Hemodynamic effects of ephedrine, phenylephrine, and the coadministration of phenylephrine with oxytocin during spinal anesthesia for elective cesarean delivery.

Background: Hemodynamic responses to vasopressors used during spinal anesthesia for elective Cesarean delivery, have not been well described. This study compared the effects of bolus phenylephrine and ephedrine on maternal cardiac output (CO). The hypothesis was that phenylephrine, but not ephedrine, decreases CO when administered in response to hypotension during spinal anesthesia.