Reset osmostat and salt and water retention in the course of severe hyponatremia.

To evaluate whether a reset osmostat and salt and water retention may be features of the course of some patients with hyponatremia, we present the long-term course of 6 selected patients. Three patients had spinal cord injury, 3 had marked psychiatric problems, and 3 had alcoholism. Five developed severe hyponatremia superimposed on chronic hyponatremia consequent to a reset osmostat. In 5 patients marked salt and water retention of unclear etiology occurred during therapy on 11 occasions. In 4 of these 11 episodes hypernatremia developed. Knowledge of a patient's past history and the possibility of developing salt and water overload should influence therapy.