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PEDIATRIC ANESTHESIOLOGY

Relative Analgesic Potencies of Levobupivacaine and Ropivacaine for Caudal Anesthesia in Children

Pablo Ingelmo, MD^*, Geoff Frawley, MD, Marinella Astuto, MD^*, Chris Duffy, MD, Susan Donath, PhD, Nicola Disma, MD, Giuseppe Rosano, MD, Roberto Fumagalli, MD^*, and Antonio Gullo, MD

From the *Department of Perioperative Medicine and Intensive, A.O. San Gerardo, Monza, Dipartimento di medicina sperimentale ambientale e biotecnologie mediche, Università degli Studi Milano Bicocca, Milan, Italy; Department of Paediatric Anesthesia and Pain Management, Royal Children’s Hospital. Melbourne Australia; Clinical Epidemiology and Biostatistics Unit, Murdoch Children’s Research Institute, University of Melbourne Australia; and Department of Anesthesia, A.O.U. Policlinico Catania, Università degli Studi di Catania, Italy.

Address correspondence and reprint requests to Dr. Geoff Frawley, Department of Paediatric Anesthesia and Pain Management, Royal Children’s Hospital, Melbourne Australia. Address e-mail to geoff.frawley{at}rch.org.au.

Abstract

BACKGROUND: Comparing relative potency of new local anesthetics, such as levobupivacaine and ropivacaine, by the minimum local analgesic concentration model has not been described for caudal anesthesia. Therefore, we performed a prospective, randomized, double-blind study to determine the minimum local analgesic concentrations of a caudal single shot of ropivacaine and levobupivacaine in children and to describe the upper dose-response curve.

METHODS: We performed a two-stage prospective, randomized, double-blind study comparing the dose-response curves of caudal ropivacaine and levobupivacaine in children. In phase 1, 80 boys were randomized to receive either ropivacaine or levobupivacaine. In the second phase a further 32 patients were randomly allocated to receive caudal anesthesia with doses designed to delineate the upper dose-response range (the 50% effective dose [ED₅₀]-ED₉₅ range).

RESULTS: There were no significant differences in ED₅₀ values for caudal ropivacaine and levobupivacaine. The ED₅₀ for levobupivacaine estimated from the Dixon Massey method was 0.069% (95% CI 0.056%-0.082%) and for ropivacaine was 0.075% (95% CI 0.058%-0.092%). Estimated by isotonic regression the ED₅₀ and ED₉₅ respectively of levobupivacaine were 0.068 (0.04-0.09) and 0.20% (95% CI 0.16%-0.24%). For ropivacaine ED 50 and ED95 were 0.066 (0.033-0.098) and 0.225% (95% CI 0.21%-0.24%).

CONCLUSIONS: In children receiving one minimum alveolar anesthetic concentration of sevoflurane, there were no significant differences in the ED₅₀ for caudal levobupivacaine and ropivacaine. The potency ratio at ED₅₀ was 0.92 and 0.89 at ED₉₅, indicating that caudal levobupivacaine and ropivacaine have a similar potency.