Optimal Interval for Intermittent Epidural Bolus with Ropivacaine-Dexmedetomidine Using the Epidural Dural Puncture Technique for Labour Analgesia: A Coin Bias Up-Down Study

Purpose: This study aimed to establish the 90% effective interval time for programmed intermittent epidural bolus (PIEB) following dural puncture epidural (DPE) analgesia with a dexmedetomidine ropivacaine combination for primiparas in the first stage of labor. Patients and Methods: This biased coin up and down sequential allocation trial enrolled 40 nulliparous women requesting labor analgesia. After an initial loading dose, analgesia was maintained with PIEB of a fixed volume of 8 mL of the same solution, starting 1 hour later. The initial PIEB interval was set at 60 minutes for the first patient and subsequently adjusted by ± 5 minutes based on the outcome of the previous patient, following the biased-coin design. A successful interval was defined as no requirement for supplemental analgesia. The primary outcome was the 90% effective PIEB interval (ED90) for the first stage of labor. Secondary outcomes included patient satisfaction, the incidence of motor and sensory block, and adverse events. Results: Isotonic regression analysis estimated the 90% effective PIEB interval as 34.5 min (95% confidence interval: 31.0– 37.0 min). All patients reported a very high level of satisfaction. The incidence of motor block was 10%, while 37.5% of patients achieved the highest sensory block at the T6 level or above. Notably, no cases of excessive sedation, hypotension, or bradycardia. Conclusion: For DPE labor analgesia using 8 mL of 0.075% ropivacaine combined with 0.4 μg/mL dexmedetomidine, the optimal PIEB interval is approximately 35 min. This interval can reduce breakthrough pain and the need for rescue analgesia. This finding provides a practical, evidence-based reference for optimizing PIEB regimens in clinical labor analgesia, contributing to improved maternal comfort and labor experience while ensuring safety. Keywords: labor analgesia, dexmedetomidine, programmed intermittent epidural bolus, dural puncture epidural, time interval