Pseudohyponatraemia can be caused by which of the following conditions?

Pseudohyponatraemia can be caused by which of the following conditions?

• A. Hypertriglyceridaemia and hyperalbuminaemia
• B. Hyponatremia due to dehydration
• C. Hyperglycemia
• D. Hypoproteinaemia

Answer: (A)

Pseudohyponatremia is a lab artifact where serum sodium appears low even though the body’s actual sodium concentration and osmolality are normal. This happens with marked increases in nonaqueous constituents of serum, because indirect ion-selective electrode methods assume a fixed plasma water fraction. When there’s a lot of lipid (hypertriglyceridemia) or protein (hyperalbuminemia/hyperproteinemia), the plasma water fraction shrinks, and the indirect measurement yields a falsely low sodium value. In this situation, the true intravascular osmolality is normal, and patients are not truly hyponatremic. Thus, severe hypertriglyceridemia or hyperproteinemia (hyperalbuminaemia) are classic causes of pseudohyponatremia. By contrast, dehydration tends to cause real hyponatremia or hypernatremia depending on fluid status, and hyperglycemia lowers measured sodium via osmotic water shift (not a measurement artifact). Hypoproteinaemia alone does not typically produce pseudohyponatremia.

Pseudohyponatremia is a lab artifact where serum sodium appears low even though the body’s actual sodium concentration and osmolality are normal. This happens with marked increases in nonaqueous constituents of serum, because indirect ion-selective electrode methods assume a fixed plasma water fraction. When there’s a lot of lipid (hypertriglyceridemia) or protein (hyperalbuminemia/hyperproteinemia), the plasma water fraction shrinks, and the indirect measurement yields a falsely low sodium value. In this situation, the true intravascular osmolality is normal, and patients are not truly hyponatremic.

Thus, severe hypertriglyceridemia or hyperproteinemia (hyperalbuminaemia) are classic causes of pseudohyponatremia. By contrast, dehydration tends to cause real hyponatremia or hypernatremia depending on fluid status, and hyperglycemia lowers measured sodium via osmotic water shift (not a measurement artifact). Hypoproteinaemia alone does not typically produce pseudohyponatremia.