Hyponatremia: cerebral symptoms and role in central pontine myelinolysis.

Central nervous system symptoms due to hyponatremia is highly dependent on its acuteness and cause. Severe acute hyponatremia (serum sodium less than 125 mEq/l) often causes confusion, lethargy, seizures or frank coma due to brain oedema. If therapy is delayed, hyponatremia carries a high mortality rate, and risk of irreversible brain damage. Hyponatremia should probably be corrected to 125-130 mEq/l at a rate of 1.5-2.0 mEq/l/h. Malnourished alcoholic patients with hyponatremia may represent a special case with possible dangers of central pontine myelinolysis if a very low serum sodium is corrected acutely to normonatremic or hypernatremic levels. Mortality in this subgroup is high whatever the therapy.