Effects of target-controlled infusion of remifentanil(4 ng/mL) on ED_(50) of minimum anesthetic concentration of sevoflurane to prevent tracheal intubation response

Objective To determine the effects of target-controlled infusion of remifentanil (4 ng/mL) on ED50 of minimum anesthetic concentration of the sevoflurane requirement to prevent tracheal intubation response. Methods Forty patients aged 22 ～ 50 years, with American Society of Anesthesiologists physical statusⅠ, were anesthetized with vecuronium and sevoflurane. Then, patients were allocated to receive no remifentanil infusion (n = 20) or a target-controlled plasma concentration of 4 ng/mL(n = 20). Sympathetic responses to tracheal intubation (presence or absence of an increase in either heart rate or mean arterial blood pressure of 15% or more above the mean of the values measured during the 2 min before tracheal intubation) were determined after a 20 min period of stable end-tidal sevoflurane and target-controlled remifentanil infusion. Predetermined end-tidal sevoflurane concentration and the ED50 for each group were determined using an up-and-down sequential-allocation technique. Results The ED50 of sevoflurane to prevent tracheal intubation response in the group receiving a target-controlled plasma concentration of 4 ng/mL remifentanil was 1.11%. The 95% confidence interval was 0.99% ～ 1.24%. The ED50 of sevoflurane to prevent tracheal intubation response in the group receiving no remifentanil was 4.59%. The 95% confidence interval was 4.21% ～ 5.00%. Conclusion A target-controlled concentration of 4 ng/mL remifentanil results in an obviously decrease in the ED50 of sevoflurane requirement to prevent tracheal intubation response.