Effect of different administration times of dexmedetomidine on the ED50 of sufentanil to inhibit the cardiovascular response in elderly patients with double lumen tracheal intubation: a randomized controlled trial

To investigate the effect of different administration timings of dexmedetomidine (DEX) on the median effective dose (ED50) of sufentanil required to suppress the cardiovascular response during double-lumen tracheal intubation in elderly patients. Ninety elderly patients (aged 65–85 years, BMI 18.5–30 kg/m2, ASA physical status I–III) scheduled for elective thoracic surgery were randomized into three groups: the Control group (induction initiated following a 10-min intravenous infusion of saline), the DEX1 group (DEX 0.6 μg/kg infused over 10 min before induction), and the DEX2 group (induction initiated 20 min after completion of a 10-min intravenous infusion of DEX at a dose of 0.6 μg/kg). Anesthesia induction was initiated with intravenous sufentanil starting at 0.5 μg/kg, and subsequent doses were determined using the Dixon up-and-down sequential method with a dose ratio of 1:1.1 between adjacent dose levels. Tracheal intubation was performed 5 min after sufentanil administration according to the predefined protocol, and the infusion-to-intubation interval was predefined according to group allocation. Sequential allocation continued until at least eight crossover pairs were obtained. Patient characteristics, hemodynamic variables, Surgical Pleth Index (SPI), and adverse events were recorded from study drug administration to 5 min after intubation. Final analysis included 87 patients (Control: n = 30, DEX1: n = 28, DEX2: n = 29). The ED50 of sufentanil was 0.675 μg/kg (95% CI: 0.634–0.732 μg/kg) in the Control group, 0.507 μg/kg (95% CI: 0.474–0.540 μg/kg) in the DEX1 group, and 0.396 μg/kg (95% CI: 0.330–0.440 μg/kg) in the DEX2 group, corresponding to relative reductions of 24.9% and 41.3%, respectively. Premedication with dexmedetomidine reduced the ED50 of sufentanil required to suppress the cardiovascular response to double-lumen tracheal intubation in elderly patients, with earlier administration producing a greater opioid-sparing effect. Administration of DEX 30 min before anesthesia induction resulted in the lowest sufentanil requirement. This study was registered at the China Clinical Trial Registration Center (ChiCTR2400083508, April 26, 2024).