General Medical Information

Management of Postoperative Pulmonary Insufficiency

David M. Barrs

Atelectasis, pulmonary edema, and aspiration are the most common causes. Exacerbations of preexisting pulmonary problems, mechanical limitations of breathing, acute bronchospasm, pulmonary embolization, congestive heart failure, and hypovolemia also should be considered. In head and neck procedures, mechanical limitations to breathing may be caused by gastric distension, pneumothorax, aspiration, or phrenic nerve injury with hemidiaphragmatic paralysis. Supplemental oxygen should be given immediately at 10 to 20 L/min while a pertinent history, physical examination, arterial blood gases, and a chest radiograph are obtained. The patient should be in a comfortable sitting position.

Treatment of atelectasis is aimed at reexpanding the collapsed segment. Deep-breathing exercises, incentive spirometry, continuous positive airway pressure, and intermittent positive pressure breathing can be used. Adequate pain medication should be provided to promote mobility and deep breathing. Increased hydration, mist, nebulized bronchodilators, and mucolytic agents should be given through the airway to liquefy thickened secretions that may be blocking the involved bronchus. Paradoxically, coughing does not clear mucus from collapsed airways, because there is no air distal to the mucous plug. Tracheal suction may be successful in removing retained secretions but should be performed with caution because it may produce increased vagal tone and hypoxemia. Five milliliters of saline may be injected through the nasotracheal catheter to help liquefy secretions and facilitate aspiration through the catheter. Suction should be applied for no longer than 10 seconds before oxygen flow is resumed to prevent cardiac arrhythmia.

ECG monitoring should be performed and atropine should be available for bradycardia. Bronchoscopy allows direct visualization of the bronchial tree, removal of debris, and culture. If adequate ventilation cannot be restored by these methods, endotracheal intubation and mechanical ventilation are indicated.

Otolaryngology patients undergoing major head and neck ablative procedures are predisposed to aspiration of saliva, blood, or gastric acid. Immediate treatment consists of mechanical removal of any foreign substance from the upper airway. Nasogastric tube placement is performed to empty the stomach of any further gastric acid. Bronchospasm may be present and respond to bronchodilators. Endotracheal intubation is performed if pulmonary insufficiency results.

Pulmonary edema is caused by an increase in lung water. A flow-directed pulmonary artery catheter can help distinguish high from low pressure pulmonary edema. Cardiogenic pulmonary edema is usually associated with a pulmonary artery wedge pressure greater than 25 mm Hg. In cardiogenic pulmonary edema, interstitial edema progresses to alveolar edema. Treatment in young patients is fluid restriction with the use of diuretics as necessary. In patients with cardiopulmonary or renal disease, dobutamine, dopamine, or both may be required for low cardiac output and to increase renal perfusion. Furosemide is the diuretic of choice because it promotes venodilation and diuresis. Nitroprusside may be necessary in patients with high systemic vascular resistance to reduce the cardiac afterload. Intravenous nitroglycerin may help patients who have coronary insufficiency. If hypoxemia or hypercapnia persists after these measures, ventilatory support may be necessary.
Adult respiratory distress syndrome is manifest as pulmonary edema in the presence of normal pulmonary artery wedge pressure. Lung damage is indirect and usually caused by infection, inflammation, or tissue destruction elsewhere in the body. It manifests as severe hypoxemia and decreased lung compliance, and it shows diffuse bilateral pulmonary infiltrates on chest x-ray. Management is directed at treating the underlying cause. The severe hypoxemia and hypercapnia may need mechanical ventilation with positive end-expiratory pressure. The inspired oxygen content should be kept as low as possible to minimize oxygen toxicity while maintaining the hemoglobin oxygen saturation above 90%. Intravascular volume is kept low, and dobutamine and dopamine may be needed for inotropic support. Nitrous oxide may reduce the pulmonary arterial pressure and improve oxygenation.