Remifentanil decreases sevoflurane requirements in children

Purpose: To establish the effect of increasing concentrations of remifentanil on sevoflurane requirements in children. Methods: Fifty-eight healthy patients, ASA status 1-11 aged two to 12 yr, undergoing abdominal wall hernia or hydrocele repairs were serially assigned to one of four test groups to receive remifentanil 0.03 μg·kg^-1·min^-1, 0.06 μg·kg^-1·min^-1, 0.12 μg·kg^-1·min^-1, or 0.25 μg·kg^-1·min^-1 iv. Patients received a bolus of remifentanil 1 μg·kg^-1 iv before the infusion began. End-tidal sevoflurane concentration was adjusted according to a Dixon up-and-down approach. Ten minutes after starting the remifentanil infusion, the surgical incision was made. The patient was observed for one minute from the time of incision by a solitary blinded rater for either flexion or withdrawal of one or more extremities in response to skin incision. Results: The mean minimum alveolar concentration of sevoflurane was 2.39 ± 0.58 with 0.03 μg·kg^-1·min^-1 remifentanil, 1.91 ± 0.36 with 0.06 μg·kg^-1·min^-1 remifentanil, and 0.92 ± 0.11 with 0.12 μg·kg^-1·min^-1 remifentanil. Remifentanil 0.25 μg·kg^-1·min^-1 lead to the sevoflurane being decreased to a level associated with spontaneous patient awakening. The effective dose (ED₅₀) values of sevoflurane were 2.44 [95% confidence interval (CI) 2.16-2.72], 2.00 (95% CI 1.78-2.22), and 1.18 (95% CI 0.99-1.36) for remifentanil infusion rates of 0.03 μg·kg^-1·min^-1, 0.06 μg·kg^-1·min^-1, and 0.12 μg·kg^-1·min^-1 respectively. Conclusion: The administration of remifentanil produced a dose-dependent decrease in the minimum alveolar concentration of sevoflurane necessary for inhibition of movement reaction in response to surgical incision. The use of remifentanil may allow for flexible analgesic control and rapid recovery in children anesthetized with sevoflurane.