Background

With estimated global post-operative mortality rates at 1-4% leading to approximately 3-12 million deaths per year, an urgent need exists for reliable measures of perioperative risk. Existing approaches suffer from poor performance, place a high burden on clinicians to gather data, or do not incorporate intraoperative data. Prior work demonstrated that intraoperative anesthetics induce prefrontal EEG oscillations in the alpha band (8-12Hz) that correlate with post-operative cognitive outcomes.

Methods

We analyzed a retrospective cohort of 1,081 patients undergoing surgery with general anesthesia at Massachusetts General Hospital with intraoperative EEG recordings. The association between EEG alpha power and adverse outcomes were characterized using statistical models that were fitted on propensity weighted data. Our primary outcome was post-operative mortality, measured from date of surgery to date of death or last follow-up. Secondary outcomes included mortality within pre-specified time windows (30-days, 90-days, 180-days, and 1-year), hospital and PACU lengths of stay, discharge to long-term care, and 30-day hospital readmission.

Results

Alpha power was associated with mortality risk (HR = 0.92, 95% CI:[ 0.85, 0.99], p=0.039). Within specified time windows, alpha power was associated with 30-day mortality (OR = 0.81, 95% CI: [0.66, 0.95], p=0.010), 90-day mortality (OR = 0.68, 95% CI: [0.55, 0.79], p<0.001), 180-day mortality (OR = 0.75, 95% CI: [0.66, 0.83], p<0.001), and 1-year mortality (OR = 0.85, 95% CI: [0.79, 0.91], p<0.001). Additionally, alpha power was associated with discharge to long-term care (OR = 0.91, 95% CI: [0.86, 0.96], p<0.001). We did not find significant associations among alpha power and 30-day readmission and hospital or PACU lengths of stay.

Conclusions

Intraoperative EEG alpha power is independently associated with post-operative mortality and adverse outcomes, suggesting it could represent a broad measure of post-operative physical resilience and provide clinicians with a low-burden, personalized measure of post-operative risk.