DESIGN AND SETTING: The study was a planned post hoc analyses of a multicenter prospective cohort study.

PATIENTS: The inclusion criteria were patients ≥45 years old undergoing major non-cardiac surgery with cardiovascular risk factors.

INTERVENTIONS AND MEASUREMENTS: All patients underwent pre-operative pulse oximetry (PULSOX-300i, Konica-Minolta Sensing, Inc). The severity of OSA was classified based on oxygen desaturation index (ODI) (mild: ≥5 to <15, moderate: ≥15 to <30, and severe OSA: ≥30 events/h). The 30 days cardiovascular events were a composite of myocardial injury, cardiac death, congestive heart failure, thromboembolism, atrial fibrillation, and stroke.

MAIN RESULTS: For 1218 patients with mild, moderate, or severe OSA (mean age: 67.2 ± 9.3 years; body mass index: 27.0 ± 5.3 kg/m2), the rate of postoperative cardiovascular events was 16.4%, 25.2%, and 29.8% respectively. The multivariable analysis showed that preoperative oxygen desaturation index (ODI) ≥30 events per hour {adjusted hazard ratio (aHR) 1.63 [95% confidence interval (CI): 1.05-2.53]}, and cumulative time spent during sleep with oxygen saturation below 80% (CT80) ≥10 min {aHR 1.79 [95% CI: 1.28-2.50]} were independent predictors of 30-day postoperative cardiovascular events.

CONCLUSIONS: Preoperative ODI ≥30 events per hour and CT80 ≥ 10 min are associated with increased risk of postoperative cardiovascular events. Preoperative screening using oximetry helps in risk stratification for unrecognized sleep apnea.