In critically ill patients, B-type natriuretic peptide (BNP) and N-terminal pro-BNP levels correlate with C-reactive protein values and leukocyte counts.

Background: B-type natriuretic peptide (BNP) and its N-terminal portion (NT-pro-BNP) are used for the assessment of cardiac dysfunction in patients with heart failure. However, it remains controversial whether or not this option is still valid in critically ill patients because of a possible interaction between the systemic inflammatory response and the natriuretic peptide levels. The aim of this study was to assess the relationship between natriuretic peptic levels, laboratory parameters of systemic inflammation, and pulmonary artery occlusion pressure (PAOP) in critically patients.

Methods: Twelve haemodyamic unstable patients, all monitored with a pulmonary artery catheter, were included in this study. Subgroups were compared using measurement values on ICU admission. Within patient associations between different variables were evaluated by a repeated measurement ancova.

Results: Acute heart failure and septic shock were diagnosed in 6 patients each. Despite significant differences in cardiac index and troponin T plasma level, BNP and NT-pro-BNP levels did not differ significantly between the two groups. Within patient, changes in BNP and NT-pro-BNP levels correlated significantly (p<0.01) with those in C-reactive protein values and those in leukocyte counts, but did not follow changes in PAOP.

Conclusion: Our results add further evidence to the hypothesis that there is an interaction between the systemic inflammatory response and the natriuretic peptides. Thus, BNP and NT-pro-BNP levels should only be used cautiously as surrogates of cardiac filling and function in haemodynamic unstable critically ill patients.