RESUMEN
BACKGROUND: Remimazolam tosilate (RT) is a newly listed benzodiazepine for sedation and anesthesia featuring quick onset of effects, short maintenance and recovery times, which is currently under research. This trial was conducted to determine the median effective dose (ED50) and the 95% effective dose (ED95) of single-dose remimazolam for moderate sedation in elderly patients undergoing transurethral resection of the prostate (TURP) under spinal anesthesia, and to evaluate its efficacy and safety. METHODS: Thirty male patients aged 65-80 years old were recruited for selective TURP. Remimazolam was administered intravenously to pain-free patients (VAS score < 1) within 1 min of successful spinal anesthesia by the same anesthesiologist. We used modified Dixon's up-and-down sequential allocation method to determine the ED50 and ED95 of the agent with an initial dosage of 0.1 mg/kg. Successful sedation was defined as an MOAA/S score ≤ 3 and above 1. A score of > 3 was deemed as failed sedation. Recruitment continued until ten independent pairs (from successful sedation to failed sedation) would give a reliable estimation of the ED50 and ED95 of RT and their 95% confidence intervals. RESULTS: The ED50 of remimazolam was 0.063 (95% C.I. 0.045-0.073) mg/kg. Its ED95 was 0.079 (95% C.I. 0.07-0.137) mg/kg. Remimazolam was safe in its application. CONCLUSIONS: A single-dose of RT proves to be safe for assisted sedation during TURP in elderly male patients under spinal anesthesia with a lower incidence of adverse events. Its ED50 and ED95 were 0.063 mg/kg and 0.079 mg/kg, respectively. TRIAL REGISTRATION: http://www.chictr.org.cn (ChiCTR2100051912).