Mason B A, Standley C A, Whitty J E, Cotton D B
Department of Obstetrics and Gynecology, Wayne State University/Hutzel Hospital, Detroit, MI 48201, USA.
Am J Obstet Gynecol. 1996 Jul;175(1):213-7. doi: 10.1016/s0002-9378(96)70277-6.
Little is known about ion regulation in fetuses. Our aim was to determine the effects of magnesium sulfate therapy on ionized (bioactive) magnesium in the cord blood of pregnancies complicated by preeclampsia.
Seventy-four pregnant women were studied (37 preeclamptic and 37 controls matched for maternal age, gravidity, and gestational age). The preeclamptic women received intravenous magnesium sulfate 6 gm load followed by 2 gm/hour for > or = 4 hours; controls were not preeclamptic and received no magnesium. Maternal venous and fetal cord blood samples were obtained from study and control patients and were analyzed for sodium, potassium, total magnesium, ionized magnesium, total calcium, and ionized calcium. Comparisons between the groups were made and analyzed by the Mann-Whitney U test.
There were no significant differences between the treatment and control group cord samples with respect to sodium or potassium. However, total magnesium and ionized magnesium were significantly elevated (p < 0.001) in cord samples of the treated group. At the same time ionized calcium and total calcium were reduced. Interestingly, ionized calcium levels were lower in preeclamptic women before magnesium sulfate therapy was begun, whereas total calcium levels were not different. Importantly, there was no difference between maternal and fetal ionized magnesium levels in either treatment or control groups.
In preeclamptic women undergoing magnesium sulfate therapy, ionized magnesium levels in cord blood parallel maternal levels. Before magnesium therapy ionized calcium levels were lower in preeclamptic women than in matched controls. In the presence of elevated magnesium levels ionized calcium appears to be tightly regulated.
关于胎儿离子调节的了解甚少。我们的目的是确定硫酸镁治疗对合并先兆子痫的妊娠孕妇脐带血中离子化（生物活性）镁的影响。
对74名孕妇进行了研究（37名先兆子痫患者和37名年龄、孕周和妊娠次数相匹配的对照组孕妇）。先兆子痫患者静脉注射6克硫酸镁负荷量，随后以2克/小时的速度注射≥4小时；对照组孕妇未患先兆子痫且未接受硫酸镁治疗。从研究组和对照组患者采集母体静脉血和胎儿脐带血样本，分析其中的钠、钾、总镁、离子化镁、总钙和离子化钙。通过Mann-Whitney U检验对两组进行比较和分析。
治疗组和对照组脐带血样本在钠或钾方面无显著差异。然而，治疗组脐带血样本中的总镁和离子化镁显著升高（p<0.001）。同时，离子化钙和总钙降低。有趣的是，在开始硫酸镁治疗前，先兆子痫患者的离子化钙水平较低，而总钙水平无差异。重要的是，治疗组和对照组的母体和胎儿离子化镁水平均无差异。
在接受硫酸镁治疗的先兆子痫患者中，脐带血中的离子化镁水平与母体水平平行。在镁治疗前，先兆子痫患者的离子化钙水平低于匹配的对照组。在镁水平升高的情况下，离子化钙似乎受到严格调节。
