Relationship between cardiac natriuretic peptide (ANP/BNP) and fluid intake in patients with subarachnoid hemorrhage

Several authors described elevated natriuretic peptides, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), in patients with subarachnoid hemorrhage (SAH), which were account for inappropriate antidiuretic hormone (SIADH) or cerebral salt wasting syndrome (CSW). Although the secretion of natriuretic peptide depends on the total blood volume, central venous pressure, and cardiac output volume, the volume of fluid intake in patients with SAH had not been taken in consideration in previous report. We here examined the relationship between fluid intake and the natriuretic peptides in two cases without cardiac failure. ANP elevated 2 or 3 days after SAH and remained in normal range for 2 weeks. BNP elevated when the volume of fluid intake was increased, and BNP did not elevate during the periods with lower fluid intake. Several authors proposed the possibility of iatrogenic factor in natriuresis after SAH and these results supported this opinion.