Fig. 2.

Adaptation of brain cells to hypernatremia. In high osmotic pressure, brain cells lose intracellular fluid and shrink in size during the first 15–30 min. To recover in size, cells take up extracellular electrolytes and water within 30–90 min and completely replace their electrolytes with organic osmolytes in a matter of a few hours to days. As organic osmolytes cannot move in and out of cells rapidly, adaptation to the osmotic change in the extracellular fluid is slower. Hence, rapid correction of hypernatremia puts the patient at risk for brain edema (revised from Strange, 1992 ¹² ).