The Effective Dose of Remifentanil Combined with Remimazolam in Inhibiting Tracheal Intubation Responses in Elderly Patients: An Up–Down Dose-Finding Study

Abstract

Purpose Hemodynamic instability during tracheal intubation in elderly patients poses significant perioperative risks. This study aimed to determine the effective doses (ED50/ED95) of remifentanil combined with remimazolam to suppress intubation-induced stress responses while minimizing hypotension in patients aged ≥60. Patients and Methods In this prospective, double-blind trial, 29 elderly patients received remimazolam (0.3 mg/kg) followed by rocuronium and remifentanil (initial dose: 1 µg/kg, adjusted via Dixon’s up-down method). Hemodynamic parameters (blood pressure, heart rate, systemic vascular resistance, cardiac output) and bispectral index (BIS) were recorded. Probit regression analyzed dose–response relationships. A positive hemodynamic response was defined as an increase in systolic blood pressure or heart rate exceeding 20% of the baseline value within 5 minutes after endotracheal intubation. Dixon’s up-and-down method and probit regression analysis to determine the ED50 and ED95 of remifentanil combined with remimazolam to suppress intubation-induced stress responses in elderly patients. Results The ED50 and ED95 of remifentanil were 0.85 µg/kg (95% CI: 0.80–0.90) and 0.97 µg/kg (95% CI: 0.91–1.21), respectively. Positive responders showed elevated blood pressure at 30s–1 min post-intubation (P<0.05), while cardiac output and systemic vascular resistance remained comparable between groups. Hypotension incidence was low (14.3–20%), with transient BIS elevations (60–70) in 51.7% of patients but no intraoperative awareness. Conclusion In this exploratory dose-finding study, the estimated ED50 and ED95 of remifentanil for suppressing intubation-related hemodynamic responses during remimazolam-based induction were 0.85 and 0.97 μg/kg, respectively.