Measurement and significance of plasma antidiuretic hormone in subarachnoid hemorrhage. The relationship between plasma ADH levels and various factors following subarachnoid hemorrhage

Abstract

The authors already reported that the incidence of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) after subarachnoid hemorrhage (SAH) was significantly higher in patients with Grade III and IV of Hunt and Hess, severe vasospasm and marked hydrocephalus than in patients without these factors. In order to clarify why the patients with these factors were susceptible to develop SIADH after SAH the plasma ADH level (PADH) in 25 control subjects and in 56 patients with SAH mainly due to cerebral aneurysms were measured using radioimmunoassay. PADH measurements, repeated 111 times, were made preoperatively within 4 weeks after SAH. PADH in 13 cases with SIADH was significantly higher than those of the control and were inappropriate for the corresponding serum osmolarities. The differences in PADH, according to clinical grades, vasospasm, hydrocephalus and aneurysmal locations were studied in 43 cases without SIADH. The results were as follows: 1) PADH in patients with Grade III and IV, specially measured within 14 days after SAH, was significantly higher than that in patients with Grade I and II. 2) Patients with mild or severe vasospasm had significantly higher PADH than patients without vasospasm. 3) In patients with hydrocephalus, the PADH was significantly higher than that without hydrocephalus. 4) The differences in PADH according to aneurysmal locations were not significant. Hematological and urinary studies showed that the excessive release of ADH recognized in the present study was a non-physiological (inappropriate) release of ADH, caused by non-osmotic factors, except blood volume depletion. These results suggest that the patients with Grade III and IV, vasospasm, and hydrocephalus in the acute stage after SAH are unable to suppress ADH release and to excrete the water load normally, even if they are under normoosmotic conditions. The present study supports the previous report by the authors that the patients with Grade III and IV, severe vasospasm, and marked hydrocephalus are susceptible to SIADH.