Xiao-Dong Huang,1 Lan Xu,2 Cai-Hong Zheng,1 Min-Min Chen,1 Hong-Yan Shou,1 Zhen-Feng Zhou1 

1Department of Anesthesiology, Hangzhou Women’s Hospital (Hangzhou Maternity and Child Health Care Hospital, Hangzhou First People’s Hospital Qianjiang New City Campus, Zhejiang Chinese Medical University), Hangzhou, 310008, People’s Republic of China; 2Department of Anesthesiology, Affiliated Xiaoshan Hospital, Hangzhou Normal University, Hangzhou, 311202, People’s Republic of China

Correspondence: Zhen-Feng Zhou, Department of Anesthesiology, Hangzhou Women’s Hospital (Hangzhou Maternity and Child Health Care Hospital, Hangzhou First People’s Hospital Qianjiang New City Campus, Zhejiang Chinese Medical University), Hangzhou, 310008, People’s Republic of China, Email zhenfeng9853@163.com

Purpose: Previous studies have reported the recommended dosage of remimazolam alone for achieving loss of consciousness (LoC). However, the effect of analgesics on the dosage of remimazolam for successful sedation remains unclear. This study evaluated the impact of fentanyl on the effective dose of remimazolam-induced sedation in female patients undergoing elective hysteroscopic surgery.
Patients and Methods: Two hundred female patients were randomly allocated into two groups, receiving with or without fentanyl (1ug/kg) during anesthetic induction. Within each group, patients were randomized to receive one of four doses (0.1, 0.2, 0.3, and 0.4 mg/kg) of remimazolam for sedation. Modified Observer’s Assessment of Alertness/Sedation (MOAA/S) was evaluated during anesthetic induction. Success was defined when the patient did not respond to painful trapezius squeeze and no requirement for rescue doses. Estimate of ED50 and ED95 with 95% confidence interval (CI) was performed by probit regression.
Results: The ED50 and ED95 values of remimazolam for patients receiving fentanyl (1 ug/kg) were 0.097 (95% CI, 0.072– 0.120) mg/kg and 0.254 (95% CI, 0.203– 0.345) mg/kg, respectively. For patients not receiving fentanyl, the ED50 and ED95 values of remimazolam were 0.181 (95% CI, 0.149– 0.215) mg/kg and 0.475 (95% CI, 0.377– 0.687) mg/kg, respectively. The estimated relative median potency of remimazolam in patients, with and without fentanyl administration, was determined to be 0.534 (95% CI, 0.327– 0.737).
Conclusion: The administration of fentanyl reduced the effective dose of remimazolam-induced sedation by 50% in female patients undergoing elective hysteroscopic surgery. The recommended ED95 dose for remimazolam-induced sedation was 0.254 mg/kg under the condition of this study.
Trial Number and Registry Url: ChiCTR2400079842; https://www.chictr.org.cn/showproj.html?proj=216480: HUANG, Date of registration: January 15, 2024.

Keywords: remimazolam, fentanyl, effective dose, sedation, side effect