Comparison of continuous norepinephrine and phenylephrine infusion for preventing hypotension during low-dose spinal anesthesia in cesarean delivery: a randomized controlled trial

Hypotension is a frequent complication of spinal anesthesia (SA) for cesarean delivery (CD). Phenylephrine is recommended for prophylaxis but may cause reflex bradycardia. Norepinephrine, with mild β-adrenergic activity, may reduce both hypotension and bradycardia. This study compared the efficacy of continuous norepinephrine versus phenylephrine infusion in preventing hypotension during low-dose SA in CD. In this randomized, controlled, single-blind trial, ninety-four term parturients undergoing elective CD under low-dose SA were randomly assigned to receive norepinephrine (0.05 mcg/kg/min) or phenylephrine (0.25 mcg/kg/min) infusion. The primary outcome was the incidence of hypotension. Secondary outcomes included bradycardia, severe hypotension, hypertension, escalation to rescue vasopressors or rescue atropine for bradycardia, nausea and vomiting, and neonatal Apgar scores. The norepinephrine group had a lower incidence of hypotension (14.9% vs. 42.6%, p=0.003; RR=0.35; 95% CI: 0.16–0.75), fewer recurrent episodes, and reduced rescue vasopressor needs (p<0.05). Area under the curve (AUC)/time analysis showed that norepinephrine provided more stable blood pressure and heart rate profiles throughout the study. Bradycardia was less frequent with norepinephrine (14.9% vs. 25.5%, p=0.2; RR=0.58; 95% CI: 0.25–1.35). Two patients in the phenylephrine group required atropine. Apgar scores and other adverse events were comparable between groups. Norepinephrine infusion at 0.05 mcg/kg/min is more effective than phenylephrine at 0.25 mcg/kg/min in preventing hypotension during low-dose SA for CD, providing better hemodynamic stability and fewer episodes of bradycardia.