Continuous extradural infusion of ropivacaine 2 mg ml-1 for pain relief during labour.

We have assessed the dose-response relationship of a solution of ropivacaine 2 mg ml-1, given as a continuous extradural infusion to women in labour. A total of 133 parturients were allocated randomly to one of four groups to receive a fixed rate ropivacaine infusion of 4, 6, 8 or 10 ml h-1 with additional bolus doses as necessary. Contraction pain, quality of analgesia, sensory block, motor block and neonatal Apgar scores were assessed. There were no significant differences between groups in terms of analgesia or motor block, although significantly more bolus doses were required by the group receiving 4 ml h-1 (P