Serum ionized magnesium during magnesium sulfate administration for preterm labor and preeclampsia

ObjectiveThe purpose of this study is to estimate the relations between ionized and total Mg levels during MgSO4 administration in patients with preterm labor and preeclampsia.MethodsForty-three pregnant patients who were candidates for MgSO4 were studied (preterm labor, 27; preeclampsia, 16). The administration method was intravenous injection of MgSO4 4 g over 30 min followed by 1–2 g/h. Ionized Mg was measured by the selective ion electrode method at bedside, and compared it with total Mg levels.ResultsSignificant correlation was existed between levels of ionized and total Mg throughout therapy for both preterm labor (ionized Mg = 0.19 × total Mg + 0.19; r = 0.61, p < 0.001) and preeclampsia (ionized Mg = 0.20 × total Mg + 0.14; r = 0.60, p < 0.001).ConclusionThere are correlations between ionized and total Mg levels during administration of MgSO4 for both preterm labor and preeclampsia.