• Ha-Jung Kim, Hyungtae Kim, Hyeok-Seong Park, Hwa Jung Kim, Young-Jin Ro, and Won Uk Koh.
• Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
• Can J Anaesth. 2024 Feb 20.

PurposeRemimazolam is a novel ultrashort-acting sedative considered appropriate for continuous infusion during surgical procedures. Nevertheless, information regarding its loading dose for sedation during surgery is limited. We aimed to determine the 90% effective dose (ED90) of the remimazolam loading dose for sedation in patients undergoing limb surgery under regional anesthesia.MethodsWe included 50 patients aged 19-80 yr undergoing limb surgery under regional anesthesia. After regional anesthesia, remimazolam besylate was administered at the assigned dose. For ten minutes after the initiation of loading, the level of sedation was evaluated using the Modified Observer's Assessment of Alertness/Sedation (MOAA/S) scale. The primary outcome was the ED90 based on whether patients reached a MOAA/S score of ≤ 3 points (loss of response to verbal command) within ten minutes. The secondary outcomes were the ED50 and the estimated effect site and plasma concentration at the time of achieving successful sedation.ResultsIn total, 49 patients were included in the final analysis, and adequate sedation with the assigned loading dose was successful in 42 patients. The log-logistic function showed that the ED90 and ED50 were 0.617 mg·kg-1·hr-1 (95% confidence interval [CI], 0.511 to 0.722; 98% CI, 0.492 to 0.741) and 0.438 mg·kg-1·hr-1 (95% CI, 0.335 to 0.541; 98% CI, 0.315 to 0.560), respectively.ConclusionThe ED90 of the remimazolam loading dose to achieve adequate sedation in patients undergoing limb surgery under regional anesthesia was 0.617 mg·kg-1·hr-1 (95% CI, 0.511 to 0.722; 98% CI, 0.492 to 0.741).Study RegistrationClinicalTrials.gov (NCT05340335); first posted 22 April 2022.© 2024. Canadian Anesthesiologists' Society.

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