# Intravenous Bolus Phenylephrine and Intravenous Bolus Norepinephrine for Treatment of Maternal Hypotension in Spinal Anesthesia During Cesarean Section: A Prospective, Randomized, Comparative Study

## TL;DR

This study compares phenylephrine and norepinephrine for treating low blood pressure during cesarean section spinal anesthesia, finding both effective but with different side effects.

## Contribution

A prospective, randomized comparison of norepinephrine and phenylephrine bolus efficacy and safety in maternal hypotension during cesarean section.

## Key findings

- Both drugs effectively managed maternal hypotension, but phenylephrine caused greater heart rate reduction.
- Fewer rescue doses were needed with phenylephrine compared to norepinephrine.
- Neonatal outcomes were similar between the two groups.

## Abstract

Background

A fall in maternal blood pressure is frequently encountered following spinal anesthesia for cesarean delivery. This hemodynamic disturbance primarily results from reduced venous return, leading to a decline in cardiac output and/or systemic vascular resistance. The primary objective of this study was to estimate the efficacy and safety of norepinephrine and phenylephrine for the treatment of maternal post-spinal hypotension during cesarean section. The secondary objective was to compare the hemodynamics and neonatal APGAR scores between the two vasopressors.

Methodology

This prospective, randomized trial included 72 parturients scheduled for cesarean section. Before the administration of spinal anesthesia, participants were allocated using computer-generated randomization into the following two groups: norepinephrine (Group A) and phenylephrine (Group B). Group A received an intravenous bolus of norepinephrine 4 μg (4 μg/mL), while Group B was administered an intravenous bolus of phenylephrine 50 μg (50 μg/mL). Both study drugs were prepared by dilution with normal saline.

Results

The mean systolic blood pressure showed a decline in both groups for up to the initial two minutes and a gradual elevation later. A significantly greater decline in heart rate was noted in the phenylephrine group (Group B) compared with the norepinephrine group (Group A) at multiple time points during observation. In addition, patients receiving phenylephrine required fewer rescue bolus doses than those receiving norepinephrine, with the difference reaching high statistical significance (p < 0.0001). Both groups showed no statistically significant difference (p = 0.3938) in neonatal outcome, assessed by the one-minute APGAR score. The majority of neonates in both groups had APGAR scores in the moderate range (4-6), accounting for 88.89% in Group A and 94.44% in Group B. There was a statistically insignificant difference in APGAR score in both groups (p = 0.3139) at five minutes, with 100% and 97.22% of patients falling under the reassuring category of score 7-9 in Group A and Group B, respectively.

Conclusions

An intermittent bolus of norepinephrine is as effective as an intermittent bolus of phenylephrine for the treatment of maternal hypotension in spinal anesthesia during cesarean section. However, the incidence of heart rate reduction was much higher with phenylephrine than with norepinephrine. The number of bolus doses required was higher with norepinephrine than with phenylephrine.