The degree of respiratory depression according to the effect-site concentration in remimazolam target-controlled infusion

BACKGROUND: Remimazolam is not only associated with a lower incidence of respiratory depression than propofol but also in itself has the risk of respiratory depression. OBJECTIVE: We investigated respiratory depression following remimazolam infusion, targeting different effect-site concentrations using target-controlled infusion. DESIGN: A prospective, double-blind, randomised controlled study. SETTING: Tertiary hospital, Suwon, South Korea, from April 2022 to November 2022. PARTICIPANTS: One hundred and seven patients scheduled for general anaesthesia were randomised into three groups targeting remimazolam effect-site concentrations of 500 (RMZ-500) ( n = 36), 1000 (RMZ-1000) ( n = 35) and 1500 ng ml -1 (RMZ-1500) ( n = 36). INTERVENTIONS: Remimazolam was solely infused for 10 min according to target effect-site concentrations. According to the degree of SpO 2 decrease, oxygen desaturations were managed with the following respiratory supports: jaw-thrust for SpO 2 less than 97%, 100% oxygen delivery for SpO 2 less than 93% and assisted ventilation for SpO 2 less than 90%. MAIN OUTCOME MEASURES: The incidence of each respiratory support, along with respiratory variables (at baseline, 5 min and 10 min after remimazolam infusion) and loss of consciousness were observed for 10 min after remimazolam target-controlled infusion. RESULTS: Both RMZ-1000 and RMZ-1500 required more frequent respiratory support than RMZ-500 (both P < 0.001), with nearly identical frequencies between RMZ-1000 and RMZ-1500. In terms of respiratory support, the incidence of assisted ventilation was significantly lower in RMZ-500 (2.8%) than RMZ-1000 (48.6%) and RMZ-1500 (50%) ( P < 0.001). RMZ-1000 and RMZ-1500 achieved loss of consciousness in all patients; RMZ-500 only achieved loss of consciousness in 86.1% of patients ( P = 0.010). In patients who maintained spontaneous respiration, tidal volume decreased by 41 to 48% and respiratory rate increased by 118 to 158% at 5 and 10 min, significantly compared to baseline in all groups ( P < 0.001). CONCLUSIONS: Remimazolam infusion, like that of other benzodiazepines, led to respiratory depression, which was more prominent at higher target effect-site concentrations. Therefore, appropriate countermeasures should be developed to prevent oxygen desaturation. TRIAL REGISTRATION: CRIS ( https://cris.nih.go.kr ), identifier: KCT0006952.