Brain natriuretic peptide in subarachnoid hemorrhage

Because of the known correlation between the brain natriuretic peptide (BNP) level and the severity of cardiac failure, cardiac function assessment often involves measuring BNP levels. In addition, BNP is produced in the hypothalamus; high BNP levels are reported in patients with subarachnoid hemorrhage (SAH), although the details of this mechanism remain to be clarified. Furthermore, there are unconfirmed reports of high BNP levels during follow up in cases of post-SAH cerebral vasospasm (CVS). In the present study, we retrospectively investigated the correlation between plasma BNP levels and severity of SAH at onset and the utility of the BNP level as a predictor for CVS. Of 149 SAH cases treated as inpatients at our institution between November 2008 and March 2010, our subjects comprised 28 SAH cases in which the plasma BNP level was measured at the time of hospitalization (≤48 hours after SAH onset). There was no significant correlation between BNP levels and SAH severity at the onset, but BNP levels tended to be high in cases accompanied by intracerebral hematoma, particularly in patients with an anterior communicating aneurysm rupture. This is thought to be the result of direct damage to the hypothalamus. The cases with normal BNP levels at the onset of SAH were apt to have favorable outcomes. The incidence of delayed ischemic neurological deficit (DIND) was investigated in 15 cases in which the BNP level was measured multiple times during follow up. The ratio of BNP at SAH onset compared to at days 3 to 7 of the illness was not significant; however, BNP levels tended to be high in cases with DIND complications. BNP levels may constitute a useful early marker for CVS, despite BNP susceptibility to surgical invasion and perioperative management.