Duration of Intraoperative Cerebral Oxygen Desaturation and Postoperative Delirium in Elderly Patients Undergoing Major Noncardiac Surgery: A Prospective Observational Study.

OBJECTIVE: To investigate whether the cumulative duration of a clinically significant decline in regional cerebral oxygen saturation (rSO₂) independently predicts postoperative delirium (POD) in elderly patients undergoing major noncardiac surgery. DESIGN: Single-center prospective observational study. SETTING: Hospital surgical department (tertiary care center, implied from the design). PARTICIPANTS: A total of 347 patients age 65 years or older undergoing major noncardiac procedures, after excluding those with preexisting delirium, incomplete monitoring data, or reoperations. INTERVENTIONS: Bilateral cerebral near-infrared spectroscopy was used to continuously monitor rSO₂ from anesthetic induction to surgical closure. The primary exposure was the total duration (minutes) of rSO₂ decline ≥20% from individual preinduction baseline. No specific intraoperative intervention to treat desaturation was mandated by the study protocol. MEASUREMENTS & MAIN RESULTS: POD was assessed twice daily for 5 postoperative days using the Confusion Assessment Method. POD occurred in 83 of 347 patients (23.9%). In multivariable logistic regression, each additional minute of rSO₂ decline ≥20% was associated with a 5% increase in the odds of POD (adjusted odds ratio [aOR], 1.05; 95% confidence interval [CI] 1.01-1.09; p = 0.012). Other independent predictors included age (aOR, 1.09), preoperative Mini-Mental State Examination score (aOR, 0.79), and surgical duration (aOR, 1.01). The full model's area under the curve was 0.743; adding rSO₂ decline duration yielded a category-free net reclassification improvement of 0.207 (p = 0.038). CONCLUSIONS: Prolonged intraoperative cerebral oxygen desaturation is independently associated with POD in elderly noncardiac surgical patients. Continuous rSO₂ monitoring may help identify patients at elevated risk who could benefit from targeted perioperative neuroprotective strategies.