration of approximately 10% assistance with treatment or who loses con- for children (100mL/kg) and 15% for infants sciousness.21 When the child is unable to take (150mL/kg). Based on this, initial fluid therapy oral glucose-containing solutions, treatment (0.9% NaCl) should be given as 5 to 10mL/kg consists of IV glucose (2cc/kg of a 10% glucose over the first hour or less to restore peripheral solution bolus followed by IV maintenance perfusion. If peripheral perfusion or blood with 10% glucose solution) or glucagon (see pressure is not restored with the initial 10-cc/kg below). Both of these solutions should be avail- bolus, further bolus doses should be given able when moving insulin-dependent diabetics until this result is achieved. Maintenance fluid in the AE system. (0.45% NaCl) can be calculated using a stan- The Glucagon Emergency Kit (Eli Lilly and dard formula (eg, 1000mL for the first 10kg + Co, Indianapolis, Ind) contains a vial of pow- 500mL for the next 10kg + 20mL/kg for over dered glucagon (1mg) together with a syringe 20kg) and administered over the subsequent 22 prefilled with 1mL of diluting solution. After to 23 hourse.22 Bicarbonate is rarely indicated. reconstitution, children <20kg are given 0.5cc Insulin therapy can be started simultaneously by subcutaneous (SC), intramuscular (IM), or with initial fluid expansion or can be held until IV injection. Larger children and adults are the fluid expansion is completed for a more given 1cc. The time of onset of action varies realistic starting glucose level. Ideally, insulin from 1 to 10 minutes and the duration of effect is administered at 0.1U/kg per hour by contin- ranges from 9 to 32 minutes, depending on the uous-infusion pump. If a pump is unavailable, 24. Pediatric Casualties 339 an alternative is to administer insulin 0.1U/kg be required, and these conditions are so IV push and 0.1U/kg IM with subsequent doses common that flying with an undiagnosed otitis of 0.1U/kg IM or SC hourly. media may be unavoidable. Common strate- During initial fluid expansion, elevated gies to prevent or alleviate this condition in- blood glucose levels can be expected to drop 10 clude chewing, yawning, and swallowing during to 15mmol/L, even without insulin infusion. ascent and especially during descent. Some Following this, insulin doses should be titrated physicians advocate the administration of oral to result in a drop of blood glucose levels of or nasal decongestants and/or antihistamines 3 to 8mmol/L per hour but not >12mmol/L prior to take-off because this approach has per hour. If the blood glucose level falls to been found to be effective in adults.24 For 15mmol/L or >12mmol/L per hour, 5% to children, administration of oral pseudoephe- 10% dextrose should be added to the IV fluids. drine hydrochloride (1mg/kg, using a 6-mg/mL If the blood glucose level falls below 8mmol/L syrup) 30 to 60 minutes prior to departure may with 10% dextrose solution running, the insulin have some benefit in decreasing the incidence dose should be reduced to 0.05U/kg per hour. of aerotitis media. The insulin dose should not be reduced below 0.05U/kg per hour because a continuous supply of insulin is needed to prevent ketosis and Sickle Cell Disease permit continued anabolism. Sickle cell disease is an inherited blood disor- Patient monitoring in a hospital setting is der that affects about 90,000 Americans, mostly extensive and includes monitoring of elec- African-Americans.25 It leaves patients vulner- trolytes and indicators of kidney function, able to repeated crises that can cause severe 22 together with assessing hydration status. pain, multisystem organ damage, and early Given the limitations of AE, monitoring during death. Although the life expectancy of patients flight should be recorded at 30-minute intervals with the most severe form of the disease is into and include vital signs, Glasgow Coma Scale the mid-40s, many patients become sympto- score (see chapter 14), blood glucose, and urine matic as children and almost 15% die before ketones. In addition, fluid intake and output the age of 20.26 and insulin administration should be carefully Sickle cell disease includes several disease recorded. states with a varying percentage of sickle cell hemoglobin (HbS), ranging from sickle cell trait (25% to 45% HbS) to sickle cell anemia Other Pediatric Conditions with (100% HbS). Intermediate conditions (in AE Implications order of increasing severity) include sickle cell hemoglobin C (SC) disease, sickle cell b+ Otitis Media and Ear Block thalassaemia, and sickle cell b0 thalassaemia. Intravascular sickling is induced by hypoxia, The failure to equilibrate tympanic cavity and but the degree of sickling depends on the com- atmospheric pressures, usually during descent bination of the concentration of HbS and the of an aircraft, can result in aerotitis media (ie, degree and duration of hypoxia. “aviation otitis”). This acute and potentially chronic inflammation of the middle ear is the Sickle Cell Pain Crises result of Eustachian tube obstruction and is especially prone to occur in the presence of an Sickle cell pain crises are acute painful episodes upper respiratory tract infection or otitis media. that typically last for 5 to 7 days but may last Preschool-aged children appear to be in partic- for only minutes or persist for weeks. These ular susceptible to ear pain during both ascent crises are usually triggered by a physiological and descent phases of air travel.23 stress, such as acute infection, dehydration, Certainly, avoiding air travel with acute extremely hot or cold temperatures, or hypoxia. upper respiratory tract infection or otitis media The result is deoxygenated HbS, which forms is ideal. However, air travel may sometimes rod-like polymers that change the normally 340 R.J. Wells, H.S. Heiman, and W.W. Hurd round and pliable red blood cells into stiff, treatment is primarily supportive. The patient sickle-shaped cells. These deformed cells cause should be placed on supplemental oxygen to vaso-occlusion, which results in a cycle of local- minimize altitude-related hypoxemia. IV hy- ized tissue hypoxia leading to further sickling dration with a balanced salt solution will help and additional vaso-occlusion. The end result reverse any degree of dehydration, especially in may be tissue infarction and necrosis. patients experiencing vomiting or known to The pain of a sickle cell crisis can be localized have kidney impairment. or diffuse, constant or intermittent. About half Pain control is an important aspect of early of all patients will also have fever, swel- treatment. Severe pain should be treated with ling in the joints of the hands or feet, long- nonsteroidal anti-inflammatory drugs and IV bone pain, tachypnea, hypertension, nausea, morphine or hydromorphone. Meperidine can and vomiting. In the severest forms, organ in- be used short term but should not be continued farction will manifest. Spleen infarction, usually for long periods of time because its metabolite resulting in severe abdominal pain, has been normeperidine can cause seizures. Pain medi- reported in patients with previously asympto- cations should be titrated aggressively to matic sickle cell trait during unpressurized ensure pain relief. flight.27 Rib and/or lung infarction results in an The patient must be monitored carefully for acute chest syndrome consisting of chest pain, signs of oversedation, and naloxone should dyspnea, fever, and leukocytosis. Other severe be readily available in the event of respiratory manifestations include stroke, pulmonary fat depression. Other common narcotic side effects embolism, and seizures.26 include constipation, urinary retention, pruri- tus, nausea, and vomiting. Diphenhydramine Implications for AE can be given for itching and prochlorperazine or other antiemetics may be required to reduce Many of the stresses associated with AE (eg, nausea. dehydration, extremely hot or cold tempera- Once the acute crisis subsides, oral narcotics tures, and hypoxia) are known to be triggers for (eg, acetaminophen with codeine or hydro- sickle cell crises. For this reason, special efforts codone) may be used. It is usually a matter of should be made to maintain a comfortable days until patients are switched to nonnarcotic cabin temperature with the liberal use of blan- oral analgesics. kets when needed. In addition, all patients with Lowering the percentage of HbS in the sickle cell disease should be well hydrated, patient to the 30% to <50% range can prevent either by frequent drinking or IV fluids. further sickling but will not necessarily elimi- The need for oxygen during flight remains nate symptoms related to sickling that has controversial. Hypoxia associated with incre- already occurred. When pain related to sickle ased altitude is known to increase the incidence cell crisis is prolonged despite the use of the of sickle cell crises.27 Nevertheless, sickle cell supportive measures mentioned above, trans- crises during air travel in pressurized aircraft fusions are commonly given. If patients with are extremely uncommon.28 In general, patients sickle cell disease and frequent sickle cell crises with sickle cell disease can fly on commercial must be transported, transfusion of packed airline flights without supplemental oxygen. red blood cells prior to AE is a reasonable However, if a patient is being transported by precaution. AE because of a complication associated with their sickle cell disease (ie, pain crisis, stroke, etc), it seems prudent to give supplemental Neonatal Transport oxygen during flight because of the certain health risks associated with crises. The transition from fetus to neonate involves a miraculous combination of physiological Treatment of Sickle Cell Pain Crises processes. One of the most challenging is estab- If a patient is transported during a sickle lishing independence from the respiratory, cir- cell pain crisis or a crisis occurs in-flight, the culatory, and homeostatic functions performed 24. Pediatric Casualties 341 by the placenta. As a result, many perturbations maturity and related conditions. A need for can occur in the transition to extrauterine transport is based on the attending physicians’ life. analysis of the availability of local institution The following section will discuss the timing and staff resources to care for this patient. and special preparations necessary for successful neonatal AE. This will be followed with a discussion of the more common neonatal Preparation for AE problems that require transportation and their Careful preparation is necessary prior to implications for AE. neonatal AE to minimize the risk of this often hazardous undertaking. A checklist of this Timing for AE somewhat complex process is included below (Table 24.3). Neonatal transportation is usually carried out on an emergency basis (ie, urgent AE) or performed after the first 12 hours of life (ie, elective AE). The key factor to consider when Table 24.3. Premature neonate AE checklist. deciding between urgent and elective AE is Baseline vital signs the ability of the neonate to effectively breath Vascular access independently. A delay for up to 12 hours for Umbilical artery and vein logistic consideration is safe if the neonate is Peripheral veins Adhesive reinforcement stable and breathing without difficulty with the Skin protection administration of 21% to 40% oxygen therapy, Thermal management as documented by physical examination, radi- Incubator prewarmed ographic imaging, monitors, and blood studies. Ambient air In these cases, the timing of transport is based Plastic wrap Chemical blanket on a thorough analysis of the capabilities of the Incubator cover institution and support staff as determined by Preflight imaging the patient’s referring physician. ET tube placement confirmed Another consideration is the gestational Central line placement confirmed age and weight of the neonate at the time of Chest X-ray interpreted Chest tube care delivery. In addition to neonates with severe Heimlich valve respiratory distress syndrome (or other related Suction available conditions), extremely low-birthweight infants Preflight laboratory (<28 weeks’ gestation, <1000g) should be Arterial blood gas transported as soon as preflight respiratory and Complete blood count Anemia therapy when indicated circulatory assessments indicate the neonate Antibiotic therapy when indicated is relatively stable. The parents must consent to Blood glucose normal, dextrose infusion started transfer with a clear understanding of the risks Full monitoring applied with gel electrocardiogram leads of transport and their child’s prognosis. Orogastric tube Very low-birthweight infants (28 to 31 weeks’ Sedation adequate Urethral catheter considered gestation, 1000 to 1500g) often have a milder Patient securing straps applied forms of respiratory distress syndrome and Check lines, cables, hoses, and tubing for security and the associated complications of prematurity, connections especially if they have received antenatal Hearing protection steroids. They may safely wait for transport for Parental considerations Time given for bonding 12 hours or more depending on their degree of Consent signed for transport and procedures illness. Crew alert Low-birthweight infants (32 to 36 weeks’ Prewarmed cabin gestation, 1500 to 2500g) usually have a milder Altitude limitations pattern of disease and will on occasion need Nonmedical attendant Bring copies of all images and infant’s chart transport to a higher level of care for pre- 342 R.J. Wells, H.S. Heiman, and W.W. Hurd

Data Collection Prior to AE where stability cannot be achieved, it must be clear that the benefits of advanced diagnostics The collection of pediatric data is similar to and therapeutics at the receiving hospital adult data with a few exceptions. For neonatal outweigh the risks of continued resuscitation transport, the mother’s history of pregnancy, during flight. If intratracheal surfactant has labor, and delivery becomes important. The been given, the neonate should be observed neonates’ weight, Apgar scores, and gestational carefully for the first 2 hours for signs of age are additional items. The use of a stan- improving lung function (eg, improved chest dardized data collection form for pediatric and expansion, improved oxygen saturation) and neonatology patients is recommended. consideration given to decreasing ventilator pressures prior to AE. Narcotic and sedative Vascular Access therapy (eg, morphine and midazolam) should Vascular access with an umbilical venous be used at doses low enough to avoid respira- catheter and umbilical arterial catheter is desir- tory suppression in an effort to promote able. An additional peripheral venous catheter comfort, control pain, and minimize swings in will create more therapeutic flexibility and can blood pressure. be used to monitor blood pressure, draw blood If ventilator dependent, an altitude restric- samples, and administer fluids and medications. tion should be required to maintain a cabin Because heat, vibration, and acceleration– altitude <2000ft or the altitude of the referring deceleration forces of flight often dislodge or accepting facility if higher. The neonate adhesives, crews must be ready to reinforce or should be stabilized on the ventilator that is replace the adhesive on all tubes and lines if going to be used for transport as far ahead of they appear unstable. transport as possible. The ventilator should be connected to hospital medical gases so that Thermal Management the ventilator tank gas can be preserved for transport. An artificial nose should be placed Closely controlled thermal management will in-line to maximize airway humidification and minimize the potentially severe problems help prevent thick secretions. The endotracheal associated with hypothermia. The ambient air (ET) tube should be suctioned with saline should be kept 24°C or greater in both the immediately before flight, and during a long ground ambulances and aircraft. The incubator flight repeat suction will be required. Even a temperature should be set at 36°C. A chemical minor pneumothorax should be treated with a warming blanket and thermal cover to the chest tube connected to a Heimlich valve prior incubator may help maintain temperature in to AE because trapped pleural air expands at transport, especially in large aircraft cabins, altitude. such as the C-141. Plastic wrap blankets will A set of arterial blood gases and serum minimize evaporative heat loss. chemistries should be reevaluated as close to the time of transport as feasible, both to help Pulmonary Function make ventilator adjustments and guide fluid Neonates that have minimal respiratory dis- therapy. Ideally, arterial blood gases on the tress syndrome may not require ventilator current ventilator settings should reveal pH support. Apnea (central or obstructive) in these 7.25, PaCO2 40 to 50mmHg, and PaO2 60 to infants is a key physical finding. In addition, 90mmHg (exception: pulmonary hypertension; it may be difficult to intubate a small infant see below). The base deficit should be 5 or during flight. If there is any doubt as to their better. respiratory reserve, the neonate should be intubated and placed on a ventilator prior to Psychosocial Considerations transport with the plan to wean from ventilator support at the receiving institution. Every effort should be made to establish a In most cases, respiratory function should warm and cordial professional relationship be stable prior to AE. In the rare situation with the referring staff and family. The parents, 24. Pediatric Casualties 343 especially the mother, will have bonded to the Table 24.4. Conditions and complications com- fetus and will often be anxious about the health monly encountered in extremely premature and challenges to their child. Every effort should be extremely low-birthweight neonates. made to safely bring the mother to the baby Difficult vascular access prior to transport. Ideally, one or both parents Hypothermia should be transported as nonmedical atten- Respiratory distress syndrome dants and the family unit transported back to Air leak syndrome Apnea the referring hospital as soon as the need for Intraventricular hemorrhage special care has been eliminated. Hypoxia Hypercarbia Final Preparation for AE Respiratory and metabolic acidosis Patent DA Immediately prior to AE, several details must Shock (distributive or cardiogenic) be accomplished. Upon examining the neonate Disseminated intravascular coagulation Bacterial or viral infection for the last time in the referring facility, a trans- Hypoglycemia port flow sheet should be started. Full electronic Hyponatremia monitoring should be instituted (temperature, Hypocalcemia blood pressure, heart rate, respiratory rate, Hyperkalemia and oxygen saturation) using gel leads to main- Immature renal and gastrointestinal function Limited skin integrity tain skin integrity. An orogastric (OG) tube Absence of parental bonding should be placed and secured to minimize the effect of swallowed intestinal air on diaphragmatic movement. The OG tube should remain open to allow for gas expansion at altitude. One problem unique to the premature infant A chest X-ray should confirm all of the follow- is extremely fragile skin. Above all, the skin ing; an OG tube tip in the stomach, ET tube must be handled gently. To minimize denuded placement in middle third of the trachea, 8 to skin and the associated infectious risks, clear 9 rib lung inflation, absence of air-leak syn- occlusive dressings should be used on the skin dromes, a normal cardiac silhouette, and appro- before applying adhesive tape or temperature priate locations of umbilical central lines. probe covers. Earplugs or muffs should be placed on the neonate (and any nonmedical and medical IV Fluid Management attendants) to protect hearing. To limit motion Maintenance fluids (80 to 100mL/kg per day) during transport, the neonate must be secured are usually given in the form of D5W for infants adequately with straps with the ET tube clearly weighting <1000g and D10W for those weighing visible. >1000g. The adequacy of fluid replacement can be judged by following the heart rate Specific Conditions (target range 120 to 160bpm), mean blood pressure (target range 25 to 35cm H O), and Prematurity 2 urine output (target range >1mL/kg per hour). Extreme prematurity (less than 28 weeks) When necessary, infusion rates can be care- and the associated extremely low birthweight fully increased or pressor therapy begun (eg, (<1000g) creates one of the greatest challenges dopamine drip at 4 to 15mg/kg per minute or found in AE, as these neonates often have mul- dobutamine drip at 5 to 15mg/kg per minute). tiple conditions that make their care extremely A urethral catheter is rarely necessary because complex (Table 24.4). The skills and knowledge posttransport diaper weights are sufficient to required for neonatal AE overlap those of measure urine output. other pediatric patients described earlier. Less Metabolic acidosis is common in premature extreme degrees of prematurity usually have infants. Judicious use of normal saline venous fewer and less severe forms of these related boluses (10mL/kg, repeated up to two to three conditions. times) may correct mild acidosis or flush acid 344 R.J. Wells, H.S. Heiman, and W.W. Hurd out of the tissues in severe acidotic states. A 5% At birth, the sudden discontinuation of the plasmanate or albumin bolus can be substituted nutrient and other supplies from the mother in the presence of hypoalbuminemia. If the requires the neonate to mobilize glucose and pH is below 7.20, sodium bicarbonate can be fatty acids from glycogen and triglyceride carefully given by slow IV bolus (4.2%, 2 to depots to meet the energy demands. Unfortu- 4mL/kg). nately, infants born prematurely or following Intraventricular hemorrhage may be caused intrauterine stress (eg, malnutrition, maternal by large fluctuations in arterial blood pressure. diabetes, endogenous fetal hyperinsulinism) For this reason, flushing fluid through the may be unable to mount an appropriate and umbilical arterial catheter at more than 1mL/ adequate counterregulatory metabolic and minute must be avoided. Therapeutic interven- endocrine response and thus develop abnor- tions (eg, line placement and tracheal suction- mally low plasma glucose concentrations for a ing) may initiate or exacerbate intraventricular prolonged period. hemorrhage by temporarily increasing blood Clinical manifestations of hypoglycemia pressure, and thus preprocedure sedations include tremor, sweating, lethargy, floppiness, should be considered. coma, and seizures. In some cases, hypoglycemia is asymptomatic. However, it remains Disseminated Intravascular Coagulation uncertain as to whether asymptomatic hypoglycemia actually causes brain damage. Disseminated intravascular coagulation (DIC) Routine measurements of blood glucose is suggested in a premature neonate by a concentration should be continued during AE < 3 platelet count 150,000/mm , a decreasing trend for any infant known to be at risk for hypo- in platelet count, or persistent bleeding from glycemia. Glucose monitoring can be initiated any skin laceration or venous puncture site. If as soon as possible after birth, within 2 to 3 the diagnosis of DIC is made, the neonate hours after birth and before feeding, or at any should be treated with fresh frozen plasma or time there are abnormal signs. If the plas- platelet transfusion prior to transport, espe- ma glucose concentration remains <36mg/dL cially with an accelerated drop or an absolute (2.0mmol/L) or if abnormal clinical signs < 3 platelet count 50,000/mm . develop, IV glucose infusion is administered to raise the plasma glucose levels to >45mg/dL Infection (2.5mmol/L). Bacterial infection is a common cause of prematurity. Ampicillin and gentamicin treatment Respiratory Distress is often begun after blood cultures are taken. Cerebrospinal fluid culture is considered when Increased work breathing and elevated oxygen the patient is physiologically stable. Acyclovir requirements often result from two conditions: treatment for herpes simplex virus can be prematurity and meconium aspiration syn- started based on history or suspicious physical drome. Premature infants have a relative sur- exam. factant deficiency that often results in diffuse atelectasis and respiratory insufficiency termed respiratory distress syndrome. The frequency Hypoglycemia and severity of this disorder has been decreased Hypoglycemia is one of the most common by the use of prenatal steroids and postnatal metabolic problems in premature infants. When installation of surfactant. However, the delivery low blood glucose levels are prolonged or and resuscitation of ever smaller premature recurrent, they may result in acute systemic infants makes respiratory distress syndrome effects and neurological sequelae. For this the most common reason for admission to the reason, the management of low blood glucose neonatal ICU. Similar symptoms of respiratory in the first postnatal days takes on some distress can occur as a result of congenital importance.29 sepsis, pneumonia, or pulmonary hemorrhage. 24. Pediatric Casualties 345

Aspiration of meconium prior to and at the abdomen, severe respiratory distress, shift of time of birth, termed meconium aspiration the heart sounds to the right, and diminished or syndrome, continues to be a common event in absent breath sounds on the left. Bowel sounds both full-term and postterm infants despite may be heard on the left. The result is often a the widespread application of aggressive lethal combination of pulmonary hypoplasia suctioning of the upper airway at the time of and persistent pulmonary hypertension. delivery. This syndrome is associated with focal If positive pressure ventilation is required, areas of atelectasis, air trapping, and persistent the infant should be intubated as soon as pulmonary hypertension of the newborn with possible because mask ventilation results in air right to left shunting through the foramen ovale entering the stomach and intestines, further or ductus arteriosus (DA). compressing already compromised lungs, especially without a gastric tube. These infants Implications for AE are at high risk of developing pneumothoraces following resuscitative efforts. Neonates with respiratory compromise are especially susceptible to the effects of alti- Implications for AE tude related hypoxia. In all cases, an altitude restriction is required to maximum cabin alti- An altitude restriction is required to maximum tudes <2000ft. Prior to transport, a ventilator- cabin altitudes <2000ft. It is essential that the dependent infant should be assessed for gastrointestinal tract remains decompressed anemia and transfused if necessary with packed and any pneumothorax is treated prior to AE. red blood cells to maintain the hematocrit The impact of altitude-related expansion of gas above 35%. in the thorax and intestine can be lessened by A pulse oximeter to measure oxygen satura- maintenance of patency and suction of the chest tion and/or a portable laboratory device to and/or gastric tubes connected to Heimlich measure blood gases should be used to assure valves. Frequent (every 15 minutes) intermit- that the patient is well oxygenated and ade- tent suction should be used to remove gastric air. quately ventilated. Endotracheal tube suction These patients often require ventilator should be done on a scheduled basis during therapy for the pulmonary hypoplasia and pul- transport to clear increased tracheal secretions monary hypertension. Surfactant therapy may associated with meconium aspiration syn- help inflate the stiff hypoplastic lungs, although drome. It is especially important to maximize one half the usual dose per kilogram should humidity in the airway through the use of an be considered because of the diminished lung artificial nose on the endotracheal tube. volume of hypoplastic lungs. Treatment for The transport team must be prepared to pulmonary hypertension is discussed below. identify and manage in-flight hypoxemia or Urgent AE is required for these patients when pneumothorax. If a pneumothorax is suspected, they present with severe respiratory distress it should be treated with needle decompression in the newborn period. Advanced pediatric and chest tube placement (betadine, 23-gauge surgical skills, inhaled nitric oxide therapy, butterfly needle, 3-way stopcock, 20-mL and ECMO are often required to treat dia- syringe, sterile gloves, scalpel, hemostat, and a phragmatic hernia. Fortunately, many neonates chest tube). afflicted with diaphragmatic hernia are being identified by antenatal ultrasound. In such cases, the maternal–fetal unit is often transported to a Diaphragmatic Hernia tertiary-care center for delivery. This congenital defect occurs in 1 of 2200 live births. A diaphragmatic hernia allows abdomi- Intestinal Obstruction nal organs to enter the thorax, thus severely affecting lung growth and development. The Intestinal obstruction can present soon after key physical exam findings include a scaphoid birth. Some obstructions can lead to severe 346 R.J. Wells, H.S. Heiman, and W.W. Hurd morbidity and death while others can be Significant heat and fluid can be lost from the stabilized and transported electively. Proximal exposed gut by evaporation. Infection can be intestinal obstructions often present antena- prevented with the use of sterile surgical-grade tally with polyhydramnios. In such cases, the gauze, sterile bowel bags, and broad-spectrum mother will often be transferred antenatally to antibiotic administration. a tertiary-care facility to allow advanced care of The circulation to the intestine should be her newborn immediately following birth. assessed in a sterile manner. The intestine Intestinal obstruction from a volvulus or con- should be pink with good capillary refill when genital obstruction may present in the neonatal blanched. Twisting of the superior mesenteric period with bilious vomiting. An X-ray of the artery or cicatrix of the surrounding abdominal abdomen may reveal a double-bubble sign, skin may compromise the circulation to the which suggests duodenal obstruction from an intestine. A compromised intestine may appear atresia or annular pancreas. Intestinal obstruc- dark purple because of venous congestion. If tion that presents after birth may result in the tight skin opening is causing ischemia, the marked abdominal distension, which will in local surgeon or transport team, in consultation turn elevate the diaphragm and compromise with a pediatric surgeon, may need to widen the respiratory function. opening before transport. Volvulus of the intestines can result in complete occlusion of the superior mesenteric Implications for AE artery. Because occlusion of this vessel can result in the necrosis of all bowel from the distal These infants require urgent AE, and the duodenum to transverse colon, volvulus can stabilization and treatment during transport lead to a severe form of short-bowel syndrome is similar for both conditions. Altitude effects with disastrous consequences. If volvulus is upon gas volumes may compromise circulation diagnosed, emergency laparotomy is indicated. to trapped segments. Prior to AE, an OG tube should be placed and open air with intermittent Implications for AE suction utilized to minimize the accumulation of intraluminal air. In the presence of suspected malrotation and/ These patients require strict attention to both or signs of volvulus with ischemic bowel, urgent temperature control and cardiovascular sup- AE is indicated because advanced diagnostic port. They should be transported in an incuba- studies are mandatory. Operative repair and/or tor that is kept at 36°C. The vehicle cabin should postoperative care will then be utilized as be kept as close as possible to 24°C (80°F). required. In the presence of respiratory com- An umbilical vessel catheter and one or two promise, gastric decompression and elective peripheral IV lines should be established for intubation prior to AE should be considered. If transport. IV maintenance fluids should be there is a distal obstruction without signs of given at 150mL/kg per day and the infant mon- bowel ischemia or respiratory compromise, the itored for skin perfusion and metabolic acido- infant can be placed on maintenance IV fluids, sis. If capillary refill is longer than 2 seconds, or OG decompression achieved, and transport if arterial blood gases indicate metabolic aci- accomplished electively. dosis, 10-mL/kg boluses of crystalloid solutions should be given and the maintenance fluids Omphalocele and Gastroschisis increased. To prevent torsion of the bowel blood supply, Omphalocele and gastroschisis can be life- the infant should be placed on one side and the threatening if not recognized, stabilized, and bowel supported with a donut-shaped roll of treated promptly. Associated defects, includ- blankets or towels. Using warm, sterile saline ing chromosomal disorders and heart disease, maintains good moisture to the sterile surgical occur more commonly with omphalocele. This gauze covering the mass. Intestinal perfusion abdominal wall defect results in exposure of should be repeatedly reassessed and the find- the GI tract to the exterior of the patient. ings documented with each set of vital signs. 24. Pediatric Casualties 347

Cyanotic Congenital Heart Disease defect. Commonly, prostaglandin therapy and SpO values in the 80s are adequate. Cyanotic congenital heart disease (CHD) rep- 2 resents a group of conditions characterized by an alteration in blood flow such that well-oxy- Implications for AE genated systemic circulation is contaminated Neonates with suspected cyanotic CHD should with deoxygenated blood. This commonly be transported by urgent AE. These patients occurs in one of three ways: require an altitude restriction to maximum cabin altitudes <2000ft or the altitude of the 1. Obstruction of blood flow to the pul- referring or accepting facility if higher. Oxy- monary circulation (eg, Fallot’s tetralogy genation that has been maximized at sea level and pulmonary or tricuspid atresia). In these will often deteriorate at altitude. In-flight deter- conditions, oxygen saturation of the blood in mination of arterial blood gases with portable both the systemic and pulmonary circulations is laboratory equipment is useful for ensuring identical. adequate acid–base balance in the presence 2. Return of the deoxygenated systemic of lower oxygenation. Close observation for blood back to the systemic circulation without apnea is warranted for any infant receiving going through the lungs, resulting in severe PGE1. If there is any concern of this, the trans- oxygen desaturation (ie, transposition of the port team will often intubate the patient prior great vessels). Although this condition allows to transport. some increase in oxygen saturation of the blood going out to the body,this type of CHD presents with the most severe cyanosis. Hypoplastic Left Heart Syndrome 3. Inability of pulmonary venous blood Hypoplastic left heart syndrome (HLHS) is return to the left atrium due to anomalous the most common cause of death from CHD return of all pulmonary veins to a systemic during the first month of life and accounts for venous structure such as the superior vena cava 9% of all newborn congenital heart defects. It (ie, total anomalous pulmonary venous return). accounts for more than one third of pediatric As is the case in 1, the oxygen saturation of cardiology cases transported by some critical- blood in both the systemic and pulmonary care transport teams.30 circulations will be identical. HLHS is characterized by underdevelop- ment of the left side of the heart in conjunction Cyanotic CHD should be suspected when- with mitral and aortic valve stenosis and nar- ever a neonate remains cyanotic in the absence rowing of the ascending aorta. For HLHS to be of respiratory distress. A neonate with a PaO2 compatible with life, both a right to left shunt <200mmHg while receiving 100% inspired and a left to right shunt must be present. These oxygen most likely has cyanotic CHD. are usually in the form of ventricular or atrial Acute nonsurgical therapy for most forms of septal defects, persistently patent foramen cyanotic CHD is dependent upon maintenance ovale, and DA. of patency of the DA and control of pulmonary Although newborns with HLHS often ap- blood flow. Prostaglandin E1 (PGE1) is used pear normal at birth, they usually display vague to maintain ductal patency. Side effects of and nonspecific signs and symptoms, including prostaglandin therapy include apnea, hypoven- increased respiratory effort and cyanosis when tilation, and hyperthermia. crying. If the foramen ovale or atrial septal Proper ventilation technique to control the defects restrict the delivery of oxygenated partial pressure of oxygen and carbon dioxide blood to the right atrium, the infant will appear and ensure optimal acid–base balance is criti- cyanotic at birth. cal. Management of the patient during trans- The abrupt closing of the DA is a medical port should be discussed in advance with the emergency for neonates who depend on it for cardiologist or cardiovascular team to deter- blood flow to either the body (right to left mine the best care plan for each specific cardiac shunting) or the lungs (left to right shunting). 348 R.J. Wells, H.S. Heiman, and W.W. Hurd

When the DA closes, cessation of blood flow to tion at the tissue level that often results from the body results in cyanosis, hypoxemia, and transport noise and vibration. Correct place- profound shock. Congestive heart failure and ment of all intravascular lines and tubes should metabolic acidosis occurs rapidly, with ensuing be confirmed radiographicaly, then firmly multiple-organ failure. This condition can be secured with suture and taped. Arterial blood reversed only by quickly reopening the DA. gas levels should be determined immediately Management centers on careful control of before transport for comparison if the neonate blood oxygen (PaO2), carbon dioxide (PaCO2), should become hemodynamically unstable en and pH. Ideally, the oxygen saturation should route. Oral or tube feedings should be stopped remain 60% to 80% and the blood slightly aci- to prevent aspiration during transport, and dotic (pH 7.34 to 7.40). HLHS neonates should blood glucose levels should be monitored. remain on room air because increased oxygen dilates the pulmonary bed, thus increasing blood flood to the lungs and decreasing blood Conclusion flow to the body. These infants should not be hyperventilated Effective and safe AE of pediatric and neona- because accumulation of CO2 and acidosis con- tal patients depends on early recognition of strict pulmonary blood vessels, thus increasing serious conditions and stabilization by the blood flow to the body. Alternatively, high referring facility and transport team before and ventilator rates and large tidal volumes lower during transport. The referring physician and

PaCO2, resulting in alkalosis, dilated pulmonary flight crew should be knowledgeable about the beds, and increased blood flow to the lungs. An risks of aeromedical transport specific to the ideal PaCO2 range is 40 to 50mmHg, titrated to patient’s condition and able to anticipate maintain adequate systemic perfusion. potential transport challenges. Infants with HLHS are routinely treated with PGE1 (0.02 to 0.05mg/kg per minute by IV infusion) to keep the DA patent, reduce pulmonary References blood flow, and enhance systemic blood flow 1. Bose CL. Neonatal transport. In: Avery GB, and coronary perfusion. PGE1 is titrated to the Fletcher MA, McDonald NG, eds. Neonatology, lowest effective dose to minimize side effects, Pathophysiology and Management of the New- including apnea, jitteriness, hypoglycemia, born. 5th ed. Philadelphia: Lippencott, Williams hyperthermia, and cutaneous vasodilatation. & Wilkins; 1999:35–47. 2. Shepard KS. Air transportation of high risk infants utilizing a flying intensive care nursery. Implications for AE J Pediatr 1970;77:148–149. 3. Pettett G, Merenstein GB, Battaglia FC, Although these neonates do better with rela- Butterfield LJ, Efird R. An analysis of air trans- tively low O2 saturations, an altitude restriction port results in the sick newborn infant: Part I. of <2000ft (or the altitude of the referring or The transport team. Pediatrics 1975;55:774–782. accepting facility, if higher) will greatly simplify 4. American Academy of Pediatrics Section on the in-flight management of HLHS. Otherwise, Transport Medicine. Guidelines for Air and the most important aspects of air transport Ground Transport of Neonatal and Pediatric are the standard general principals of neonatal Patients. 2nd ed. Elk Grove Village, Ill: care, including maintenance of normothermia American Academy of Pediatrics; 2000. and prevention of hypoglycemia.30 The neonate 5. McClosky KA, Orr R. Transportation of criti- should have IV access before transport and an cally ill children. In: Ropers MC, ed. Textbook of Pediatric Intensive Care. 3rd ed. Baltimore: OG or NG tube for stomach decompression. William & Wilkins; 1996:77–95. Elective intubation before AE should be con- 6. Freedman SH, King BR. Aeromedical transport sidered if the infant appears to be at risk for procedures. In: Henretig EM, King C, eds. airway compromise or for apnea related to Textbook of Pediatric Emergency Procedures. PGE1 infusion. Neuromuscular blockade with Baltimore: Williams & Wilkins; 1997:1407– sedation helps minimize the oxygen consump- 1416. 24. Pediatric Casualties 349

7. Woodward GA, King BR. Transport medicine. 19. Alldredge BK, Wall DB, Ferriero DM. Effect of In: Fleischer GR, Ludwig S, eds. Textbook prehospital treatment on the outcome of status of Pediatric Emergency Medicine. 4th ed., epilepticus in children. Pediatr Neurol 1995; Philadelphia: Lippincott, Williams & Wilkins; 12:213–216. 2000:103– 128. 20. Kaufman FR, Halvorson M, Kaufman ND. 8. Seidal JS, Knapp JF. Pediatric emergencies in Evaluation of a snack bar containing uncooked the office, hospital and community: Organizing cornstarch in subjects with diabetes. Diabetes systems of care. Pediatrics 2000;106:337–338. Res Clin Pract 1997;35:27–33. 9. Air Force Medical Equipment Laboratory. 21. Clarke WL, Gonder-Frederick L, Cox DJ. The https://afml.ft-detrick.af.mil//afmlo/afmedl/ frequency of severe hypoglycaemia in child- afmedl.htm. ren with insulin-dependent diabetes mellitus. 10. United States Army Aeromedical Research Hormone Res 1996;45:48–52. Laboratory. http://www.usaarl.army.mil. 22. Rosenbloom AL, Hanas R. Diabetic keto- 11. Bartlett RH, Roloff DW,Custer JR,Younger JG, acidosis (DKA): Treatment guidelines. Clin Hirschl RB. Extracorporeal life support: The Pediatr 1996;35:261–266. University of Michigan experience. JAMA 2000; 23. Buchanan BJ, Hoagland J, Fischer PR. Pseu- 283:904–908. doephedrine and air travel-associated ear pain in 12. Gleissner M, Jorch G, Avenarius S. Risk factors children. Arch Pediatr Adolesc Med 1999; for intraventricular hemorrhage in a birth cohort 153:466–468. of 3721 premature infants. J Perinat Med 2000; 24. Csortan E, Jones J, Haan M, Brown M. Efficacy 28:104–110. of pseudoephedrine for the prevention of baro- 13. Shenai JP. Sound levels for neonates in transit. trauma during air travel. Ann Emerg Med J Pediatr 1977;90:811–812. 1994;23:1324–1327. 14. United States Centers for Disease Control and 25. Food and Drug Administration, US Department Prevention. Vital and Health Statistics. National of Health and Human Services, Public Health Hospital Discharge Survey: Annual Summary, Service. Approves Droxia for sickle cell anemia. 1993. Washington, DC: US Government Printing Rockville, MD: FDA; 1998. Office; 1995. DHHS Publication PHS 95-1782. 26. Platt OS, Brambilla DJ, Platt OS, Brambilla DJ, 15. Centers for Disease Control and National Rosse WF, Milner PF, Castro O, Steinberg MH, Center for Health Statistics. National Vital Klug PP. Mortality in sickle cell disease: Life Statistics Report. vol 47(4). Washington, DC: expectancy and risk factors for early death. N US Government Printing Office; 1997. Engl J Med 1994;330:1639–1644. 16. Volovitz B, Bentur L, Finkelstein Y, Mansour Y, 27. Green RL, Huntsman RG, Sergeant GR. Shalitin S, Nussinovitch M, Varsano I. Effective- Sickle-cell and altitude. Br Med J 1972;1: ness and safety of inhaled corticosteroids in 803–804. controlling acute asthma attacks in children who 28. Ware M, Tyghter D, Staniforth S, Serjeant G. were treated in the emergency department: Airline travel in sickle-cell disease. Lancet A controlled comparative study with oral 1998;352(9128):652. prednisolone. J Allergy Clin Immunol 1998;102: 29. Cornblath M, Hawdon JM, Williams AF, 605–609. Aynsley-Green A, Ward-Platt MP, Schwartz R, 17. Mayo-Smith MF, Spinale JW, Donskey CJ, Kalhan SC. Controversies regarding definition Yukawa M, Li RH, Schiffman FJ. Acute epiglot- of neonatal hypoglycemia: Suggested opera- titis. An 18-year experience in Rhode Island. tional thresholds. Pediatrics 2000;105:1141– Chest 1995;108:1640–1647. 1145. 18. Tasker RC. Emergency treatment of acute 30. Haselhuhn MR. Go blue: When blue is better seizures and status epilepticus. Arch Dis Child for the neonate with hypoplastic left heart 1998;79:78–83. syndrome. J Emerg Nurs 1999;25:392–396. 25 Aeromedical Evacuation of Psychiatric Casualties

Elspeth Cameron Ritchie

Military operations generate a significant num- not have the medical personnel or facilities to ber of psychiatric casualties, most commonly in evaluate and treat problematic service mem- the form of combat stress, adjustment disorders, bers locally. However, with psychiatric patients and on occasion more severe psychiatric casu- the doctrine is to treat in-place if at all possible. alties. While most psychiatric patients can be The branches of the US military vary in the treated at the locations where their disease mental health resources that they station over- begins, some will require aeromedical evacua- seas or deploy in the field. The USA places tion (AE) out of the theater of military opera- mental health personnel far forward in a Divi- tions. Military medicine and the associated sion Mental Health or Combat Stress Control AE system thus have a significant amount of unit.1 The USN and USAF have fewer assets experience with psychiatric patients. Although on-ship or in the field so most symptomatic the military approach is, by necessity, different sailors, marines, and airmen will require AE for than the civilian approach, much that has been appropriate evaluation. learned is applicable to both situations. From a military perspective, one of the most By tradition, military members suffering important concepts covered in this chapter will from combat stress have been treated as close be criteria for determining who can be best “to the front” and unit of assignment as possi- treated locally and who should be evacuated ble. As many as 95% of these patients can be out of the theater. More universally applicable returned to duty after appropriate treatment topics covered include classification and pre- with basic combat stress control principles, paration of the psychiatric patient for AE, the including rest, reassurance, command involve- use of attendants, medications, and restraints ment, and stabilizing medications. Only those during the flight, and special considerations for few patients with more severe symptoms, such AE of children and adolescents. as strong suicidal ideations, mania, or psychosis, absolutely require immediate AE out of the theater. The Decision to Evacuate In modern military operations, the trend has been away from the traditional “treat and Most patients presenting to a military mental return to duty” approach toward an “evacuate health clinic will suffer from loneliness, inabil- and replace” approach for two reasons. Perhaps ity to fit into their unit, worry about family the most important reason is the fast pace of matters or marital infidelity, or legal charges. most modern deployments, where few fixed Adjustment disorders or occupational problems medical facilities are available and retention may manifest as suicide threats or attempts. of a symptomatic psychiatric patient in-theater Finally, some military members are referred represents too much of a liability. A second for a psychiatric clearance prior to disciplinary reason is that many duty stations and ships do action or administrative separation.

350 25. Aeromedical Evacuation of Psychiatric Casualties 351

How these complaints are handled depends patient should be treated in close proximity to on the situation (Fig 25.1). During a large-scale the unit. The treatment should be immediate. war, members with mild psychiatric symptoms They should expect to quickly return to duty. and complaints are rarely evacuated as this Finally, the treatment for most service mem- could lead to an epidemic. Similarly, when bers should be simple, consisting primarily of service members are stationed abroad in a counseling, rest, and reassurance, ie, “three hot tedious deployment situation great caution meals and a cot.” A “B” and “C” can be added must be used before deciding to evacuate a to transform the mnemonic to BICEPS for soldier. Many soldiers on remote assignments Brevity (the treatment should be brief) and have to be reminded that, “If the military evac- Centrality (the treatment principles should be uated everybody who was worried about their centralized). family, there would be no one left here.” While If a patient still needs evacuation after initial this approach may seem callous from a civilian treatment according to the above principles, the perspective, it has been found to be both effec- patient will usually be transported by ground tive and necessary in light of the unique cir- vehicle to the next treatment echelon that cumstances and responsibilities associated with has a mental health facility, a small hospital, military service. or a Combat Stress Control restoration unit. The principles of combat psychiatry are The distance they are evacuated is purposely well described.2,3 Treatment of mild psychiatric limited both so that they will be able to be symptoms, including combat stress, may be returned to duty in an expeditious manner and summed up in the mnemonic PIES: Proximity, so that they retain contact with fellow soldiers Immediacy, Expectancy, and Simplicity. The and their warﬁghting chain of command. Their

Figure 25.1. Flow chart for treatment and evacuation of psychiatric patients in the military. 352 E.C. Ritchie continued status as a military member and a ships have no procedures to administratively member of the unit increases their chance for separate sailors. rapid recovery. Psychiatric Medications Indications for AE of Military Members Medications Prior To and During AE Medical Indications Psychiatric patients with significant symptoms Not all psychiatric patients can be treated should be treated medically for a long enough locally and therefore will be in need of AE. period that their symptoms are controlled prior The most common medical indication for ur- to AE. This is especially true for patients who gent AE of a psychiatric patient would be the are actively psychotic, manic, or seriously suici- sequela of a serious suicide attempt. Other dal because it is potentially dangerous to put patients may require AE for purely psychiatric these patients on a long flight. Most psychiatric symptoms, including persistent severe depres- symptoms, such as agitation, psychosis, and sion (especially with suicidal ideation), mania, mania, will be adequately controlled after 3 to or overt psychosis. Even patients with less 5 days of treatment. Depressive symptoms may severe psychiatric symptoms may have to be last much longer but are less of a management evacuated if their unit has no mental health problem aboard an aircraft. resources, as often happens aboard a ship or at Once a patient’s symptoms have decreased a small base. An attendant should accompany enough to make AE safe, they should receive a certain psychiatric patients, and most will 7-day supply of medications for the flight, plus require sedation, as described below. extra medications for agitation of sedation in case they are needed. The following is a discus- Military Administrative Indications sion of some of the most commonly used psychiatric medications used prior to and during Military members with psychiatric conditions AE (Table 25.1). may be separated from the military for either medical or administrative indications. When the Agitation member has a major psychiatric illness, they will usually be transported to a military medical In general, the type of medicine the patient re- center for thorough evaluation and determina- quires will depend on the diagnosis. However, tion of disposition. If they are stationed over- a complete diagnostic work-up may not be seas, or a long distance from such a facility, AE possible prior to flight. All severely agitated is usually the transportation of choice. patients will need to be sedated prior to Administrative separations are used for mil- AE regardless of their diagnoses. The most itary members determined to have personality common medications used for sedation are disorders rather than a major mental illness. the benzodiazapines because of their speed of The mechanisms used for this type of separa- onset and relative lack of side effects. More tion from the military are different depending specific antipsychotic, antimanic, and antide- on the branch of service. When members are pressant medications are used after the patient administratively separated from the USA or has been more completely evaluated. USAF, the unit of assignment must complete The most commonly used benzodiazapines the necessary paperwork. If the member is sta- are diazepam (Valium), lorazepam (Ativan), tioned overseas, it is usually better for them to and clonazepam (Klonopin). Standard doses separate from the military directly from the and time of administration vary depending on unit and then return to the United States on a the agent used (Table 25.1). However, doses sig- commercial airline.4,5 This is in contrast to the nificantly higher than standard may be required USN, where members stationed on a ship are to calm an agitated patient prior to flight. transported by AE to a US military medical One should begin with the standard dose and facility for administrative separations because repeat in 1 hour if necessary. Benzodiazapines 25. Aeromedical Evacuation of Psychiatric Casualties 353

Table 25.1. Common psychiatric medications, doses, and side effects. Medications Typical dose (mg) Route Interval Side effect

Sedation Diazepam 5–10 PO Every 4–12h Sedation, respiratory depression (rare) Lorazepam 1–2 PO, IM, IV Every 1–4h As above Clonazepam 0.5–1 PO Every 8–12h As above Antipsychotic Haloperidol 5 PO, IM, IV Every 4–6h Extrapyramidal symptoms, akathesia, 1 as needed dystonias Olanzapine 5–20 PO At bedtime Sedation, extrapyramidal symptoms (mild) Risperidone 2–6 PO At bedtime Extrapyramidal symptoms Anticholinergic Benztropine 1–2 PO, IM, IV 1–4h as Dry mouth, constipation needed Diphenhydramine 25–50 PO, IM, IV 1–4h as As above needed Mood stabilizer Lithium 300–600 PO 2–3/d Polyuria, polydipsia, toxic at high doses Valproic acid 500–750 PO 2/d Sedation Carbamazepine 200–400 PO 2/d Ataxia, decreased white blood cell count Antidepressant Fluoxetine 20–40 PO Once daily Sedation, nausea Sertaline 50–200 PO Once daily As above Paroxetine 20–40 PO At bedtime As above Bupropion and 100–300 PO 2–3/d bupropion SR 1–2/d Nortriptyline 75–150 PO At bedtime Sedation, dry mouth, constipation Amitriptyline 75–300 PO At bedtime As above Doxepin 100–300 PO At bedtime As above

may be then repeated every 4 to 6 hours, if or risperidone) have a significantly decreased necessary, but the patient needs to be closely risk of dystonias. However, these patients monitored. should still be provided with an anticholinergic agent to use, if needed, during an AE flight. Manic and Psychotic Patients The antipsychotic chlorpromazine (Thorazine) should be avoided because of the high inci- Manic and psychotic patients should be stabi- dence of anticholinergic symptoms. lized for 3 to 5 days on antipsychotic agents Of the anticholinergic agents, benztropine is before the flight if at all possible. Some calming more commonly used because it is less sedating effect of these agents is usually evident within than diphenhydramine. The side effects of both, 1 or 2 hours, but the antipsychotic properties especially at high doses, include dry mouth, do not begin to take effect for 24 to 76 hours. constipation, inability to regulate heat, and It should be kept in mind that most antipsy- confusion. All these medications may be given chotic agents work synergistically with the by the oral (PO), intramuscular (IM), or intra- benzodiazapines. venous (IV) route. One of the most commonly used antipsychotic agents is still haloperidol (Haldol). Bipolar Mood Disorders Because this drug is associated with a high incidence of extrapyramidal symptoms (EPSs) Patients with bipolar (ie, manic–depressive) and dystonias, all patients on haloperidol mood disorders are most commonly treated should simultaneously be given an anticholi- with lithium, carbamazepine (Tegretol), or val- nergic agent such as benztropine (Cogentin) proic acid (Depakote), although the latter two or diphenhydramine (Benadryl). Some of the have not been approved for this purpose by the newer antipsychotic agents (eg, olanzapine FDA. These medications will normally have to 354 E.C. Ritchie be administered for 3 to 7 days before they will Table 25.2. Medical management of the violent or achieve a therapeutic effect. Because of their agitated patient. potential toxicity, all three must be monitored Haloperidol 5mg Oral, IM, IV by following blood levels. Lithium has an espe- Diphenhydramine 50mg As above cially narrow therapeutic window, with a thera- Lorazepam 2mg As above peutic range between 0.6 and 1.2mmol/L and > All three may be repeated in 30min if the patient is not yet toxicity 1.5mmol/L. If a patient has been sedated. started on any of these drugs immediately prior to AE, they should be used only in the lowest effective dose because blood levels will be dif- often readily available and have a relatively fast ficult or impossible to obtain while in-transit. onset of action and relatively broad safety margin. The combination of haloperidol, di- Depression phenhydramine, and lorazepam may also be mixed in the same syringe. The most commonly prescribed antidepressant If the patient agrees, these medications medications are the selective serotonic reup- should be given by mouth. If they are uncoop- date inhibitors (SSRIs), both because of their erative, they may need to be restrained and the relative effectiveness and because of the mini- medications given by shot. It is not wise to mal risk of side effects. SSRIs in common use attempt to restrain an agitated person without include sertraline (Zoloft), paroxetine (Paxil), sufficient help—at least five people need to and fluoxetine (Prozac). Bupropion (Wellbutrin form the restraint team, one for each limb and or Zyban) is also extensively used. The major one for the head. Indications for IM medica- drawback of all antidepressants is the 1- to 2- tions include severe disruption and danger to week delay between the start of administration self, others, or property (see Table 25.2). and onset of therapeutic effects. Tricyclic agents are an older class of antidepressants less commonly prescribed because of anticholinergic side effects and the danger of overdose. They Preparation for AE include nortriptyline (Pamelor), amitriptyline The first step in the AE of a psychiatric patient (Elavil), and doxepin (Sinequan). is communication and coordination between Acute Management of the Violent or the referring physician and the accepting physician in a hospital facility. The referring physi- Agitated Patient cian should prepare a detailed AE summary, On occasion, an apparently stable psychiatric or which includes the history of present illness nonpsychiatric patient may become acutely agi- and reason for continued psychiatric treatment. tated and possibly violent during AE. These Often, the patient’s mental status when they patients can be a risk to the crew, other patients present to the receiving facility is vastly differ- on-board, and the patients themselves. Several ent from when they initially sought treatment. medications, both oral and parenteral, are In many cases, this is related to the therapeutic useful to treat these patients acutely even if effects of any psychotropic drugs they may be they are on other psychotropic medications taking. (Table 25.2). The ideal psychotropic for use Military members and their dependents in such a situation should have a quick calm- may be treated at any military medical facility. ing effect with minimal risk of oversedation. However, medical and personnel records are An oversedated patient can have potentially usually best managed by the same branch of the life-threatening respiratory depression or de- military in which the patient serves. Patients pression of the normal gag reflexes. The most returning from overseas should bring with commonly used drugs for acute patient seda- them any important personnel documents and tion include haloperidol (Haldol), diphenhy- belongings, as it is unlikely that they will return dramine (Benadryl), and lorazepam (Ativan). to their unit. Active-duty members should bring These drugs have been chosen because they are their uniforms as well because most military 25. Aeromedical Evacuation of Psychiatric Casualties 355 hospitals require that psychiatric patients wear transported by litter in restraints and require them. an attendant. If changes in their condition Both active-duty personnel and dependents warrant, their restraints can be cautiously loos- should be encourage to sign a voluntary admis- ened or removed during flight, but they must sion form for the destination medical facility remain under close observation with restraints before the AE flight. This will avoid the less immediately available8,9 (see also the section than ideal situation in which a patient is trans- below on restraints). ported great distances by AE only to immedi- The most common category of psychiatric ately sign out against medical advice. If a patients transported by AE are of intermediate dependent declines to sign a voluntary admis- severity (1B). These patients need some super- sion form, it may be best to delay AE. If vision but do not need to be flown in restraints. an active-duty member disagrees with the They can fly in a seated position if they desire plan for AE and voluntary admission, an invo- but must have both a litter and restraints avail- luntary admission can be ordered. This will able. An attendant will accompany them in require a command memorandum that details almost all cases, but the ultimate decision as to the need for continued psychiatric evaluation the need for an attendant is left to the judge- and/or treatment. The guidelines for command- ment of the referring physician and flight directed mental health evaluations are covered surgeon clearing the patient for AE. All poten- in Mental Health Evaluations of Members tially dangerous objects, including sharp items of the Armed Forces (DODD 6490.1) and and lighters, will be removed from psychiatric Requirements for Mental Health Evaluations patients classified as 1A and 1B according to of Members of the Armed Forces (DODI USAF regulations.9 6490.4).6,7 Attendants are an essential part of the AE care for 1A and 1B psychiatric patients, especially if they are dangerous to themselves or AE Classification and others (ie, suicidal, threatening, manic, or psychotic). If possible, the attendant should be of Attendants for the same sex as the patient to allow close mon- Psychiatric Patients itoring of bathing and sleeping habits. This is especially critical if they have a history Psychiatric patients entering the AE system of sexual assault. If an adult family member are by tradition classified into three categories is available, and their relationship with the based on their special needs and potential to patient is healthy, they can accompany the cause problems en route (Table 25.3). Patients patient (either active-duty or dependent) as a with severe psychiatric conditions (1A) are nonmedical attendant. However, this does not

Table 25.3 AE classiﬁcation of psychiatric patients. Aeromedical Mode of Sedating classiﬁcation Description transport medication Restraint Attendant

1A Severe; dangerous Litter Yes Yes Yes 1B Intermediate; severity: Potentially Litter (may Recommended Must be Optional dangerous, but not at present fly seated) available disturbed 1C Moderately severe: Cooperative and Ambulatory Recommended No No reliable under observation 3C Patient with drug or alcohol abuse Ambulatory No No No going for treatment 5B Patient with drug or alcohol abuse Ambulatory No No No going for treatment 5C Outpatient psychiatric patient Ambulatory Optional No No going for treatment 356 E.C. Ritchie negate the need for a medical attendant for all except that they may sit by an exit door or 1A and most 1B patients. oxygen shut-off value. A potential problem for the attendant occurs when the entire AE process takes several days and involves long stopovers, as is common Restraints when patients are transported from overseas back to the United States. To avoid an exces- Only those patients who are a danger to them- sive workload on the attendant, the referring selves or others and cannot be controlled med- physician or clearing flight surgeon should ically are transported in restraints (Fig 25.2). write orders that direct the patient to be ad- The restraints most commonly used for AE are mitted to a local psychiatric hospital when a still the traditional four-point leather restraints. stopover is expected to last for more than 24 They include two leather wrist cuffs and two hours. larger ankle cuffs secured to the bed or litter The potential risks associated with moving by belts. There is also an optional waist belt. 1A and 1B patients by AE should not be under- Because these restraints must be locked, the estimated, even in the presence of an attendant. crew should verify prior to flight that they While few patients become disruptive on an air- have the correct key to unlock the restraints craft, an uncontrolled psychiatric patient during in the event of an emergency. Hospitals ac- flight could have a disastrous effect. If the refer- credited by Joint Commision on Accreditation ring physician is uncertain about how stable the of Health Care Organizations (JCAHO) are patient will remain during AE, it is best to keep now required to use Velcro nonlocking cuffs. the patient at the referring facility until he or These do not require a key and are more she is no longer a threat. Patients should be sent comfortable for the patient. in restraints only when absolutely necessary. The written orders for the use of restraints Stable psychiatric patients with moderately during AE must be detailed, specific, and severe conditions (1C) are allowed to fly in written by the referring physician prior to uniform with no attendant. However, the aero- flight.9 The orders must specify the justification medical crew must be prepared to deal with any for placement, the date and time restraint will patient who becomes disruptive during flight, be used, the type of restraint, and the positions including medical and surgical patients. In ad- on the extremities. The orders should also dition, no psychiatric patient (1A, 1B, or 1C) is outline other less restrictive means to control allowed to sit by an exit door or an oxygen shut- the patient, such as medication and family off value.9 involvement. By regulation, the use of restrains Recently, three other categories of psychi- must be time limited and cannot exceed 24 atric patients have been added to the classifica- hours. Within those 24 hours, the restraints tion system. Ambulatory patients going for cannot be used for more than 4 hours for adults, drug, alcohol, or substance abuse treatment are 2 hours for adolescents and children over age classified as 3C if they are in-patients and 5B if 9, or 1 hour for children under age 9. In prac- they are outpatients. USAF regulation requires tice, restraints are rarely used in young children that these patients must have undergone three for transoceanic flights. to five days of detoxification prior to the flight.9 Restraint orders can authorize a flight nurse Other psychiatric outpatients going for treat- to continue restraints for an additional 24 hours ment or evaluation are in classified as 5C. at his or her discretion. However, even if However, sending a psychiatric patient as an no restraint orders have been given, the com- outpatient requires careful coordination with manding officer of the aeromedical crew may the receiving facility. Arrangements must be initiate the use of leather restraints in an emer- made prior to departure regarding where the gency. If the commander is a flight nurse, as in patient will stay and how the temporary room most cases, a physician must be contacted for and board will be funded. Patients in all three verbal authorization within 1 hour.9 of these classifications (3C, 5B, or 5C) are The use of restraints have certain risks to the treated the same as 1C patients during the flight patient. Most will be medicated. Some sedation 25. Aeromedical Evacuation of Psychiatric Casualties 357

Figure 25.2. Four-point restraints (A) are required only for patients who are a danger to themselves or others. Velcro nonlocking cuffs (B) do not require a key and are more comfortable for patients. 358 E.C. Ritchie

(eg, a benzodiazapine) is recommended to min- antipsychotic medications are administered, imize the associated discomfort and humilia- coadministration of an anticholinergic agent is tion. In any case, the patient will need to be recommended. In all cases, adequate medica- carefully monitored by a dedicated attendant tion for sedation should be available for use for signs of oversedation, resulting in hypo- during the flight. An attendant should accom- ventilation or aspiration, or for evidence of pany patients who are seriously depressed or circulatory problems related to the restraints suicidal or have persistent manic or psychotic themselves. Hydration and elimination needs symptoms. Restraints should be used only when must also be meet. This intensive monitoring absolutely necessary and be closely monitored should be documented on a flow sheet at 15- when used. minute intervals. References Children and Adolescents 1. US Department of the Army. Combat Stress Control in a Theater of Operations. Washington, Young children and adolescents are less com- DC: US Government Printing Office; 1994. FM monly transported by AE for psychiatric indi- 8-51. cations than are adults. If AE is required, a 2. Jones FD, Sparacino LR, Wilcox VL, Rothberg JM, Stokes JW. War psychiatry. In: Zajtchuk R, family member should accompany children Bellamy RF, eds. Textbook of Military Medicine. when possible. Fortunately, young children are Washington, DC: US Department of the Army, less likely to become disruptive during flight. Office of the Surgeon General, and Borden For this reason, consideration should be given Institute; 1995:1–33. to moving children on faster and more com- 3. Artiss KL. Human behavior under stress: From fortable commercial airlines rather than on mil- combat to social psychiatry. Milit Med 1963; itary AE aircraft. 128:1011–1015. Adolescents have a greater risk of becoming 4. US Department of the Army. Standards of disruptive during AE or running away (termed Medical Fitness. Washington, DC: US Govern- “elopement”). If elopement is at all likely, the ment Printing Office; 1987. AR 40-501. military AE system may be preferable to com- 5. US Department of the Army. Enlisted Personnel. Washington, DC: US Government Printing mercial airlines. Essentially the same medica- Office; 1996. AR 635-200. tion and restraint protocols as for adults can be 6. Department of Defense. Requirements of Mental utilized if required. Informed consent should be Health Evaluations of Members of the Armed obtained from the parents prior to the flight. Forces. Washington, DC: US Government Print- ing Office; 1997. Directive 6490.1. 7. Department of Defense. Requirements of Mental Conclusion Health Evaluations of Members of the Armed Forces. Washington, DC: US Government Print- The psychiatric patient presents many unique ing Office; 1997. Instruction 6490.4. problems for AE. When possible, the patient 8. Department of the Air Force. Aeromedical Evac- uation Worldwide Aeromedical Evacuation. should be treated medically for 3 to 7 days Washington, DC: US Government Printing so psychotic or manic symptoms can be ade- Office; 1975. AFR 164-5. quately controlled before flight. If urgent AE 9. Deparment of the Air Force. Aeromedical Evac- of the acutely disturbed psychiatric patient is uation Patient Considerations and Standards of required, appropriate amounts of medication Care. Washington, DC: US Government Printing are needed for safe transportation. If traditional Office; 1997. AFI 41-307. Index

A strengths, 97–98 Abdominal pain, postpartum patient, 304 weaknesses, 98 Abdominal trauma, 173–178 C-17 Globemaster, 101–103 colorectal injuries, 176–177 configurations, 103 damage control surgery, 174 general characteristics, 101–102 hepatic injury, 178 strengths, 102 historical perspective, 173–174 weaknesses, 102 hollow-organ injuries, 174–175 C-21 Lear Jet, 103–106 pancreatic injury, 178 configuration, 105–106 solid-organ injuries, 177–178 general characteristics, 105 spleen, 177–178 strengths, 105 surgical approach, 174 weaknesses, 105 upper gastrointestinal injuries, 175–176 C-130 Hercules, 92–95 duodenal injuries, 175 configurations, 94–95 gastric injuries, 175 general characteristics, 92–93 small-bowel injuries, 176 strengths, 93 Acceleration forces, 69, 121–122 weaknesses, 94 Acoustic neuroma, 212 C-141 Starlifter, 98–101 Acute respiratory failure, 257–258, 320 configurations, 101 basic life support, 258 general characteristics, 100 emergency treatment of, 257–258 strengths, 100–101 Aeromedical evacuation, medical evacuation, weaknesses, 101 distinguished, 3 cabin lighting, 91 Aerosols, microbial, 150–151 cabin noise levels, 91 Air cabin space, 91 equipment containing, gas expansion and, characteristics of, 91 117 civilian airframes, 108–109 filtration, cabin, 149–150 Challenger 601–3R, 108 intracranial, 116 climate control, 91–92 intrathoracic, 116 commercial airline seats, 110 Aircraft, 88–110 distance, 89–90 Boeing 767, 106–107 electrical requirements, 91 configurations, 106 en route stops, 89 general characteristics, 106 entry doors, 91 strengths, 106 feeding station, 90 weaknesses, 106 helicopters, 15 C-9A Nightingale, 95–98 landing limitations, 90 configurations, 98 lavatory, 90 general characteristics, 97 medical care, at en route stop, 90

359 360 Index

Aircraft (cont.): Bladder injury, 179 medical oxygen, 91 Blood products, 168 number of patients, 88–89 Blunt aortic trauma, 253–254 palletized patient, 109 Blunt injury, triage, 66 pressurization, 90 Boeing 767, 106–107 range, 89 configurations, 106 runway length, 90 general characteristics, 106 special equipment, 91 strengths, 106 suction, 91 weaknesses, 106 types of, 14–17 Breast engorgement, postpartum patient, 304 Air ecology, cabin, 147–151 Breathing, 163–166 Air embolism, 249–250 Breech presentation, in delivery, 299 Airsickness, 325 Bupropin, 353 Airway, 161–163 Burns, 274–286 compromise, 24, 162 acute thermal burn injury, 275–281 management of, 206–207 American Burn Association criteria, burn center Alcoholism, 325–326 referral, 275 Alcohol withdrawal syndrome, 362 chemical burn injury, 284–285 Altitude chorioretinal, 221 cabin, 117–119, 235 contingency evacuation, 285–286 fetus, effect on, 288 contraindications, aeromedical transfer, 282 hypoxia, mass-casualty triage, 69 elective evacuation, 283 pulmonary patient, effect on, 256–257 electrical injury, 283–284 restrictions, 119–120 in-flight emergencies, 282–283 testing, 125 mass-casualty triage, 66–67 American Burn Association criteria, burn center preflight checklist, 282 referral, 275 preparation for evacuation, 276–281 American Civil war, U.S. combatants dying of time for transfer, 275 wounds, 29 urgent evacuation, 281–283 Amitriptyline, 353 Anaphylactic shock, 167 C Anemia, 323–324 C-9A Nightingale, 95–98 Angina, unstable, 321–322 configurations, 98 Anticoagulation, 234–235 general characteristics, 97 Antiplatelet therapy, 234–235 strengths, 97–98 Aortic aneurysm, dissecting, 20 weaknesses, 98 Arterial patency, 233–234 C-17 Globemaster, 101–103 Asthma, 335–336 configurations, 103 Atracurium, 261 general characteristics, 101–102 Atropine, 132 strengths, 102 duration of effect, 218 weaknesses, 102 Autonomic dysreflexia, 199 C-21 Lear Jet, 103–106 configuration, 105–106 B general characteristics, 105 Barodontalgia, 116, 205–206 strengths, 105 Barogastralgia, 116 weaknesses, 105 Barometric pressure changes, 112 C-130 Hercules, 92–95 Barosinusitis, 116 configurations, 94–95 Barotitis media, 115 general characteristics, 92–93 Barotrauma, 115 strengths, 93 pulmonary, 262 weaknesses, 94 Bell 206 helicopter, 15 C-141 Starlifter, 98–101 Bell 222 helicopter, 15 configurations, 101 Benztropine, 353 general characteristics, 100 Biological warfare, 155, 327–328 strengths, 100–101 triage, 63 weaknesses, 101 Index 361

Cabin Civilian peacetime transport, 13–26 air ecology, 147–151 aircraft, types of, 14–17 altitude, 117–119, 235 crew, 17–18 lighting, 91 military crews, 18 noise levels, aboard aircraft, 91 nurse-only crews, 18 space, 91 nurse-paramedic crews, 18 Carbamazepine, 353 physician-nurse crews, 17–18 Cardiac arrest, recent, 20 fixed-wing aircraft, 16–17 Cardiac complications, of mechanical ventilation, helicopters, for civilian medical transport, 15 263 rotary-wing aircraft, 14–16 Cardiac defibrillation, 168 Climate control, aboard aircraft, 91–92 Cardiac trauma, 253 Clonazepam, 353 Cardiogenic shock, 19–20, 167 Coagulopathies, 168, 344 Cardiothoracic casualties, 241–255 Colorectal injuries, 176–177 air embolism, 249–250 Combat evacuation, 27–44, 45–59. See also under blunt aortic trauma, 253–254 specific medical emergency cardiac trauma, 253 assessment, 49–52 chest tube management, checklist, 245 biologic threat, characteristics of, 35 chest tubes, 251 blast injuries, 32–33 diaphragmatic rupture, 255 bullet wounds, 31–32 esophageal perforation, 254 burn injuries, 32–33 flail chest, 251–252 chemical agents, characteristics of, 35, 37 fluid management, 251 disease, 34–35 hemothorax, 246–247 echelons of care, 47–49 in-flight complications, 247 field treatment, 33–34 pain control, 250 history of, 27–31, 45–46 pleural effusion, 246 limitations of, 57–58 pneumomediastinum, 247–249 mass destructions, weapons of, 36–39 pneumothorax, 243–246 modern military operations, 29–30 chest tube management, 243–244 nonbattle injuries, 34–35 postoperative cardiothoracic patient, 250 nuclear attack pulmonary contusion, 251–252 characteristics of, 35 respiratory hygiene, 250 effects of, at various distances, 38 tracheobronchial bleeding, 249 precedence, 49 tracheobronchial injuries, 252–253 principles of, 46–47 venous thrombosis prophylaxis, 251 shrapnel wounds, 31–32 Cervical immobilization devices, 195–197 transfer of care, 52 Challenger 601–3R, 108 transportation, 52–57 configuration, 109 ground vehicles, 55 general characteristics, 108 helicopters, 55–57 strengths, 108–109 litter carries, 55 weaknesses, 109 manual carries, 52–54 Chemical agents, 327–328 Commercial airline seats, 110 burn injury, 284–285 Compartment pressure, measurement of, 229–230 contamination, 142 Compartment syndrome, 229–230, 271 mass-casualty triage, 63, 67 Congenital heart disease, cyanotic, 347 Chest trauma, mass-casualty triage, 67 Congestive heart failure, 322–323 Chest tubes, 245, 251 Consciousness, level of, 192–194 Chlorpromazine, 261 Contingency evacuation, 314–315 Chorio-vitreoretinal injuries, 221–222 Continuous-wave doppler, 233–234, 236 chorioretinal burns, 221 Contusions, 187 chorioretinal tears, 221 COPD. See Chronic obstructive pulmonary disease retinal detachment, 222 Cord prolapse, in delivery, 299–301 vitreoretinal hemorrhages, 221 Corneal injuries, 218 Chronic obstructive pulmonary disease, 320–321 corneal abrasions, 218 Circulation, 166–168 corneal lacerations, 218 362 Index

Crew, 17–18 cord prolapse, 299–301 military crews, 18 postpartum hemorrhage, 301–302 nurse-only crews, 18 shoulder dystocia, 299 nurse-paramedic crews, 18 uterine inversion, 302 physician-nurse crews, 17–18 placenta, delivery of, 297–299 safety, mass-casualty triage, 70–71 signs of labor, 296 Cricothyrotomy stages of labor, 296–299 needle, 207 vertex presentation, 297 surgical, 207 Deployable diagnostic equipment, 236 Criteria, for triage, 61–62 Dermatomes, pinprick localization, 195 exclusion criteria, 61–62 Destination, evacuation, mass-casualty triage, 71 inclusion criteria, 61 Dexamethasone, 132 Critical-care, 111–135 Dextrose, 132 acceleration, 121–122 Diabetes, 338 decreased humidity, 121 ketoacidosis, 338–339 equipment, 125–130 Diagnosis, organization by, staging and, 85 drugs, 131–132 Diaphragmatic hernia, 345 infusion devices, 129–130 Diaphragmatic rupture, 255 monitors, 125–128 Diazepam, 132, 261, 262, 353 personal equipment, 132–133 Diffuse axonal injury, 187 point-or-care devices, 130–131 Diphenhydramine, 353, 354 ventilators, 128–129 Disease transmission, in cabin, 151–153 fatigue, 122 Dissecting aortic aneurysm, 20 noise, 120–121 Disseminated intravascular coagulation, 344 organizational issues, 122–133 Dobutamine, 132 physiology, 111–123 Dopamine, 132 altitude restrictions, 119–120 Doppler, continuous-wave, 233–234 barometric pressure changes, 112 Doxepin, 353 cabin altitude/pressurization, 117–119 Dressings, 235 gas expansion, 114–117 Droperidol, 261 gas laws, 112–113 Duodenal injuries, 175 hypoxia, 113–114 Dysbarism, 115 stresses of flights, 112–122 Dysreflexia, autonomic, 199 team composition, 122–125 Dysrhythmias, 323 nurses, 122–123 Dystocia, shoulder, 299 paramedics/other technicians, 123 physicians, 123–124 E temperature, 120 Ear block, 115 vibration, 121 Elective evacuation, 313–314 Crush injury, mass-casualty triage, 66 vs. urgent evacuation, 313–315 Crush syndrome, 272 Electrical injury, 283–284 Cuff, tracheostomy, 209 Electrical requirements, aircraft, 91 Cyanides, characteristics of, 37 Elevation, injured limbs, 266 Cyanogen, characteristics of, 37 Embolism Cyanotic congenital heart disease, 347 air, 249–250 Cycloplegic agent effects, duration of, 218 pulmonary, 310 Endoscopic sinus surgery, 210–211 D Endotracheal intubation, complications, 263 Decompression, 115, 125 En route stops, 89 Decreased humidity, 121 Entry doors, aircraft, 91 Defibrillation, cardiac, 168 Environmental tests, aeromedical equipment, Dehiscence, gynecological patient wound, 311 125 Delivery, vaginal, 296–302 Epidural hematoma, 186 complications, 299–302 Epiglottitis, 336 breech presentation, 299 Epinephrine, 132 Index 363

Epixtaxis, 207 preparation for evacuation, 307, 308 Esophageal perforation, 254 pulmonary embolism, 310 Etomidate, 262 sexual assault, 305–306 EuroCopter B-117 helicopter, 15 uterine bleeding, 307–308 EuroCopter BO-105 helicopter, 15 wound complications, 311 EuroCopter Dauphine helicopter, 15 Gynecology patient, emergency equipment, 288 Exclusion criteria, in triage, 61–62 Extracorporeal membrane oxygenation, 332–333 H Extremity vascular trauma, 237 Haloperidol, 261, 353, 354 Head, neck surgery patient, 203–214 F acoustic neuroma, 212 Fat embolism syndrome, 266, 271–272 airway management, 206–207 Fatigue, 122 endoscopic sinus surgery, 210–211 Feeding station, aboard aircraft, 90 epixtaxis, 207 Fentanyl, 262 flight, otolaryngologic problems with, Filtration, air, cabin, 149–150 203–206 Finger dermatome localization, 195 barodontalgia, 205–206 Fixed-wing aircraft, 16–17 inner-ear barotrauma, 204 Flail chest, 166, 251–252 inner-ear decompression sickness, 204–205 Flight crew procedures, mass-casualty triage, middle-ear barotrauma, 203–204 68–69 sinus barotrauma, 205 Flight preparation, 139–145 hemorrhage, 207 Fluid management, 251 laryngectomy, 212–213 Flumezanil, 262 mandible fractures, 213 Fluoxetine, 353 midfacial trauma, 207–208 Foot dermatome localization, 195 neck dissection, 213 Fracture, mandible, 213 needle cricothyrotomy, 207 Furosemide, 132 orotracheal/nasotracheal intubation, 206 otolaryngologic trauma, 206–213 G injury patterns, 206 Gangrene, 272 postoperative otolaryngologic patient, 208 Gas, 112–113 pressure equalization tubes, 211 expansion, 114–117 rhinoplasty, 210 gangrene, 272 skull base fracture, 208 intraocular, 222 stapedotomy, 211 mass-casualty triage, 69 surgical cricothyrotomy, 207 Gastric injuries, 175 temporal bone trauma, 208 Gastrointestinal disease, 324–325 tonsillectomy, 209–210 Genital trauma, 305–306 tracheostomy, 208–209 G-forces, effects on fetus, 289 tracheostomy cuff, 209 Globe rupture, 219–220 tympanoplasty, 211–212 field management, 220 Head injury, 184–187 Goals, of air transport, 112 classification of, 185 Gynecologic patient, 304 contusions, 187 abdominal pain, 310–311 diffuse axonal injury, 187 bleeding, 311 epidural hematoma, 186 chronic conditions, 304–305 intracerebral hematoma, 187 complications, 307, 308 mass-casualty triage, 66 dehiscence, 311 mechanism, 185 genital trauma, 305–306 morphology, 185 intra-abdominal hemorrhage, 310 severity, 185 pelvic infections, 306–307 skull fractures, 185–186 postoperative, 308–311 subdural hematoma, 186–187 complications, 309–311 types of, 185–187 infection, 311 Helicopters, for civilian medical transport, 15 364 Index

Hematoma pelvic, 306–307 epidural, 186 preventive measures, 153–154 intracerebral, 187 smallpox, 152 subdural, 186–187 staging, 85 Hemorrhage, 207, 227–228 tuberculosis, 151–152 intra-abdominal, 310 ventilation, 148–149 intracranial, 21 viral hemorrhagic fevers, 152–153 postpartum, 301–302 Infection control, 141–142 postpartum patient, 303–304 In-flight emergencies, 160–172 vitreoretinal, 221 airway, 161–163 Hemorrhagic fever, viral, 152–153 compromise, 162 Hemorrhagic shock, 166 breathing, 163–166 Hemothorax, 166, 246–247 cardiac defibrillation, 168 in-flight complications, 247 circulation, 166–168 Hepatic injury, 178 coagulopathies, 168 Hernia, diaphragmatic, 345 diagnosis, 161 Herniation syndrome, 189–190 disability, 168 History, recent warfare, 6–13 etiology of ventilation problems, 164 Korean war, 9–10 IV therapy, 167–168 post-Vietnam war, 11–12 primary survey, 161–168 present, 12 safety, 161 pre-Vietnam war, 10 status asthmaticus, 165 Vietnam war, 10–11 stress factors, 160–161 World War I, 6–7 treatment, 161, 162–163 before World War I, 6 Influenza, 152 World War II, 8–9 Infusion devices, 129–130 between World Wars, 7–8 Injury patterns, 206 Histoxic hypoxia, 114 Inner-ear Hollow-organ injuries, 174–175 barotrauma, 204 Homatropine, duration of effect, 218 decompression sickness, 204–205 Hospital ward care, 85 Intensive-care support, staging and, 84 Humidity, 125, 318 Intestinal obstruction, 345–346 Hypemic hypoxia, 113 Intra-abdominal hemorrhage, 310 Hypoglycemia, 338, 344 Intracerebral hematoma, 187 Hypoplastic left heart syndrome, 347–348 Intracranial air, 116 Hypotension, 189 Intracranial hemorrhage, 21 Hypoxia, 113–114, 189 Intracranial pressure histoxic, 114 increased, 189–190, 191–192 hypemic, 113 recognizing, 189–190 hypoxic, 113 monitoring, 190–192 stagnant, 114 Intraocular gases, 222 Intrathoracic air, 116 I Intravascular coagulation, disseminated, 344 Inclusion criteria, in triage, 61 Intravenous therapy, 167–168 Incubators, 331–332 Intubation Infection, 147–179 endotracheal, complications, 263 aerosols, microbial, 150–151 nasotracheal, 206 air, filtration, 149–150 orotracheal, 206 biologic warfare casualties, 155 Ischemia, 226–227 cabin, air ecology, 147–151 reperfusion injury, 228–229 disease transmission, 151–153 Isolation, during evacuation, 327–328 influenza, 152 Isotonic solutions, 167 legal issues, 155–156 measles, 152 K microbial environment, airframe as, 147–151 Ketamine, 132, 262 military regulations, 156 Ketoacidosis, diabetic, 338–339 Index 365

Korean war, 9–10 telemedicine, 71–72 U.S. combatants dying of wounds, 29 transportation management, 68–72 physiological factors, 69 L violent patient, 68 Labor weapons of mass destruction, 62–63 during flight, 289 weather conditions, 71 signs of, 296 Measles, 152 stages of, 296–299 Mechanical ventilation, 256–264 Landing limitations, aircraft, 90 acute respiratory failure, 257–258 Laryngectomy, 212–213 basic life support, 258 Laser injuries, 217–219 emergency treatment of, 257–258 Lavatory aboard aircraft, 90 altitude, effect on pulmonary patient, 256–257 Left heart syndrome, hypoplastic, 347–348 cardiac complications of, 263 Legal issues, 142–143 complications of, 262–264 Lidocaine, 132 endotracheal intubation, complications, 263 Lighting, cabin, 91 institution of, 259–261 Lithium, 353 medications Lorazepam, 261, 262, 353, 354 adult patient, 261 Low-temperature operation, 125 pediatric patient, 262 Lumbar spinal immobilization, 197–198 pediatric patient, 261–262 principles of, 258–259 M pulmonary barotrauma, 262 Malleolus dermatome localization, 195 ventilator operation, modes of, 259 Mandible fractures, 213 MEDEVAC, 27–44, 45–59. See also under specific Mannitol, 192 medical emergency Masks, medical, 257 assessment, 49–52 Mass-casualty triage, 60–74 blast injuries, 32–33 accelerative forces, 69 bullet wounds, 31–32 aeromedical triage, 63–64 burn injuries, 32–33 altitude hypoxia, 69 care, 49–52 biological terrorism, 63 chemical agents, characteristics of, 35, 37 blunt/crush injury, 66 disease, 34–35 burn injuries, 66–67 echelons of care, 47–49 categories, 65 field treatment, 33–34 chemical agents, 63 history of, 27–31, 45–46 surgical trauma casualty, 67 limitations of, 57–58 chest trauma, 67 mass destructions, weapons of, 36–39 crew safety, 70–71 modern military operations, 29–30 criteria, 61–62 nonbattle injuries, 34–35 exclusion criteria, 61–62 nuclear attack inclusion criteria, 61 characteristics of, 35 evacuation destination, 71 effects of, at various distances, 38 flight crew procedures, 68–69 precedence, 49 gas expansion, 69 principles of, 46–47 head injury, 66 shrapnel wounds, 31–32 mixed agent terrorism, 63 transfer of care, 52 mode of transportation, 69–70 transportation, 52–57 nuclear attack, 63 ground vehicles, 55 orthopedic injuries, 67 helicopters, 55–57 pediatric, 67–68 litter carries, 55 priorities, 64–65 manual carries, 52–54 quantitative scoring methods, 65–68 war, operations other than, 39 number of casualties, 66 Medical evacuation, aeromedical evacuation, types of casualties, 66–68 distinguished, 3 rotary-wing vs fixed-wing aircraft, 70 Medical oxygen, aboard aircraft, 91 situations, 60–61 Medicolegal issues, 142–143 366 Index

Methylprednisolone administration, 198–199 classification of, 185 Mexican war, U.S. combatants dying of wounds, contusions, 187 29 diffuse axonal injury, 187 Microbial aerosols, 150–151 epidural hematoma, 186 Microbial environment, airframe as, 147–151 intracerebral hematoma, 187 Midazolam, 132, 261, 262 mechanism, 185 Middle-ear barotrauma, 203–204 morphology, 185 Midfacial trauma, 207–208 severity, 185 Military crews, 18 skull fractures, 185–186 Military evacuation, 27–44, 45–59. See also under subdural hematoma, 186–187 specific medical emergency types of, 185–187 assessment, 49–52 herniation syndrome, 189–190 blast injuries, 32–33 hypotension, 189 bullet wounds, 31–32 hypoxia, 189 chemical agents, characteristics of, 37 intracranial pressure disease, 34–35 increased, 189–190, 191–192 echelons of care, 47–49 monitoring, 190–192 field treatment, 33–34 mannitol, 192 history, 27–31, 45–46 pentobarbital coma, 192 limitations of, 57–58 secondary neurological insults, avoidance of, mass destructions, weapons of, 36–39 188–192 modern military operations, 29–30 spinal cord injury, 194–199 nuclear attack autonomic dysreflexia, 199 characteristics of, 35 cervical immobilization devices, 195–197 effects of, at various distances, 38 dermatomes, pinprick localization, 195 precedence, 49 general principles, 194–199 principles of, 46–47 in-flight care, 199 transfer of care, 52 lumbar spinal immobilization, 197–198 transportation, 52–57 methylprednisolone administration, ground vehicles, 55 198–199 helicopters, 55–57 thoracic spinal immobilization, 197–198 litter carries, 55 Neurovascular compromise, 270–271 manual carries, 52–54 Neurovascular status checks, 266 war, operations other than, 39 Nifedipine, 132 Monitoring devices, 319 Nipple dermatome localization, 195 Monitors, 125–128 Nitroglycerin, 132 Morphine, 132, 262 Noise, 91, 120–121 sulfate, 261 Non-re-breathing mask, 257 Mustard gas, characteristics of, 37 Nontraumatic vascular disease, 232 Myocardial infarction, 19, 321–322 Nortiptyline, 353 Nuclear attack, mass-casualty triage, 63 N Number of patients, 88–89 Naloxone, 132, 262 Nurse-only crews, 18 Nasal cannula, 257 Nurse-paramedic crews, 18 Nasal catheter, 257 Nursing care, 122–123, 136–146 Nasotracheal intubation, 206 biologic contamination, 142 Neck dissection, 213 chemical contamination, 142 Needle cricothyrotomy, 207 flight preparation, 139–145 Neonatal transport, 22–23, 340–348 infection control, 141–142 Nerve gas, characteristics of, 37 laboratory, 143 Neurogenic shock, 167 medicolegal issues, 142–143 Neurological disorders, 325 patient care during flight, 144–145 Neurosurgical patient, 184–202 postflight, 145 consciousness, level of, 192–194 preflight preparation, 136–139 head injury, 184–187 patient history, 136 Index 367

physical assessment, 136–137 Olanzapine, 353 stresses of flight, 137–139 Omphalocele, 346 safety, 143–144 Operational casualties, 27–44, 45–59. See also under stresses of flight, 138 specific medical emergency assessment, 49–52 O blast injuries, 32–33 Obstetric patient, 23, 288–304 bullet wounds, 31–32 abruptio placenta, 294 burn injuries, 32–33 altitude, effects of, 288 chemical agents, characteristics of, 35, 37 emergency equipment, 288 disease, 34–35 fetal demise, 293 echelons of care, 47–49 fever, 296 field treatment, 33–34 first half of pregnancy, 289–293 history of, 27–31, 45–46 ectopic pregnancy, 291–292 limitations of, 57–58 first-trimester bleeding, 289–291 mass destructions, weapons of, 36–39 hyperemesis of pregnancy, 292–293 modern military operations, 29–30 in-flight emergencies, 291 nonbattle injuries, 34–35 miscarriages, 289–291 nuclear attack preparation for evacuation, 291 characteristics of, 35 G-forces, effects of, 289 effects of, at various distances, 38 hemorrhage, 295 precedence, 49 immobilization, 288–289 principles of, 46–47 incompetent cervix, 293 shrapnel wounds, 31–32 labor, 289, 296 transfer of care, 52 placenta previa, 294 transportation, 52–57 postpartum patient, 302–304 ground vehicles, 55 abdominal pain, 304 helicopters, 55–57 breast engorgement, 304 litter carries, 55 complications, 303–304 manual carries, 52–54 hemorrhage, 303–304 war, operations other than, 39 postpartum seizure, 304 Ophthalmic patient, 215–224 preparation for evacuation, 303 atropine, duration of effect, 218 prerequisites for evacuation, 303 chorio-vitreoretinal injuries, 221–222 potential in-flight emergencies, 295 chorioretinal burns, 221 pregnancy-induced hypertension, 294 chorioretinal tears, 221 premature labor, 293 retinal detachment, 222 premature rupture of membranes, vitreoretinal hemorrhages, 221 293–294 corneal injuries, 218 preparation for evacuation, 295 corneal abrasions, 218 second half of pregnancy, 293–296 corneal lacerations, 218 seizure, 295–296 cycloplegic agent effects, duration of, 218 third-trimester uterine bleeding, 294 globe rupture, 219–220 uncomplicated pregnancy, 288 field management, 220 vaginal delivery, 296–302 history, 216 breech presentation, 299 homatropine, duration of effect, 218 complications, 299–302 in-flight issues, 222–223 cord prolapse, 299–301 intraocular gases, 222 placenta, delivery of, 297–299 laser injuries, 219 postpartum hemorrhage, 301–302 mechanism of injury, 216–218 shoulder dystocia, 299 ballistic injuries, 217 signs of labor, 296 laser injuries, 217–218 stages of labor, 296–299 scopolamine, duration of effect, 218 uterine inversion, 302 tropicamide, duration of effect, 218 vertex presentation, 297 Organizational issues, 122–133 Obstructive lung diseases, medications, 258 Orotracheal intubation, 206 368 Index

Orthopedic injuries, 265–274 P compartment syndrome, 271 Palletized patient, aircraft requirements, 109 crush syndrome, 272 Pancreatic injury, 178 danger zone, 266 Pancuronium, 261, 262 elevation, injured limbs, 266 Paramedics, 123 fat embolism syndrome, 266, 271–272 Paroxetine, 353 gas gangrene, 272 Pathophysiology of, 265–266 in-flight care, 269–270 Patient staging, 75–87 in-flight emergencies, 270–272 case report, 86–87 mass-casualty triage, 67 contingency role, 81–85 neurovascular compromise, 270–271 diagnosis, organization by, 85 neurovascular status checks, 266 facility, 79–85 pathophysiology of, 265–266 hospital ward care, 85 preflight checklists, 268–270 infectious disease, 85 preparation for transport, 267–272 intensive-care support, 84 pulmonary thromboembolism, 272 medical care, 79–80 shock, 271 medical clearance, 75–77, 83–84 splintage, 266, 267–268 contingency, 78 vital signs, monitoring, 266 peacetime, 77–78 Otitis media, 339 medical stability, 86 Otorhinolaryngology, 203–214 movement precedence, 78–79 acoustic neuroma, 212 priority, 78–79 airway management, 206–207 routine, 78 endoscopic sinus surgery, 210–211 urgent, 78 epixtaxis, 207 patient subsistence, comfort, 84 flight, otolaryngologic problems with, 203–206 patient sustenance, comfort, 80–81 barodontalgia, 205–206 patient transportation, 80, 84 inner-ear barotrauma, 204 peacetime, 79–81 inner-ear decompression sickness, 204–205 prioritization of patient, 84 middle-ear barotrauma, 203–204 psychiatric patient, 85–86 sinus barotrauma, 205 second-echelon response, 85 hemorrhage, 207 security, 80 laryngectomy, 212–213 stable, vs. stabilized patient, 81–83 mandible fractures, 213 triage, 79 midfacial trauma, 207–208 Peacetime casualties, 13–26 neck dissection, 213 aircraft, types of, 14–17 needle cricothyrotomy, 207 crew, 17–18 orotracheal/nasotracheal intubation, 206 military crews, 18 otolaryngologic trauma, 206–213 nurse-only crews, 18 injury patterns, 206 nurse-paramedic crews, 18 postoperative otolaryngologic patient, 208 physician-nurse crews, 17–18 pressure equalization tubes, 211 fixed-wing aircraft, 16–17 rhinoplasty, 210 helicopters, for civilian medical transport, 15 skull base fracture, 208 patient, 18–25 stapedotomy, 211 cardiac, 19–20 surgical cricothyrotomy, 207 intracranial hemorrhage, 21 temporal bone trauma, 208 neonatal transportation, 22–23 tonsillectomy, 209–210 obstetric patient, 23 tracheostomy, 208–209 pediatric, 23–24 tracheostomy cuff, 209 pulmonary, 22 tympanoplasty, 211–212 trauma, 24–25 Oxygen, 132 patient staging, 77–78, 79–81 aboard aircraft, 91 rotary-wing aircraft, 14–16 delivery systems, compared, 257 Pediatric patient, 23–24, 329–349 Oxygen therapy, 317 airway compromise, 24 Index 369

asthma, 335–336 dressings, drainage, 235 cyanotic congenital heart disease, 347 extremity vascular trauma, 237 diabetes mellitus, 338 hemorrhage, 227–228 diabetic ketoacidosis, 338–339 ischemia, 226–227 diaphragmatic hernia, 345 ischemia reperfusion injury, 228–229 disseminated intravascular coagulation, 344 laboratory evaluation, 236 ear block, 339 medications, treatment supplies, 235–236 epiglottitis, 336 nontraumatic vascular disease, 232 extracorporeal membrane oxygenation, 332–333 pulmonary thromboembolism, 231–232 gastroschisis, 346 secondary infection, 235 hypoglycemia, 338, 344 shock, 228 hypoplastic left heart syndrome, 347–348 shunts, 232–233 incubators, 331–332 soft-tissues coverage, 232 infection, 344 thromboembolism, 239 intestinal obstruction, 345–346 vascular imaging in field, 234 mass-casualty triage, 67–68 venous thrombosis, 230–232, 239 mechanical ventilation, 261–262 Personal equipment, 132–133 medications, 262 Phosgene, characteristics of, 37 neonatal transport, 340–348 Phosgene oxime, characteristics of, 37 omphalocele, 346 Physical assessment, preflight, 136–137 otitis media, 339 Physician-nurse crews, 17–18 peacetime casualty, 23–24 Physicians, 123–124 airway compromise, 24 Physiology, 111–123 sepsis, 24 altitude restrictions, 119–120 trauma, 23–24 barometric pressure changes, 112 prematurity, 343–344 cabin altitude/pressurization, 117–119 preparation for evacuation, 341–342 gas expansion, 114–117 respiratory distress, 344–345 gas laws, 112–113 seizure disorders, 336–338 hypoxia, 113–114 sepsis, 24 stresses of flights, 112–122 sickle cell disease, 339–340 Pinprick localization of key dermatomes to timing for evacuation, 341 localize, level of spinal injury, 195 transportation risks, 333–335 Placenta, delivery of, 297–299 aeromedical environment, 333 Pleural effusion, 246 altitude, 334 Pneumomediastinum, 247–249 isolation, 334–335 Pneumothorax, 165, 243–246, 318 thermal stress, 333–334 chest tube management, 243–244 trauma, 23–24 Point-or-care devices, 130–131 triage, 67–68 Postflight issues, 145 upper-airway obstruction, 336 Postoperative gynecological patient, 308–311 ventilators, 332 complications, 309–311 Pelvic infections, 306–307 abdominal pain, 310–311 Penile injury, scrotal injury, 179 bleeding, 311 Pentobarbital coma, 192 dehiscence, 311 Perianal dermatome localization, 195 intra-abdominal hemorrhage, 310 Peripheral vascular casualties, 225–240 postoperative infection, 311 aircraft configuration, 235 pulmonary embolism, 310 anticoagulation, antiplatelet therapy, 234–235 wound complications, 311 arterial patency, 233–234 preparation for evacuation, 309 cabin altitude, 235 Postpartum, 302–304 compartment pressure, measurement of, 229–230 abdominal pain, 304 compartment syndrome, 229–230 breast engorgement, 304 continuous-wave doppler, 233–234, 236 complications, 303–304 deployable diagnostic equipment, monitoring, hemorrhage, 301–302, 303–304 236 postpartum seizure, 304 370 Index

Postpartum (cont.): barotrauma, 262 preparation for evacuation, 303 chronic obstructive pulmonary disease, 320–321 prerequisites for evacuation, 303 embolism, 310 seizure, 304 medical conditions, 22 Preflight preparation, 136–139 pneumothorax, 319–320 patient history, 136 thromboembolism, 231–232, 272 physical assessment, 136–137 trauma, 22 stresses of flight, 137–139 Pregnancy R first half of, 289–293 Range of aircraft, 89 ectopic pregnancy, 291–292 Rapid decompressions, 125 first-trimester bleeding, 289–291 Rebreathing mask, 257 hyperemesis of pregnancy, 292–293 Recent cardiac arrest, 20 in-flight emergencies, 291 Renal failure, 325 preparation for evacuation, 291 Renal injuries, 179 second half of, 293–296 Reperfusion injury, ischemia, 228–229 abruptio placenta, 294 Respiratory distress, 344–345 fetal demise, 293 Respiratory failure, 257–258, 320 fever, 296 basic life support, 258 hemorrhage, 295 emergency treatment of, 257–258 incompetent cervix, 293 Respiratory hygiene, 250 labor, 296 Retinal detachment, 222 placenta previa, 2943 Rhinoplasty, 210 potential in-flight emergencies, 295 Risperidone, 353 pregnancy-induced hypertension, 294 Rotary-wing aircraft, 14–16 premature labor, 293 vs fixed-wing aircraft, mass-casualty triage, 70 premature rupture of membranes, 293–294 Runway length, 90 preparation for evacuation, 295 seizure, 295–296 S third-trimester uterine bleeding, 294 Sarin, characteristics of, 37 uncomplicated, 288 Scopolamine, duration of effect, 218 Premature infant, 343–344 Scrotal injury, 179 Pressure Seats, commercial airline, 110 changes in, 112 Second-echelon response, 85 decreased, 317–318 Seizure, postpartum, 304 Pressure equalization tubes, 211 Seizure disorders, 336–338 Pressurization, cabin, 90, 117–119 Sepsis, 24 Primary survey, 161–168 Septic shock, 167, 326–327 Propofol, 261 Sertaline, 353 Psychiatric patient, 85–86, 350–358 Shock, 228, 271 adolescents, 358 anaphylactic, 167 agitation, 352–353, 354 cardiogenic, 19–20, 167 bipolar mood disorders, 353–354 hemorrhagic, 166 children, 358 neurogenic, 167 depression, 354 septic, 167 evacuation classification, 355 Shoulder dermatome localization, 195 manic patient, 353 Shoulder dystocia, in delivery, 299 medications, 52–354 Shunts, 232–233 dose, side effects, 353 Sickle cell disease, 324, 339–340 preparation for evacuation, 354–355 Sikorsky S-76B helicopter, 15 psychotic patient, 353 Sinus barotrauma, 205 restraints, 356–358 Skull fracture, 185–186, 208 violent patient, 354 Small-bowel injuries, 176 Pulmonary conditions Smallpox, 152 acute respiratory failure, 320 Sodium bicarbonate, 132 Index 371

Soft-tissues coverage, 232 Succinylcholine, 262 Soft-tissue wounds, 181–183 Suction, aboard aircraft, 91 Solid-organ injuries, 177–178 Surgical casualties, 173–183 Soman, characteristics of, 37 abdominal trauma care, 173–178 Spanish-American war, U.S. combatants dying of colorectal injuries, 176–177 wounds, 29 damage control surgery, 174 Spinal cord injury, 194–199 duodenal injuries, 175 autonomic dysreflexia, 199 gastric injuries, 175 cervical immobilization devices, 195–197 hepatic injury, 178 dermatomes, pinprick localization, 195 historical perspective, 173–174 general principles, 194–199 hollow-organ injuries, 174–175 in-flight care, 199 pancreatic injury, 178 lumbar spinal immobilization, 197–198 small-bowel injuries, 176 methylprednisolone administration, 198–199 solid-organ injuries, 177–178 thoracic spinal immobilization, 197–198 spleen, 177–178 Spleen, 177–178 surgical approach, 174 Splintage, 266, 267–268 upper gastrointestinal injuries, 175–176 Stable, vs. stabilized patient, 81–83 soft-tissue wounds, 181–183 Stable patient, stabilized, unstable patient, 315–316 urogenital casualties, supplies needed, 181 Staging, patient, 75–87 urogenital injuries, 178–181 case report, 86–87 renal injuries, 179 contingency role, 81–85 scrotal injury, 179 diagnosis, organization by, 85 ureteral injuries, 179 facility, 79–85 urethral injury, 179 hospital ward care, 85 Surgical cricothyrotomy, 207 infectious disease, 85 intensive-care support, 84 T medical care, 79–80 Tabun, characteristics of, 3 medical clearance, 75–77, 83–84 Team composition, 122–125 contingency, 78 nurses, 122–123 peacetime, 77–78 paramedics, 123 medical stability, 86 physicians, 123–124 movement precedence, 78–79 Telemedicine, in mass-casualty triage, 71–72 priority, 78–79 Temperature, 120 routine, 78 changes in, 318 urgent, 78 high, 125 patient subsistence, comfort, 84 low, 125 patient sustenance, comfort, 80–81 Temporal bone trauma, 208 patient transportation, 80, 84 Theophylline, 132 peacetime, 79–81 Thermal burn injury, 275–281 prioritization of patient, 84 Thigh dermatome localization, 195 psychiatric patient, 85–86 Thoracic spinal immobilization, 197–198 second-echelon response, 85 Thromboembolism, pulmonary, 231–232 security, 80 Thumb dermatome localization, 195 stable, vs. stabilized patient, 81–83 Thyroidectomy, 213 triage, 79 Toe dermatome localization, 195 Stagnant hypoxia, 114 Tonsillectomy, 209–210 Stapedotomy, 211 Tracheobronchial bleeding, 249 Status asthmaticus, 165 Tracheobronchial injuries, 252–253 emergency treatment of, 165 Tracheostomy, 208–209 Storage Tracheostomy cuff, 209 high-temperature, 125 Triage, 60–74 low-temperature, 125 accelerative forces, 69 Stressors of flight, 112–122, 137–139, 316–317 aeromedical triage, 63–64 Subdural hematoma, 186–187 altitude hypoxia, 69 372 Index

Triage (cont.): scrotal injury, 179 biological terrorism, 63 supplies needed, 181 blunt/crush injury, 66 ureteral injuries, 179 burn injuries, 66–67 Uterine bleeding, 307–308 categories, 65 Uterine inversion, 302 chemical agents, 63 contamination, 67 chest trauma, 67 V crew safety, 70–71 Vaginal delivery, emergency, 296–302 criteria, 61–62 breech presentation, 299 exclusion criteria, 61–62 complications, 299–302 inclusion criteria, 61 cord prolapse, 299–301 evacuation destination, 71 placenta, delivery of, 297–299 flight crew procedures, 68–69 postpartum hemorrhage, 301–302 gas expansion, 69 shoulder dystocia, 299 head injury, 66 signs of labor, 296 mixed agent terrorism, 63 stages of labor, 296–299 mode of transportation, 69–70 uterine inversion, 302 nuclear attack, 63 vertex presentation, 297 orthopedic injuries, 67 Valproic acid, 353 patient staging, 79 Vascular casualties, peripheral, 225–240 pediatric, 67–68 aircraft configuration, 235 priorities, 64–65 anticoagulation, antiplatelet therapy, 234–235 quantitative scoring methods, 65–68 arterial patency, 233–234 number of casualties, 66 cabin altitude, 235 types of casualties, 66–68 compartment pressure, measurement of, rotary-wing vs fixed-wing aircraft, 70 229–230 situations, 60–61 compartment syndrome, 229–230 telemedicine, 71–72 continuous-wave doppler, 233–234, 236 transportation management, 68–72 deployable diagnostic equipment, monitoring, physiological factors, 69 236 violent patient, 68 dressings, drainage, 235 weapons of mass destruction, 62–63 extremity vascular trauma, 237 weather conditions, 71 hemorrhage, 227–228 Tropicamide, duration of effect, 218 ischemia, 226–227, 228–229 Tuberculosis, 151–152 laboratory evaluation, 236 Tubes medications, treatment supplies, 235–236 chest, 251 nontraumatic vascular disease, 232 pressure equalization, 211 pulmonary thromboembolism, 231–232 Tympanoplasty, 211–212 secondary infection, 235 Types of aircraft, 14–17 shock, 228 shunts, 232–233 soft-tissues coverage, 232 U vascular imaging in field, 234 Unstable angina, 321–322 venous thrombosis, 230–232, 239 Upper gastrointestinal injuries, 175–176 Vascular imaging, in field, 234 duodenal injuries, 175 Vecuronium, 261, 262 gastric injuries, 175 Venous thrombosis, 230–232, 239 small-bowel injuries, 176 prophylaxis, 251 Ureteral injuries, 179 Ventilation, 148–149 Urethral injury, 179 mechanical Urogenital injuries, 178–181 medications for adult patient on, 261 bladder injury, 179 medications for pediatric patient on, 262 penile injury, 179 problems, etiology of, 164 renal injuries, 179 Ventilator, 128–129, 332 Index 373

Venturi mask, 257 W Verapamil, 132 Weapons development, geographical site of, 36 Vertex presentation, vaginal delivery, 297 Weapons of mass destruction, in triage, 62–63 Vesicant, characteristics of, 37 Weather conditions, mass-casualty triage, 71 Vibration, 121, 125 World War I, 6–7 Vietnam war, 10–12 U.S. combatants dying of wounds, 29 U.S. combatants dying of wounds, 29 World War II, 8–9 Violent patient, mass-casualty triage, 68 U.S. combatants dying of wounds, 29 Viral hemorrhagic fevers, 152–153 Vital signs, monitoring, 266 X Vitreoretinal hemorrhages, 221 Xiphoid dermatome localization, 195