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

Abstract

Background: 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. Design: 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. Method: Contraction parameters were compared using data from fetal monitor strips with intrauterine pressure catheter instrumentation. Results: 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. Conclusions: 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.