What causes pseudohyponatremia and how is it avoided?

Updated: Jun 17, 2019
  • Author: Eric E Simon, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Severe hyperlipidemia and paraproteinemia can lead to low measured serum sodium concentrations with normal serum osmolality. Normally, the plasma water comprises 92-94% of plasma volume. The plasma water fraction falls with an increase in fats and proteins. The measured sodium concentration in the total plasma volume is respectively reduced, although the plasma water sodium concentration and plasma osmolality are unchanged. This artifactual low sodium (so-called pseudohyponatremia) is secondary to measurement by flame photometry. It can be avoided by direct ion-selective electrode measurement.


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