[Hyponatremia in the aged person]

Hyponatremia occurs frequently in the elderly. During aging, mechanisms which regulate the renal handling of water are modified, making easier the occurrence of hyponatremia: osmotic and non osmotic release of ADH is increased whereas renal diluting capacity is depressed. Hyponatremia occurs predominantly during administration of diuretic therapy and/or in congestive cardiac failure. In those circumstances, hyponatremia results from increased non osmotic release of ADH, changes in renal hemodynamics and excessive water intake, as compared to renal diluting capacity. Intracellular hyperhydratation may lead to neurologic damage resulting either from the disorder itself or from a too rapid correction. The latter may be complicated by a cerebral demyelination syndrome. This risk makes necessary to define rules for correction of hyponatremia.