Correction of Dilutional Hyponatremia in Severe Chronic Heart Failure by Converting-Enzyme Inhibition

Abstract

To determine the effects of vasodilator and inotropic therapy on hyponatremia in patients with severe heart failure, serum Na concentration was measured before and after treatment with captopril (70 patients), hydralazine (42 patients), prazosin (22 patients) and amrinone (19 patients), while diuretic dosages were kept constant. Serum Na concentration increased only in hyponatremic patients treated with captopril (131.2 .+-. 0.5 to 135.9 .+-. 0.5 SE; P < 0.001), but not during therapy with the other agents and not in patients with normal serum Na concentration before treatment. Serum Na began to rise 48 h after the initiation of captopril therapy and reached its peak after 14-16 days. Correction of hyponatremia was related to functional interference with the renin-angiotensin system, but not to changes in renal function, serum K concentration, body weight or the magnitude of hemodynamic or clinical improvement. The renin-angiotensin system is apparently important in the pathogenesis of hyponatremia in patients with severe heart failure treated with diuretics [furosemide].