Objective: To investigate the effective interval of programmed intermittent epidural bolus (PIEB) in labor analgesia with ropivacaine and hydromorphone. Methods: A total of 101 puerpera with singleton pregnancy, head position, aged 20-40 years, BMI 20-35 kg/m2, ASA physical status Ⅰ or Ⅱ, gestational age 37-42 weeks, were randomly allocated into five different PIEB intervals groups: PIEB 40 minutes group (group P40, n = 20), PIEB 50 minutes group (group P50, n = 19), PIEB 60 minutes group (group P60, n = 20), PIEB 70 minutes group (group P70, n = 20), and PIEB 80 minutes group (group P80, n = 22). The PIEB dose was fixed at 10 ml with the first bolus given 1 hour after the initial manual loading dose with subsequent boluses continued at intervals according to different group allocation. Analgesia was provided using PIEB with 0.1% ropivacaine combined with hydromorphone 15 μg/ml for a total of 12 ml. Based on effective analgesia rate (proportion of women who do not require additional analgesic drugs by the end of the first stage of labor). Probit regression was used to estimate median effective interval (EI50) and 90% effective interval (EI90). VAS pain scores before analgesia, 20 minutes, 1 hour, 2, 3, and 4 hours, at full opening of the cervix were recorded. The highest level of sensory blockade and motor blockade (modified Bromage score) were recorded, maternal adverse effects were recorded. Neonatal weight, 1 minute and 5 minutes postnatal Apgar scores were recorded. Results: Effective analgesia rates were 95.0%, 84.2%, 70.0%, 55.0%, and 50.0% in groups P40, P50, P60, P70, and P80, respectively. The EI50 and EI90 were 76.5 minutes (95% CI 69.0-93.9 minutes) and 43.4 minutes (95% CI 17.6-52.7 minutes) analysing by Probit regression. There were no significant differences in VAS pain score at different time, maximum sensory block plane, modified Bromage score, incidence of maternal adverse reactions and neonatal conditions between the two groups. Conclusion: The EI50 and EI90 of PIEB 0.1% ropivacaine combined with hydromorphone 15 μg/ml for labor analgesia were 76.5 minutes (95% CI 69.0-93.9 minutes) and 43.4 minutes (95% CI 17.6-52.7 minutes), respectively. |