What condition can cause hypertonic hyponatremia?

Hypertonic hyponatremia occurs when there is an increase in solutes outside the cells, which leads to a dilution of sodium levels in the serum despite normal or even increased total body sodium. Hyperglycemia is a classic cause of hypertonic hyponatremia. When serum glucose levels rise, as seen in uncontrolled diabetes mellitus, glucose molecules in the bloodstream exert an osmotic effect that draws water out of cells. Consequently, this leads to increased plasma volume and diluted sodium levels, resulting in hypertonic hyponatremia.

In this scenario, the movement of water from the intracellular to the extracellular space due to the osmotic pull of high glucose concentrations causes a decrease in serum sodium concentration, despite the presence of normal or elevated sodium levels in the total body. Therefore, the relationship between elevated glucose levels and the corresponding dilutional effect on sodium levels is essential in understanding how hypertonic hyponatremia can develop.