Chronic hypernatremia is hypernatremia that has been present for longer than 48 hours. Nearly all pts with hypernatremia will have chronic hypernatremia, even those who present with acute changes in mentation who are discovered to have hypernatremia.
Hypernatremia due to water loss is called dehydration. This is different from hypovolemia, in which both salt and water are lost.
Excessive water loss seldom leads to hypernatremia because the increase in plasma osmolality stimulates thirst.
Patients who present with hypernatremia usually have a serious underlying condition that impairs either their ability to respond to thirst or to experience thirst.