The Perioperative Frontal Relative Ratio of the Alpha Power of Electroencephalography for Predicting Postoperative Delirium After Highly Invasive Surgery: A Prospective Observational Study

BACKGROUND: We investigated the associations between postoperative delirium (POD) and both the relative ratio of the alpha (α)-power of electroencephalography (EEG) and inflammatory markers in a prospective, single-center observational study. METHODS: We enrolled 84 patients who underwent radical cancer surgeries with reconstruction for esophageal cancer, oral floor cancer, or pharyngeal cancer under total intravenous anesthesia. We collected the perioperative EEG data and the perioperative data of the inflammatory markers, including neutrophil gelatinase-associated lipocalin, presepsin, procalcitonin, C-reactive protein, and the neutrophil-lymphocyte ratio (NLR). The existence of POD was evaluated based on the Intensive Care Delirium Screening Checklist. We compared the time-dependent changes in the relative ratio of the EEG α-power and inflammatory markers between the patients with and without POD. RESULTS: Four of the 84 patients were excluded from the analysis. Of the remaining 80 patients, 25 developed POD and the other 55 did not. The relative ratio of the α-power at baseline was significantly lower in the POD group than the non-POD group (0.18 ± 0.08 vs 0.28 ± 0.11, P < .001). A time-dependent decline in the relative ratio of α-power in the EEG during surgery was observed in both groups. There were significant differences between the POD and non-POD groups in the baseline, 3-h, 6-h, and 9-h values of the relative ratio of α-power. The preoperative NLR of the POD group was significantly higher than that of the non-POD group (2.88 ± 1.04 vs 2.22 ± 1.00, P < .001), but other intraoperative inflammatory markers were comparable between the groups. Two multivariable logistic regression models demonstrated that the relative ratio of the α-power at baseline was significantly associated with POD. CONCLUSIONS: Intraoperative frontal relative ratios of the α-power of EEG were associated with POD in patients who underwent radical cancer surgery. Intraoperative EEG monitoring could be a simple and more useful tool for predicting the development of postoperative delirium than measuring perioperative acute inflammatory markers. A lower relative ratio of α-power might be an effective marker for vulnerability of brain and ultimately for the development of POD.