The Characteristics and Prognostic Importance of NT-ProBNP Concentrations in Critically Ill Patients

Background There are limited data for prognostic and diagnostic use of natriuretic peptides in intensive care unit (ICU) patients. We evaluate amino-terminal brain natriuretic peptide (NT-proBNP) in the medical ICU, specifically its correlation with noncardiac admission diagnosis and prognosis of critically ill patients. Methods NT-proBNP (pg/mL) was measured in 179 ICU patients without acute decompensated heart failure or acute coronary syndrome. Death during hospitalization (mortality), APACHE II score, laboratory data, echocardiograms, medical history, and demographics were assessed. NT-proBNP concentrations were compared with established cutoffs for congestive heart failure (>450 pg/mL for patients <50 years of age, >900 pg/mL for patients 50-70 years of age, and >1800 pg/mL for patients >70 years of age). Predictors of mortality and of NT-proBNP were analyzed by regression analysis. Tertiles were compared by analysis of variance and chi-squared test. Results NT-proBNP was elevated in these ICU patients (median 2139 pg/mL, 25th percentile 540 pg/mL, 75% percentile 7389 pg/mL). Severity of illness and renal dysfunction (APACHE II score and serum creatinine) increased with rising NT-proBNP. The incidence of acute respiratory distress syndrome, sepsis, death, history of coronary artery disease (CAD) or congestive heart failure (all P<.05) increased with each tertile. Independent predictors of increased NT-proBNP were creatinine (P<.001), CAD (P<.001), APACHE II score (P<.05), and sepsis (P ≤.001). Overall hospital mortality was 26%, and log NT-proBNP (P<.05), APACHE II (P ≤.001), and CAD (P<.05) were independent predictors of mortality. Conclusions For patients admitted to the ICU without decompensated heart failure or acute coronary syndrome, NT-proBNP concentrations are markedly elevated, especially in patients with sepsis. NT-proBNP strongly and independently predicts mortality. However, NT-proBNP should not be used to direct volume management in critically ill patients.