PLASMA-CONCENTRATIONS OF BRAIN NATRIURETIC PEPTIDE IN PATIENTS WITH SUBARACHNOID HEMORRHAGE

Background and Purpose-Hyponatremia after subarachnoid hemorrhage (SAH ) is commonly associated with diuresis and natriuresis, but the causes are still controversial. We investigated whether brain natriuretic pe ptide (BNP) was related to such hyponatremia. Methods-Plasma BNP conce ntrations were measured by immunoradiometric assay in 18 patients at 0 to 2 days (period 1), 7 to 9 days (period 2), and >14 days (period 3) after SAH. Plasma concentrations of antidiuretic hormone (ADH), atria l natriuretic peptide (ANP), and noradrenaline were also measured duri ng period 2. Results-The 11 patients with hyponatremia (serum sodium c oncentration of <135 mEq/L) had much higher plasma BNP concentrations during each period than did healthy controls (P<0.05), whereas the 7 p atients with normonatremia did not show statistically higher values. I n the patients with hyponatremia, the plasma BNP concentration during period 2 was statistically higher than that during periods 1 and 3 (P< 0.05). The plasma nonadrenaline concentration during period 2 was high er in patients with hyponatremia than in those with normonatremia (P<0 .05), whereas the plasma concentrations of ADH and ANP during period 2 were not statistically different between the hyponatremic and normona tremic patients. Conclusions-We conclude that BNP may be related to hy ponatremia associated with natriuresis following SAH. The increase of noradrenaline may promote the secretion of BNP.