Uterine Contraction Parameters Before and During the Pre-Epidural Fluid Bolus: A Pilot Study

The first stage of labor is significantly longer with epidural analgesia use, implying an alteration in uterine contractility. Although the pre-epidural fluid bolus is used with every epidural and affects as many as 80% of laboring women, its effects on uterine contraction parameters are unknown.

Using a retrospective descriptive repeated measures design, we compared uterine contraction parameters including frequency, duration, peak intensity, resting tone, and Montevideo units at baseline and during the intravascular pre-epidural fluid bolus (Bolus) epochs for healthy laboring women at term gestation undergoing augmentation or induction.

Contraction parameters were compared using data from fetal monitor strips with intrauterine pressure catheter instrumentation.

No significant differences were found between epochs for women receiving constant Pitocin dosages (n = 10) using Wilcoxon signed rank tests at .05 α level, but all parameters trended in the direction of improved contractility except frequency, which was unchanged.

These pilot study findings do not support the proposal that the pre-epidural fluid bolus is a contributor to decreased uterine contractility in any parameter. It is possible that the bolus improved myometrial perfusion and metabolic function in the contracting and resting states in less hydrated women.