(hī‵pō-nā-trē'mē-ă )

[hypo- + natremia]

A decreased concentration of sodium in the bloodstream, typically less than 135 mmol/L. Hyponatremia is extremely common in clinical medicine and is caused by one of the following conditions: congestive heart failure, renal failure, cirrhosis; syndrome of inappropriate antidiuretic hormone (SIADH); dehydration; thyroid or adrenal hormone dysfunction; side effects of drugs; psychogenic polydipsia; or laboratory error, i.e., pseudohyponatremia. Symptoms of hyponatremia include weakness, confusion, and anorexia. If serum sodium levels drop rapidly, seizures may occur. Treatment of hyponatremia depends on the underlying cause.

hyponatremic,

(hī‵pō-nā-trē'mik )

acute h.Hyponatremia that develops in 48 hr or less. It may be corrected rapidly without concern for neurological dysfunction.

chronic h.Hyponatremia of gradual onset, present for 48 hr or more. It should be corrected slowly to avoid neurological complications, e.g., by about 10–12 meq/L per day.