Isotonic hyponatremia

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Isotonic hyponatremia
Classification and external resources
ICD-10 Xxx.x
ICD-9-CM xxx

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, such as extraordinarily high blood levels of lipid (hyperlipidemia/hypertriglyceridemia) or protein (hyperparaproteinemia), magnify the electrolyte exclusion effect. This interferes with the measurement of serum sodium concentration by certain methods, leading to an erroneously low measurement of sodium, or pseudohyponatremia. The methods affected are 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 MM, Matarese LE (2003). Contemporary nutrition support practice: a clinical guide. Philadelphia: Saunders. p. 130. ISBN 0-7216-9357-1. 
  2. ^ Weisberg LS (Mar 1989). "Pseudohyponatremia: a reappraisal". The American Journal of Medicine. 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". American Journal of Physiology. Renal Physiology. 292 (5): F1652–6. doi:10.1152/ajprenal.00493.2006. PMID 17299138. 
  4. ^ Garibaldi BT, Cameron SJ, Choi M (Feb 2008). "Pseudohyponatremia in a patient with HIV and hepatitis C coinfection". Journal of General Internal Medicine. 23 (2): 202–5. doi:10.1007/s11606-007-0446-3. PMC 2359164free to read. PMID 17994269.