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Generalizability of Randomized Trials of the Programmed Intermittent Epidural Bolus Technique for Maintenance of Labor Analgesia: A Prospective Single-Centre Cohort Study

N euraxial analgesia is the most widely used labor pain relief method, and patient-controlled epidural analgesia (PCEA) used in combination with a low-dose continuous epidural infusion has been shown to boost patient satisfaction while also increasing the volume of local anesthetics that are used. Researchers who have conducted randomized controlled trials (RCTs) have shown that substituting a programmed intermittent epidural bolus (PIEB) in place of PCEA can decrease local anesthetic consumption, but it is unclear if the maternal motor block in this method has a negative effect on labor progression. Because RCTs are almost always conducted on healthy nulliparous women, their results cannot easily be applied to the variety of patients seen in daily clinical practices. Gabriel and colleagues conducted their study on epidural labor analgesia data in order to compare the maternal motor function of RCT-eligible nulliparous women to parous women who are usually considered RCT-ineligible. The authors conducted this prospective cohort study by examining the data of all parturients who received PIEB analgesia at the University Hospital of Basel in Basel, Switzerland between June 2013 and October 2014. Standard practice at this hospital was to use a PIEB maintenance solution of bupivacaine 0.1% with fentanyl 2 mcg/mL, delivering a 5mL automated bolus every 60 minutes at 250mL/ h. The system also allowed additional PCEA boluses of 5mL with a lockout time of 20 minutes, and patients were instructed to request a PCEA bolus if they felt any discomfort. Motor function was assessed by an anesthesiologist according to the modified Bromage score, while pain was scored by a Verbal Analogue Scale from 0 to 10 every 60 to 90 minutes or whenever breakthrough pain occurred. In total, 839 parturients were included in this study, with 553 (66%) in the nulliparous group and 286 (34%) in the parous group. Compared with the nulliparous women, parous women had a shorter median duration of epidural analgesia (3 h 59min vs. 5 h 45min). In addition, parous women had a higher rate of spontaneous delivery (55% vs. 37%). After adjusting for epidural analgesia duration, number of rescue top-ups, and number of catheter manipulations, both groups had a similar probability of being in a certain Bromage category at birth. However, parous women needed a higher time-weighted number and volume of rescue top-ups. After conducting this study, Gabriel and colleagues concluded that RCT results on PIEB appear to be generalizable to both nulliparous and parous women. While both groups had a similar increase in motor block, the higher frequency and volume of rescue top-ups in parous women would indicate that their labor is shorter and has more intense pain. The authors recommended that care providers take this into account when planning a PIEB labor analgesia dosing scheme for parous women.