Ropivacaine 2mg/mL vs. bupivacaine 1.25mg/mL with sufentanil using patient-controlled epidural analgesia in labour

Background: In recent studies, minimum local analgesic concentrations have been defined as 0.93 mg/mL for bupivacaine and 1.56 mg/mL for ropivacaine for epidural analgesia for the first stage of tabour, resulting in an analgesic potency ratio of 1:0.6. In the current study we compared ropivacaine and bupivacaine in a PCEA system (combined with sufentanil) taking this potency ratio into account but administering drug doses providing sufficient analgesia for all stages of tabour. Methods: In a prospective, double-blinded study 114 parturients were randomised to receive either ropivacaine 2 mg/mL with sufentanil 0.75 mug/mL or bupivacaine 1.25 mg/with sufentanil 0.75 mug/mL. After epidural catheter placement, PCEA was available with boluses of 4 mL, a lock-out time of 20 min and no basal infusion rate. We evaluated pain intensity during contractions, sensory and motor function, duration of tabour, mode of delivery and neonatal outcome. Consumption of local anaesthetic and opioid drugs and PCEA system variables were recorded. Results: Mean total consumption as well as mean hourly drug consumption was significantly increased in the ropivacaine-sufentanil group. No differences in analgesic quality, sensory or motor blocking potencies or neonatal outcome variables between groups were detected. Frequency of instrumental deliveries was significantly increased in the ropivacaine-sufentanil group. Conclusions: The results support the findings of previously published studies postulating ropivacaine to be 40-50% less potent for tabour epidural analgesia compared to bupivacaine. However, we observed an increased frequency of instrumental deliveries with ropivacaine. To evaluate the clinical relevance of these findings, further investigations are warranted.