Association Between Entropy Monitoring, Burst Suppression and Early Postoperative Cognitive Dysfunction in Emergency Surgery: A Retrospective Cohort Study

Background/Objectives: Emergency surgical patients are at increased risk of acute postoperative delirium. Processed EEG monitoring, such as entropy indices and burst suppression ratio (BSR), may optimize anesthetic dosing, yet their role in non-elective surgery remains underexplored. This retrospective cohort study aimed to examine whether entropy monitoring and intraoperative burst suppression are associated with the incidence of early postoperative delirium during the first 72 h after emergency surgery. Methods: Adult patients undergoing emergency surgery between March 2022 and March 2024 were classified into two groups based on anesthesia records: the entropy-monitored group (EG) and the standard care group without processed EEG (SG). Demographic, intraoperative, and cognitive data (NEECHAM scores during the first 72 h) were extracted from institutional perioperative records. The primary outcome was postoperative delirium (NEECHAM ≤ 24), with secondary analyses examining anesthetic exposure, burst suppression, and intraoperative hemodynamics. Results: Entropy-monitored patients received lower sevoflurane and fentanyl doses and exhibited improved hemodynamic stability, including fewer hypotensive episodes and lower norepinephrine requirements. Early postoperative cognitive dysfunction (NEECHAM ≤ 24) was more frequent among patients with intraoperative burst suppression, with BSR > 15% or suppression duration > 6 min strongly associated with cognitive decline within the first 72 h. Conclusions: In this retrospective cohort, entropy-guided anesthesia was associated with more precise anesthetic titration and more stable hemodynamic parameters. Burst suppression characteristics may serve as indicators of neurocognitive vulnerability rather than solely reflecting direct effects of anesthetic dosing. These results support the use of processed EEG monitoring in emergency surgery, though prospective studies are needed to confirm these findings.