Pseudohyponatremia is most notably associated with which condition?

• A. Hyperlipidemia
• B. Hyperproteinemia
• C. Hyperglycemia
• D. Sorbitol/mannitol

Answer: (A)

Pseudohyponatremia arises from an analytical artifact in sodium measurement when the plasma contains an abnormally large non-water fraction. Indirect ion-selective electrode methods assume most of plasma is water, so they estimate sodium based on that water fraction. If lipids or proteins are greatly elevated, the water portion of plasma is proportionally reduced, so the measured sodium per liter of plasma appears falsely low even though the actual sodium concentration in the plasma water is normal. Hyperlipidemia is the classic condition associated with this artifact, which is why it’s the best answer. Hyperproteinemia can cause it as well, but the association with high lipids is the most notable. In hyperglycemia, the low sodium is real, due to osmotic water movement (dilutional hyponatremia), not an artifact of measurement. Sorbitol or mannitol can affect osmolar balance but do not produce pseudohyponatremia in the same way.