Maternal Pulse Pressure and the Risk of Postepidural Complications: A Randomized Controlled Trial.

Objective: To test the hypothesis that increasing the intravenous fluid bolus volume at the time of epidural placement in women with narrow pulse pressure would reduce postepidural fetal heart rate (FHR) abnormalities, hypotension, and resuscitative obstetric interventions.

Methods: We performed a single-center randomized controlled trial. Eligible participants were normotensive with a nonanomalous singleton gestation at or after 35 weeks and with a narrow pulse pressure (less than 45 mm Hg) on admission. Enrolled patients remained eligible for randomization at epidural request if they were within 6 hours of admission and the FHR remained category 1. Patients were allocated to a 500-mL (institutional standard) or 1,500-mL intravenous fluid bolus at epidural placement. A reference group with admission pulse pressure 50 mm Hg or greater was also evaluated. The primary outcome was a category 2 or 3 FHR pattern within 60 minutes after the epidural test dose. Evaluated secondary outcomes included maternal hypotension and composite resuscitative interventions to correct FHR abnormalities or hypotension. We calculated that 276 women (138/group) would provide 80% power to detect a relative 50% reduction in the occurrence of the primary outcome from 27% in the 500-mL group to 13.5% in the 1,500-mL group (two-sided α=0.05).

Results: From October 2015 to November 2016, 276 women were allocated to receive a 500-mL (n=139) or 1,500-mL (n=137) fluid bolus. One hundred thirty-eight women were evaluated in the reference group. Demographic, obstetric, and labor characteristics were similar between groups. The 1,500-mL group had significantly fewer postepidural FHR abnormalities (38.0% compared with 51.8%, relative risk 0.73, 95% CI 0.56-0.96, P=.02). Maternal systolic hypotension (10.2% compared with 34.5%, relative risk 0.30, 95% CI 0.17-0.51, P<.001) and composite postepidural interventions (18.3% compared with 44.2%, relative risk 0.42, 95% CI 0.28-0.62, P<.001) were also less frequent in the 1,500-mL group. Fetal heart rate abnormalities remained significantly less frequent in the reference group than among women with a narrow pulse pressure on admission for delivery.

Conclusion: A 1,500-mL intravenous fluid bolus in women with a narrow pulse pressure decreases the risk of postepidural FHR abnormalities (number needed to treat=7), results in less frequent postepidural hypotension, and reduces the need for resuscitative interventions. Admission pulse pressure may be used to individualize intrapartum fluid management at the time of initiation of neuraxial labor analgesia.

Clinical Trial Registration: ClinicalTrials.gov, NCT02565485.