Universal risk assessment strategies are needed to enhance perioperative care, especially for vulnerable patients at increased risk for adverse postoperative outcomes. Lower baseline regional cerebral oxygen saturation (rSO₂) was previously associated with increased mortality in cardiac surgical patients. We hypothesised that lower baseline rSO₂ could be a surrogate of increased vulnerability to adverse postoperative outcomes in older noncardiac surgical patients.

We conducted an exploratory secondary analysis of a prospective observational cohort study. Patients over 65 years scheduled for elective noncardiac surgery between 2017 and 2019 were included. Unilateral baseline rSO₂ was measured upon admission to the surgical ward. Our primary outcomes were morbidity and mortality rates within 30 days of the surgical procedure.

Among 254 analysed patients (median [25th percentile, 75th percentile] age 73 [68, 78], 65 % males), 17 (7 %) were readmitted to the hospital within 30 days after surgery, and five died in this period (2 %). Baseline rSO₂ values were significantly associated with readmission (mean (SD), 58 (10) vs 65 (8), P = 0.003) and mortality (mean (SD), 51 (15) vs 64 (8), P < 0.001). Mortality prediction based on baseline rSO₂ revealed an AUC of 0.801 (p = 0.021).

The utility of baseline rSO₂ as a biomarker of adverse postoperative outcomes can potentially extend to noncardiac surgical patients, especially for older populations.