Pneumonia and respiratory failure requiring prolonged mechanical ventilation are the most important postoperative pulmonary complications. The occurrence of these complications has been associated with a significant increase in mortality and hospital length of stay. Pulmonary thromboembolism is another serious complication; prophylaxis against venous thromboembolic disease is described in Chapter 14.
RISK FACTORS FOR THE DEVELOPMENT OF POSTOPERATIVE PULMONARY COMPLICATIONS
Procedure-related risk factors for postoperative pulmonary complications include location of surgery (with highest rates occurring in cardiac, thoracic, and upper abdominal cases), prolonged anesthesia, and emergency cases. Operations not requiring general anesthesia tend to have lower rates of postoperative pulmonary complications, and laparoscopic procedures tend to have lower risk than comparable open procedures. In one series of over 1500 patients who underwent laparoscopic cholecystectomy, the pulmonary complication rate was less than 1%.
It remains unclear which of the many patient-specific risk factors that have been identified are independent predictors. Advanced age appears to confer increased risk. The presence and severity of systemic disease of any type is associated with pulmonary complications. In particular, patients with chronic obstructive pulmonary disease (COPD) or HF have at least twice the risk of postoperative pulmonary complications compared with patients without these conditions. As with preoperative cardiac risk assessment, physical debility and poor functional capacity predict higher risk of postoperative pulmonary complications. A summary of risk factors for pulmonary complications is presented in Table 3–4. A risk calculator for predicting postoperative respiratory failure derived from the NSQIP patient database (http://www.qxmd.com/calculate-online/respirology/postoperative-respiratory-failure-risk-calculator) includes the type of surgery, emergency surgery, preoperative sepsis, dependency in activities of daily living, and the patient’s American Society of Anesthesiologists physical status classification.
Table 3–4.Clinical risk factors for postoperative pulmonary complications. |Favorite Table|Download (.pdf) Table 3–4. Clinical risk factors for postoperative pulmonary complications.
Upper abdominal or cardiothoracic surgery
Prolonged anesthesia time (> 4 hours)
Age > 60 years
Chronic obstructive pulmonary disease
Severe systemic disease
Tobacco use (> 20 pack-years)
Impaired cognition or sensorium
Functional dependency or prior stroke
Low serum albumin level
Obstructive sleep apnea
Patients with well-controlled asthma are not at increased risk for pulmonary complications. Obstructive sleep apnea has been associated with a variety of postoperative complications, including postoperative pulmonary complications and atrial fibrillation. The STOP-BANG screening questionnaire asks whether a patient has snoring, tiredness during the day, observed apnea, high blood pressure, body mass index greater than 35, age greater than 50, neck circumference greater than 17 inches for males or 16 inches for females, and male gender. The presence of five or more of these findings or at least two STOP criteria plus B, N, or G had a 78% positive predictive value for obstructive sleep apnea and was associated with a doubled risk for postoperative pulmonary complications.
PULMONARY FUNCTION TESTING & LABORATORY STUDIES