Hyponatremia as a complication of cardiac catheterization: a prospective study.

Background: A decrease in plasma sodium (P(Na)) concentration is common after surgery and attributed to the secretion of antidiuretic hormone in response to such nonosmotic stimuli as pain or nausea. In this setting, acute hyponatremia may lead to seizures, coma, and permanent neurological damage. Sporadic case reports have described severe neurological symptoms caused by hyponatremia occurring within hours after cardiac catheterization.