Postoperative delirium and the limits of EEG monitoring without goal-directed anesthetic management

BACKGROUND: Postoperative delirium (POD) remains a major cause of morbidity after surgery. Understanding its relationship with anesthetic depth and EEG monitoring could optimize perioperative management and improve patient recovery. This study aimed to determine whether intraoperative monitoring of anesthetic depth using integrated EEG is associated with a reduced incidence of POD. METHODS: Observational multicentre study conducted across 43 hospitals. 1,690 adults (≥18 years) undergoing surgery under general anesthesia were included. The primary outcome was the incidence of POD at 48 hours post-surgery, comparing patients who received intraoperative EEG-based anesthetic depth monitoring with those who did not. POD diagnosis was based on established clinical criteria. In addition, a cross-sectional survey was administered to participating anesthesiologists to assess patterns of EEG monitor use, target ranges, training, and perceptions regarding its role in delirium prevention. RESULTS: POD occurred in 4.25% (61/1434) of patients who received EEG monitoring and in 1.56% (4/256) of those without (P=0.833). Logistic regression identified age as significantly associated with POD (OR 1.06, 95% CI: 1.04-1.09, P<0.001), while neither EEG monitoring (OR 2.66, 95% CI: 0.95-7.45, P=0.063) nor sex (OR 1.15, 95% CI: 0.69-1.91, P=0.586) were independent predictors. In a survey involving 493 anesthesiologists, a widespread use of EEG monitoring was observed in clinical practice (61% use it consistently, and 35% frequently), with the most common target range being 40-60 (82.6%). The vast majority of respondents (96.7%) perceived a potential benefit in delirium prevention. However, only 35.2% had received formal training, and the application of goal-directed, protocolized EEG monitoring remained heterogeneous. CONCLUSIONS: In real-world clinical practice, intraoperative anesthetic depth monitoring was not associated with a lower incidence of POD at 48 hours. Heterogeneous, non-protocolized use and lack of structured training may limit its effectiveness. These findings should be considered hypothesis-generating and highlight the need for implementation strategies and goal-directed use.