Median effective concentration of levobupivacaine for motor block in epidural labor analgesia

Objective To determine the median effective concentration (EC50) of levobupivacaine for motor block in epidural labor analgesia.Methods Thirty ASA I nulliparous parturients with 2-3 cm cervical dilatation in the first stage of labor who requested epidural analgesia were enrolled in this study.Epidural catheter Was placed at L2,3 interspace and advanced for 3 cm cephalad in the epidural space.Each parturient received a bolus of 10 ml epidural levobupivacaine.The initial levobupivacaine concentration wag O.5%.Up-and-down sequential allocation was used to determine EC50.The ratio between adjacent concentration was O.95.Thirty minutes after epidural administration the degree of motor block of lower extremities was assessed and scored using modified Bromage scale.Results The motor block EC50 of epidural levobupivacaine was 0.562% and the 95% confidence interval was 0.542%-0.584%.Conclusion The EC50 of epidural levobupivacaine(10 m1)in the first stage of labor is 0.562% with 95% confidenee imerval between 0.542%-0.584%. Key words: Dose-response relationship,drug; Analgesia,0bstetrical; Analgesia,epidural; Levobupivacaine