Ephedrine, Phenylephrine and Metaraminol Effects on Maternal Cardiac Output, Uterine Blood Flow and Fetal Circulation in Patients With Preeclampsia Under Spinal Anesthesia for Cesarean

Spinal anesthesia has become the main anesthetic technique for cesarean delivery due to avoidance of failed tracheal intubation risk, improvement of post-operative analgesia and promotion of early mother-neonate bonding. Spinal anesthesia should be safe and comfortable for mother and child when referring to the side effects, including hypotension. The choice of the best vasopressor in this context is approaching to a resolution, favoring phenylephrine use. However, studies on high-risk pregnancies are still required, such as uteroplacental insufficiency, preeclampsia and intra-uterine growth restriction cases. The purpose of this study is to compare the effects of the vasopressors ephedrine, phenylephrine and metaraminol on maternal cardiac output, uteroplacental and cerebral fetal blood flow in patients with preeclampsia under spinal anesthesia for cesarean delivery. Sixty pregnant patients will be recruited and randomly assigned to receive either ephedrine, phenylephrine or metaraminol, making a total of three groups with 20 patients each. Variables to be analyzed are uterine arterial pulsatility index, umbilical arterial pulsatility index, fetus middle cerebral artery pulsatility index, maternal cardiac output, maternal cardiac frequency, maternal mean arterial blood pressure and maternal peripheral vascular resistance. These variables will be recorded in three moments: before the spinal anesthesia with the patient in dorsal recumbent and left displacement of the uterus, after spinal anesthesia in dorsal recumbent and after vasopressor bolus. Averages will be calculated in these intervals and then compared to the alteration caused by spinal anesthesia and the return to basal levels after drug intervention.