Increased Concentration of Atrial Natriuretic Factor in the Cerebrospinal Fluid of Patients with Aneurysmal Subarachnoid Hemorrhage and Raised Intracranial Pressure

Abstract

Plasma and cerebrospinal fluid (CSF) atrial natriuretic factors/peptides (ANFs/ANPs) were measured in 26 patients with normal or raised intracranial pressure (ICP) by means of an instant radioreceptor assay. All 26 patients were suffering from aneurysmal subarachnoid hemorrhage (SAH), and 11 had also developed raised ICP (ICP ≥ 20 mm Hg). In SAH patients with normal ICP, the plasma levels of ANF were 20 to 200 pg/ml (mean ± SE, 89 ± 68 pg/ml); in the 11 SAH patients with raised ICP, however, ANF levels were 14 to 262 pg/ml (mean 114 ± 79 pg/ml). The difference was not statistically significant. The ANF/ANP plasma levels in 6 healthy volunteers were 15 to 167 pg/ml (mean 77 ± 32 pg/ml). Although the ANF/ANP concentration in the CSF of patients with normal ICP did not reach the lower limit of detectability (i.e., 4 pg/ml) in any case, in those with elevated ICP it was 14 to 120 pg/ml (mean 49 ± 37 pg/ml). This difference was statistically highly significant. The results of this preliminary study suggest that the ANF/ANP concentration in human CSF is 1 to 2 orders lower than that in the plasma and that there is no significant correlation between ANF/ANP levels in the CSF and the plasma. After SAH in patients with raised ICP, there was an accompanying increase in the ANF/ANP concentration in the CSF, but the ANF/ANP concentration in the plasma was not changed significantly. Accordingly, a central ANF/ANP release might be hypothesized to play a causative or adaptive role in the neuroendocrine regulation of ICP dynamics, although this may simply be an epiphenomenon.