Simulation of an epidural test dose with intravenous isoproterenol in sevoflurane- and halothane-anesthetized children.

UNLABELLED Isoproterenol has been suggested as an alternative marker for epidural test dosing in children receiving halothane anesthesia. The purpose of this prospective, randomized, double-blind study was to determine the chronotropic response to IV isoproterenol in sevoflurane-anesthetized children. Thirty-six ASA physical status I children (0.5-8 yr) were anesthetized with either halothane or sevoflurane at 1 minimum alveolar anesthetic concentration adjusted for age in 70% nitrous oxide. Patients received incremental IV injections of isoproterenol until their heart rate increased > or = 20 bpm above baseline. The minimal effective dose of isoproterenol required to produce an increase of > or = 20 bpm was 55 ng/kg (42-72 ng/kg; 95% confidence interval) in sevoflurane-anesthetized children and 32 ng/kg (26-38 ng/kg; 95% confidence interval) in halothane-anesthetized children (P < 0.05). This dose-response study suggests that sevoflurane antagonizes beta-adrenergic-mediated chronotropic responses to isoproterenol more than halothane. These observations also suggest that larger doses of isoproterenol will be necessary for epidural test dosing in children receiving sevoflurane rather than halothane anesthesia. IMPLICATIONS Isoproterenol has been suggested as an alternative marker for epidural test dosing in children receiving halothane anesthesia. This isoproterenol dose-response study indicates that larger doses of isoproterenol will be necessary for epidural test dosing in children undergoing sevoflurane rather than halothane anesthesia.