The dose-response relationship of fentanil for tracheal intubation during sevoflurane induction without neuromuscular blockade

Abstract

Objective To determine the bolus dose of fentanil required to provide successful intu-bating conditions following inhalation induction of anesthesia using sevoflurane without neuromuscular blockade in adult anesthesia. Methods Twenty-six ASA Ⅰ or Ⅱ patients aged 25-45 years undergoing general anesthesia for short surgery were enrolled into this study. Anesthesia was induced with seveflurane 8% in oxygen,after the loss of eyelash reflex, end-tidal sevoflurane concentration 3% was maintained, and predetermined dose of fentanil was injected over 30s. The dose of fentanil was determined by modified Dix-on's up-and-down method (0.4 μg/kg as a step size). Four minutes after the end of bolus administration of fentanil ,the trachea was intubated. Mean blood pressure,heart rate and Entropy indices were recorded at anesthetic induction, before, 1 min and 3 min after intubation. Results The bolus dose of fentanil for suc-cessful tracheal intubation was (1.2±0.3 ) μg/kg in 50% of patients during inhalation induction. From probit anlysis,50% effective dose (ED_(50)) and ED95 values (95% confidence limits) of fentanil were 1.2 μg/kg (0.9-1.6) μg/kg and 1.9 μg/kg (1.6-3.9) μg/kg,respectively. Conclusion Using the modi-fied Dixon's up-and-down method, the bolus dose of fentanil for successful tracheal intubation was (1.2±0.3) μg/kg in 50% of adult patients during 8% sevoflurane induction and maintained with end-tidal con-centration 3% without neuromuscular blocking agent in anesthesia. Key words: Fentanil; Sevoflurane; Dose-response relationship; General anesthesia