Vaptans and hyponatremia in critical patients

Hyponatremia is the most frequent fluid and electrolyte disorder in hospitalized patients (20%), particularly in ICU, associated with an increase in morbility and mortality. While hypovolaemic hyponatremia needs to be corrected with the replacement of the lost extracellular fluid by isotonic saline, euvolaemic (SIADH) and hypervolaemic hyponatremia (oedematous states like decompensated heart failure, liver cirrhosis, i.e.) are treated by restriction of fluid intake, loop diuretics and hypertonic saline. A novel approach consists in use of vaptans, non-peptide arginine vasopressin (AVP) receptor antagonists. Vaptans cause "aquaresis", which results in the correction of plasma osmolality and serum sodium levels, without activation of the renin-angiotensin-aldosterone system or changes in blood pressure and renal function. In this paper we critically reviewed the results of the available randomized controlled critical trials, discussing the effectiveness and safety of vaptans in treating hypervolaemic and euvolaemic hyponatremia in critical patients.