Determination the ED90s of Different Concentrations of Initial Ropivacaine Volume for Labor Analgesia with Dural Puncture Epidural: A Randomized Sequential Allocation Study

This study aims to determine the 90% effective doses (ED90) of the initial ropivacaine volume at varying concentrations (0.075%, 0.1%, 0.125%) administered under dural puncture epidural (DPE) for epidural labor analgesia. Ninety ASA II-class patients with cervical dilation < 5 cm and VAS scores >5 were allocated into three groups (0.075%, 0.1%, and 0.125% ropivacaine concentrations) for epidural labor analgesia. The first patient in each group received an initial bolus of ropivacaine combined with sufentanil 0.3 µg/mL in a 10 mL volume. Subsequent doses were determined by an up-and-down sequential allocation method based on adequate analgesia (VAS score <3) within 30 minutes post-administration, using 2 mL incremental/decremental adjustments. The primary outcome was the ED90s of the initial ropivacaine bolus required for effective analgesia under DPE. Maternal analgesia characteristics and neonatal outcomes were recorded. The ED90 values for the 0.075%, 0.1%, and 0.125% ropivacaine groups were 13.30 mL (95% CI, 10.00-14.00), 10.80 mL (95% CI, 8.00-12.00), and 8.90 mL (95% CI, 8.00-10.00), respectively. Maternal and neonatal outcomes were comparable across groups. Compared to 0.075% concentration of ropivacaine, the 0.1% and 0.125% concentrations achieved 18.8% and 33.0% reductions in initial analgesic volume requirements. However, comparable analgesic effects and maternal satisfaction were observed across all groups.