Isotonic hyponatremia

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Isotonic hyponatremia is a form of hyponatremia with mOsm measured between 280 and 295. It can be associated with pseudohyponatremia, or with isotonic infusion of glucose or mannitol.[1]


Certain conditions that interfere with laboratory tests of serum sodium concentration such as extraordinarily high blood levels of lipid (hyperlipidemia/hypertriglyceridemia) or protein (hyperparaproteinemia) may lead to an erroneously low measurement of sodium. This is called pseudohyponatremia, and can occur when laboratories use the flame-photometric and indirect (but not direct) ion-selective electrode assays.[2][3] This is distinct from a true dilutional hyponatremia that can be caused by an osmotic shift of water from cells to the bloodstream after large infusions of mannitol or intravenous immunoglobulin.

It is associated with hyperlipidemia more frequently than with elevated protein.[4]


  1. ^ Gottschlich, Michele M.; Matarese, Laura E. (2003). Contemporary nutrition support practice: a clinical guide. Philadelphia: Saunders. p. 130. ISBN 0-7216-9357-1. 
  2. ^ Weisberg LS (March 1989). "Pseudohyponatremia: a reappraisal". Am. J. Med. 86 (3): 315–8. doi:10.1016/0002-9343(89)90302-1. PMID 2645773. 
  3. ^ Nguyen MK, Ornekian V, Butch AW, Kurtz I (May 2007). "A new method for determining plasma water content: application in pseudohyponatremia". Am. J. Physiol. Renal Physiol. 292 (5): F1652–6. doi:10.1152/ajprenal.00493.2006. PMID 17299138. 
  4. ^ Garibaldi BT, Cameron SJ, Choi M (February 2008). "Pseudohyponatremia in a patient with HIV and hepatitis C coinfection". J Gen Intern Med 23 (2): 202–5. doi:10.1007/s11606-007-0446-3. PMC 2359164. PMID 17994269.