title: Symptomatic hyponatremia: pathophysiology and management.
abstract: In summary, we believe that the osmotic difference between the brain cell and the extracellular fluid is the critical parameter in determining therapy. A gradient of 30 mosm/kg or more produces significant shifts of intracellular water and cell damage. Seizure and coma are the neurologic signs associated with acute life-threatening osmotic imbalance between swelling brain cells and the extracellular space. Treatment is designed to decrease this osmotic gradient to less than 30 mosm/kg to prevent this cell swelling. Thus in acute symptomatic hyponatremia, treatment (fluid restriction alone if urine osmolality is less than 100 mosm/kg or 3% saline if needed or both) is needed to decrease this osmotic gradient. If hyponatremia is chronic and brain osmotic adaptations have already taken place, increased extracellular osmolality would cause brain cells to undergo water loss, which may result in cell shrinkage and neurologic damage (for example, central pontine myelinosis). Unfortunately, there is as yet no clinically available tool to rapidly assess intracellular brain osmolality. Clinical judgment is therefore mandatory in trying to estimate the osmotic gradient between the intracellular and extracellular environment. Appropriate treatment must be initiated to prevent excessive changes in cell volume.
authors.affiliation: Department of Medicine, University of Health Sciences, Chicago Medical School, Ill.
authors.forename: J C
authors.initials: JC
authors.lastname: Cheng
authors.forename: D
authors.initials: D
authors.lastname: Zikos
authors.forename: D R
authors.initials: DR
authors.lastname: Peterson
authors.forename: K A
authors.initials: KA
authors.lastname: Fisher
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001812:Blood-Brain Barrier; D001834:Body Water / Q000378:metabolism; D002985:Clinical Protocols / Q000592:standards*; D003663:Decision Trees; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009994:Osmolar Concentration; D014882:Water-Electrolyte Balance