The Effects of Subanesthetic S-ketamine on Postoperative Delirium and Cognitive Function in the Elderly Undergoing Non-cardiac Thoracic Surgery

Postoperative delirium (POD) is a common and distressing complication after thoracic surgery. S-ketamine has neuroprotective properties as a dissociative anesthetic. Emerging literature has indicated that S-ketamine can reduce cognitive impairment in depressed patients. However, the role of S-ketamine in preventing postoperative delirium is still unknown. Therefore, this study aims to evaluate the effect of intraoperatively prophylactic S-ketamine compared to dexmedetomidine on the incidence of postoperative delirium in elderly patients undergoing non-cardiac thoracic surgery. This will be a randomized, double-blinded, placebo-and positive-controlled, non-inferiority trial that enrolls patients aged 60 or over undergoing thoracic surgery. The primary outcome will be the incidence of postoperative delirium within 4 days after surgery and assessed using a 3-minute Diagnostic Confusion Assessment Method (3D-CAM) twice a day. The main secondary outcomes will be the severity and duration of postoperative delirium. Other prespecified secondary outcomes will be the incidence of emergency delirium, postoperative pain, quality of sleep, cognitive function, and the plasm concentration of acetylcholine, brain-derived neurotrophic factor, and tumor necrosis factor.