The optimal dose of remifentanil for intubation during sevoflurane induction without neuromuscular blockade in children.

The optimal dose of remifentanil needed to produce successful intubating conditions following inhalation induction of anaesthesia using 5% sevoflurane without the use of neuromuscular blocking drugs, was investigated in 25 children aged 3-10 years. Sixty seconds after inhalation induction of anaesthesia using sevoflurane 5% in 100% oxygen, a predetermined dose of remifentanil was injected over 30 s. The dose of remifentanil was determined using the modified Dixon's up-and-down method (0.2 microg x kg(-1) as a step size). The first patient was tested at 1.0 microg x kg(-1) remifentanil. Ninety seconds following the bolus administration of remifentanil, the child's trachea was intubated. The optimal bolus dose of remifentanil required for successful tracheal intubation was 0.56 (0.15) microg x kg(-1) in 50% of children during inhalation induction using 5% sevoflurane in the absence of neuromuscular blocking drugs. Using probit analysis, the 95% effective dose (ED(95)) of remifentanil was 0.75 microg x kg(-1) (95% confidence limits 0.63-1.38 microg x kg(-1)).