Brain natriuretic peptide (BNP) regulates electrolyte and water balance, and we know that BNP levels increase immediately after traumatic brain injury or stroke. The result of this BNP increase can be a higher risk of brain edema and elevated intracranial pressure.
In a study that sought to clarify the relationship of BNP and traumatic brain injury, researchers found that BNP levels peak 3-4 days after injury and were closely related to more severe cases of traumatic brain injury, elevated intracranial pressure and hyponatremia (from cerebral salt wasting syndrome). BNP levels quickly dropped by the fifth day after injury.
Since hyponatremia, edema, and elevated intracranial pressure are predictive of a more negative outcome after brain injury, studies of BNP levels can help guide appropriate treatment to normalize electrolyte and water balances.
Wu X, Sha H, Sun Y, et al. N-terminal pro-B-type natriuretic peptide in patients with isolated traumatic brain injury: A prospective cohort study. The Journal of Trauma Injury, Infection, and Critical Care. (September 2011).