Impact of dexmedetomidine administration timing on postoperative delirium in elderly patients with lower limb fractures: a study protocol for a randomised controlled trial.

introductionPostoperative delirium (POD) is a prevalent perioperative complication among geriatric orthopaedic patients, leading to extended hospitalisation, escalated medical expenditures and persistent cognitive impairment. Although existing studies suggest that dexmedetomidine can reduce the risk of POD, the optimal timing of administration remains undetermined. METHODS AND ANALYSIS: This is a prospective, randomised controlled trial. Patients aged ≥65 years undergoing lower limb fracture surgery under neuraxial anaesthesia will be randomised into a preoperative administration group, an intraoperative administration group or a control group. The study employed a double-dummy technique, with all patients receiving an intravenous infusion at two time points: 15 min prior to neuraxial anaesthesia puncture (T1) and 15 min prior to skin incision (T2). The preoperative group will receive dexmedetomidine at T1 and placebo at T2; the intraoperative group will receive placebo at T1 and dexmedetomidine at T2 and the control group will receive placebo at both T1 and T2. The dexmedetomidine dose is 0.5 µg/kg (infused over ≥10 min), and the placebo is an equivalent volume of 0.9% saline. The primary outcome is the incidence of POD within the first 3 postoperative days. Secondary outcomes include the Mini-Mental State Examination, Leeds Sleep Evaluation Questionnaire, visual analogue scale for resting pain, Activities of Daily Living and Quality of Recovery-15, as well as serum biomarkers (neuron-specific enolase, S100 calcium-binding protein B, interleukin-6, C-reactive protein) measured preoperatively and on postoperative day 1. Additionally, regional cerebral oxygen saturation, Bispectral Index and haemodynamics will be monitored. ETHICS AND DISSEMINATION: Ethical approval for this protocol was obtained from the Medical Ethics Committee of Rugao People's Hospital (approval number: 2025-YJ-011-01). We plan to publish the study findings in peer-reviewed journals and present them at relevant scientific meetings. TRIAL REGISTRATION NUMBER: ChiCTR2500114299.