Postoperative delirium (POD) is a common complication in elderly patients undergoing anesthesia. Even though it is increasingly recognized as an important health issue, the early detection of patients at risk for POD remains a challenge. This study aims to identify predictors of POD by analyzing frontal electroencephalogram (EEG) at propofol induced loss of consciousness (LOC).


In this prospective, observational single-center study, we included patients over 70 years undergoing general anesthesia for a planned surgery. Frontal EEG was recorded on the day before surgery (baseline), and during anesthesia induction (1 minute, 2 minutes and 15 minutes after LOC). Postoperative patients were screened for POD twice daily for five days. Spectral analysis was performed using the multitaper method. The EEG Spectrum was decomposed in periodic and aperiodic (correlates to asynchronous spectrum wide activity) components. The aperiodic component is characterized by its offset (y-intercept) and exponent (the slope of the curve). Computed EEG parameters were compared between patients who developed POD and those who did not (noPOD). Significant EEG parameters were included in a binary logistic regression analysis to predict vulnerability for POD.


Out of 151 patients, 50 (33%) developed POD. At 1 minute after LOC POD patients demonstrated decreased alpha [POD: 0.3 μV 2 (0,21-0,71), noPOD: 0.55 μV 2 (0.36-0.74), p=0.019] and beta band power [POD: 0.27 μV 2 (0.12-0.38), noPOD:0.38 μV 2 (0.25-0.48): p=0.003] and lower spectral edge frequency (SEF95) [POD: 10.45 Hz (5.65-15.04), noPOD: 14.56 Hz (9.51-16.65), p=0.01]. 15 minutes after LOC, POD patients displayed a decreased aperiodic offset [POD: 0.42 μV 2 (0.11-0.69), noPOD: 0.62 μV 2 (0.37-0.79), p=0.004]. The logistic regression model predicting POD vulnerability demonstrated an area under the curve (AUC) of 0.738 (0.69-0.75).


The findings suggest that EEG markers obtained during LOC at anesthesia induction may serve as EEG-based biomarkers to early identify patients at risk to develop POD.