Effect of Phenylephrine vs Ephedrine on Cardiac Output for Treatment of Spinal Hypotension during Cesarean Section: a Retrospective Non-Inferiority Analysis

Abstract

Objective: As the first study to evaluate maternal cardiac output in Thai parturients, we compared the hemodynamic effects of phenylephrine and ephedrine during the management of spinal-induced hypotension for elective cesarean delivery. Materials and methods: This study was a secondary analysis of a previously published randomized controlled multi-centered trial. Data from 33 parturients experiencing spinal hypotension during cesarean section wasanalyzed retrospectively; 19 received phenylephrine (group P) and 14 received ephedrine (group E). Case enrollment was done from December 2019 to September 2020. The primary aim was to compare alterations in maternal cardiac output between before and after vasopressor administration of phenylephrine and ephedrine treatment group, in healthy parturients undergoing an elective cesarean section. The secondary outcomes were to assess the changes in maternal cardiac output and systolic blood pressure, as well as to determine correlation between cardiac output and heart rate after vasopressor administration. Results: The maternal cardiac output change between pre- and post-vasopressor treatment in group P, -0.08 l/min (95%CI -0.44, 0.28), is non-inferior to group E, -0.01 l/min (95%CI -0.44, 0.41). The change in cardiac output in the phenylephrine group did not cross the pre- specified non-inferior margin of -1.17 l/min. There were no significant differences in changes of heart rate and cardiac output before after vasopressor administration between and two groups. In addition, it is found that cardiac output is positively correlated with heart rate (Pearson correlation = 0.512) after vasopressor administration. Conclusion: Cardiac output difference after vasopressor administration in the phenylephrine was non-inferior to ephedrine. Heart rate, rather than choice of vasopressor, might have a role on maternal cardiac output. Additional research focusing on high-risk pregnancies is necessary to gain insights into specific patient populations.