The Effects of Ephedrine and Phenylephrine on Placental Vascular Resistance During Cesarean Section Under Epidual Anesthesia

Abstract

The purpose of this article is to study the effect of ephedrine and phenylephrine on placental vascular resistance during cesarean section under epidural anesthesia via Doppler ultrasonography. Sixty female subjects, scheduled for elective cesarean section and had an intrathecal injection of bupivacaine, were randomly divided into two groups to receive phenylephrine (50 μg/min) or ephedrine (4 mg/min) via titration to maintain systolic blood pressure at baseline. Doppler ultrasonography was used to measure baseline vascular resistance values prior to administration of anesthesia, and resistance index (RI) and systolic peak velocity/diastolic velocity (S/D) values of umbilical artery and uterine artery were measured at each time point within first 20 min following intrathecal injection. Blood samples were collected from umbilical artery and umbilical vein during delivery to assess the blood gas values. No significant differences in RI and S/D values of umbilical artery and uterine artery after intrathecal injection were found between two groups. RI and S/D values of uterine artery slightly increased in both groups at each time point after anesthesia, but remained within the normal range. No significant differences were observed in blood gas values and the total amount of vasoconstriction drugs between two groups. In contrast to previous reports that used animal models, our study did not show increased placental vascular resistance in patients following phenylephrine (50 μg/min) or ephedrine (4 mg/min) infusion, as well as no significant differences in the effect of either of these two. The discrepancy between the results of human and animal studies may be related to species differences and the mechanism of human placental vascular remodeling.

Comparison of Phenylephrine and Ephedrine in Treatment of Spinal-Induced Hypotension in High-Risk Pregnancies: A Narrative Review

“…Alahuhta et al compared the effects of phenylephrine and ephedrine infusions on uteroplacental vascular resistance during spinal anesthesia in healthy parturients and observed a significant increase in the PI of uterine and placental arcuate arteries with phenylephrine administration, though no significant change from baseline with ephedrine (18). Recently, Guo et al examined the effects of phenylephrine or ephedrine infusion on placental vascular resistance during spinal anesthesia and observed no significant differences in the umbilical artery or uterine artery vascular resistance, though the uterine arterial vascular resistance was elevated from baseline in both study groups (25). No significant differences in fetal acid–base status or clinical outcomes were noted between phenylephrine and ephedrine study groups in either study (18, 25).…”

“…Recently, Guo et al examined the effects of phenylephrine or ephedrine infusion on placental vascular resistance during spinal anesthesia and observed no significant differences in the umbilical artery or uterine artery vascular resistance, though the uterine arterial vascular resistance was elevated from baseline in both study groups (25). No significant differences in fetal acid–base status or clinical outcomes were noted between phenylephrine and ephedrine study groups in either study (18, 25). Ngan Kee et al investigated the effects of ephedrine and metaraminol on uterine vascular resistance in healthy parturients undergoing elective cesarean section.…”

Height-based dosing algorithm of bupivacaine in spinal anaesthesia for decreasing maternal hypotension in caesarean section without prophylactic fluid preloading and vasopressors: study protocol for a randomised controlled non-inferiority trial

“…The unsuccessful parturients will be excluded from the study. For unsuccessful parturients, an epidural injection of 2% lidocaine (3 mL, test dose) +0.75% ropivacaine (12 mL) will be given (3 mL/5 min) until the sensory block level is higher than T8 (total volume will be less than 15 mL) 7 29 or the anaesthetic technique will be changed into general anaesthesia.…”

“…The prophylactic use of fluid (crystalloid 7 or colloid 8 ) and/or vasopressors (phenylephrine 9 or ephedrine 7 ) is usually applied to decrease maternal hypotension. However, the blood volume of the parturient is obviously increased in the later trimesters of pregnancy.…”

Comparison of ephedrine and phenylephrine in incidence of headache during spinal anesthesia in cesarean delivery

“…The influence of ephedrine and phenylephrine on systolic blood pressure under spinal anesthesia was found to be equal, for both agents [11]. Furthermore, investigations on the effect of either of ephedrine and phenylephrine on placental vascular resistance did not detect any differences and supported the equal value for both of them [15]. Also, no differences were observed between the effect of ephedrine and phenylephrine on chemical components of umbilical arterial and venous [13].…”