A Prospective Single-Center Brazilian Study Investigating the Efficacy and Safety of Prophylactic Phenylephrine Infusion for the Management of Hypotension During Cesarean Section Under Spinal Anesthesia

Background Maternal hypotension occurs in up to 80% of parturients during cesarean section (CS) under spinal anesthesia. Phenylephrine, a direct-acting α-1 agonist, has been widely recommended for the prevention of hypotension. We evaluated the efficacy and safety of phenylephrine infusion to prevent hypotension in obese and non-obese patients during cesarean section. Methods One hundred forty-one patients were included in this single-arm study. Patients received prophylactic phenylephrine infusion at a rate of 50 μg/min(-1) immediately after spinal local anesthetic injection until delivery. Hypotension was defined as a systolic blood pressure <100 mmHg or <20% of baseline. The primary outcome was the incidence of hypotension. Results The incidence of hypotension was 17%. The median and interquartile range (IQR) of the number of hypotensive episodes was 0 (0-0). It was observed that 79.1% of the patients had hypotension in the first six minutes. Reactive hypertension and bradycardia occurred in 20.5 and 12.7% of the patients, respectively. In addition, there was a higher incidence of bradycardia in pregnant women with a body index mass of < 30 kg/m(-2). Patients with baseline systolic blood pressure <120 mmHg had a threefold increased risk of hypotension. The incidence of nausea and vomiting was 13.4 and 2.8%, respectively. The incidence of an Apgar score <7 at the first minute was 2.8%, and no neonates presented an Apgar score <7 at the fifth minute. A pH of <7.2 occurred in 6.3% of the neonates. All neonates had no sequelae and were discharged together with their mothers. Conclusion The prophylactic infusion of phenylephrine 50 μg/min(-1) is safe and demonstrates efficacy in reducing maternal hypotension providing adequate maternal hemodynamic stability during CS under spinal anesthesia.