Natriuretic peptide testing for the evaluation of critically ill patients with shock in the intensive care unit: a prospective cohort study

Introduction Amino-terminal pro-brain natriuretic peptide (NTproBNP) is useful in evaluating heart failure, but its role in evaluating patients with shock in the intensive care unit (ICU) is not clear. Method Forty-nine consecutive patients in four different ICUs with shock of various types and with an indication for pulmonary artery catheter placement were evaluated. Analyses for NTproBNP were performed on blood obtained at the time of catheter placement and results were correlated with pulmonary artery catheter findings. Logistic regression identified independent predictors of mortality. Results A wide range of NT-proBNP levels were observed ( 106 to > 35,000 pg/ml). There was no difference in median NTproBNP levels between patients with a cardiac and those with a noncardiac origin to their shock ( 3,046 pg/ml versus 2,959 pg/ ml; P = 0.80), but an NT-proBNP value below 1,200 pg/ ml had a negative predictive value of 92% for cardiogenic shock. NTproBNP levels did not correlate with filling pressures or hemodynamics ( findings not significant). NT-proBNP concentrations were higher in patients who died in the ICU ( 11,859 versus 2,534 pg/ml; P = 0.03), and the mortality rate of patients in the highest log-quartile of NT-proBNP (66.7%) was significantly higher than those in other log-quartiles ( P < 0.001); NT-proBNP independently predicted ICU mortality ( odds ratio 14.8, 95% confidence interval 1.8 - 125.2; P = 0.013), and was superior to Acute Physiology and Chronic Health Evaluation II score and brain natriuretic peptide in this regard. Conclusion Elevated levels of NT-proBNP do not necessarily correlate with high filling pressures among patients with ICU shock, but marked elevation in NT-proBNP is strongly associated with ICU death. Low NT-proBNP values in patients with ICU shock identifed those at lower risk for death, and may be useful in excluding the need for pulmonary artery catheter placement in such patients.