Inappropriate secretion of antidiuretic hormone after open heart surgery.

After open heart surgery for the closure of an atrial septal defect, acute brain syndrome developed in a 5-year-old girl, this being documented by laboratory evidence of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Irritability and total disorientation were the first symptoms observed. She completely recovered after being treated with hypertonic saline solution and fluid restriction. The potentially serious outcome of the SIADH warrants early recognition and appropriate measures in children who suffer acute brain syndrome after open heart surgery.