Background: Ropivacaine has been claimed to produce less motor block than bupivacaine during epidural analgesia. However, this advantage has not been clearly confirmed in obstetric studies using low analgesic concentrations in a ratio close to that suggested to be equianalgesic.
Methods: This double-blind, randomized, prospective study was performed in 140 parturients who requested epidural analgesia. After a lumbar epidural catheter had been placed, patients received either 0.10% bupivacaine plus sufentanil 0.5 microgram ml-1 or 0.15% ropivacaine plus sufentanil 0.5 microgram ml-1 followed by a continuous infusion. Additional boluses were used for inadequate levels of analgesia. Visual analogue pain scores, motor block, level of sensory block, supplementary boluses and main characteristics of labour were recorded.
Results: No differences were observed between the two groups for pain scores, total volume of anaesthetic solution used [59 (23) and 57 (24) ml in the bupivacaine and ropivacaine groups respectively], duration of labour, mode of delivery, side-effects or satisfaction score. The incidence of motor block was not statistically different between the groups (54 and 69% in the bupivacaine and ropivacaine groups respectively, P = 0.07). However, when motor block occurred, survival analysis showed that it occurred sooner in the course of labour with ropivacaine compared with bupivacaine (log rank test, P = 0.012).
Conclusion: Combined with sufentanil 0.5 microgram ml-1, 0.10% bupivacaine and 0.15% ropivacaine produce effective and equivalent analgesia during labour, with similar incidences of motor block.