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Phenylephrine versus Ephedrine for the Management of Spinal Anesthesia-Induced Hypotension in Preeclamptic Patients During Cesarean Delivery
Abstract Number: O2-03
Abstract Type: Original Research
Introduction: Hypotension is the most common complication of spinal anesthesia for cesarean delivery and is associated with considerable morbidity. Preemptive use of vasopressors appears to reduce the severity of hypotension. (1) Phenylephine has surpassed ephedrine as the preferred vasopressor for healthy parturients, as it has been shown to have similar efficacy in managing spinal anesthesia-induced hypotension, with less associated fetal acidosis. (2-5) Yet, the optimal vasopressor for preeclamptic women remains unknown. We hypothesized that phenylephrine compared to ephedrine for the management of hypotension during spinal anesthesia in preeclamptic patients would result in higher umbilical artery (UA) pH.
Methods: 110 preeclamptic parturients >18yo presenting for cesarean delivery under spinal anesthesia were recruited. Women were randomized to receive: phenylephrine infusion (100µcg/min) or ephedrine infusion (8mg/min) at completion of spinal anesthesia and titrated to keep systolic blood pressure > 80% of baseline but not > 160mmHg until delivery of infant. Preparation and initiation of spinal anesthesia was standardized. The primary outcome was UA pH. Nominal data was compared by using the Fishers-exact test, continuous and interval data were compared between groups using the Mann-Whitney U-test. P < 0.05 was significant.
Results: There were no differences in subject characteristics (Table). The median UA pH was not different between the groups: phenylephrine UA pH=7.23 (IQR 7.19 to 7.25) vs ephedrine UA pH=7.23 (IQR 7.16 to 7.28), P=0.91. The overall incidence of fetal acidosis, defined as UA <7.20, was 29%; 24% in the phenylephrine group and 33% in the ephedrine group, P=0.49 (mean 7.20 + 0.09; Range 6.91-7.38). There was no difference in neonatal ICU admission between the phenylephrine and ephedrine groups, 46% vs 39%(P=0.55), respectively.
Discussion: UA pH was not different between vasopressor groups, although the overall incidence of absolute fetal acidosis was higher than in studies of healthy parturients; most likely due to the uteroplacental insufficiency associated with preeclampsia. Phenylephrine and ephedrine appear to be safe although neither one offered a clear advantage over the other in regards to improved neonatal acid-base status.
1. Ayorinde et al. Br J Anaesth 2001: 86:372-6
2. Lee et al. Anesth Analg 2002;94:920-6
3. Cooper et al. Anesthesiology 2002;97:1582-90
4. Ngan Kee et al. Anesth Analg 2004;98:815-2