Undiagnosed Obstructive Sleep Apnea and Postoperative Outcomes: A Prospective Observational Study

The prevalence of undiagnosed obstructive sleep apnea (OSA) during preoperative evaluation and the best method to screen OSA and its association with postoperative complications remain unclear.

To determine the prevalence of undiagnosed OSA in preoperative Indian patients undergoing noncardiac surgery, to compare the diagnostic accuracy of the STOP-BANG questionnaire to a preoperative level III sleep study, and to assess the association of OSA with postoperative complications.

A prospective cohort of 245 consecutive adults with ≥2 risk factors for OSA who underwent noncardiac surgery between July 2011 and February 2013 were studied. The STOP-BANG questionnaire was administered to all patients, and 182/245 (74.2%) patients underwent a preoperative level III sleep study. Patients were followed for postoperative complications in hospital and contacted at 30 days after surgery.

70/182 (38.5%) obtained a new diagnosis of OSA, including 11/182 (6%) with moderate to severe OSA (apnea-hypopnea index ≥15/h). On logistic regression analyses, the presence of OSA was independently associated with postoperative oxygen desaturation (OR 5.96, 95% CI 2.35-15.1, p < 0.01), a postoperative complication within 7 days (OR 3.63, 95% CI 1.77-7.45, p < 0.01) and within 30 days (OR 3.5, 95% CI 1.74-7.1, p < 0.01). The STOP-BANG questionnaire did not identify 12/70 (17%) of the patients diagnosed with OSA and classified 28% of the cohort as OSA when the level III sleep study was negative.

Unrecognized OSA is common in preoperative patients and is independently associated with postoperative complications. The STOP-BANG questionnaire had a lower performance in the diagnosis of OSA in a South Indian population than the level III sleep study.