Effects of Different Bispectral Index Target Depths on Early Postoperative Recovery Quality in Elderly Patients Undergoing Total Knee Arthroplasty

This is a prospective, single-center, randomized, double-blind controlled trial. The purpose of this study is to determine whether depth-controlled anesthesia with ciprofol guided by Bispectral Index (BIS) can improve early postoperative recovery quality in elderly patients undergoing knee replacement surgery. A total of 130 eligible participants aged 60 years or older will be enrolled. Participants will be randomly assigned to two groups using block randomization based on the Charlson Comorbidity Index (CCI): Deep-anesthesia group: general anesthesia maintained with ciprofol targeting a BIS value of 35-50. Light-anesthesia group: general anesthesia maintained with ciprofol targeting a BIS value of 50-65. Intraoperative BIS values will be continuously monitored, and ciprofol infusion rates will be adjusted to keep BIS within the target range in each group. Standardized pain management including peripheral nerve blocks and postoperative ultrasound-guided continuous femoral nerve block will be provided for all participants. Blood pressure will be managed following the same protocol in both groups. The primary outcome is postoperative recovery quality assessed by the Quality of Recovery-15 (QOR-15) questionnaire on the first day after surgery. Investigators will also collect QOR-15 scores on postoperative day 2 and day 3, and record other clinical outcomes including intraoperative hemodynamic events, postoperative delirium, nausea and vomiting, pain level, sleep quality and hospital length of stay. This study aims to compare postoperative recovery between two different BIS-targeted anesthesia depths for older adults receiving joint-replacement surgery.