Diagnostic and Prognostic Utility of Brain Natriuretic Peptide in Subjects Admitted to the ICU With Hypoxic Respiratory Failure Due to Noncardiogenic and Cardiogenic Pulmonary Edema

Dimitri Karmpaliotis, MD

Abstract
Background: Brain natriuretic peptide (BNP) is useful in diagnosing congestive heart failure (CHF) in patients presenting in the emergency department with acute dyspnea. We prospectively tested the utility of BNP for discriminating ARDS vs cardiogenic pulmonary edema (CPE).
Methods: We enrolled ICU patients with acute hypoxemic respiratory failure and bilateral pulmonary infiltrates who were undergoing right-heart catheterization (RHC) to aid in diagnosis. Patients with acute coronary syndrome, end-stage renal disease, recent coronary artery bypass graft surgery, or preexisting left ventricular ejection fraction 30% were excluded. BNP was measured at RHC. Two intensivists independently reviewed the records to determine the final diagnosis.
Results: Eighty patients were enrolled. Median BNP was 325 pg/mL (interquartile range [IQR], 82 to 767 pg/mL) in acute lung injury/ARDS patients, vs 1,260 pg/mL (IQR, 541 to 2,020 pg/mL) in CPE patients (p = 0.0001). The correlation between BNP and pulmonary capillary wedge pressure was modest (r = 0.27, p = 0.02). BNP offered good discriminatory performance for the final diagnosis (C-statistic, 0.80). At a cut point 200 pg/mL, BNP provided specificity of 91% for ARDS. At a cut point 1,200 pg/mL, BNP had a specificity of 92% for CPE. Higher levels of BNP were associated with a decreased odds for ARDS (odds ratio, 0.4 per log increase; p = 0.007) after adjustment for age, history of CHF, and right atrial pressure. BNP was associated with in-hospital mortality (p = 0.03) irrespective of the final diagnosis and independent of APACHE (acute physiology and chronic health evaluation) II score.
Conclusion: In ICU patients with hypoxemic respiratory failure, BNP appears useful in excluding CPE and identifying patients with a high probability of ARDS, and was associated with mortality in patients with both ARDS and CPE. Larger studies are necessary to validate these findings.