Pulmonary Disease In patients undergoing abdominal surgery, several pulmonary physiologic changes manifest secondary to immobilization, anesthetic irritation of the airways, and the splinting of breathing that inevitably occurs secondary to incisional pain. Pulmonary physiologic changes include a decrease in the functional residual capacity (FRC), an increase in ventilation perfusion mismatching, and impaired mucociliary clearance of secretions from the tracheobronchial tree (236). Risk factors for postoperative pulmonary complications include the following (237,238) (Table 22.20):
Upper abdominal or thoracic, or abdominal aortic aneurysm surgery
Smoking within 2 months of surgery
Use of pancuronium for general anesthesia
Table 22.20 Predictors of Postoperative Pulmonary Complicationsa
FEV, forced expiration volume; FVC, forced vital capacity; PaO2, partial pressure of oxygen, arterial; PaCO2, partial pressure of carbon dioxide, arterial. aComplication defined as atelectasis or pneumonia. Adapted from Blosser SA, Rock P. Asthma and chronic obstructive lung disease. In: Breslow MJ, Miller CJ, Rogers MC, eds. Perioperative management. St. Louis, MO: Mosby, 1990:259–280.
Poor nutrition (serum albumin <3.5mg/dL or BUN <8).
Probable risk factors include general anesthesia, preoperative partial pressure of carbon dioxide, arterial (PaCO2) greater than 45 mm Hg, and emergency surgery. Risk factors that could increase the postoperative risk are upper respiratory infection, abnormal chest x-ray, and age. Preoperative pulmonary function testing is of unproven value in patients not undergoing thoracic surgery (237). This is based on multiple reasons: first, a lower limit of forced expiration volume (FEV1) did not correlate with pulmonary complications; second, pulmonary complications can occur in the context of a normal FEV1; and third, if an FEV1 were able to predict a pulmonary complication putting the patient at increased risk, it would not change the need for aggressive postoperative prophylactic measures (237). The routine performance of preoperative arterial blood gas measurements does not improve assessment of risk (236). Noninvasive pulse-oximetry measurements can detect patients with hypoxemia (236). The presence of hypercarbia on arterial blood gas measurements does not predict postoperative pulmonary complications (236).
Young, healthy patients rarely have abnormal chest x-rays. Chest x-rays should not be performed routinely in these patients. Most patients with abnormal chest x-rays have history or physical examination findings suggestive of pulmonary disease. Chest x-rays should be limited to patients older than 50 years of age, with a history of smoking or of pulmonary disease, who have evidence of cardiopulmonary disease and in whom a metastatic malignancy is suspected. Although they have limited usefulness in predicting postoperative pulmonary complications, chest x-rays provide a valuable baseline in elderly patients, patients with chronic pulmonary diseases, and those with known lung metastases (236–238).