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 microg of fentanyl into the subarachnoid space. Group B received 2.5 mg of intrathecal L-bupivacaine and 25 microg 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.