A Comparison of Phenylephrine and Norepinephrine Infusions in Preventing Hypotension After Subarachnoid Block in Caesarean Section: A Randomized, Double-Blind Study

Background Prophylactic vasopressor infusion is commonly recommended during cesarean section under spinal anesthesia to prevent hypotension. Norepinephrine is gaining recognition as a viable alternative to phenylephrine in obstetric anesthesia, primarily due to its lower propensity to cause reflex bradycardia. This study compares the efficacy and safety of prophylactic intravenous infusions of norepinephrine and phenylephrine, administered at varying infusion rates, on maternal hemodynamics and neonatal outcomes during cesarean delivery. Methods In this prospective, randomized, double-blinded study, 102 parturients of ASA physical status 2, undergoing cesarean section under Lucas Grade 1 and 2, were randomized into two groups to receive prophylactic manually adjusted intravenous infusions of norepinephrine or phenylephrine. The primary objective was to compare the efficacy of norepinephrine and phenylephrine in preventing post-spinal hypotension. The safety of these two drugs with respect to the neonatal outcome and maternal bradycardia, nausea, and vomiting was the secondary objective. Results Ninety-five parturients were analyzed, and the incidence of hypotension was similar between the two groups (27.08% vs. 21.28%, p = 0.509). However, the phenylephrine (PE) group had a significantly higher incidence of bradycardia compared to the norepinephrine (NE) group (19.15% vs. 0%, p = 0.001). The incidence of nausea and vomiting was comparable in groups NE and PE ( 4.17% vs. 10.64%, p = 0.268). The number of manual physician interventions was similar between the groups (27.08% vs 21.28%, p = 0.509). Neonatal cord blood ABG parameters were comparable between the groups. Conclusion Prophylactic intravenous infusions of phenylephrine and norepinephrine showed similar efficacy in preventing hypotension. However, the use of norepinephrine did not cause bradycardia as compared to phenylephrine.