MIAMI BEACH — Obstructive sleep apnea is an emerging risk factor for postoperative pulmonary complications, and although evidence does not yet support universal screening, it may be worthwhile to test some elective surgery patients for apnea, Dr. Gerald W. Smetana said.
“If it's not urgent surgery, take a time out and test to confirm sleep apnea,” Dr. Smetana said. “The evidence is more compelling now.”
In one study, researchers prospectively assessed 172 patients with at least two risk factors for obstructive sleep apnea before surgery and measured clinical severity using home nocturnal oximetry (Chest 2008;133:1128–34). They found that patients who experienced five or more oxygen desaturations per hour had significantly higher rates of postoperative pulmonary complications, compared with those with fewer episodes (15% vs. 3%, adjusted odds ratio 7.2).
Postop complications in the study were respiratory (nine patients), cardiovascular (five patients), bleeding (two patients), and gastrointestinal (one patient). Although the numbers were small, results were “pretty significant” for pulmonary complications, Dr. Smetana said at a meeting on perioperative medicine sponsored by the University of Miami.
Older age, American Society of Anesthesiologists' class of 2 or greater, chronic obstructive pulmonary disorder, and heart failure are other risk factors identified in the American College of Physicians guidelines on “risk assessment for and strategies to reduce perioperative pulmonary complications for patients undergoing non-cardiothoracic surgery” (Ann. Intern. Med. 2006;144:575–80).
“There is class A evidence that these are risk factors,” said Dr. Smetana, a coauthor of the ACP guidelines and an attending physician in the division of general medicine and primary care at Beth Israel Deaconess Medical Center in Boston.
“Pulmonary vary from cardiovascular risks in an important way—procedural risks are more important than patient risk factors. Even relatively healthy patients can have risk of pulmonary complications,” Dr. Smetana said. Pulmonary complications include pneumonia, respiratory failure, atelectasis, bronchospasm, and exacerbation of COPD.
A meeting attendee asked about asthma. “If it is well controlled, surprisingly, it is not a risk factor for postoperative pulmonary complications,” said Dr. Smetana, who is also on the medicine faculty at Harvard Medical School, Boston.
In terms of risk reduction, lung expansion modalities are the only intervention with good evidence, he said.
Active muscle training before surgery reduces pulmonary complications in high-risk patients, according to a randomized, controlled trial of 279 elective coronary artery bypass graft patients (JAMA 2006;296:1851–7). Preoperative inspiratory muscle training reduced postoperative high-grade pulmonary complications (OR 0.52) and pneumonia (OR 0.40), compared with a usual care group.
A meta-analysis indicated that postoperative continuous positive airway pressure lowers the overall pulmonary complication rate after abdominal surgery (Ann. Surg. 2008;247:617–24), making it “a good option for patients who cannot tolerate active muscle training,” he said.
'If it's not urgent surgery, take a time out and test to confirm sleep apnea.' DR. SMETANA