INTRACELLULAR AND EXTRACELLULAR BLOOD MAGNESIUM FRACTIONS IN HEMODIALYSIS-PATIENTS - IS THE IONIZED FRACTION A MEASURE OF MAGNESIUM EXCESS

To establish the best measure for determining magnesium overload, we m easured ionized and total magnesium in serum and mononuclear blood cel ls and total magnesium in erythrocytes in blood of 23 hemodialysis pat ients, known for their disturbed magnesium homeostasis. When comparing the mean magnesium values obtained in the patient population with tho se of a control population, all of these magnesium markers, including the biologically active fractions, were significantly (P <0.05) increa sed. Because serum total magnesium was not increased in all dialysis p atients studied, the population was divided into two groups, according to total serum magnesium >1.0 mmol/L or less than that. Results in th ese two populations showed that ionized serum magnesium and ionized ma gnesium in mononuclear blood cells might give a better indication abou t the magnesium status of the tested patients than the currently used total serum magnesium data. However, neither of the two markers, espec ially ionized serum magnesium, was able to discriminate fully between normal magnesium homeostasis and magnesium excess. We therefore conclu de that the two ionized magnesium markers offer minimal advantage for this discrimination, and that the total magnesium concentration in ser um remains the measurement of choice.