Serum ionized magnesium levels during intravenous MGSO4 therapy of preeclamptic women.

Using a novel ion-selective electrode, we have shown that there is over a 100% increase in venous serum levels of ionized Mg during intravenous MgSO4 therapy of preeclamptic patients. By 6 hours of therapy, the range is 0.92-1.65 mmol/l (95% C.I.). There are strong correlations between levels of ionized and total Mg throughout therapy (r = 0.92-0.95, p < 0.01).