DELIRIUM AFTER MAJOR ABDOMINAL SURGERY: THE ROLE OF FRAILTY, ANESTHETIC MANAGEMENT, AND MULTIMODAL ANALGESIA

Abstract

Introduction: Postoperative delirium (POD) is an acute and fluctuating disturbance of attention, awareness, and cognition that frequently affects older adults after major abdominal surgery. Its development reflects an interaction between pre-existing vulnerability and perioperative precipitating factors. Frailty, excessive anesthetic exposure, hemodynamic instability, uncontrolled pain, opioid burden, and sleep disruption are potentially relevant components of this interaction. Objective: To evaluate the association between frailty and POD after major abdominal surgery and to examine whether anesthetic management and multimodal analgesia modify its incidence. Methods: PubMed/MEDLINE, Embase, Scopus, Web of Science, and the Cochrane Library were searched for studies published from January 2015 through August 31, 2026. Randomized trials, prospective or retrospective cohorts, and controlled before-and-after studies involving adults undergoing major abdominal surgery were eligible. Mixed major-surgery populations were included when they provided directly relevant evidence regarding anesthetic depth, anesthetic agents, regional techniques, or analgesic interventions. Risk of bias was assessed according to study design, and the certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation framework. Clinical and methodological heterogeneity precluded quantitative pooling. Results: Twenty-two publications representing 21 independent cohorts were included. Frailty was consistently associated with POD, although its predictive performance improved when combined with cognition, nutritional status, surgical complexity, and perioperative variables. A contemporary meta-analysis reported an odds ratio of 2.47 (95% confidence interval [CI] 2.04–2.99) for POD in frail surgical patients. In abdominal-specific cohorts, POD incidence ranged from 5.5% to 34%. Multimodal prehabilitation reduced delirium from 11.7% to 8.2% in a nonrandomized study, while multidisciplinary geriatric care was associated with a reduction from 29.2% to 11.3%. Evidence regarding anesthetic depth was inconsistent: the Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes trial found no benefit from electroencephalography guidance, whereas a separate targeted-depth trial reported POD in 19% with lighter anesthesia versus 28% with deeper anesthesia. Combined epidural–general anesthesia reduced POD from 5.0% to 1.8% but increased intraoperative hypotension from 33% to 49%. Moderate-to-severe pain on postoperative day 1 was independently associated with delirium (adjusted odds ratio 1.63; 95% CI 1.27–2.08). A small colorectal trial reported less POD with preemptive multimodal analgesia, whereas opioid-free anesthesia, ketamine, and gabapentin did not demonstrate consistent preventive effects. Conclusion: Frailty is an important marker of vulnerability to delirium after major abdominal surgery but should be interpreted within a multidimensional assessment that includes cognition, nutrition, functional performance, and surgical stress. Anesthetic management should prioritize avoidance of excessive hypnotic exposure, prolonged electroencephalographic suppression, and hemodynamic instability rather than a single anesthetic drug or numerical depth target. Multimodal analgesia should provide effective pain control while limiting unnecessary opioid exposure, but neither complete opioid avoidance nor routine administration of a specific adjunct is supported. The most defensible preventive strategy is an individualized, multidisciplinary pathway combining frailty screening, geriatric optimization, physiologically tailored anesthesia, adequate analgesia, early mobilization, sleep preservation, and systematic delirium surveillance.