Pneumonia and respiratory failure requiring prolonged mechanical ventilation are the most important postoperative pulmonary complications and occur in 2–19% of surgical procedures. The occurrence of a postoperative pulmonary complication has been associated with a significant increase in hospital length of stay.
Risk Factors for the Development of Postoperative Pulmonary Complications
The risk of developing a pulmonary complication is highest in patients undergoing cardiac, thoracic, and upper abdominal surgery, with reported complication rates ranging from 9% to 19%. The risk in patients undergoing lower abdominal or pelvic procedures ranges from 2% to 5%, and for extremity procedures the range is < 1–3%. The pulmonary complication rate for laparoscopic procedures appears to be much lower than that for open procedures. In one series of over 1500 patients who underwent laparoscopic cholecystectomy, the pulmonary complication rate was < 1%. Other procedure-related risk factors include prolonged anesthesia time, need for general anesthesia, and emergency operations.
Among the many patient-specific risk factors for postoperative pulmonary complications, the strongest predictor appears to be advanced age. Surgical patients in their seventh decade had a fourfold higher risk of pulmonary complications compared with patients under age 50. Patients with chronic obstructive pulmonary disease (COPD) or CHF have at least twice the risk compared with patients without these conditions. In a large prospective cohort of US military veterans, additional clinical risk factors for the development of postoperative pneumonia included dependent functional status, impaired sensorium, prior stroke, long-term corticosteroid use, heavy alcohol consumption, and current cigarette smoking.
Patients with asthma are at slightly increased risk for bronchospasm during tracheal intubation and extubation and during the postoperative period. However, if patients are at their optimal pulmonary function (as determined by symptoms, physical examination, or peak flow rate) at the time of surgery, they are not at increased risk for other pulmonary complications. Obesity causes restrictive pulmonary physiology, which may increase pulmonary risk in surgical patients. However, it is unclear if obesity is an independent risk predictor. Obstructive sleep apnea has been associated with a variety of postoperative complications, particularly in patients undergoing bariatric surgery. The STOP screening questionnaire asks whether a patient has snoring, tiredness during the day, observed apnea, and high blood pressure. The presence of two or more of these findings had a 78% positive predictive value for obstructive sleep apnea and was associated with a doubled risk for postoperative pulmonary complications. A summary of risk factors for pulmonary complications is presented in Table 3–4.
CHF have at least twice the risk compared with patients without these conditions. In a large prospective cohort of US military veterans, additional clinical risk factors for the development of postoperative pneumonia included dependent functional status, impaired sensorium, prior stroke, long-term corticosteroid use, heavy alcohol consumption, and current cigarette smoking.
Patients with asthma are at slightly increased risk for bronchospasm during tracheal intubation and extubation and during the postoperative period. However, if patients are at their optimal pulmonary function (as determined by symptoms, physical examination, or peak flow rate) at the time of surgery, they are not at increased risk for other pulmonary complications. Obesity causes restrictive pulmonary physiology, which may increase pulmonary risk in surgical patients. However, it is unclear if obesity is an independent risk predictor. Obstructive sleep apnea has been associated with a variety of postoperative complications, particularly in patients undergoing bariatric surgery. The STOP screening questionnaire asks whether a patient has snoring, tiredness during the day, observed apnea, and high blood pressure. The presence of two or more of these findings had a 78% positive predictive value for obstructive sleep apnea and was associated with a doubled risk for postoperative pulmonary complications. A summary of risk factors for pulmonary complications is presented in Table 3–4.
Pulmonary Function Testing & Laboratory Studies
Few data support the use of preoperative testing to assess pulmonary risk. Pulmonary function testing (PFT) in unselected patients is not helpful in predicting postoperative pulmonary complications. The main role for preoperative PFT is to help identify and characterize pulmonary disease in patients with unexplained symptoms prior to major abdominal or cardiothoracic surgery. In patients with diagnosed lung disease, PFT often adds little information above clinical assessment. Furthermore, there is no clear degree of PFT abnormality that can be used as an absolute contraindication to non–lung resection surgery. Chest radiographs in unselected patients also rarely add clinically useful information. In one study, only 0.1% of routine preoperative chest radiographs changed clinical management. They may be more useful in patients who are undergoing abdominal or thoracic surgery who are over age 50 or have known cardiopulmonary disease. Some experts have also advocated polysomnography to diagnose obstructive sleep apnea prior to bariatric surgery, but the benefits of this approach are unproven. Abnormally low or high blood urea nitrogen levels (indicating malnutrition and renal insufficiency, respectively) and hypoalbuminemia predict postoperative pulmonary complications and mortality, although the role of laboratory testing is uncertain. Arterial blood gas measurement is not routinely recommended except in patients with known lung disease and suspected hypoxemia or hypercapnia.
Perioperative Management
The preoperative period may be an optimal time to initiate smoking cessation efforts. A systematic review found that smoking cessation programs started in a preoperative evaluation clinic increased the odds of abstinence at 3–6 months by nearly 60%. Retrospective studies have shown that smoking cessation reduced the incidence of pulmonary complications, but only if it was initiated at least 1–2 months before surgery. In several randomized trials, preoperative smoking cessation programs reduced surgical wound complications, but these studies did not have adequate statistical power to detect an impact on respiratory complications.
The incidence of postoperative pulmonary complications in patients with COPD or asthma may be reduced by preoperative optimization of pulmonary function. Patients who are wheezing should receive preoperative therapy with bronchodilators and, in certain cases, corticosteroids. Antibiotics may be beneficial for patients with COPD who cough with purulent sputum. Patients receiving oral theophylline should continue taking the drug perioperatively. A serum theophylline level should be measured to rule out toxicity. Most patients with COPD can be treated with cardioselective β-blockers if indicated to prevent perioperative cardiac complications without suffering respiratory
compromise.
compromise.
Postoperative risk reduction strategies have centered on promoting lung expansion through the use of incentive spirometry, continuous positive airway pressure (CPAP), intermittent positive-pressure breathing (IPPB), and deep breathing exercises. Although trial results have been mixed, all these techniques have been shown to reduce the incidence of postoperative atelectasis and, in a few studies, to reduce the incidence of postoperative pulmonary complications. In most comparative trials, these methods were equally effective. Given the higher cost of CPAP and IPPB, incentive spirometry and deep breathing exercises are the preferred methods for most patients. Incentive spirometry must be performed for 15 minutes every 2 hours. Deep breathing exercises must be performed hourly and consist of 3-second breath-holding, pursed lip breathing, and coughing. These measures should be started preoperatively and be continued for 1–2 days postoperatively.
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