Moderate sedation with single-dose remimazolam tosilate in elderly male patients undergoing transurethral resection of the prostate with spinal anesthesia: a prospective, single-arm, single-centre clinical trial

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 (ED(50)) and the 95% effective dose (ED(95)) 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 ED(50) and ED(95) 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 ED(50) and ED(95) of RT and their 95% confidence intervals. RESULTS: The ED(50) of remimazolam was 0.063 (95% C.I. 0.045–0.073) mg/kg. Its ED(95) 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 ED(50) and ED(95) were 0.063 mg/kg and 0.079 mg/kg, respectively. TRIAL REGISTRATION: http://www.chictr.org.cn (ChiCTR2100051912). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-022-01788-1.