BNP and NT-proBNP concentrations in paired cerebrospinal fluid and plasma samples of patients with traumatic brain injury.

BACKGROUND The aim of this study was to investigate the secretion patterns of brain natriuretic peptide (BNP) and N-terminal-proBNP (NT-proBNP) after traumatic brain injury (TBI) and to analyze the source of them in cerebrospinal fluid (CSF). MATERIALS AND METHODS We synchronously measured BNP and NT-proBNP concentrations in paired CSF and plasma samples from 22 moderate to severe TBI patients and 40 healthy control patients. The CSF and/or plasma ratio of albumin (QAlbumin) was calculated daily. The BNP and NT-proBNP levels of CSF and plasma were compared between TBI patients and control patients. RESULTS CSF BNP and NT-proBNP levels peaked on day 3 after injury, as did the plasma BNP and NT-proBNP levels. The CSF BNP and NT-proBNP levels in TBI patients were elevated from day 1, which was significantly higher than control group (P < 0.05 and P < 0.01, respectively). However, in plasma, only NT-proBNP levels were significantly higher than in the control group from day 2 (P < 0.05). In addition, QBNP, defined as CSF BNP concentration and/or plasma BNP concentration, was significantly higher in TBI patients than in the control group (P < 0.01). However, QAlbumin remained within ranges of a mild to moderate dysfunction of blood-brain-barrier in TBI patients. CONCLUSIONS CSF BNP concentrations are elevated and peak on day 3 after moderate to severe TBI. CSF BNP may originate from the brain and may be a potential biomarker of TBI.