Remimazolam dosing for intraoperative sedation in elderly patients undergoing hip replacement with combined spinal-epidural anesthesia.

The aim of the study was to investigate the 50% and 95% effective doses (ED50 and ED95) of remimazolam for intraoperative sedation in elderly patients undergoing hip replacement with combined spinal-epidural anesthesia (CSEA).We retrospectively analyzed the clinical data of 50 patients who underwent hip replacement with CSEA in our hospital from October 2021 to June 2022. There were 29 males and 21 females, aged 60-80 years old, with body mass indexes (BMI) ranging from 18 to 24 kg/m2, and American Society of Anesthesiologists (ASA) classifications of I or II. The modified Dixon sequential method was used to determine the dose of remimazolam for each patient. Each patient's initial dose was 0.1 mg/kg/h, and the dose gradient was 0.01 mg/kg/h. The bispectral index (BIS) and the modified observer's assessment of alertness/sedation score (MOAA/S) were used to evaluate the sedation of the patient. An MOAA/S score ≤3 and a BIS <85 at three or more time points during surgery indicated the sedation was satisfactory. The induction dose of the next patient was adjusted by 0.01 mg/kg/h based on the level of sedation achieved, and the study was terminated after eight crossovers.The ED50 and ED95 of remimazolam for sedation of elderly patients undergoing hip replacement with CSEA are 0.212 mg/kg/h (95% CI: 0.121-0.231 mg/kg/h) and 0.288 mg/kg/h (95% CI: 0.254-0.884 mg/kg/h), respectively. Two patients experienced transient bradycardia, five experienced hypoxemia, three experienced postoperative nausea, and three experienced postoperative delirium. No patients experienced adverse reactions such as injection pain, hypotension, vomiting, delayed awakening, or emergence agitation.The ED50 and ED95 of remimazolam for sedation of elderly patients undergoing hip replacement with CSEA are 0.212 mg/kg/h and 0.288 mg/kg/h, respectively.