Comparative Efficacy of Phenylephrine and Mephentermine in Mitigating Hemodynamic Responses to Oxytocin Administration during Elective Cesarean Section

Introduction: Cesarean sections performed under spinal anaesthesia are associated with maternal hypotension, exacerbated by oxytocin administration during surgery. Effective management of these hemodynamic changes is crucial for maternal and fetal safety. Phenylephrine, a selective α1-adrenergic agonist, and mephentermine, a mixed-action sympathomimetic, are commonly used vasopressors. However, comparative data on their efficacy in mitigating oxytocin-induced hemodynamic responses during cesarean sections is limited. Materials and Methods: This randomized, prospective study was conducted on 60 patients undergoing elective cesarean section under spinal anaesthesia. Participants were allocated to receive either phenylephrine (Group P, 75 mcg) or mephentermine (Group M, 12 mg) intravenously post-oxytocin administration. Hemodynamic parameters, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR), were recorded at baseline and at 2-minute intervals for 15 minutes. Secondary outcomes included bradycardia, nausea, and vomiting. Data were analyzed using independent t-tests and chi-square tests, with p<0.05 considered statistically significant. Results: Group P demonstrated superior maintenance of SBP and DBP (p<0.05) compared to Group M throughout the observation period. Group M exhibited more stable HR but required repeated dosing. Reflex bradycardia was more frequent in Group P but manageable. Neonatal outcomes, including Apgar scores, were similar across groups. Conclusion: Phenylephrine provides rapid and effective blood pressure stabilization, while mephentermine ensures greater overall hemodynamic stability. Tailored vasopressor selection based on clinical scenarios is recommended to optimize maternal and neonatal outcomes during cesarean sections.