C. Hypertonic Hyponatremia

This situation is also known as redistributive hyponatremia. It is caused by the presence of excess osmotically active molecules in the plasma. Examples of osmotically active substances are glucose and mannitol. Water from inside the cells moves outside the cells (redistributes) through the cell membrane in an attempt to equilibrate the osmotic pressures of inside and outside the cells. The result is hyponatremia by reducing the sodium concentration in the plasma by increasing the water content of the plasma (extracellular fluid). It is to note that all the other forms of hyponatremia are hypotonic, not hypertonic as this type.

Marco A. Ramos MD

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Read the other sections of this series:

Introduction
What Causes Hyponatremia? A
What Causes Hyponatremia? B