Efficacy of systemic lidocaine in postoperative delirium in elderly patients undergoing laparoscopic colorectal surgery: study protocol for a multicentre, prospective, double-blind, randomised, parallel-group, superiority, placebo-controlled trial.

INTRODUCTION: Systemic lidocaine may reduce pain intensity and accelerate postoperative recovery. However, the efficacy of systemic lidocaine in cognitive function has not been established. This study protocol is designed to clarify the effectiveness of lidocaine in postoperative delirium (POD) in elderly patients scheduled for elective laparoscopic colorectal surgery. METHODS AND ANALYSIS: This is a prospective, multicentre, randomised, double-blind, parallel-group, placebo-controlled trial. One thousand and twenty elderly patients will be randomly allocated in a ratio of 1:1 to receive either systemic lidocaine (a bolus of 1.5 mg/kg, followed by an infusion of 1.5 mg/kg/hour until the end of the surgery) or identical volumes and rates of 0.9% saline. The primary outcome measure is the prevalence of POD during the first 5 postoperative days. Secondary outcomes include emergence agitation, the area under the curve of the Numeric Rating Scale pain scores over 48 hours, postoperative 48-hour cumulative opioid consumption, postoperative nausea and vomiting (PONV), recovery of bowel function, quality of recovery, and patient satisfaction with postoperative analgesia. ETHICS AND DISSEMINATION: The Ethical Committee of the Fujian Provincial Hospital approved the study protocol (ref: K2021-06-018). Other participating subcentres must also obtain ethics committee approval before the start of the study. We will obtain written informed consent from each patient before they are randomised. This study will be presented at scientific conferences and submitted to international journals. TRIAL REGISTRATION NUMBER: ChiCTR2100050314.