The psychiatrist has commonly dealt with hiponatremia (sodium blood level lower than 135 mEq/l) in psychiatry department, and by consulting other hospital departments. The prevalence of hiponatremia is estimated as about 0,36% to 4% in general hospitals, and 0,36% to 6,4% in psychiatric departments. By the sodium level lower than120 mEq/l, the psychiatric and neurological symptoms are appearing, with the threat of irreversible brain damage and death. The possible causes of hiponatremia in chronic mentally ill patients are psychogenic polidypsia, somatic illnesses, and undesirable drug effects. The common mechanism is the induction of inappropriate high secretion of anti diuretic hormone (ADH).
Sodium level correction is urgently needed, but it is necessary to consider carefully the risk of quick intravenous infusion of NaCl solution. According to the causes of hiponatremia, the correction of previous pharmacotherapy, and needed somatic or psychiatric treatment must be undertaken.