An Analysis of Negative Pressure Pulmonary Edema Cases after Acute Upper Airway Obstruction

Abstract

Objective: Negative-pressure pulmonary edema (NPPE) occurs when significant negative intrathoracic pressure develops against an obstructed airway, causing fluid to shift into the pulmonary interstitium. NPPE is a rare complication of all anesthetics with an incidence of less than 0.1%. However, the occurrence of NPPE has been suggested to be under-reported, as it is often unrecognized or misdiagnosed. The morbidity and mortality of an unrecognized event of NPPE is as high as 40%. The present study reviews the cases of NPPE and discusses the occurrence, predisposing factors, and recommendations for treatment and prevention.Methods: All patients with general anesthesia from January 1, 2006 through December 31, 2008 were retrospectively analyzed from our Quality Assurance (QA) anesthesiology database. NPPE was diagnosed according to the clinical findings of tachypnea, rales on lung auscultation, pink frothy sputum in the endotracheal tube, hypoxemia on pulse oximetry or on arterial blood gas determination, radiological findings of pulmonary edema, and pulmonary edema which resolved within 24 hours.Results: Of the 126,589 patients who underwent general anesthesia with endotracheal intubation, 13 (0.01%) cases of NPPE were reported (8 males and 5 females). All cases were American Society of Anesthesiologists (ASA) physical status I or II. The age ranged from 11 months to 56 years and the body weight ranged from 9 kg to 90 kg. Most of the patients showed a rapid onset of pulmonary edema after acute upper airway obstruction in the induction and emergency periods. Resolution occurred within 24 hours after reestablishment of airway, adequate oxygenation, and positive pressure ventilation.Conclusions: An early diagnosis of NPPE with reestablishment of the airway, adequate oxygenation, and application of positive airway pressure represent an effective treatment. NPPE can be prevented by identification of high-risk patients, gentle airway manipulation during induction, and extubation at the right time when the patient's airway reflexes have fully recovered.