ALTERATIONS IN PLASMA-CONCENTRATIONS OF NATRIURETIC PEPTIDES AND ANTIDIURETIC-HORMONE AFTER SUBARACHNOID HEMORRHAGE

Background and Purpose Hyponatremia is a common complication after sub arachnoid hemorrhage. In this study we investigated the relations amon g hyponatremia, plasma natriuretic peptides, and antidiuretic hormone concentrations after subarachnoid hemorrhage. Methods Blood samples fo r radioimmunoassay measurement of plasma brain natriuretic peptide-lik e immunoreactivity, atrial natriuretic peptide-like immunoreactivity, and antidiuretic hormone were obtained every 2 to 4 days until day 14 after subarachnoid hemorrhage. Results Eleven of 20 patients with veri fied subarachnoid hemorrhage demonstrated mild hyponatremia (126 mEq/L <serum sodium<135 mEq/L) during their clinical course. Atrial natriure tic peptide and antidiuretic hormone concentrations were significantly elevated on days 0 to 2 after onset of subarachnoid hemorrhage. Atria l natriuretic peptide concentrations remained high in patients who dev eloped mild hyponatremia on days 6 to 14 after onset of subarachnoid h emorrhage. In contrast, antidiuretic hormone concentrations became sig nificantly lower during the second week in these patients. Conclusions Mild hyponatremia after subarachnoid hemorrhage may be attributable n ot to the syndrome of inappropriate secretion of antidiuretic hormone but to cerebral salt-wasting syndrome. Atrial natriuretic peptide may be a causal natriuretic factor in cerebral salt-wasting syndrome.