pseudohiponatrêmicas

Pseudohyponatremia refers to a laboratory finding of low serum sodium concentration that is not due to a true depletion of total body sodium or an excess of total body water. Instead, it is an artifact caused by the presence of other substances in the blood that dilute the sodium measurement.

The most common cause of pseudohyponatremia is hyperlipidemia, a condition where there are excessively high levels of fats (lipids) in the blood. In laboratory tests, when the blood sample is processed, the lipids can occupy a significant portion of the plasma volume, leading to a falsely reduced sodium concentration. Similarly, severe hyperproteinemia, characterized by abnormally high levels of protein in the blood, can also cause pseudohyponatremia through the same dilutional effect.

Another less common cause is the presence of exogenous substances, such as certain medications or contrast agents used in medical imaging. These substances can interfere with the sodium assay methods used in laboratories.

Diagnosing pseudohyponatremia involves recognizing that the patient is asymptomatic and has normal signs of hydration and volume status. Confirmation typically requires a repeat sodium measurement using an assay that corrects for the dilutional effect, such as an ion-selective electrode method, or by measuring the osmolarity of the serum. If pseudohyponatremia is suspected, it is crucial to address the underlying cause, such as managing hyperlipidemia or discontinuing offending medications, rather than treating the low sodium level itself.