Determination of the Optimal Volume of Programmed Intermittent Epidural Bolus When Combined With the Dural Puncture Epidural Technique for Labor Analgesia: A Random-Allocation Graded Dose-Response Study.

BACKGROUND: The dural puncture epidural (DPE) and the programmed intermittent epidural bolus (PIEB) techniques are recent innovations for labor analgesia. The optimal volume of PIEB during traditional epidural analgesia has been investigated previously but it is unknown whether these findings are applicable to DPE. This study aimed to determine the optimal volume of PIEB for effective labor analgesia after initiation of analgesia using DPE.

METHODS: Parturients requesting labor analgesia received dural puncture with a 25-gauge Whitacre spinal needle and then had analgesia initiated with 15 mL of ropivacaine 0.1% with sufentanil 0.5 μg/mL. Analgesia was maintained using the same solution delivered by PIEB with boluses given at a fixed interval of 40 minutes starting 1 hour after the completion of the initial epidural dose. Parturients were randomized to 1 of 4 PIEB volume groups: 6, 8, 10, or 12 mL. Effective analgesia was defined as no requirement for a patient-controlled or manual epidural bolus for 6 hours after the completion of the initial epidural dose or until full cervical dilation. The PIEB volumes for effective analgesia in 50% of parturients (EV50) and 90% of parturients (EV90) were determined using probit regression.

RESULTS: The proportions of parturients with effective labor analgesia were 32%, 64%, 76%, and 96% in the 6-, 8-, 10-, and 12-mL groups, respectively. The estimated values for EV50 and EV90 were 7.1 (95% confidence interval [CI], 5.9-7.9) mL and 11.3 (95% CI, 9.9-15.2) mL, respectively. There were no differences in side effects, including hypotension, nausea and vomiting, and fetal heart rate (FHR) abnormalities among groups.

CONCLUSION: Under the conditions of the study, after initiation of analgesia using DPE, the EV90 of PIEB for effective labor analgesia using ropivacaine 0.1% with sufentanil 0.5 μg/mL was approximately 11.3 mL.