The effective dose of remimazolam in adult gastroscopy.

Objectives: The objectives of this study were to explore the median effective dose (ED50) and the dose required for successful anesthesia in 95% of the patients (ED95) of remimazolam for intravenous anesthesia in adult outpatients undergoing gastroscopy.

Methods: This pilot study was conducted in patients scheduled to undergo painless gastroscopy at the authors' hospital between March 15, 2022 and March 25, 2022. The ED of remimazolam was determined using the modified Dixon sequential method, using an initial induction dose of 0.2 mg/kg. With successful or failed anesthesia, the remimazolam dose was decreased or increased by 0.05 mg/kg for the next patient, respectively.

Results: Twenty-two patients (43.6 ± 10.5 years of age) were enrolled. During gastroscopy, the remimazolam induction dose was 19.93 ± 2.96 mg (0.2-0.45 mg/kg). Eighteen patients could complete anesthesia with remimazolam alone, and four patients needed propofol to complete anesthesia. The induction time after the injection of remimazolam was 20.8 ± 8.4 s, the gastroscopy time was 5.1 ± 1.3 min, and the anesthesia recovery time was 17.5 ± 5.6 min. The ED50 and the ED95 of remimazolam were 0.362 mg/kg (95% confidence interval [CI]: 0.313-0.455 mg/kg) and 0.464 mg/kg (95% CI: 0.403-2.242 mg/kg), respectively. The vital signs of all patients remained within the predefined acceptable limits. No patients required antagonist rescue.

Conclusion: The ED50 and ED95 of remimazolam for adult gastroscopy were 0.362 mg/kg and 0.464 mg/kg, respectively. Additional anesthetics might be required during gastroscopy in some patients.

Trial registration: The trial was registered. The number is ChiCTR2200057446.