Comparison of Phenylephrine Bolus and Infusion Regimens on Maternal and Fetal Outcomes During Cesarean Delivery: A Systematic Review and Meta-Analysis

BACKGROUND: A systematic review and meta-analysis was conducted to compare phenylephrine boluses versus prophylactic infusion in parturients undergoing cesarean delivery under spinal or combined spinal-epidural anesthesia on feto-maternal outcomes. METHODS: Medline, Embase, Cochrane, and US Clinical registry databases were searched. Studies comparing phenylephrine boluses (both therapeutic and prophylactic) with infusion (both fixed- and variable-rate) assessing various feto-maternal outcomes were included. The primary outcome was the incidence of maternal hypotension. Secondary maternal outcomes included the incidence of reactive hypertension, bradycardia, nausea, or vomiting; secondary neonatal outcomes included umbilical arterial pH, partial pressure of oxygen (paO2), umbilical venous pH, fetal acidosis, Apgar Scores at 1 and 5 minutes. All outcomes were quantitatively analyzed using the random effects model. Risk of bias was assessed using the Cochrane Collaboration R0B 2.0 tool. RESULTS: We included 15 studies with 2153 parturients. The parturients receiving phenylephrine bolus during cesarean delivery under spinal or combined spinal-epidural anesthesia had a significant increase in the incidence of predelivery hypotension compared to phenylephrine infusion (risk ratio [RR], 2.34, 95% confidence interval [CI], 1.72–3.18). Reactive hypertension (RR, 0.48, 95% CI, 0.29–0.79) and bradycardia (RR, 0.57, 95% CI, 0.41–0.79) were less common in the parturients receiving phenylephrine bolus; whereas, vomiting (RR, 2.15, 95% CI, 1.53–3.03) was more common compared to the infusion group. No statistically significant difference was observed in the incidence of nausea or any fetal outcomes (umbilical artery pH, paO2, umbilical venous pH, fetal acidosis, and Apgar scores at 1 and 5 minutes) between either of the groups. Three studies had a high risk of bias. CONCLUSIONS: A prophylactic phenylephrine infusion significantly reduces the incidence of predelivery hypotension in parturients undergoing cesarean delivery under neuraxial anesthesia in comparison to the therapeutic or prophylactic phenylephrine bolus group. A prophylactic phenylephrine infusion may be considered in all parturients without preexisting hypertensive disorder or cardiovascular disorders to reduce the risk of predelivery hypotension. More evidence is needed to guide optimal hemodynamic management for patients with hypertensive or cardiovascular disorders.