Bupivacaine versus L-bupivacaine for labor analgesia via combined spinal-epidural: A randomized, double-blinded study

Study objective: To compare the intensity and duration of motor block and the duration of sensory block with racemic bupivacaine and L-bupivacaine for combined spinal-epidural analgesia, as previous studies have shown contradictory results. Design: A prospective, randomized, double-blinded study. Setting: Birth Center at Magee-Womens Hospital, Pittsburgh, Pa. Patients: Multiparous American Society of Anesthesiologists physical status I and II patients requesting labor analgesia. There were 2 groups: group A with 34 patients and group B with 33. Interventions: Group A received a mixture of 2.5 mg of racemic bupivacaine and 25 mu g of fentanyl into the subarachnoid space. Group B received 2.5 mu g of intrathecal L-bupivacaine and 25 mu g of fentanyl. Pain verbal analog score (VAS, 0-10) scores and Bromage scores were recorded at 5, 15, 30, and every 30 minutes thereafter until the VAS increased to 3 or higher, at which time the epidural block was activated with 0.125% bupivacaine and fentanyl. Patients' vital signs and fetal heart rate were monitored for 30 minutes after the block. Main results: None of the patients in both groups had any demonstrable motor block. The median VAS decreased from 7 to 0 in 5 minutes in group A and from 7.5 to 0 in group B. The average durations of sensory block in groups A and B were 114.85 +/- 26.27 and 101.9 +/- 35.20 minutes (P = NS), respectively. Conclusion: Contrary to earlier studies, we did not find any difference in the intensity and duration of sensory or motor blocks between racemic bupivacaine and L-bupivacaine. Based on our findings in the parturient population studied, we conclude that L-bupivacaine does not offer any advantages over racemic bupivacaine when used for combined spinal-epidural for labor analgesia. (c) 2005 Elsevier Inc. All rights reserved.