Effective volume of ropivacaine 0.1% plus sufentanil 0.3 μg·mL-1 for labour epidural analgesia initiation after dural puncture epidural technique: a biased-coin up-and-down sequential allocation study.

PURPOSE: We sought to determine the effective initiation volume of ropivacaine 0.1% with sufentanil 0.3 μg·mL-1 in 90% of patients (EV90) for labour epidural analgesia using the dural puncture epidural (DPE) technique. METHODS: In this biased-coin up-and-down sequential allocation study of labour analgesia, we included patients with a singleton pregnancy who were nulliparous; who had an American Society of Anesthesiologists Physical Status II-III classification, a numerical rating scale (NRS) pain score > 5, and cervical dilation < 5 cm; and who requested labour analgesia. We used a 25 G Whitacre needle to puncture the dura mater and initiated labour analgesia with epidural ropivacaine 0.1% with sufentanil 0.3 μg·mL-1, omitting a lidocaine test dose. The initiation volume for the first parturient was 12 mL and was modified for the next parturient per the study design (groups 12, 14, 16, 18, and 20 with an initiation volume of 12, 14, 16, 18, and 20 mL, respectively). We defined effective analgesia as an NRS ≤ 3 at 20 min and assessed sensory blockade levels, Bromage scores, and maternal or neonatal adverse effects. RESULTS: We analyzed data from 40 participants. The estimated EV90 was 18 mL (95% confidence interval [CI], 14 to 18) with isotonic regression. The proportion of patients with the highest sensory block level reaching or exceeding T6 was 0/2 (0%), 0/4 (0%), 2/15 (13%), and 1/19 (5%) in groups 12, 14, 16, and 18, respectively. One patient who received 18 mL experienced hypotension but did not require vasopressor treatment. CONCLUSIONS: When using the DPE technique to initiate labour analgesia without a lidocaine test dose, the EV90 of ropivacaine 0.1% with sufentanil 0.3 μg·mL-1 was 18 mL (95% CI, 14 to 18). STUDY REGISTRATION: ChiCTR.org.cn ( ChiCTR2300074502 ); first submitted 8 August 2023.