Ionized magnesium supplementation in critically ill patients: Comparing ionized and total magnesium

Purpose: The purpose of this study was to assess the effect of magnesium su pplementation on total magnesium. ionized magnesium, ionized calcium, potas sium, and pH in critically ill cancer patients and to compare the validity of the measurements. Materials and Methods:Thirty-three consecutive critically ill patients rece iving magnesium supplementation were placed in this prospective observation al study at the Comprehensive Cancer Center, University Hospital. One gram (4.1 mmol) magnesium in 50 mL D5W was administered to critically ill patien ts, and the following were measured: total magnesium, ionized magnesium, io nized calcium, potassium, albumin, pH, BUN, creatinine, creatinine. Results: Total magnesium and ionized magnesium increased by a mean of .11 /- .02 and .05 +/- .01 mmol/L, respectively, after supplementation with 4.1 mmol of magnesium sulfate (P = .0001). Total magnesium, ionized magnesium, albumin, ionized calcium, potassium, and pH did not change significantly b y the administration of 1 g of magnesium sulfate. Conclusion: The mean ionized magnesium (IMg+2) relationship to total magnes ium (TMg) cannot be predicted before the supplementation with the available technology. After supplementation of 4.1 mmol/L the ionized magnesium leve l increased by .05 +/- .01 mmol/L. Magnesium supplementation had no signifi cant effect on ionized calcium, potassium, and pH. TMS and IMg+2 should be followed Independently. Copyright (C) 2000 by W.B. Saunders Company.