Effect of intraoperative 40-hz gamma-frequency auditory stimulation on postoperative delirium in older adults undergoing major surgery: a randomized clinical trial protocol.
INTRODUCTION: Postoperative delirium (POD) is a common and clinically significant complication among older adults undergoing major surgery under general anesthesia. Gamma-frequency (40-Hz) auditory stimulation has demonstrated potential neuroprotective and cognition-enhancing effects, suggesting a plausible role in perioperative delirium prevention. However, direct clinical evidence supporting intraoperative 40-Hz auditory stimulation in reducing POD remains limited, warranting rigorous evaluation in a randomized trial. PATIENTS AND METHODS: This prospective, parallel-group, randomized controlled trial will enroll 550 older adults scheduled for major noncardiac, nonneurosurgical surgery under general anesthesia. Participants will be randomized in a 1:1 ratio to either the active stimulation group, receiving intraoperative 40-Hz gamma-frequency auditory stimulation delivered via headphones for 2 h following successful anesthesia induction, or the sham stimulation group, wearing headphones without active auditory output. The primary outcome is the incidence of POD on postoperative day 1 though 3, assessed using the Confusion Assessment Method (CAM) or the CAM for the ICU (CAM-ICU). Secondary outcomes include POD severity, sleep quality, pain scores, analgesic consumption, the incidence of postoperative nausea and vomiting (PONV), rescue antiemetic use, duration of post-anesthesia care unit (PACU) stay, length of hospital stay, quality of postoperative recovery, incidence of perioperative adverse events; postoperative morbidity, health-related quality of life, and all-cause 30-day mortality. DISCUSSION: This trial will determine whether intraoperative 40-Hz gamma-frequency auditory stimulation reduces the incidence of POD among older adults undergoing major surgery under general anesthesia. If efficacious, this noninvasive intervention could constitute a feasible perioperative strategy to mitigate delirium risk and enhance postoperative recovery. CLINICAL TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2500115156).