Objective: To report a case of hyponatremia in a patient receiving systemic unfractionated heparin (UFH) therapy and parenteral nutrition.
Case summary: A 70-year-old African American woman was started on parenteral nutrition for postoperative ileus following an elective surgical procedure. Three days later, she was diagnosed with a pulmonary embolism and intravenous UFH therapy was initiated. During the 7-day course of UFH therapy, the patient's serum sodium concentration steadily declined and urine sodium concentration progressively increased. Physical examination revealed no signs or symptoms of hypo- or hypervolemia. The patient's serum potassium concentration increased modestly, although significant hyperkalemia was not observed. After discontinuation of UFH, serum concentrations of both sodium and potassium returned to baseline levels.
Discussion: Although heparin-induced hyperkalemia is well documented, cases associated with substantial hyponatremia have been reported less frequently. An objective causality assessment revealed that the adverse drug reaction was probable in this case. Hyponatremia and hyperkalemia result from the antagonism of aldosterone by UFH within the zona glomerulosa of the adrenal glands.
Conclusions: The use of UFH may result in significant hyponatremia as well as hyperkalemia. Reversal of these electrolyte disturbances occurs after discontinuation of heparin.