Fluid loading in rats increases serum brain natriuretic peptide concentration

Hyponatremia after subarachnoid hemorrhage has been linked to high plasma concentration of atrial natriuretic peptide and brain natriuretic peptide. Volume expansion therapy to prevent symptomatic vasospasm, such as intensive hypertensive and hypervoremic therapy, may alter systemic concentration of these peptides. We therefore examine brain natriuretic peptide secretion in rats in response to acute volume expansion, infusing to 10 ml of saline over 1 h. In the 70 ml group, brain natriuretic peptide concentrations showed a significant increase from pre-infusion concentrations 7 h after initiation of infusion, but had begun to fall 7 h later. We suspect that high plasma concentration of brain natriuretic peptide after subarachnoid hemorrhage is partly caused by hypervoremic therapy.