Continuous Positive Airway Pressure for Treatment of Postoperative Hypoxemia a Randomized Controlled Trial
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CARING FOR THE CRITICALLY ILL PATIENT Continuous Positive Airway Pressure for Treatment of Postoperative Hypoxemia A Randomized Controlled Trial Vincenzo Squadrone, MD Context Hypoxemia complicates the recovery of 30% to 50% of patients after ab- Massimiliano Coha, MD dominal surgery; endotracheal intubation and mechanical ventilation may be re- Elisabetta Cerutti, MD quired in 8% to 10% of cases, increasing morbidity and mortality and prolonging in- tensive care unit and hospital stay. Maria Maddalena Schellino, MD Objective To determine the effectiveness of continuous positive airway pressure com- Piera Biolino, MD pared with standard treatment in preventing the need for intubation and mechanical Paolo Occella, MD ventilation in patients who develop acute hypoxemia after elective major abdominal surgery. Giuseppe Belloni, MD Design and Setting Randomized, controlled, unblinded study with concealed al- Giuseppe Vilianis, MD location conducted between June 2002 and November 2003 at 15 intensive care units Gilberto Fiore, MD of the Piedmont Intensive Care Units Network in Italy. Franco Cavallo, MD Patients Consecutive patients who developed severe hypoxemia after major elec- V. Marco Ranieri, MD tive abdominal surgery. The trial was stopped for efficacy after 209 patients had been enrolled. for the Piedmont Intensive Care Units Interventions Patients were randomly assigned to receive oxygen (n=104) or oxy- Network (PICUN) gen plus continuous positive airway pressure (n=105). Main Outcome Measures The primary end point was incidence of endotracheal ECOVERY FROM ABDOMINAL intubation; secondary end points were intensive care unit and hospital lengths of stay, surgery is usually fast and un- incidence of pneumonia, infection and sepsis, and hospital mortality. complicated, but postopera- tive hypoxemia complicates Results Patients who received oxygen plus continuous positive airway pressure had a lower intubation rate (1% vs 10%; P=.005; relative risk [RR], 0.099; 95% confidence Rbetween 30% and 50% of cases, even interval [CI], 0.01-0.76) and had a lower occurrence rate of pneumonia (2% vs 10%, among those undergoing uneventful RR, 0.19; 95% CI, 0.04-0.88; P=.02), infection (3% vs 10%, RR, 0.27; 95% CI, 0.07- procedures.1 Although oxygen admin- 0.94; P=.03), and sepsis (2% vs 9%; RR, 0.22; 95% CI, 0.04-0.99; P=.03) than did pa- istration and incentive spirometry are tients treated with oxygen alone. Patients who received oxygen plus continuous positive effective in treating the vast majority of airway pressure also spent fewer mean (SD) days in the intensive care unit (1.4 [1.6] vs cases of postoperative hypoxemia,2 res- 2.6 [4.2], P=.09) than patients treated with oxygen alone. The treatments did not affect piratory failure may occur early in the the mean (SD) days that patients spent in the hospital (15 [13] vs 17 [15], respectively; postoperative course,3 requiring endo- P=.10). None of those treated with oxygen plus continuous positive airway pressure died in the hospital while 3 deaths occurred among those treated with oxygen alone (P=.12). tracheal intubation and mechanical ven- tilation in 8% to 10% of patients, thus Conclusion Continuous positive airway pressure may decrease the incidence of en- increasing morbidity and mortality and dotracheal intubation and other severe complications in patients who develop hypox- prolonging intensive care unit (ICU) emia after elective major abdominal surgery. and hospital stay.1-4 Loss of function- JAMA. 2005;293:589-595 www.jama.com ing alveolar units has been recognized Author Affiliations and PICUN Members are listed at Caring for the Critically Ill Patient Section Editor: as the underlying mechanism respon- the end of this article. Deborah J. Cook, MD, Consulting Editor, JAMA. sible for postoperative hypoxemia.5-7 Corresponding Author: V. Marco Ranieri, MD, Uni- Advisory Board: David Bihari, MD; Christian versità di Torino, Dipartimento di Anestesia, Azienda Brun-Buisson, MD; Timothy Evans, MD; John Pulmonary atelectasis after abdominal Ospedaliera S. Giovanni Battista-Molinette, Corso Heffner, MD; Norman Paradis, MD; Adrienne surgery is, in fact, common. It may ex- Dogliotti 14, 10126 Torino ([email protected]). Randolph, MD. ©2005 American Medical Association. All rights reserved. (Reprinted) JAMA, February 2, 2005—Vol 293, No. 5 589 Downloaded From: http://jama.jamanetwork.com/ on 02/11/2013 CPAP FOR POSTOPERATIVE HYPOXEMIA ceed 25% of the total lung volume and METHODS tional class of II, III, or IV; had valvu- is seen several days after surgery.5-7 Patients lar heart disease, history of dilated car- Continuous positive airway pres- From June 2002 to November 2003, pa- diomyopathy, implanted cardiac pace sure (CPAP) is a breathing mode by tients were recruited from the centers maker, unstable angina, or myocar- which the patient spontaneously of the Piedmont Intensive Care Units dial infarction and cardiac surgery breathes through a pressurized circuit Network (PICUN; members and insti- within the previous 3 months; had a his- against a threshold resistor that main- tutions are listed in the acknowledg- tory of chronic obstructive pulmo- tains a preset positive airway pressure ment). Ethics committees approved the nary disease, asthma, or sleep disor- during both inspiration and expira- protocol and written informed con- ders; had preoperative infection, sepsis, tion. Although several studies have sent was obtained from the patients. or both13; had a body mass index higher demonstrated the efficacy of CPAP to Patients scheduled for elective ab- than 40; had a presence of tracheos- reduce atelectasis and improve oxygen- dominal surgery and general anesthe- tomy, facial, neck, or chest wall abnor- ation in patients after abdominal sur- sia were eligible to participate in the malities; required an emergency pro- gery,8-11 no clinical trials have con- study if they met the following crite- cedure (operation that must be firmed that the improvement of gas ria: abdominal surgery requiring lapa- performed as soon as possible and no exchange with CPAP actually results in rotomy and time of viscera exposure longer than 12 hours after admis- a reduced need for intubation and me- longer than 90 minutes. At the end of sion); or had undergone abdominal aor- chanical ventilation in patients who de- the surgical procedure, patients were tic aneurysm surgery, chemotherapy, or velop hypoxemia after abdominal sur- extubated and underwent a 1-hour immunosuppressive therapy within the gery.12 We conducted a multicenter, screening test breathing oxygen previous 3 months. Patients were also prospective, randomized clinical trial through a Venturi mask at an inspira- excluded if before randomization they to compare the efficacy of CPAP with tory fraction of 0.3. Patients were in- had arterial pH lower than 7.30 with an standard oxygen therapy in the treat- cluded in the study if they developed arterial carbon dioxide tension higher ment of postoperative hypoxemia. We an arterial oxygen tension to inspira- than 50 mm Hg; arterial oxygen satu- also set out to examine the hypothesis tory oxygen fraction ratio (PaO2/FiO2) ration lower than 80% with the maxi- that early application of CPAP may pre- of 300 or less (FIGURE 1). Patients were mal fraction of inspiratory oxygen; clini- vent intubation and mechanical venti- excluded if before surgery they were cal signs of acute myocardial infarction; lation in patients who develop acute hy- older than 80 or younger than 18 years; systolic arterial pressure lower than 90 poxemia after major abdominal surgery. had a New York Heart Association func- mm Hg under optimal fluid therapy; presence of criteria for acute respira- tory distress syndrome14; hemoglobin Figure 1. Patient Flow Chart concentration lower than 7 g/dL, se- rum albumin level lower than 3 g/dL; 1322 Patients Enrolled creatinine level higher than 3.5 mg/dL (309 µmol/L); or a Glasgow Coma Scale 12 Refused to Participate 1080 Excluded (Did Not Meet lower than 12. Postoperative Eligibility Criteria) Study Design 230 Met Postoperative Eligibility Criteria Concealed randomization was con- 21 Excluded ducted centrally through a dedicated 11 Lack of Intensive Care Web site using a computer-generated Unit Beds 6 Arterial Oxygen Saturation block randomization schedule. <80% With Maximal Fraction of Inspired Oxygen Patients were randomly assigned to 3 Arterial pH <7.30 With be treated for 6 hours with oxygen PaCO2 >50 mm Hg 1 Systolic Blood Pressure through a Venturi mask at an FiO2 of <90 mm Hg 0.5 (control patients) or with oxygen at an FiO2 of 0.5 plus a CPAP of 7.5 cm 209 Randomized 8,15 H2O. At the end of the 6-hour pe- riod, patients underwent a 1-hour 104 Assigned to Receive Oxygen Therapy by 105 Assigned to Receive Oxygen Therapy With Venturi Mask (Control) Continuous Positive Airway Pressure screening test breathing oxygen through a Venturi mask at an FiO2 of 2 Developed Treatment Intolerance and 4 Developed Treatment Intolerance and 8,15 Discontinued Study Treatment Discontinued Study Treatment 0.3. Patients returned to the as- signed treatment if the PaO2/FiO2 ratio 104 Included in Analysis 105 Included in Analysis was 300 or less; treatment was inter- rupted if the PaO2/FiO2 ratio was higher 590 JAMA, February 2, 2005—Vol 293, No. 5 (Reprinted) ©2005 American Medical Association. All rights reserved. Downloaded From: http://jama.jamanetwork.com/ on 02/11/2013 CPAP FOR POSTOPERATIVE HYPOXEMIA than 300. Nasal oxygen (8-10 L/min) tubate a patient was made by the at- analyses were conducted