Phenylephrine in the prevention of hypotension following spinal anesthesia for cesarean delivery

Study Objective: Phenylephrine and ephedrine were compared in the prevention of maternal hypotension following spinal anesthesia for elective cesarean delivery. Design: Randomized, double-blind trial. Setting: Obstetric suite at a university-affiliated hospital. Patients: Sixty healthy patients electively scheduled for cesarean delivery under spinal anesthesia. Interventions: Patients were randomly assigned to receive either ephedrine (n = 29) in 10 mg intravenous (IV) bolus injections or phenylephrine (n = 31) in 80 μg IV bolus injections to maintain systolic blood pressure (SBP) above 100 mmHg. Measurements and Main Results: Maternal venous, umbilical artery, and umbilical vein blood gases were measured, and neonatal Apgar scores and Early Neonatal Neurobehavior Scale scores were assessed. In the ephedrine group, umbilical artery pH was 7.28 ± 0.01 (mean ± SEM), umbilical artery partial pressure of carbon dioxide (PCO 2) was 56.6 ± 1.4 mmHg, and umbilical artery base deficit was 2.2 ± 0.04 meq. In the phenylephrine group, umbilical artery pH was 7.32 ± 0.01, umbilical artery PCO 2 was 52.1 ± 1.3 torr, and umbilical artery base deficit was 0.38 ± 0.35 meq. There were significant differences between the groups in mean umbilical artery pH, PCO 2 and base deficit, although all values obtained were within normal limits. There were no significant differences between the groups in the remaining acid-base values, neonatal Apgar scores, Early Neonatal Neurobehavior Scale scores, or frequency of maternal nausea and vomiting. Conclusions: Phenylephrine is as effective as ephedrine in the treatment of maternal hypotension, and when used in small incremental bolus injections, it appears to have no adverse neonatal effects in healthy, nonlaboring parturients.