To assess whether baseline EEG abnormalities and transient intraoperative EEG changes independently and interactively predict POD, supporting a double-hit model of cerebral frailty.

Cerebral resilience, the brain’s ability to maintain function under stress, varies across individuals and is difficult to measure. Postoperative delirium (POD) may signal failure of this reserve, particularly in vulnerable patients with latent cerebral frailty. Intraoperative EEG offers a real-time, noninvasive window into cerebral resilience by detecting transient and baseline vasculo-electrical abnormalities that may precede clinical deterioration.

This retrospective observational study included 1,808 adult patients who underwent cardiovascular surgery with continuous EEG monitoring at a single academic center between 2014 and 2021. POD was defined as an ICDSC score ≥4 during the ICU stay. Patients were stratified by the presence of transient EEG changes and baseline EEG abnormalities. Subgroup analyses evaluated interaction by sex, age, and baseline EEG status.

Of the 1,808 patients, 122 (6.7%) exhibited transient EEG changes. These patients were slightly older (72.05 vs. 70.59 years), more likely to develop POD (8.2% vs. 3.4%, p =0.013), and had more hypotensive episodes (mean 4.30vs.3.27, p =0.04), despite similar overall hypotension rates. Baseline EEG abnormalities alone were not significantly different between groups (20.5% vs. 17.3%, p = 0.433), but their interaction with transient EEG changes was strongly predictive of POD (interaction p = 0.02). The highest risk was seen in patients with both findings (OR= 7.16; 95% CI:2.48–19.40), while those with transient changes but normal baseline EEGs showed no elevated risk (OR= 1.03; 95% CI:0.25–2.89).

Transient EEG changes likely reflect acute cerebral blood flow alterations. When combined with baseline EEG abnormalities, suggesting preexisting vulnerability, this dual pattern may represent failure of cerebral resilience. EEG may serve as a functional stress test to unmask latent brain frailty and guide early, targeted perioperative interventions to reduce POD risk.