Can Maternal Pulse Pressure be Used to Determine the Need for Fluid Bolus Prior to Epidural?

BACKGROUND AND PURPOSE: 

  • Epidural anesthesia can be associated with maternal hypotension and consequent changes in fetal status 
    • Fetal heart rate (FHR) can be abnormal in 14-30% of cases following an epidural  
  • No set guidelines exist as to necessity of a fluid bolus 
  • Literature exists that low maternal pulse pressure, indicating hypovolemia, may be a helpful guide in determining requirement for fluid bolus  
  • Lappen et al. (Obstetrics & Gynecology, 2017) sought to determine whether increasing the IV fluid bolus volume at the time of epidural placement in women with narrow pulse pressure would reduce adverse fetal cardiac events   

METHODS: 

  • Randomized controlled trial (RCT) 
  • Inclusion Criteria 
    • Normotensive 
    • Presented for either spontaneous or induction of labor 
    • Narrow pulse pressure (systolic BP–diastolic BP) <45 mm Hg on admission 
    • Nonanomalous fetus 
  • Eligibility for randomization at epidural request if within 6 hours of admission and FHR category 1
  • Patients were randomized into 2 arms, both receiving lactated Ringer’s over 30 minutes initiated with patient epidural request and with preparation for or initiation of epidural placement by the anesthesiology team  
    • 500-mL (institutional standard) with programmed infusion pump (rate 999 mL/h) 
    • 1,500-mL intravenous fluid bolus using a pressure bag over 30 minutes  
  • A reference group with admission pulse pressure ≥50 mm Hg or greater was also evaluated 
  • Primary outcome  
    • Category 2 or 3 FHR within 60 minutes after epidural test dose 
  • Secondary outcomes 
    • Maternal hypotension  
    • Composite resuscitative interventions to correct FHR and maternal hypotension 

RESULTS: 

  • 139 women received 500-mL and 137 women received 1,500-mL fluid bolus 
  • 138 women were evaluated in the reference group 
  • Demographic, obstetric, and labor characteristics were generally similar between groups 
    • 1,500-mL arm had higher rate of admission for induction  
  • Comparing the 1,500-mL group to the 500-mL group, there were  
    • Fewer FHR abnormalities (38.0% vs 51.8%) with relative risk (RR) of 0.73, 95% CI 0.56–0.96; P=.02 
    • Fewer episodes of maternal systolic hypotension (10.2% vs 34.5%) with RR of 0.30, 95% CI 0.17–0.51; P<.001 
    • Fewer composite interventions (18.3% vs 44.2%) with RR of 0.42, 95% CI 0.28–0.62; P<.001 
  • FHR abnormalities remained significantly less frequent in the reference group than among women with a narrow pulse pressure on admission for delivery 

CONCLUSION: 

  • An 1,500-mL intravenous fluid bolus in women with a narrow pulse pressure decreases FHR abnormalities, frequency of postepidural hypotension, and need for interventions to reverse maternal hypotension and abnormal FHR patterns  
  • Admission maternal pulse pressure can be used as a surrogate for central volume status and may identify women who would benefit from a larger IV bolus prior to epidural  

Learn More – Primary Sources:  

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