Acute hyponatremia
Sodium levels drop rapidly over less than 48 hours. This can lead to potentially dangerous effects, such as brain swelling, which can cause coma and death. Acute hyponatremia requires emergency treatment to prevent cerebral herniation and death. Treatment involves increasing serum sodium levels by about 4–6 mEq/L/h until neurological symptoms subside or to prevent brain herniation.
Chronic hyponatremia
Sodium levels drop gradually over 48 hours or longer. Chronic hyponatremia is more common and may be better tolerated than acute hyponatremia because the brain can compensate by reducing intracellular solute content. Patients with chronic hyponatremia are less likely to develop neurological symptoms because cerebral adaptation protects against raised intracranial pressure.