Pseudohyponatremia

Pseudohyponatremia is a laboratory artifact in which the measured concentration of sodium in the blood is falsely low. This condition arises due to the presence of high levels of lipids (hyperlipidemia) or proteins (hyperproteinemia) in the blood, which reduces the aqueous phase in which sodium is dissolved. As a result, when sodium concentration is measured by volume, it appears diluted. It's important to distinguish pseudohyponatremia from true hyponatremia, where there is an actual decrease in the sodium content of the body.

Causes

Pseudohyponatremia is primarily caused by two conditions:

• Hyperlipidemia: High levels of lipids in the blood can physically displace the aqueous phase, leading to a relative decrease in plasma water volume and a falsely low sodium concentration.
• Hyperproteinemia: Similarly, elevated protein levels, such as those seen in multiple myeloma, can decrease the relative volume of plasma water, leading to pseudohyponatremia.

Diagnosis

The diagnosis of pseudohyponatremia involves recognizing the discrepancy between the measured low sodium concentration and the absence of symptoms of hyponatremia. It is also identified by measuring sodium concentration using a method that is not affected by the plasma's lipid or protein content, such as direct ion-selective electrode (ISE) measurement, which measures sodium concentration in the water phase directly, providing an accurate result.

Management

Management of pseudohyponatremia focuses on addressing the underlying cause of the elevated lipid or protein levels. It does not require treatment aimed at correcting the sodium level, as the sodium concentration is not truly low. Treatment may involve lifestyle changes, medication, or other interventions to manage the underlying hyperlipidemia or hyperproteinemia.

See Also

• Hyponatremia
• Hyperlipidemia
• Hyperproteinemia
• Electrolyte imbalance