Acute magnesium depletion and excess induced by hemodialysis

¹ Departments of Surgery and Medicine and the Surgical Research Laboratories, University of Kansas School of Medicine, Kansas City, Kansas

The present study was undertaken to investigate in dogs the effects of acute magnesium depletion and excess induced by hemodialysis. Bath fluid for the hemodialyzer was normal in extracellular electrolyte concentrations and pH, except for magnesium which was omitted or added for the respective depletion and excess studies. Plasma depletion 58% of the original magnesium concentration was observed in a steady state following 90 minutes of dialysis. The rate of magnesium extraction during this steady state was 0.7 mEq/hr. Following 150 minutes of dialysis to induce depletion, blood pressure, electrocardiogram and observed physical signs demonstrated no remarkable aberrations when compared with the control animals, other than giant hives which developed in two of the depletion animals. With loading studies, plasma magnesium concentrations which were increased to 15 mEq/l. in nephrectomized dogs, were accompanied by anesthesia, slowing of pulse rate and minimal lengthening of the P-R and Q-T intervals. It is concluded that marked alterations of the extracellular magnesium ion concentration are accompanied by slower compensatory changes in nonextracellular magnesium.