Difficult Airway in Obstetric Anesthesia

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Volume 56, Number 10 OBSTETRICAL AND GYNECOLOGICAL SURVEY Copyright © 2001 by Lippincott Williams & Wilkins, Inc. CME REVIEWARTICLE 28 CHIEF EDITOR’S NOTE: This article is the 28th of 36 that will be published in 2001 for which a total of up to 36 Category 1 CME credits can be earned. Instructions for how credits can be earned appear on the last page of the Table of Contents.

Difficult Airway in Obstetric Anesthesia: A Review Tiberiu Ezri, MD,* Peter Szmuk, MD,† Shmuel Evron, MD,‡ Daniel Geva, MD,§ Zion Hagay, MD,¶ and Jeffrey Katz, MDʈ From the *Director, Department of Anesthesia and ‡Head, Obstetric Anesthesia Unit, Wolfson Medical Center, Holon, Israel; §Director, Department of Anesthesiology and ¶Professor and Chairman, Department of Obstetrics and Gynecology, Kaplan Hospital, Rehovot, Israel; and †Assistant Professor and Head, P.A.C.U. and ʈProfessor and Chairman, Department of Anesthesiology, University of Texas-Houston Medical School, Houston, Texas

Failed intubation and ventilation are important causes of anesthetic-related maternal mortality. The purpose of this article is to review the complex issues in managing the difficult airway in obstetric patients. The importance of prompt and competent decision making in managing difficult airways, as well as a need for appropriate equipment is emphasized. Four case reports reinforce the importance of a systematic approach to management. The overall preference for regional rather than general anesthesia is strongly encouraged. The review also emphasizes the need for professional and experienced team cooperation between the obstetrician and the anesthesiologist for the successful management of these challenging cases. Target Audience: Obstetricians & Gynecologists, Family Physicians Learning Objectives: After completion of this article, the reader will be able to break down the complex issues in managing the difficult airway in the obstetric patient, outline the reasons for difficult intubations in pregnancy, and describe the evaluation used to predict a difficult intubation.

The inability to maintain a patent airway after tical points of this review are exemplified by presen- failed or difficult intubation and ventilation remains a tation of reports of problematic airway cases. major concern of anesthesia-related maternal morbidity or mortality and a significant source of mal- practice claims in obstetrics (1, 2). The purpose of DEFINITION OF DIFFICULT AIRWAY this review is to define the difficult airway, highlight The difficult airway is defined according to the the main reasons for difficult or failed intubation, and stage of airway management in which it is encoun- propose a practical approach to management. It is tered; i.e., laryngoscopy, intubation, or ventilation intended that this review will enrich the practitioner’s (3). Difficult laryngoscopy is defined as the inability knowledge of the complex issues of airway manage- to visualize any portion of the vocal cords. Endotra- ment and enhance his involvement in anesthetic de- cheal intubation is considered difficult if it requires cision making. As noted throughout the review, an more than three attempts or takes longer than 10 important component is the necessity for teamwork minutes. This definition has been recently challenged between anesthesiologist and obstetrician. The prac- by Benumof (4), who considers that a reasonably experienced anesthesiologist would be able to recog- Reprint requests to: Tiberiu Ezri, MD, Director, Department of nize a difficult intubation (laryngoscopy) from the Anesthesia, Wolfson Medical Center, Holon, Israel. Email: [email protected] first attempt. Difficult mask ventilation means an The authors have disclosed no significant financial or other inability to maintain oxygen saturation (SaO2) over relationship with any commercial entity. 90% with an inspired oxygen concentration of 100% 631 632 Obstetrical and Gynecological Survey

(O2) and positive-pressure ventilation. These defini- Preexisting airway deformities. Airway abnormal- tions are intended to establish clear-cut criteria and ities may interfere with intubation mainly by one or an exact quantification of the time and number of more of the following mechanisms: decreased mo- attempts at intubation and may help the anesthesiol- bility of the neck, limited mouth opening, and re- ogist in deciding whether to call for assistance or to duced submandibular space. Table 1 depicts some choose another approach for securing the airway. changes in airway anatomy (not specific for pregnant However, it should be understood that it is the failure patients) that interfere with the normal visualization in oxygenation and ventilation that causes a fatal of the cords. Of these, the most frequently encoun- outcome and not the inability to intubate per se. tered are “bull neck,” “buck teeth” and micrognathia. Thus, the ability to ventilate the patient effectively is In any of these cases, the anesthesiologist should of paramount importance. expect difficult intubation. Pilkington et al. (10) dem- onstrated in 242 pregnant women that the incidence of Class III airway (Mallampati classification) in- INCIDENCE OF DIFFICULT INTUBATION creased by 34% as pregnancy progressed. Mallam- AND VENTILATION pati classification is based on the view of the back of In obstetric anesthesia, difficult intubation is fre- the mouth with the tongue protruded. The higher the quently unexpected. Although the incidences of air- grade (grade IV), the less visible is the junction way difficulties encountered were low (7.9%) (5), between the soft and hard palate. The lower the grade they were still greater than those in the nonobstetric (grade I), the more visible is the whole soft palate population (2.5%) (6). The reasons for the higher (uvula). incidence of difficult airway in obstetric patients are Airway edema. Airway edema results from hor- not always evident. Interestingly, the incidence of monally induced fluid retention during pregnancy. very difficult intubation is very similar in both ob- This process is augmented by pregnancy-induced stetric and nonobstetric populations, 2% versus hypertension, if present, and by other conditions, 1.8%, respectively (6, 7). However according to such as excess weight gain, fluid overload, head- Hawthorne et al. (8), the incidence of failed intuba- down position, oxytocin infusion (fluid retention due tion in the obstetric population is 0.4%—approxi- to the antidiuretic effect), and prolonged Valsalva mately 10 times more frequent than in the general efforts (11). Repeated intubation attempts may result surgical patient population. The number of failed in mucosal congestion that may lead to airway edema intubations has not decreased over the last 10 years. and bleeding. Edema of the face and neck should Mask ventilation was found to be laborious or im- alert the anesthesiologist to the possibility of difficult possible in 0.02% of patients (9), an incidence com- intubation, whereas edema of the tongue may herald mon to obstetric and other surgical patients. It is imminent airway compromise. evident that not only pregnancy itself, but also other Diseases involving the airway. Table 2 presents factors (i.e., distorted anatomy of the airway) are some of the more frequently encountered diseases causes for intubation difficulties in pregnancy, al- involving the airway. As a typical example, rheuma- though airway edema in pregnancy may certainly toid arthritis may render standard intubation impos- worsen the problem. sible, necessitating the use of alternative airway management techniques (see “Airway Management for Cesarean Delivery”). REASONS FOR DIFFICULT INTUBATION Obesity. Obesity is frequently encountered during IN PREGNANCY pregnancy. Difficult intubation in the obese patient The reasons for difficult intubation in pregnancy may be divided into two groups: problems related to changes in airway anatomy and problems with the TABLE 1 Abnormal airway anatomy (individual variations) intubation technique. 1 Bull neck 2 Large breasts 3 Large floppy epiglottis Airway Anatomy 4 Large tongue 5 Limited cervical movement The anatomy of the airway may be impacted by 6 Limited mouth opening and narrow mouth four mechanisms: preexisting anatomical deformi- 7 Limited movement of the jaw ties, airway edema, coexisting diseases involving the 8 Prominent upper teeth airway, and obesity. 9 Receding jaw Difficult Airway in Obstetric Anesthesia Y CME Review Article 633

TABLE 2 Diseases involving the airway No. Disease Problem 1 Ankylosing spondylitis Immobility and fractures of the cervical spine 2 Congenital syndromes Down Macroglossia Klippel-Feil Fusion of cervical vertebrae with limited cervical movement 3 Goiter Deviation of the airway 4 Infections Epiglottitis Supralaryngeal and laryngeal edema; poor visualization of the larynx Ludwig’s angina Trismus, distortion of the airway 5 Preeclampsia Laryngeal edema 6 Rheumatoid arthritis Restricted cervical spine and jaw (TMJ*) mobility; cricoarytenoid joint arthritis; intubation with conventional laryngoscopy may be impossible. 7 Tumors of the upper airway Distortion of the airway 8 Airway trauma Cervical spine and laryngeal damage due to edema, hematoma and fractures leading to difficult intubation and ventilation * TMJ ϭ temporomandibular joint. may be due to a short neck or large tongue and axes for a better laryngoscopic view. The application of breasts, which make laryngoscopy and intubation cricoid pressure (used to prevent regurgitation of gastric laborious (12). In the morbidly obese parturient contents) distorts the airway and makes the alignment (greater than 300 lb), the cesarean delivery rate ex- of the head and neck into the “sniffing” position diffi- ceeds 50% (13). One third of the tracheal intubations cult. Other technical reasons for failure to intubate are were difficult, with a failure rate of 6% (13). Mask related to the clinical expertise of the anesthesiologist ventilation is often difficult in obese patients because dealing with the case. In pregnant patients, the problems of low chest compliance and increased intra-abdom- encountered with intubation and ventilation are compli- inal pressure. Finally, hypoxemia may ensue very cated by an impaired balance between oxygen delivery rapidly in cases of failed intubation due to the de- and consumption (18). creased functional residual capacity and increased O2 Oxygen delivery and arterial oxygenation are de- consumption. creased as a result of elevation of the diaphragm, obesity, and a decreased expiratory reserve volume (a component of functional residual capacity), which Problems With the Intubation Technique all give rise to ventilation/perfusion mismatches. The goal of laryngoscopy is to visualize the vocal These lead to early airway closure in the supine cords, whereas the goal of intubation is to introduce the position, which is worsened by general anesthesia endotracheal tube between them. Full visualization of itself. Oxygen consumption is increased throughout the vocal cords is feasible in only 75% of patients (14). pregnancy and even more so during active labor. The A grading of the laryngoscopic view (15) may aid in net result is a rapid fall in arterial and tissue oxygen- understanding the role of airway maneuvers (such as ation. Failure to control the airway and ventilate the external cricoid pressure) and use of devices, such as patient would worsen hypoxemia and endanger both the gum elastic bougie (16) in improving the laryngo- the mother and fetus. The practical implication of the scopic view or enabling intubation without full visual- tendency to develop hypoxemia very rapidly, is the ization of the cords. Failure to visualize the cords may need for preoxygenation (or denitrogenation) consist- be related to incorrect position for intubation, inade- ing of administration of 100% oxygen (for 3–5 min- quate technique of laryngoscopy, inadequate muscle utes) before induction of anesthesia. relaxation, or failure to apply laryngeal backpressure to facilitate the visualization of the cords. External pres- PREOPERATIVE ASSESSMENT: sure on the larynx should be applied backward, upward, PREDICTING A DIFFICULT INTUBATION and to the right (BURP maneuver) (17). The head and the neck of the patient should be placed in the so-called An excellent interobserver reliability is necessary “sniffing” position. This position consists of 30-degree for any test to be predictive for difficult intubation flexion of the neck on the chest and 15-degree exten- (19). Table 3 lists some of the examinations and tests sion of the head at the atlanto-occipital joint necessary used to predict a difficult airway. None of these has to bring into one line the pharyngeal, oral, and laryngeal a highly predictive value as a single tool. Nonethe- 634 Obstetrical and Gynecological Survey less, Rocke et al. (5), by evaluating prospectively mask ventilation is avoided during induction of an- 1500 cases of elective and emergency intubations, esthesia in the obstetric patient. There are many has found that two or more abnormal airway findings well-recognized risk factors, which may lead to a are needed for prediction of difficult intubation. He higher propensity for regurgitation in pregnancy, in- also found that a highly predictive sign was a neutral cluding hormonal changes, physical factors, and par- to extension sterno mental distance of less than 5 cm. enteral analgesics or induction agents (21). Among Rocke has built a scale of predictive factors showing the hormonal factors, increased gastrin secretin and clearly that the greater the number of abnormal find- progesterone and decreased secretion of motilin are ings, the higher the prediction accuracy for a difficult responsible for the delay in gastric emptying. Phys- intubation. Regional anesthesia should be considered if ical factors include a decreased lower esophageal two or more risk factors are found. In addition, anes- sphincter tone and increased intragastric pressures, thesiologists should be familiar with the American So- which are both worsened by the lithotomy position ciety of Anesthesiologists (ASA) Practice Guidelines and the stress and pain of labor. Use of narcotics for management of the difficult airway (20). Some during labor and delivery may also delay gastric practitioners may have more experience with fiberoptic emptying. Anesthetic agents (e.g., thiopental) relax airway management than with establishing a well-func- the upper esophageal sphincter (the last barrier tioning epidural. Regardless of how skillfully a regional against regurgitation of gastric content) shortly be- anesthetic is installed, it still may not be satisfactory— fore the patient loses consciousness (22). These block level is too high, duration too short, or toxicity of changes emphasize the need for the application of local anesthetics—so that practitioners prefer to use a cricoid pressure before the patient loses conscious- general anesthesia. ness (23). Cricoid pressure is applied directly over the cricoid cartilage, the only solid structure in the larynx, with the intent of applying backpressure on ASPIRATION OF GASTRIC CONTENTS: the esophagus and preventing regurgitation into the A POSSIBLE RESULT OF oropharynx. However, the effectiveness of cricoid DIFFICULT INTUBATION pressure has been questioned (24), inasmuch as pa- Regurgitation of stomach contents into the oro- tients have died despite its application (25). Gastric pharynx is more likely to occur when there is an distention produced by poor mask ventilation and increase in abdominal contents, slowing of gastric escape of anesthetic gases into the stomach further emptying, or dysfunction of the gastroesophageal increase the intragastric pressure and hamper venti- sphincter, all present during pregnancy. One of the lation. A critical scenario is created due to failure to purposes of intubation is to seal off the entrance to oxygenate the patient as a result of failed intubation, the larynx with a cuffed endotracheal tube. There- inadequate mask ventilation, and aspiration of gastric fore, aspiration of gastric contents may result from contents. The incidence of aspiration in obstetrics failure to intubate. Once intubation fails, the chances ranges from 1/10,000 to 15/10,000 (26) and it seems of not being able to ventilate increase markedly. to be significantly higher in cesarean deliveries than With mask ventilation, there is also a risk of disten- with other obstetric procedures performed under an- tion of the stomach, and the inherent danger of aspi- esthesia. In a retrospective study, Ezri et al. (27) have ration of stomach contents. It is for this reason that found a low incidence of aspiration in parturients

TABLE 3 Preoperative tests useful in predicting difficult intubation No. Test Meaning 1 Atlanto-occipital movement Ability to extend head on the neck. 15 degrees is needed for “sniffing” position. 2 Back of the mouth view Class I: (the whole uvula is visible)—easy intubation (Mallampati classification) Class IV (only the hard palate is visible)—intubation may be difficult 3 Jaw movement The ability to protrude the lower teeth over the upper teeth. With prominent (buck’s) upper teeth, insertion of the laryngoscope may be difficult. 4 Mouth opening Should be at least 4 cm. Reflects the movement of the TMJ* joint 5 Thyromandibular distance Ͻ6 cm, a difficult laryngoscopy is predicted. 6 Thyrosternal distance Ͻ12.5 cm, a difficult laryngoscopy is predicted. * TMJ ϭ temporomandibular joint. Difficult Airway in Obstetric Anesthesia Y CME Review Article 635 requiring short peripartum procedures under general rent overall maternal mortality rate is approximately anesthesia without endotracheal intubation. 9.2 per 100,000 live births (33, 34). Today, failed intubation is the most common cause of anesthesia- related maternal mortality (31) occurring during ce- MATERNAL MORTALITY DUE TO sarean deliveries. One of the important factors con- DIFFICULT INTUBATION tributing to maternal death was the failure of The net result of failure to intubate/ventilate is communication between the anesthesiologist and the hypoxemia, which may eventually lead to brain dam- obstetrician. Risk factors for increased anesthetic- age or death. Failure to intubate/ventilate is respon- related mortality in obstetrics include age over 30 sible for 30% of the overall anesthetic brain damage years, obesity, pregnancy-induced hypertension, and death in the general surgical population (28). nonwhite race, and emergency cesarean delivery Information on maternal mortality in the medical (35). These findings may point to two important literature is scarce, possibly related to fear of recommendations: 1) increase the use of regional litigation. anesthesia for cesarean delivery and 2) improve the Nevertheless, data available from the “Confidential safety of general anesthesia (36). This review will Inquires into Maternal Death in England and Wales,” emphasize the second recommendation of improving are comprehensive and reliable and provide contin- safety for the patients requiring general anesthesia uous information since 1952. In the United Kingdom, and intubation. The American College of Obstetri- between 1970 and 1987 (29), maternal death related cians and Gynecologists (ACOG) Committee on Ob- to anesthesia decreased by 80% from 12.8 to 1.9 per stetrics (1992) recommends early consultation with one million live births. Death was associated only an anesthesiologist in patients at high risk for general with general anesthesia and was caused by aspiration anesthesia to encourage early decision making and of gastric contents and failed intubation. In the improve the cooperation between the obstetricians United States, the anesthesia-related maternal death and anesthesiologists (37). rate has fallen from 4.3 per one million live births in 1979 to 1981 to 1.7 per one million in 1988 to 1990, mainly owing to the increasing use of regional anes- DECISION MAKING thesia for cesarean delivery (30). Most deaths were attributed to airway management difficulties. Sur- When difficult intubation is suspected in airway prisingly, despite the widespread use of pulse oxim- management, an experienced anesthesiologist and etry (early detection of hypoxemia) and capnography the obstetrician should decide which anesthetic tech- (detection of esophageal intubation) mortality related nique is most appropriate. If feasible under these to general anesthesia did not decrease, and anesthe- circumstances, the procedure should be performed sia-related death is still the sixth leading cause of under regional anesthesia. Appropriate airway man- maternal mortality in the U.S. (5, 30–32). The cur- agement equipment should always be available. Ta-

TABLE 4 Equipment necessary for airway management No. Device Comment* 1 Airways Oropharyngeal, nasopharyngeal—3 sizes of each 2 Bougie Eschmann, gum-elastic (a long introducer inserted blindly underneath the epiglottis, then the ET tube is “railroaded” over it) 3 ET tubes At least 3 different sizes 4 Laryngoscopes Two sizes of curved (Macintosh) and straight (Miller) blades 5 LMA and combitube Size 3 and 4 LMA 6 Suction device 7 Fiberoptic bronchoscope 8 Jet injector 9 Percutaneous cricothyrotomy kit 10 Drugs for topical anesthesia Lidocaine, ephedrine 11 Drugs for general anesthesia Thiopental, succinylcholine, opiates, etc 12 Drugs for CPR Atropine, epinephrine, etc 13 Monitoring equipment ECG, pulse oximeter, noninvasive blood pressure, capnography (detection of expi-

ratory CO2 indicates the correct placement of the ET tube), disconnection alarm * ET ϭ endotracheal; LMA ϭ laryngeal mask airway; CPR ϭ cardiopulmonary resuscitation. 636 Obstetrical and Gynecological Survey ble 4 lists the basic equipment necessary for the esthesia (38). Spinal anesthesia is preferred over epi- management of a difficult airway. dural anesthesia because of its faster onset, higher success rate and lower risk of total spinal anesthesia and local anesthetic toxic reaction, owing to admin- AIRWAY MANAGEMENT FOR istration of a smaller dose of drug. Although the use CESAREAN DELIVERY of spinal anesthesia for urgent cesarean remains con- Management depends on whether surgery is elec- troversial, especially concerning the final level of the tive or urgent and whether a difficult airway is pre- block, its duration of action, and the consequences of dicted. Furthermore, the condition of the fetus (dis- hypotension, it has gained more acceptance during tressed or not) may influence the anesthetic the last decade (39). According to the ACOG com- approach. It is generally accepted that if in an ex- mittee opinion (37), cesarean deliveries that are per- treme emergency a choice has to be made between formed for nonreassuring fetal heart rate pattern do survival of the fetus or of the mother, the mother not necessarily preclude the use of regional anesthe- should be protected in preference to the fetus, and sia. A combination spinal-epidural anesthesia (CSE), this would be an extraordinarily rare occurrence. a relatively new technique, has gained popularity. It Nonetheless, it is prudent to emphasize that, in al- provides the combined advantage of rapid onset of most all emergency situations, support and resusci- spinal anesthesia together with flexibility of extend- tation of the mother will benefit the fetus. One major ing or prolonging the duration of the block (40). exception to this is when CPR must be administered When the fetus is in acute distress, surgery could to the mother in the third trimester of pregnancy. In proceed even if intubation failed provided oxygen- this situation, immediate delivery of the fetus will ation and ventilation are adequate. If the airway likely benefit both the mother and the fetus/infant (oxygenation and ventilation) cannot be maintained because CPR attempts can be ineffective because of by a facemask or other airway devices [LMA (laryn- the pressure of the pregnant uterus on the great geal mask airway), Combitube], an artificial airway vessels. should be created (i.e., transtracheal needle jet ventilation, cricothyroidotomy, or tracheostomy) before proceeding with surgery (41). Induction of Anesthesia for Cesarean Delivery With an Apparently Normal Airway Patients With Known or Suspected Airway Table 5 depicts the steps of a standard general Problems Before Cesarean Delivery anesthesia for cesarean deliveries. When an unexpected difficult intubation is encountered during in- Regional anesthesia is indicated if surgery is not duction of anesthesia, the patient should be awak- urgent (no signs of severe maternal bleeding, severe ened (if there is no indication for an emergency fetal distress, etc.) and the coagulation tests are ac- operation) and surgery performed under regional an- ceptable (platelet count Ͼ50,000/ml, bleeding time

TABLE 5 Steps of standard general anesthesia for cesarean delivery No. Steps Comments 1 Equipment ready See Table 4 2 Patient’s position Left lateral tilt (15 degrees) to avoid supine hypotension airway— “sniffing” position 3 Monitoring attached ECG, blood pressure, pulse oximetry, capnography, temperature

4 Preoxygenation (denitrogenation) 3–5 min of 100% O2 with normal breathing, or 4 deep breaths of 100% O2 if there is no time for the first option 5 Another anesthesiologist available for help For cricoid pressure For unexpected difficult intubation 6 Induction of anesthesia Inject thiopental or other hypnotic Apply cricoid pressure before the patient losses consciousness Inject succinylcholine Wait for 30–40 sec and intubate the trachea Inflate the tube’s cuff Confirm the tube’s correct position by capnography Release cricoid pressure Continue with general anesthesia Difficult Airway in Obstetric Anesthesia Y CME Review Article 637

Ͻ10 minutes; no significant drop in the platelet count an anesthesiologist-obstetrician team consulta- in a short time or evidence of clinical bleeding) (42). tion should decide which approach is safest. In the case of patient refusal or if regional anesthesia ACOG defines fetal distress as acute continuous is contraindicated, awake fiberoptic intubation may bradycardia of less than 60 to 80 beats per minute or be an option (38, 41). In the case of failure of severe decelerations. Because the term fetal distress regional anesthesia, a more experienced anesthesiol- is imprecise, the recommendation is to use the term ogist may succeed in performing spinal anesthesia. non-reassuring fetal stress. Their recent committee Equipment for managing the difficult airway should opinion does not give a definition of acute fetal be ready for use in the operating room suite and distress. They also state that non-reassuring fetal treatment possibilities discussed with the obstetri- status is absolutely not contradicted to the use of cian. Risks and benefits should be thoroughly ex- regional anesthesia (43). plained to the patient, and she should be strongly encouraged to accept regional anesthesia. If general anesthesia is chosen in the case of failure of regional SPECIAL AIRWAY DEVICES anesthesia, a comprehensive plan of action should be AND TECHNIQUES ready. Two devices have revolutionized the management of difficult airway: the fiberoptic bronchoscope and Emergency Cesarean Delivery: Urgent Delivery the laryngeal mask airway (LMA). A detailed dis- Versus Airway Management cussion on fiberoptic intubation (FI) is beyond the scope of this review, but it should be noted that An emergency cesarean delivery is performed for expertise is needed to perform FI quickly and safely maternal or fetal indications. Severe maternal bleed- (44, 45). FI may not succeed if the view is impaired ing and/or fetal distress is among the most common by blood and/or secretions (“red out” or “white out”) indications for an emergent cesarean. as may be the case after a failed intubation. Also, FI Even if problems are recognized preoperatively, may be time consuming and, therefore, does not some surgery cannot be delayed by performing re- provide an emergency means of securing the airway. gional anesthesia or fiberoptic intubation. Harmev, Awake intubation may be an alternative to control Latto, and Vaughan (38) had proposed an urgency the airway if regional anesthesia fails in a patient delivery scoring system to help answer the dilemma with known or suspected airway problems (46). of whether to delay surgery if a difficult intubation is LMA may sometimes be the only option when mask anticipated or occurs with induction of general anes- ventilation is not possible, even with mandibular thesia. A simplified form of this scoring is the traction and insertion of oral and nasal airways. Suc- following: cessful ventilation provided by the LMA after failed • Group 1: Surgery should be started even if intubation has been reported in patients undergoing difficult intubation is anticipated. This group cesarean delivery (47–49). An endotracheal tube can includes severe maternal bleeding and severe also be inserted through an LMA, either blindly or fetal distress. In these cases, surgery must be with the aid of a fiberscope. The main drawback of performed even if intubation was unsuccessful, the LMA is the lack of protection against aspiration. provided ventilation and oxygenation of the Despite that, in a critical scenario of impossible in- mother is possible. By no means should surgery tubation and ventilation, the crucial role of LMA in begin if oxygenation and ventilation are providing ventilation overweighs its drawbacks. unsatisfactory. LMA is inserted blindly without the help of a laryn- • Group 2: Regional anesthesia is permitted and goscope and, thus, is less traumatic. LMA is com- indicated, and there is no urgency to perform posed of a soft mask connected to a tube. Its distal surgery. inflated cuff provides a seal around the entrance to • Group 3: An intermediate group that includes the larynx (glottis), and the three apertures on the patients with relative contraindications to re- anterior aspect of the cuff enable ventilation and gional anesthesia, such as cardiac disease or monitoring of respiration. There are three sizes avail- bleeding, but stable hemodynamics; neverthe- able for adults: 3, 4, and 5. The new intubating LMA less, there is a strong indication for regional (LMA, Fastrach, WM Bamford, New Zealand) is anesthesia due to airway pathology. In these designed to increase the success rate of intubation cases, clinical common sense, experience, and through an LMA. The esophageal-tracheal Combi- 638 Obstetrical and Gynecological Survey

Fig. 1. Difficult intubation algorithm for cesarean delivery. RA ϭ regional anesthesia; FI ϭ fiberoptic intubation; LMA ϭ laryngeal mask airway; TTJV ϭ transtracheal jet ventilation; GA ϭ general anesthesia; CI ϭ contraindication. tube is a relatively new device designed for manage- regulator, and emptying of the lungs is not fully ment of difficult airway especially after failure of allowed by maintenance of an inspiration to expira- intubation and impossible ventilation. It has two lu- tion ratio of at least 1:3. mens and two cuffs (they help in fixation of the Combitube and sealing of the airway). The “esophageal” lumen provides ventilation through the eight FAILED INTUBATION ALGORITHM side holes facing the glottic aperture, while the “tra- A universal failed intubation/ventilation algorithm cheal” lumen enables suction of the stomach and was proposed by Benumof (20) and is currently ventilation of the lungs in the rare cases where the recommended by the American Society of Anesthe- tube enters the trachea accidentally. There are two siologists. A practical difficult and failed intubation sizes available: one for standard size patients and one and ventilation drill, as shown in Figure 1, is pro- for patients with short stature (Ͻ150-cm height). At posed by the authors of this review to cover almost the moment, the Combitube, like the LMA, is indi- every possible clinical situation encountered during cated in cases when ventilation through a facemask is anesthesia for cesarean delivery. The main manage- impossible. It has the advantage over the LMA of ment principle in this algorithm is the overall pref- protecting against aspiration of gastric contents. Like erence of regional over general anesthesia. the LMA, it is inserted blindly, but is somewhat more traumatic than the LMA. The Combitube has been used successfully for management of failed intuba- CASE REPORTS AND DISCUSSION tion in cesarean delivery (50). A transtracheal jet Case 1: Use of LMA for Failure to ventilation (TTJV) device consists of a simple I.V. Intubate/Ventilate plastic cannula (14 or 16 gauge) inserted through the cricothyroid membrane. A jet injector provides ven- A 31-year-old, otherwise healthy full-term preg- tilation with oxygen pressurized to 50 pounds per nant woman was scheduled for cesarean delivery square inch (psi). Jet ventilation is used when other because of breech presentation. Her medical history modalities of ventilation, including LMA and Com- revealed no diseases and no previous surgery. Her bitube, fail or are not available (51). The major risk airway looked normal. She refused spinal anesthesia. of TTJV is barotrauma, which may occur if the General anesthesia was induced with thiopental and inflation pressure was not controlled by a pressure- succinylcholine in a rapid sequence manner, while Difficult Airway in Obstetric Anesthesia Y CME Review Article 639 cricoid pressure was applied. No part of the glottic fiberoptic intubation was planned. The nose was structures could be visualized on three successive anesthetized topically with lidocaine, and ephedrine attempts at laryngoscopy, and the SaO2 dropped was used as nasal vasoconstrictor. Once the cords gradually to 90% at the end of the third attempt. were visualized, lidocaine was sprayed over them Mask ventilation with mandibular thrust and oral and through the working channel of the fiberoptic bron- nasal airways was ineffective, and the SaO2 further choscope and the trachea was intubated easily. dropped to 80%. At this point, a number 3 LMA was Throughout the procedure, boluses of labetalol were placed successfully, and ventilation resumed effec- administered for controlling the hypertension. The tively. Surgery started immediately, and the baby rest of the management was uneventful. With ex- was delivered with Apgar scores of 8 and 9 at 1 and pected difficult intubation and failed regional anes- 5 minutes, respectively. The patient was allowed to thesia, awake fiberoptic intubation may be a safer breathe spontaneously through the LMA while anes- alternative airway management. thesia was maintained with isoflurane. Cricoid pressure was applied until the end of surgery. This case Case 4: Failed Intubation—Use of LMA as a and the others emphasize the crucial role of LMA in Conduit for Fiberoptic Intubation maintaining oxygenation and ventilation with failed intubation and failed mask ventilation. A 34-year-old primipara with a ruptured uterus and severe fetal bradycardia (Ͻ50 bpm) was rushed to Case 2: Failure to Intubate/Ventilate—Use of the operating room for emergent CD. The patient was Transtracheal Jet Ventilation pale, tachycardic (135 bpm), with blood pressure A 30-year-old primipara was scheduled for emer- 60/40, and barely responsive to verbal stimuli. gency CD due to fetal distress (fetal bradycardia Ͻ80 She was connected to standard monitoring, and bpm). On inspection, the airway appeared problem- four vital capacity breath preoxygenation and rapid atic (short neck, protruding teeth), but the obstetri- sequence induction (ketamine, succinylcholine) with cian determined that there was no time for perform- cricoid pressure were performed immediately. The ing regional anesthesia. After three failed attempts at laryngoscopy proved to be difficult, but some glottic intubation and failed mask ventilation, the SaO2 structures were identified and the endotracheal tube dropped to 70%. Attempts to ventilate through an inserted. Surgery started immediately. On ausculta- LMA and then a Combitube were futile. A 14-gauge tion, although breath sounds were noticed over the I.V. cannula was inserted through the cricothyroid lungs, the capnograph trace remained flat, and the membrane. The plastic catheter was connected to a patient desaturated rapidly. The tube was removed, jet injector, and the patient was ventilated effectively and mask ventilation was performed effectively. The over the next 10 minutes. The baby was delivered baby was delivered with Apgar scores of 1 and 5 at with Apgar scores of 6 and 9 at 1 and 5 minutes, 1 and 5 minutes, respectively. The patient was bleed- respectively. After 10 minutes of transtracheal jet ing actively and intensive resuscitation with blood, ventilation, the trachea was intubated with a fiber- blood products, and crystalloids was necessary. At scope. When intubation, mask ventilation, and the this stage, uterine suture was performed and cesarean insertion of an LMA or Combitube all fail, the fastest hysterectomy was planned. Because of the extent of option to oxygenate the patient is a cannula inserted surgery, the airway had to be secured. An oral fiber- through the cricothyroid membrane and connected to optic intubation failed due to copious bloody secre- a patient ventilator. tions. A number 4 intubating LMA was easily in- Case 3: Failed Regional serted, and the patient ventilated through it for a few Anesthesia—Fiberoptic Intubation minutes. A second attempt at fiberoptic intubation A 25-year-old morbidly obese patient was sched- with a number 6 endotracheal tube through the LMA uled for an elective CD because of severe preeclamp- was successful. The LMA and the endotracheal tube sia. She had a short neck and limited mouth opening were left in place until the end of the procedure. (Ͻ3 cm). Her blood pressure was 190/110 despite of During the next hour, seven packed cell blood units treatment with magnesium sulfate, nifedipine, and were administered, and a hysterectomy was per- hydralazine. Many attempts at performing epidural formed. With extensive surgery, the airway should be or spinal anesthesia were unsuccessful. A small sed- secured with an endotracheal tube (ETT). This may ative bolus of midazolam and an antisialagogue dose be more feasible than using a fiberscope inserted of atropine were administered intravenously. A nasal through an LMA. 640 Obstetrical and Gynecological Survey

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