Comparison of Intermittent Intravenous Boluses of Phenylephrine and Norepinephrine to Prevent and Treat Spinal-Induced Hypotension in Cesarean Deliveries: Randomized Controlled Trial

BACKGROUND: Phenylephrine (PE) is currently the vasopressor of choice to prevent and treat spinal-induced hypotension at cesarean delivery (CD). However, its use is often associated with reflex bradycardia. Norepinephrine (NE) has been put forward as an alternative vasopressor during CD due to its ability to treat hypotension while maintaining heart rate (HR). Recent studies have focused on the role of NE used as an infusion with favorable results compared to PE. No studies have compared equipotent bolus doses of PE and NE at CD. We hypothesized that when used in equipotent doses as an intermittent bolus regimen to prevent and treat spinal-induced hypotension, NE would result in a reduction in the incidence of bradycardia compared to PE. METHODS: This was a double-blind, randomized clinical trial of women undergoing elective CD under spinal anesthesia. Women were randomized to receive either PE 100 µg or NE 6 µg when the systolic blood pressure (SBP) was below baseline. In addition to the randomized treatment, ephedrine was given intravenously to both groups if the SBP was below baseline and the HR 120% of baseline), tachycardia (HR >120% of baseline), ≥2 episodes of bradycardia, nausea, vomiting, umbilical artery and vein blood gases, and Apgar scores. RESULTS: One hundred twelve patients were randomized. The incidence of bradycardia was lower in the NE group compared to the PE group (10.9% vs 37.5%; P

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