An Adequate Infusion Rate of Remimazolam for Induction of General Anesthesia in Adult Patients: A Prospective Up-and-Down Dose-Finding Study

Remimazolam is a recently developed anesthetic agent for general anesthesia and sedation. Currently, the optimal infusion rate for the induction of general anesthesia within two minutes remains unclear. We estimated the 50% and 90% effective doses (ED(50) and ED(90)) of remimazolam required for loss of responsiveness within two minutes in adult patients using the up-and-down method. The starting infusion rate of remimazolam was 0.1 mg/kg/min and was increased or decreased by 0.02 mg/kg/min intervals in the following patient according to the success or failure of the previous patient. Success was defined as a loss of responsiveness within two minutes. Patient enrollment continued until six crossover pairs were observed. The ED(50) and ED(90) were estimated by centered isotonic regression and the pooled adjacent violators algorithm with bootstrapping, respectively. Twenty patients were included in the analysis. The ED(50) and ED(90) of remimazolam for loss of responsiveness within two minutes were 0.07 mg/kg/min (90% CI: 0.05, 0.09 mg/kg/min) and 0.10 mg/kg/min (90% CI: 0.10, 0.15 mg/kg/min), respectively. Vital signs were stable with an infusion rate of 0.10 mg/kg/min, and no patients required inotrope/vasopressor. Intravenous infusion of remimazolam at a rate of 0.10 mg/kg/min can be an effective approach to inducing general anesthesia in adult patients.