Determination of the 95% effective dose of remimazolam to achieve loss of consciousness during anesthesia induction in different age groups

BACKGROUND: Remimazolam is a new ultra short-acting benzodiazepine originally developed as an improved version of midazolam. Recent studies have demonstrated non-inferiority of remimazolam to propofol in general anesthesia. However, to date, few studies have investigated the induction bolus dose of remimazolam required to achieve general anesthesia. We aimed to determine the 95% effective dose (ED(95)) of remimazolam bolus required to achieve loss of consciousness (LOC) and the appropriate doses for different age groups. METHODS: Patients aged 20–79 years with the American Society of Anesthesiologists physical status of I or II were enrolled in this study. A total of 120 patients were included representing young, middle-aged, and elderly groups. Loss of eyelash reflex and verbal response after the administration of remimazolam was considered successful LOC. The ED(95) of remimazolam was determined using a biased coin up-and-down design with sequential allocation and the isotonic regression method. RESULTS: The ED(95) of remimazolam for induction of general anesthesia was 0.367 mg/kg (95% CI [0.277, 0.392]) in the young group, 0.369 mg/kg (95% CI [0.266, 0.394]) in the middle-aged group, and 0.249 mg/kg (95% CI [0.199, 0.288]) in the elderly group. During the study period, none of the patients required rescue medications for hypotension or bradycardia. CONCLUSIONS: This study investigated the ED(95) of remimazolam bolus for anesthesia induction. The precise dosing of the ED(95) can help maintain hemodynamic stability during the induction of anesthesia.