Ngan Kee Warwick D, Khaw Kim S, Tan Perpetua E, Ng Floria F, Karmakar Manoj K
Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China.
Anesthesiology. 2009 Sep;111(3):506-12. doi: 10.1097/ALN.0b013e3181b160a3.
Use of ephedrine in obstetric patients is associated with depression of fetal acid-base status. The authors hypothesized that the mechanism underlying this is transfer of ephedrine across the placenta and stimulation of metabolism in the fetus.
A total of 104 women having elective Cesarean delivery under spinal anesthesia randomly received infusion of phenylephrine (100 microg/ml) or ephedrine (8 mg/ml) titrated to maintain systolic blood pressure near baseline. At delivery, maternal arterial, umbilical arterial, and umbilical venous blood samples were taken for measurement of blood gases and plasma concentrations of phenylephrine, ephedrine, lactate, glucose, epinephrine, and norepinephrine.
In the ephedrine group, umbilical arterial and umbilical venous pH and base excess were lower, whereas umbilical arterial and umbilical venous plasma concentrations of lactate, glucose, epinephrine, and norepinephrine were greater. Umbilical arterial Pco2 and umbilical venous Po2 were greater in the ephedrine group. Placental transfer was greater for ephedrine (median umbilical venous/maternal arterial plasma concentration ratio 1.13 vs. 0.17). The umbilical arterial/umbilical venous plasma concentration ratio was greater for ephedrine (median 0.83 vs. 0.71).
Ephedrine crosses the placenta to a greater extent and undergoes less early metabolism and/or redistribution in the fetus compared with phenylephrine. The associated increased fetal concentrations of lactate, glucose, and catecholamines support the hypothesis that depression of fetal pH and base excess with ephedrine is related to metabolic effects secondary to stimulation of fetal beta-adrenergic receptors. Despite historical evidence suggesting uteroplacental blood flow may be better maintained with ephedrine, the overall effect of the vasopressors on fetal oxygen supply and demand balance may favor phenylephrine.
产科患者使用麻黄碱与胎儿酸碱状态受抑制有关。作者推测其潜在机制是麻黄碱穿过胎盘并刺激胎儿代谢。
104例在脊麻下行择期剖宫产的妇女随机接受去氧肾上腺素（100微克/毫升）或麻黄碱（8毫克/毫升）输注，滴定以维持收缩压接近基线水平。分娩时，采集母体动脉血、脐动脉血和脐静脉血样本，用于测定血气以及去氧肾上腺素、麻黄碱、乳酸、葡萄糖、肾上腺素和去甲肾上腺素的血浆浓度。
在麻黄碱组中，脐动脉血和脐静脉血的pH值及碱剩余较低，而脐动脉血和脐静脉血中乳酸、葡萄糖、肾上腺素和去甲肾上腺素的血浆浓度较高。麻黄碱组的脐动脉血二氧化碳分压和脐静脉血氧分压较高。麻黄碱的胎盘转运量更大（脐静脉/母体动脉血浆浓度中位数比值为1.13对0.17）。麻黄碱的脐动脉/脐静脉血浆浓度比值更高（中位数为0.83对0.71）。
与去氧肾上腺素相比，麻黄碱更易穿过胎盘，且在胎儿体内早期代谢和/或再分布较少。与之相关的胎儿乳酸、葡萄糖和儿茶酚胺浓度升高支持了以下假说：麻黄碱导致胎儿pH值和碱剩余降低与刺激胎儿β-肾上腺素能受体继发的代谢效应有关。尽管有历史证据表明麻黄碱可能能更好地维持子宫胎盘血流，但血管升压药对胎儿氧供需平衡的总体影响可能更有利于去氧肾上腺素。
