Heart Rate Variability Changes and Postoperative Delirium After Major Abdominal Surgery

This prospective observational cohort study aims to investigate whether early postoperative changes in heart rate variability (HRV) relative to baseline are associated with the development of postoperative delirium (POD) in older patients undergoing elective major abdominal surgery under general anesthesia. Patients aged 65-85 years will be enrolled. Resting HRV will be measured at 10:00 AM on the day of surgery before anesthesia induction and at the same time point on the first postoperative day using a validated heart rate monitoring device. HRV parameters will be derived from standardized 5-minute recordings. Changes in HRV parameters from baseline will be calculated, and their associations with POD occurrence will be evaluated. Postoperative delirium will be assessed daily from 24 hours after surgery to postoperative day 7, using the 3-Minute Diagnostic Interview for Confusion Assessment Method (3D-CAM). The study will also explore the potential utility of HRV-derived markers for early POD risk stratification. Approximately 500 participants will be enrolled.