Could B-type Natriuretic Peptide (BNP) plasma concentration be useful to predict fluid responsiveness [corrected] in critically ill patients with acute circulatory failure?

BACKGROUND AND OBJECTIVES: As B-type Natriuretic Peptide (BNP) is a marker of ventricular wall stress, the present study was aimed at determining whether plasma BNP concentration could predict fluid responsiveness in critically ill patients with acute circulatory failure.

METHODS: This prospective and non randomized interventional study included 33 sedated, mechanically ventilated patients, with acute circulatory failure requiring cardiac output measurement and fluid challenge. Plasma BNP concentration was measured before and after fluid challenge (250 to 500 ml with infusion rate=999 ml/h). An increase in stroke index (SI) greater than or equal to 15% allowed separation of responders from nonresponders. Receiver operating characteristic (ROC) curves were generated for BNP and compared to that of central venous pressure (CVP) that is routinely considered as a marker of cardiac preload.

RESULTS: Among 33 patients, there were 24 responders. At baseline, BNP plasma values were less in responders (328 [35-1190] pg/ml versus 535 [223-5000] pg/ml, p<0.03). The area under the ROC curves was 0.74+/-0.11, that was similar to the area under the ROC curve for CVP (0.77+/-0.10). The best cut-off value of plasma BNP level for predicting fluid responsiveness was 193 pg/ml (sensitivity: 38%, specificity: 100%, positive predictive value: 100%, negative predictive value: 38%, accuracy: 55%). Fluid challenge did not increase plasma BNP concentrations in responders and nonresponders.

CONCLUSION: In critically ill patients with acute circulatory failure, BNP does not accurately predict fluid responsiveness.