Comparison of the optimal effect-site concentrations of remifentanil for preventing cough during emergence from desflurane or sevoflurane anaesthesia.

OBJECTIVE: To compare the effect-site concentrations of remifentanil target-controlled infusion (TCI) that produced 50% and 95% of the maximal effect (EC50 and EC95, respectively) for preventing cough during emergence from desflurane or sevoflurane anaesthesia, in patients undergoing elective thyroidectomy. METHODS: Adults undergoing elective thyroidectomy were randomized to receive anaesthesia with desflurane or sevoflurane. The EC50 and EC95 values for remifentanil TCI were determined using Dixon's up-and-down method and probit analysis with sigmoid curve. RESULTS: In total, 48 patients aged 20 - 64 years were enrolled in the study. The EC50 +/- SD of remifentanil TCI, determined by Dixon's up-and-down method, were 1.54 +/- 0.70 and 1.11 +/- 0.24 ng/ml for desflurane and sevoflurane, respectively. The EC95 of remifentanil TCI, analysed by probit analysis, were 2.88 ng/ml and 2.29 ng/ml for desflurane and sevoflurane, respectively. The effect-site concentration of remifentanil TCI for preventing cough during emergence from desflurane anaesthesia was not significantly higher than that observed for sevoflurane. CONCLUSIONS: During emergence from anaesthesia, variations in effect-site concentrations of remifentanil for preventing cough are of limited importance as they do not generate significant differences in results.