BACKGROUND: Optimum dose of remimazolam for inducing loss of consciousness in elderly patients has been suggested by prior studies. Opioids can enhance their sedative effects, thereby permitting dose reduction. However, the dose-response of remimazolam when combined remifentanil for attenuating stress response during laryngeal mask airway (LMA) insertion in elderly female patients is still unknown. Moreover, the ideal dose of medications is especially critical in elderly patients due to their compromised cardiopulmonary function. The objective of this study was to determine the median effective dose (ED50) and ED95 of remimazolam in inhibiting the stress response associated with LMA insertion. METHODS: Sixty aged ≥ 65 and <
80 years old female patients were randomized allocated into 1 of 4 groups receiving doses of 0.2, 0.25, 0.3, and 0.35 mg/kg remimazolam. Following a dosage of 2.0 ng/mL of remifentanil, patients received different doses of remimazolam. Effective dose is defined as the prevention of stress response associated with LMA insertion, characterized by a post-sedation induction SBP variation <
20% of baseline value, jaw relaxation and absence of patient body motion during the initial 2 minutes following LMA insertion. Probit regression analysis was utilized to estimate the ED50 and ED90 values. RESULTS: The ED50 and ED95 of effective remimazolam of general induction for elderly female patients not suffer intubation stress response were 0.24 mg/kg (95% CI 0.20-0.27 mg/kg) and 0.37 mg/kg (95% CI 0.32-0.49 mg/kg), respectively. The incidence of hypotension was 33.3% (5/15), 46.7% (7/15), 73.3% (11/15), and 80% (12/15) in the four groups, respectively. CONCLUSION: The ED50 and ED95 values of intravenous remimazolam for preventing stress response during LMA insertion were 0.24 and 0.37 mg/kg, respectively in elderly female. TRIAL NUMBER AND REGISTRY URL: Registration number, ChiCTR2400083990, https://www.chictr.org.cn/showproj.html?proj=229006.