[Treatment of severe hyponatremia (<120mEq/l)]

Inadequate treatment of severe hyponatremia (< 120 mEq/l) can be associated with severe neurological damage. Acute hyponatremia (< 48 h) is usually observed in the postoperative period, these patients need prompt treatment with hypertonic saline (3%) to avoid epilepsia and respiratory arrest. Patients with chronic symptomatic hyponatremia (> 48-72 h) need a rapid correction of SNa the first hours (to decrease brain oedema) followed by a slow correction so that the daily increase in SNa stay under 10 mEq/l/24 h, to avoid the "Osmotic Demyelinating Syndrome" (ODS). Patients with asymptomatic hyponatremia need a slow correction. In patients who are overtreated, decreasing the SNa by giving hypotonic solutions (eventually with DDAVP) so that the daily increase in SNa stays under 10 mEq/l/24 h could protect them again ODS. Frequent measurements of SNa during the correction phase of SNa are mandatory to avoid overcorrection. The use of urea for the management of hyponatremia could represent a good alternative to hypertonic saline. In animals, urea treatment has been clearly shown to protect again ODS, this protective effect could be due to its ability to induce quickly brain "organic osmolytes" reaccumulation.