SIMULATION OF AN EPIDURAL TEST DOSE WITH INTRAVENOUS ISOPROTERENOL INSEVOFLURANE-ANESTHETIZED AND HALOTHANE-ANESTHETIZED CHILDREN

Isoproterenol has been suggested as an alternative marker for epidural test dosing in children receiving halothane anesthesia. The purpose o f this prospective, randomized, double-blind study was to determine th e chronotropic response to IV isoproterenol in sevoflurane-anesthetize d children. Thirty-six ASA physical status I children (0.5-8 yr) were anesthetized with either halothane or sevoflurane at 1 minimum alveola r anesthetic concentration adjusted for age in 70% nitrous oxide. Pati ents received incremental TV injections of isoproterenol until their h eart rate increased greater than or equal to 20 bpm above baseline. Th e minimal effective dose of isoproterenol required to produce an incre ase of greater than or equal to 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 chil dren (P < 0.05). This dose-response study suggests that sevoflurane an tagonizes P-adrenergic-mediated chronotropic responses to isoprotereno l more than halothane. These observations also suggest that larger dos es of isoproterenol will be necessary for epidural test dosing in chil dren receiving sevoflurane rather than halothane anesthesia. Implicati ons: Isoproterenol has been suggested as an alternative marker for epi dural test dosing in children receiving halothane anesthesia. This iso proterenol dose-response study indicates that larger doses of isoprote renol will be necessary for epidural test dosing in children undergoin g sevoflurane rather than halothane anesthesia.