Exploration of the optimal programmed intermittent epidural bolus volume with the dural puncture epidural technique for labour analgesia: a biased-coin up-and-down sequential allocation study.

Purpose: To determine the optimal programmed intermittent epidural bolus (PIEB) volume for providing effective analgesia in 90% of patients (EV₉₀) during the first stage of labour using the dural puncture epidural (DPE) technique to initiate labour analgesia.

Methods: We conducted a biased-coin up-and-down sequential allocation study. We included 40 nulliparous women requiring epidural labour analgesia. We used a 25G Whitacre spinal needle to puncture the dural mater and then administered a loading dose of 12 mL of ropivacaine 0.1% and sufentanil 0.3 μg·mL^-1. Subsequently, the PIEB pump delivered boluses with an identical solution at a fixed 40-min interval, starting 1 hr after epidural initiation. The bolus volume for the first patient was 7 mL and was adjusted for subsequent patients according to the study protocol (bolus volume, 7-12 mL). The primary endpoint was effective analgesia, indicated by no need for patient-controlled or manual boluses within 6 hr after analgesia initiation or until complete cervical dilation, whichever came first. Outcome evaluators assessed the patients' pain ratings, Bromage scores, sensory blockade level, and maternal blood pressure hourly.

Results: Using the truncated Dixon and Mood method, the estimated EV₉₀ was 9.2 mL (95% confidence interval [CI], 8.5 to 9.9) whereas the isotonic regression method yielded a value of 8.8 mL (95% CI, 8.6 to 9.8). None of the patients experienced a motor block. Two patients experienced hypotension without the need for vasopressors.

Conclusions: The estimated PIEB EV₉₀ for ropivacaine 0.1% and sufentanil 0.3 μg·mL^-1 approached 9 mL when DPE was combined with a fixed 40-min interval.

Study registration: ChiCTR.org.cn ( ChiCTR2300067281 ); first submitted 3 January 2023.