The initial, and often definitive, management of hyponatremia is free-water restriction. Symptomatic hyponatremia, which occurs at serum sodium levels less than or equal to 120 mEq/L, can result in headache, seizures, coma, and signs of increased intracranial pressure and may require infusion of hypeonic saline. Rapid correction should be avoided so as not to cause central pontine myelinolysis, manifested by neurologic symptoms ranging from seizures to brain damage and death. Additionally, a search for the underlying etiology of the hyponatremia should be undeaken. Acute severe hyponatremia sometimes occurs following elective surgical procedures due to a combination of appropriate stimulation of antidiuretic hormone and injudicious administration of excess free water in the first few postoperative days. Other potential etiologies include hyperosmolarity with free-water shifts from the intra- to the extracellular compament (eg, hyperglycemia), sodium depletion (eg, gastrointestinal or renal losses, insufficient intake), dilution (eg, drug-induced), and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).