Effect-site concentration of remifentanil for laryngeal mask airway insertion during target-controlled infusion of propofol.

The purpose of this study was to determine the effect-site concentration of remifentanil that would provide optimal conditions for successful laryngeal mask airway insertion during a target-controlled infusion (TCI) of propofol at 3.5 microg.ml(-1) without the use of neuromuscular blockade. Five minutes after propofol infusion, remifentanil was infused at a dose determined by a modified Dixon's up-and-down method. Five minutes after remifentanil infusion, the laryngeal mask was inserted. The effect-site concentration of remifentanil for successful laryngeal mask insertion in 50% of adults (EC(50)) was 3.04 (SD 0.49) ng.ml(-1) during a TCI of 3.5 microg.ml(-1) propofol without neuromuscular blockade. From the probit analysis, the EC(50) and EC(95) of remifentanil were 2.84 ng.ml(-1) (95% CI 2.09-3.57 ng.ml(-1)) and 3.79 ng.ml(-1) (95% CI 3.26-9.25 ng.ml(-1)), respectively.