Epidural infusion of low-dose bupivacaine and opioid in labour. Does reducing motor block increase the spontaneous delivery rate?

Labouring women were randomly allocated to receive epidural infusions during labour of either 0.125% plain bupivacaine (n = 200) or a combination of 0.0625% bupivacaine with either 2.5 micrograms.ml-1 fentanyl or 0.25 micrograms.ml-1 sufentanil (n = 199) each starting at 12 ml.h-1 and adjusted as necessary to maintain analgesia. The dose of bupivacaine, both hourly (p < 0.001) and total (p < 0.001), was significantly lower in the group receiving the combination. Motor block was significantly less common and less severe in the combination group (p < 0.001). These reductions did not result in a significant increase in spontaneous deliveries. Maternal satisfaction with first (p < 0.001) and second stage analgesia (p < 0.001) was significantly increased in the combination group. The addition of opioid to the epidural infusion did not reduce the incidence of perineal pain. There were no significant differences between the groups in neonatal outcome or the incidence of early postnatal symptoms.