Pseudohyponatremia refers to apparent hyponatremia associated with macromolecules that displace water, resulting in a reduced percentage of serum water. Recognition is important since the patient does not require to be treated for hyponatremia.
Basis: Normally serum consists of about 93% w/v water. If a higher than normal concentration of macromolecules is present, then water is displaced and shows a reduced percent of the serum volume. The concentration of sodium and other electrolytes in the serum water are normal.
Situations where encountered:
(1) severe hypertriglyceridemia
(2) paraproteinemia
Features:
(1) reduced serum sodium concentration using an indirect assay on an automated analyzer
(2) normal serum osmolality
(3) normal serum sodium using an ion specific electrode
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