B-type natriuretic peptide or BNP is a neurohormone. It is secreted by the ventricles of the heart in response to excessive stretching of heart muscle cells (cardiomyocytes). Thus fluid overload increases the secretion of the hormone. BNP is elevated in those with left ventricular dysfunction. It is elevated in both symptomatic and asymptomatic left ventricular dysfunction. Whether BNP can be used as a test to diagnose congestive heart failure or CHF in early stages is a much debated topic. In many situations, BNP has been used as a screen for heart failure and to determine whether a patient has hypoxia secondary to CHF or pulmonary disease.
Thus, BNP levels can help establish the cause of shortness of breath. This test is also frequently used in those with trauma to detect early CHF and institute early treatment. However, in many situations, especially in those with trauma, a positive test can give scope for unnecessary introduction of medications. Infact, the most ideal method to detect early CHF is to monitor airway, breathing and circulation. In cases where BNP levels are elevated, the levels can help determine the severity of CHF and hence daily measurement of BNP levels may be useful.
They may be useful to establish prognosis of heart. Nurses taking care of trauma or other sick patients must prioritize assessing breathing, circulation and neurological status and not just depend on laboratory values of BNP. There is no level of BNP that perfectly separates patients with and without heart failure. BNP test has a high sensitivity but rather low specificity, meaning that low values are accurate at excluding heart failure as a diagnosis, but high values are not conclusive in identifying heart failure.