Smooth emergence in men undergoing nasal surgery: the effect site concentration of remifentanil for preventing cough after sevoflurane-balanced anaesthesia

Background: Suppression of cough during emergence after nasal surgery is practical to avoid bleeding from the surgical site. Previously recommended effect-site concentration of remifentanil for preventing cough during emergence is restricted to female patients undergoing thyroid surgery, so we evaluated effective effect-site concentration of remifentanil for preventing cough during emergence for men undergoing nasal surgery. Methods: Twenty-four American Society of Anesthesiologists ( ASA) physical status I or II, between the ages of 18 and 60 years old, non-smoker male patients undergoing nasal surgery were enrolled in this study. The effective effect-site concentration for 50% of patients ( EC50) and and that for 95% of patients ( EC95) of remifentanil for preventing cough were determined by Dixon's up-and-down method and by isotonic regression method with a bootstrapping approach. Haemodynamic variables were compared in patients with cough and without cough during emergence. Results: The EC50 of remifentanil for preventing cough during emergence by Dixon's method was 2.17 ng/ml [standard deviation ( SD) 0.38]. The estimated EC50 and EC95 of remifentanil using isotonic regression model with a bootstrapping approach were 2.35 ng/ml [95% confidence interval (CI) 1.89- 2.66] and 2.94 ng/ml (95% CI 2.83- 2.97), respectively. Mean arterial pressure and heart rate were significantly higher in patients with cough during emergence. Three out of 13 patients that received more than 2.5 ng/ml of remifentanil experienced a brief episode of bradypnea. Conclusions: The EC95 of remifentanil for preventing cough in men after nasal surgery is 2.94 ng/ml. Remifentanil targetcontrolled infusion with established effect- site concentration could suppress cough in men during emergence from sevoflurane anaesthesia after nasal surgery, though reversible respiratory depression might arise at high effect- site concentration of remifentanil.