Optimum interval time of programmed intermittent epidural bolus of ropivacaine 0.08% with sufentanyl 0.3 μg/mL for labor analgesia: a biased-coin up-and-down sequential allocation trial

BACKGROUND: The programmed intermittent epidural bolus (PIEB) technique is widely used in labor analgesia, but the parameter settings of PIEB have not yet been standardized. We designed a study to identify the optimal interval duration for PIEB using 10 mL of ropivacaine 0.08% and sufentanyl 0.3 mug/mL, a regimen commonly used to control labor pain in China, to provide effective analgesia in 90% of women during the first stage of labor without breakthrough pain. METHODS: We conducted a double-blind sequential allocation trial to obtain the effective interval 90% (EI90%) during the first stage of labor between April 2019 and May 2019. This study included the American Society of Anesthesiologists physical status II-III nulliparous parturients at term, who requested epidural analgesia. The bolus volume was fixed at 10 mL of ropivacaine 0.08% with sufentanyl 0.3 mug/mL. Participants were divided into four groups (groups 60, 50, 40, and 30) according to the PIEB intervals (60, 50, 40, and 30 min, respectively). The interval duration of the first parturient was set at 60 min and that of subsequent parturients varied according to a biased-coin design. The truncated Dixon and Mood method and the isotonic regression analysis method were used to estimate the EI90% and its 95% confidence intervals (CIs). RESULTS: Forty-four women were enrolled in this study. The estimated optimal interval was 44.1 min (95% CI 41.7-46.5 min) and 39.5 min (95% CI 32.5-50.0 min), using the truncated Dixon and Mood method and isotonic regression analysis, respectively. The maximum sensory block level above T6 was in nearly 20% of parturients in group 30; however, 5.3%, 0%, and 0% of the parturients presented with sensory block level above T6 in groups 40, 50, and 60, respectively. There were no cases of hypotension and only one parturient complained of motor block. CONCLUSION: With a fixed 10 mL dose of ropivacaine 0.08% with sufentanyl 0.3 mug/mL, the optimal PIEB interval is about 42 min. Further studies are warranted to define the efficacy of this regimen throughout all stages of labor. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1900022199; http://www.chictr.org.cn/com/25/historyversionpuben.aspx?regno=ChiCTR1900022199.