Repeated measurements of N-terminal pro-brain natriuretic peptide enable dynamic risk stratification in critically ill patients

Introduction

Risk stratification is a major problem in the care of critically ill patients. To date, there is no widespread acceptance of any prognostic marker for ongoing risk stratification. In the present study we aim to determine whether N-terminal pro-brain natriuretic peptide (NT-pro-BNP) serves as a marker of dynamic risk stratification.

Methods

This prospective observational study was performed in the ICU of the Department of Cardiology/Medical University of Vienna between August 2004 and June 2007. Adult patients with a length of ICU stay ≥ 48 hours were included. In addition to routine clinical and laboratory assessment, blood samples for determination of NT-pro-BNP were obtained in all patients on admission (NT-pro-BNP-0 h) and after 48 hours (NT-pro-BNP-48 h). NT-pro-BNP plasma levels were assessed by use of commercially available kits.

Results

Out of 286 patients included (196 male (68.5%), age 64 ± 14 years), there were 226 ICU survivors (79%). ICU survivors had significantly lower NT-pro-BNP-0 h as well as NT-pro-BNP-48 h levels compared with ICU nonsurvivors (7,063 ± 9,183 vs. 15,254 ± 12,850 pg/ml, P < 0.0001, NT-pro-BNP-0 h; and 8,304 ± 9,147 vs. 17,302 ± 12,687 pg/ml, P < 0.0001, NT-pro-BNP-48 h, respectively). There was no statistically significant change in NT-pro-BNP levels in ICU survivors compared with ICU nonsurvivors (Δ-NT-pro-BNP 1,240 ± 7,814 vs. 2,047 ± 11,081 pg/ml, P = 0.624), but significantly more ICU survivors had a decrease in NT-pro-BNP within 48 hours (37% vs. 33%, P < 0.0001). In Cox regression models, NT-pro-BNP-0 h, NT-pro-BNP-48 h and increase/decrease of NT-pro-BNP were independent predictors of ICU mortality within 28 days, with NT-pro-BNP-48 h being the most potent parameter (NT-pro-BNP-0 h Wald 11.289, P = 0.001; NT-pro-BNP-48 h Wald 17.630, P < 0.001; increase/decrease Wald 4.992, P = 0.025, respectively). The area under the receiver operating characteristic curve with respect to prediction of ICU survival was 0.714 (P < 0.0001) for NT-pro-BNP-0 h, 0.713 (P < 0.0001) for NT-pro-BNP-48 h and 0.489 (P = 0.800) for Δ-NT-pro-BNP.

Conclusion

NT-pro-BNP reflects not only the severity of the disease on ICU admission, but – more importantly – the plasticity of NT-pro-BNP monitors the severity of the disease during the ICU stay.