INTRODUCTION: An uncommon cause of post-operative pulmonary edema of rapid onset is negative pressure pulmonary edema (NPPE). Incidence is thought to be about 0.05 to 1 percent of all procedures involving intubation. We present here two cases of healthy individuals who presented for routine surgery and subsequently developed acute respiratory failure.
CASE PRESENTATION: CASE 1: 47-yr-old male presented to our hospital with difficulty breathing and hypoxia. He underwent a septoplasty at a surgical clinic requiring endotracheal intubation. After extubation, he became acutely short of breath and was re-intubated with a laryngeal mask with improvement. The patient was again extubated, after which he became dyspneic and hypoxic and transferred to our hospital. He denied any chest pain, palpitations or cough. Physical exam revealed a healthy young man in moderate respiratory distress, with pink frothy sputum and bilateral rales on chest examination. EKG findings were normal. Chest radiograph showed bilateral alveolar opacification without cardiomegaly. The patient was treated with diuretics and non-invasive positive pressure ventilation, which resulted in remarkable improvement and was discharged the next day. CASE 2: We admitted a 28-yr-old healthy young man to our ICU because of acute respiratory failure. The patient underwent arthroscopic surgery for repair of his left anterior cruciate ligament. A laryngeal mask [LMA] was utilized to secure his airway for the surgery. History revealed that the patient bit on the LMA prior to its removal. After the LMA was removed he started having difficulty breathing, without any other accompanying symptoms. He became hypoxic. Chest exam was remarkable for diminished air entry in both lung fields. The rest of his exam was normal. Chest radiograph showed bilateral pulmonary infiltrates without cardiomegaly He was monitored and given supplemental oxygen and diuretics with significant clinical improvement. Patient was discharged in stable condition. Below is a chest radiograph [Case 1]showing increased pulmonary vascular markings and dense interstitial infiltrates.
DISCUSSIONS: NPPE can be due to forced inspiration against a closed glottis (Mueller maneuver), as occurs when laryngospasm or other types of upper airway obstruction occur after extubation. This leads to the development of markedly negative intrathoracic pressures that increases venous return to the right heart and pulmonary arteries. Starling forces then favor the transudation of fluid from the pulmonary capillaries to the interstitium. While strangulation, laryngeal trauma, epiglottitis , croup, foreign-body aspiration and even hiccups have been reported to cause NPPE, the majority of cases occur due to laryngospasm after extubation from surgery. Predisposing factors include obesity, short neck, obstructive sleep apnea and upper airway surgery. The pulmonary edema usually occurs immediately after the laryngospasm develops but may be delayed up to 6 hours. The patients typically present with stridor, dyspnea, pink frothy sputum and bilateral pulmonary infiltrates on chest radiography. Treatment is supportive and requires maintenance of a patent airway and oxygenation. Some patients may require diuretics, steroids and ventilatory support.
CONCLUSION: We report here two cases of negative pressure pulmonary edema that occurred after surgery. One case occurred after a septoplasty and would be considered high risk for this complication. The other occurred in a patient whose airway was secured by an LMA, which is very rarely reported. This condition must be recognized early and prompt intervention instituted, which may range from using Noninvasive Positive Pressure Ventilation to intubation.
DISCLOSURE: Francis Ansa, None.