HYPOCALCEMIC TETANY AND METABOLIC ALKALOSIS IN A DIALYSIS PATIENT - AN UNUSUAL EVENT

The case is described of a 29-year-old man with renal failure and recu rrent hyperparathyroidism who 3 weeks postparathyroidectomy developed hypocalcemic tetany because he was taking one-half the prescribed dose of calcitriol, He interpreted his symptoms as those of potassium into xication and self-administered almost 1,500 mEq sodium bicarbonate, Sh e increase in plasma sodium and osmolarity led to increased fluid inta ke, and at presentation he had an ionized calcium of 0.50 mmol/L, K 5. 3 nnmol/L, Na 148 mmol/F, total CO2 52.6 mmol/L, pO(2) 51,2 mm Hg, and pH of 7.61, He had gained 7 kg in weight, All abnormalities were corr ected by dialysis, using initially a calcium-free dialyzate with extra calcium infused, The case illustrates the effect of alkalosis in redu cing the amount of calcium that exists in ionized form, and it is sugg ested that complexing of calcium as calcium bicarbonate together with the pH change contributed to the decrease in ionized calcium, It is al so an example of the hazards of treating patients who devise their own therapeutic regimens, (C) 1997 by the National Kidney Foundation, Inc .