Comparison of remimazolam and dexmedetomidine for intraoperative sedation in patients undergoing lower extremity surgery under spinal anesthesia: a randomized clinical trial

Background Dexmedetomidine sedation has advantages, such as low incidence of respiratory depression and prolonged block duration, but also significant disadvantages, such as slow onset, high rate of sedation failure, and a long context-sensitive half-life. Remimazolam provides rapid sedation and recovery, high sedation efficacy and has minimal hemodynamic effects. We hypothesized that patients who received remimazolam would require less rescue midazolam than dexmedetomidine. Methods Patients (n=103) scheduled for surgery under spinal anesthesia were randomized to receive dexmedetomidine (DEX group) or remimazolam (RMZ group) targeting a Modified Observer’s Assessment of Alertness/Sedation score of 3 or 4. Rescue midazolam was administered if the patient failed to be sedated after the initial loading dose or despite infusion rate adjustment. Results Rescue midazolam administration was significantly higher in the DEX group (0% vs 39.2%; p<0.001). Patients in the RMZ group reached the target sedation level more rapidly. The incidences of bradycardia (0% vs 25.5%; p<0.001) and hypertension (0% vs 21.6%; p<0.001) were higher in the DEX group. Respiratory depression occurred at a higher rate in the RMZ group (21.2% vs 2.0%; p=0.002), but no patients required manual ventilation. Patients in the RMZ group recovered faster, had a shorter PACU stay and higher satisfaction scores. Hypotensive episodes in the PACU were more frequent in the DEX group (1.9% vs 29.4%; p<0.001). Conclusions Remimazolam showed excellent sedation efficacy, minimal hemodynamic effects, and fewer adverse events in the PACU than dexmedetomidine. However, it is important to note that respiratory depression was more frequent with the use of remimazolam. Trial registration number NCT05447507 .