Hyponatremia in the syndrome of inappropriate secretion of antidiuretic hormone. Rapid correction with urea, sodium chloride, and water restriction therapy

Abstract

In the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), rapid elevation of serum Na concentration may be imperative to correct neurological symptoms. Seven patients with hyponatremia secondary to SIADH were treated by oral intake of 2-3 doses of 30 g of urea over 24 h or infusion of 80 g of urea as a 30% solution over 6 h, water restriction (500 ml/24 h) and Na supplements (120-360 mmol/24 h). Serum Na concentration increased from 117 .+-. 2 to 126 .+-. 1.4 mmol/l (mean .+-. standard error of the mean) after 8 h, to 130 .+-. 1.3 mmol/l after 12 h, and to 134.5 .+-. 1.2 mmol/l after 24 h. The normalization of serum Na was secondary to osmotic diuresis and to Na retention induced by urea. Use of urea should be considered when symptomatic hyponatremia in SIADH must be quickly corrected.