Suprasellar and intraventricular blood predict elevated plasma atrial natriuretic factor in subarachnoid hemorrhage

Following subarachnoid hemorrhage, the plasma concentration of atrial natriuretic factor is elevated and appears to be independent of atrial stretch. While the hypothalamus and circumventricular organs contribute to sodium and intravascular volume regulation, their influence on atrial natriuretic factor is not known. We tested the hypothesis that, following subarachnoid hemorrhage, suprasellar cisternal blood, intraventricular blood, or ventricular enlargement would be associated with elevated plasma levels of atrial natriuretic factor. Computed tomograms of 26 patients performed ≤3 days after hemorrhage were analyzed to determine the presence of suprasellar or intraventricular blood and enlargement of the third or lateral ventricle. These results were correlated with the plasma atrial natriuretic factor and serum sodium concentrations. The initial atrial natriuretic factor concentration was elevated and was higher in patients with suprasellar or intraventricular blood than in those without (suprasellar: 131±20 and 54±10 pg/ml, respectively; intraventricular: 137±25 and 84±31 pg/ml, respectively). The atrial natriuretic factor concentration remained higher over the week following hemorrhage in patients with suprasellar blood than in those without (127±16 and 68±12 pg/ml, respectively). The atrial natriuretic factor concentration was not correlated with hyponatremia (125–134 meq/I) or age-corrected ventricular size. Hyponatremia did not correlate with the presence of intraventricular or suprasellar blood. Our data suggest that suprasellar and intraventricular blood disturb hypothalamic function, resulting in an elevated plasma atrial natriuretic factor concentration. The presence of a direct relation between atrial natriuretic factor and hyponatremia remains unclear.