BACKGROUND: The role of brain natriuretic peptide (BNP) after traumatic brain 
injury (TBI) remains unclear, and its relationship with hyponatremia is still 
controversial. The aim of this study is to investigate the secretion pattern of 
N-terminal (NT)-proBNP in patients with TBI and to assess the relationship 
between NT-proBNP, sodium balance, and intracranial pressure (ICP).
METHODS: We measured serum NT-proBNP levels of 84 patients with isolated TBI on 
a daily basis from day 1 to day 14 after injury.
RESULTS: In average, the peak of BNP level was measured at 703.9 pg/mL±179.1 
pg/mL on day 3 after injury, which was correlated to the severity of TBI. Among 
patients with severe TBI, plasma NT-proBNP concentrations in patients with 
hyponatremia were statistically higher than those without hyponatremia (p<0.05). 
In the hyponatremic group, the plasma NT-proBNP increased to a peak of 1001.16 
pg/mL±131.52 pg/mL within 48 hours after injury and maintained at a high level 
for 3 days. In the normonatremic group, the plasma NT-proBNP reached a peak of 
826.43 pg/mL±337.43 pg/mL on day 5 and quickly decreased thereafter. In 
addition, we found plasma NT-proBNP concentrations in patients with ICP>15 mm Hg 
were significantly higher than those in patients with ICP≤15 mm Hg (p<0.01).
CONCLUSIONS: This study provides evidence that BNP plasma concentrations 
increase rapidly after TBI. Plasma BNP concentrations are correlated with 
hyponatremia in severe TBI patients but not in mild and moderate TBI patients. 
Furthermore, patients with elevated ICP have a higher serum BNP level in first 4 
days after injury.