Fuquan Fang,1,* Huiling Li,1,* Lei Li,1 Bing Yan,2 Pengfei Yin,1 Binwei Hu,3 Shengmei Zhu,1 Xianhui Kang1 

1Department of Anesthesiology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China; 2Department of Anesthesiology, The First Affiliated Hospital of Zhejiang University of Medicine, Haining Branch, Haining, Zhejiang, People’s Republic of China; 3Department of Anesthesiology, Tongde Hospital of Zhejiang Province, Hangzhou, Zhejiang, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xianhui Kang; Shengmei Zhu, The First Affiliated Hospital, Zhejiang University School of Medicine, No. 79 Qingchun Road, Hangzhou, Zhejiang, 310003, People’s Republic of China, Email kxhui66@zju.edu.cn; smzhu20088@zju.edu.cn

Background: Remimazolam is widely employed in surgical abortions. However, its dosing references from clinical studies such as gastrointestinal and bronchoscopic anesthesia have resulted in high incidence of physical movement.
Purpose: Determining the optimal dosage (the 90% effective dose [ED90]) for preventing physical movement during surgical abortions.
Patients and Methods: Fifty-seven individuals aged 18 to 45 undergoing surgical abortion were included. Remimazolam, combined with remifentanil, was utilized for anesthesia induction. Commencing at an initial dose of 0.25 mg/kg of remimazolam, subsequent adjustments relied on the preceding patient’s response, employing an up-down sequential allocation utilizing a biased-coin design.
Results: Patients received remimazolam doses ranging from 0.25 to 0.65 mg/kg. The estimated ED90, along with its 95% confidence interval (CI), for preventing physical movement was 0.615 mg/kg (0.398– 0.629 mg/kg). Patients maintained stable circulation, and no significant adverse events were recorded. Patients reported a satisfaction score of 4.63 ± 0.62 points. Anesthesiologists rated their satisfaction at 4.19 ± 0.61 points, and endoscopists expressed a satisfaction level of 4.53 ± 0.57 points (based on a full score of 5 points, with a minimum of 1 point).
Conclusion: The ED90 of remimazolam during surgical abortion to prevent physical movement was determined to be 0.615 mg/kg (95% CI, 0.398– 0.629 mg/kg).

Keywords: surgical abortion, 90% effective dose, remimazolam, anesthesia