Syndrome of inappropriate secretion of antidiuretic hormone after subarachnoid hemorrhage.

The authors report a review of 290 patients admitted for the treatment of subarachnoid hemorrhage. Twenty-seven (9.3%) patients developed the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). The diagnosis was established by means of daily laboratory investigations (serum electrolytes and osmolality; urine sodium and osmolality; and fluid balance). The patients were divided into two groups (severe and mild SIADH) on the basis of clinical symptoms and signs and laboratory findings. High values of urine osmolality and sodium concentration in patients with low values of serum osmolality and sodium concentration were demonstrated. Thirteen (4.5%) patients had severe and 14 (4.8%) patients had mild SIADH. The source of bleeding was not discovered in 14 patients (4.8%). Nearly 10% of the patients with an aneurysm on the anterior communicating artery developed SIADH. Fluid therapy for these patients is described, and the treatment of SIADH is discussed.