When hemorrhage and trauma occur during a surgical procedure, ADH secretion is appropriately elevated. In this situation, SIADH can be induced as a result of overzealous fluid administration. Because of the urinary sodium loss that occurs along with the water retention, the syndrome of acute water intoxication may be seen in the PACU. The symptoms of water intoxication derive from increased brain water, inoperative sodium pump, and hyponatremia. The symptoms begin with headache, muscular weakness, anorexia, nausea, and vomiting and lead to confusion, hostility, disorientation, uncooperativeness, drowsiness, and terminal convulsions or coma. These symptoms usually do not occur if the serum sodium level is higher than 120 mEq/L. Therefore in patients who have had major vascular surgery, trauma, or hemorrhage, the perianesthesia nurse should assess frequently for the symptoms of SIADH and notify the attending physician if the symptoms become evident. The focus of treatment for SIADH is fluid restriction, diuresis with mannitol or furosemide, and administration of sodium chloride. In addition, the perianesthesia nurse should frequently assess the neurologic signs and cardiorespiratory status of the patient with SIADH and measure and record accurately the intake and output of all fluids.^7,9–13