Phenylephrine Infusion for the Prevention of Hypotension in Obese Patients During Cesarean Delivery Under Spinal Anesthesia: A Randomized, Placebo-Controlled, Double-Blind Study.

Background: Spinal anesthesia-induced hypotension can lead to adverse consequences for the mother-fetus binomial. We compared two prophylactic phenylephrine infusions with placebo in obese patients during cesarean delivery (CD) under spinal anesthesia.

Methods: In this randomized, placebo-controlled, double-blind study, 121 patients were randomly allocated to receive 0.9% saline in Group C, prophylactic phenylephrine infusion 50 μg/min in Group P50, or prophylactic phenylephrine infusion 100 μg/min in Group P100, starting immediately after anesthesia induction until delivery. The primary outcome was the number of episodes of hypotension.

Results: The median (interquartile range) of the number of episodes of hypotension in Group P100 [0.0 (0.0-0.0)] and Group P50 [0.0 (0.0-1.5)] were lower in Group C [3.0 (2.0-5.0)], P < 0.001. There was also a smaller number of episodes of hypotension in Group P100 than in Group P50, P = 0.016. The phenylephrine infusion groups had a significantly lower incidence of hypotension, increased time until the first episode of hypotension, and fewer physician interventions but a higher incidence of reactive hypertension in Group P100 than in Group C. Nausea and vomiting, bradycardia, and neonatal outcomes were not different among the groups.

Conclusion: Prophylactic phenylephrine infusion of 100 or 50 μg/min in obese women during CD under spinal anesthesia reduced the number of episodes of hypotension, the incidence of hypotension, the number of physician interventions, and the number of rescue phenylephrine boluses, and increased the time until the first hypotension episode. However, 100 μg/min could lead to more reactive hypertension.