Comparison of Three Different Concentrations of Levobupivacaine for Epidural Labor Analgesia: Clinical Effect and Pharmacokinetic Profile.

Background: The aim is to compare the clinical effect of three different concentrations of levobupivacaine (0.25%, 0.125%, and 0.0625%) on the sensory and motor block characteristics and mode of delivery during epidural labor analgesia. We also studied the pharmacokinetic profile of the three concentrations during labor.

Materials And Methods: Sixty pregnant females undergoing normal vaginal delivery under epidural analgesia were divided into three groups according to the concentration of levobupivacaine used. All parturients received an epidural bolus dose of 15 ml of the desired concentration followed by a continuous infusion of the same concentration at 10 mL/h, each combined with fentanyl 2 μg/mL. Sensory block was assessed by the visual analog score (VAS), whereas motor block was evaluated by the Bromage score. Assessments were performed every 5 min in the first 20 min after initiation of epidural analgesia and then at 30 min interval. The incidence of instrumental delivery and cesarean section was also recorded. The total plasma concentrations of levobupivacaine were determined before the start of epidural analgesia, 5 and 10 min after starting the infusion, at infusion stop time, and 3-8 h after infusion termination.

Results: The VAS was significantly lower with levobupivacaine concentrations of 0.25% and 0.125% than 0.0625%. Motor block in the form of Bromage score 1 was observed in 39% of parturients receiving levobupivacaine 0.25% of which 43% were converted to cesarean delivery. No motor block was observed with the other two concentrations. Levobupivacaine peak plasma concentrations increased with increasing the concentration of the local anesthetic. There was no difference in other pharmacokinetic parameters between the three groups.

Conclusion: levobupivacaine concentration of 0.125% is superior to other concentrations for epidural labor analgesia as it provides adequate analgesia without motor affection which reflects in a lower incidence of instrumental delivery or cesarean section.