24 Interestingly, as MgSO 4 infusion caused significant increases in ionized Mg 2+ levels, serum ionized calcium (Ca 2+) concentrations were unchanged, 26 suggesting that the effect of MgSO 4 is not exerted through modulations of ionized calcium levels. 19 Similar results have been found by other groups using the same infusion protocol. 19,24 In preeclamptic patients treated with a loading dose of 4 g intravenously followed by 2 g per hour infusion, it was found that both total and ionized Mg 2+ concentrations increased quickly after infusion, but steady-state concentrations for total magnesium were 4.84☐.24 mg/dL, whereas for ionized magnesium it was 2.04☐.14 mg/dL. Studies have shown little correlation between total and ionized magnesium levels, either at baseline before treatment or during MgSO 4 treatment for preeclampsia. In addition, there are reports that in some patients eclamptic seizures do not cease even with elevated levels of MgSO 4, 6,7,25 suggesting that MgSO 4 is not effective in treating all cases of eclampsia.Īs technological advances allow for ionized magnesium to be more readily measured, questions have arisen as to whether it is more appropriate to monitor total serum magnesium or the ionized physiologically active form. 18,22,23 Some suggest that using standard infusion protocols may not lead to therapeutic serum magnesium levels in all patients, with 36.2% of patients found to have total serum magnesium lower than 4 mEq/L at 30 minutes after treatment initiation in one study, 24 though no eclamptic seizures were reported during MgSO 4 treatment. 6,18,22 Progressively higher serum magnesium levels can ultimately lead to cardiac arrest. 6,18,22 Areflexia, particularly loss of the patellar deep tendon reflex, has been observed at 8 to 10 mEq/L, and respiratory paralysis seen at >13 mEq/L. 18,19 Total magnesium serum concentrations advocated for the treatment of eclamptic convulsions are 3.5 to 7 mEq/L (4.2 to 8.4 mg/dL), 2,20,21 which can be obtained by administering it intramuscularly (6 g loading dose followed by 2 g/h), intravenously (2 to 4 g dose up to 1 g/min), or a combination of both. Normal serum concentrations of Mg 2+ are 1.5 to 2.5 mEq/L (1.8 to 3.0 mg/dL), with one-third to one-half bound to plasma proteins. There are concerns regarding the possibility of hypermagnesemia toxicity in eclampsia treatment. 16,17Īlthough the effectiveness of MgSO 4 in treating and preventing eclampsia has been established, questions still exist as to its safety. 16 In addition, 60% of providers surveyed indicated they would use magnesium as an anticonvulsant for eclampsia in 1998, up from only 2% of eclamptic women who received MgSO 4 in 1992. 15 The publication of these clinical trials significantly increased the use of MgSO 4 versus other anticonvulsants in the United Kingdom and Ireland, where the reported use in preeclampsia increased from 2% to 40%. 9 In the multinational Collaborative Eclampsia Trial, MgSO 4 reduced the risk of recurrent seizures in eclamptic women by 52% when compared to diazepam and by 67% when compared to phenytoin. 5,9,10 For eclamptic seizure prophylaxis in preeclamptic women, MgSO 4 is superior to phenytoin, 11,12 nimodipine, 13 diazepam, 14 and placebo. 3–5 Empirical evidence supports the effectiveness of MgSO 4 in preventing and treating eclamptic seizures, 1,6–8 in addition to recent controlled clinical trials. Magnesium sulfate (MgSO 4) has been used throughout the 20th century for prevention of eclamptic seizures, 1,2 and it continues to be used extensively. Additionally, magnesium sulfate may also protect the blood-brain barrier and limit cerebral edema formation, or it may act through a central anticonvulsant action. Magnesium sulfate may act as a vasodilator, with actions in the peripheral vasculature or the cerebrovasculature, to decrease peripheral vascular resistance or relieve vasoconstriction. Summary of Review- Several mechanisms are presented, including the effects of magnesium sulfate on peripheral and cerebral vasodilation, blood-brain barrier protection, and as an anticonvulsant.Ĭonclusions- Though the specific mechanisms of action remain unclear, the effect of magnesium sulfate in the prevention of eclampsia is likely multi-factorial. This review summarizes current evidence supporting the possible mechanisms of action and several controversies for magnesium sulfate treatment. Empirical and clinical evidence supports the effectiveness of magnesium sulfate however, questions remain as to its safety and mechanism. Customer Service and Ordering Informationīackground and Purpose- Magnesium sulfate is used extensively for prevention of eclamptic seizures.Stroke: Vascular and Interventional Neurology.Journal of the American Heart Association (JAHA).Circ: Cardiovascular Quality & Outcomes.Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB).
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