IONIZED AND TOTAL MAGNESIUM SERUM CONCENTRATIONS IN RENAL AND HEPATICDISEASES

Ionised and total magnesium concentrations were determined in the seru m of different groups of patients suffering from renal or hepatic dise ases. Ionised magnesium was measured by Microlyte 6 (KONE, Espoo, Finl and) and total magnesium by atomic absorption spectrometry. In renal i nsufficiency ionised and total magnesium concentrations were almost eq ually increased. In proteinuria with a normal glomerular filtration ra te, ''pseudohypomagnesaemia'' was observed, i. e. decreased total magn esium concentration in parallel with a decreased albumin concentration with no significant change in the concentration of ionised magnesium. Hypermagnesaemia occurred in liver diseases combined with renal insuf ficiency, whereas ''pseudohypomagnesaemia'' was most often found in th e absence of renal failure. Also treatment with an aldosterone antagon ist was associated with a normal ionised magnesium concentration, but the total magnesium concentration was decreased; when additional magne sium was administered, the total magnesium concentration approached a normal value, while ionised magnesium slightly exceeded reference valu es. Only during cyclosporin treatment did both ionised and total magne sium concentrations become lowered. However, the decrease of total mag nesium exceeded that of ionised magnesium due to concomitant hypoalbum inaemia with reduction of the protein-bound fraction. It is concluded that especially low total magnesium concentrations should be investiga ted by measurement of ionised magnesium to exclude ''pseudohypomagnesa emia''.