Determining the 90% Effective Dose of Remimazolam to Prevent Physical Movement in Surgical Abortions: A Biased-Coin Up-and-Down Sequential Allocation Trial.

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).