Usage of B-type natriuretic peptide for prediction of weaning outcome by spontaneous breathing trial

Prediction of weaning success remains a major clinical challenge. Cardiovascular dysfunction could be a major underlying mechanism of weaning failure. Recent data suggest that BNP; a marker for cardiovascular dysfunction, may predict the outcome of weaning from assisted mechanical ventilation. BNP variations during spontaneous breathing trial may be of predictive value concerning the outcome of weaning process. To evaluate the role of BNP levels measured during a 2 h. SBT as a predictive value for weaning outcome. A prospective observational study included forty patients on mechanical ventilation who underwent an SBT. Echocardiography was done 2 h, before SBT and sampling of BNP was performed immediately before and at the end of SBT to determine the predictive value of BNP. Patients were divided according to the result of the 2-h SBT into 3 groups: SBT failure [8 pts.], extubation success [25 pts.] and extubation failure [7 pts.]. The BNP level was significantly higher in SBT failure and extubation failure groups after SBT than before SBT while it was significantly lower in the extubation success group after SBT than before SBT with a p-value of 0.004. It was found that both extubation and SBT failure groups had significantly larger percent increase in BNP level unlike the extubation success group who had significantly percent decrease in the BNP level with a p-value <0.001. The area under the ROC curve was 0.96. A change of BNP level <20% from baseline had the best combination of sensitivity [85.71%], specificity [90.91%], positive [96.77%] and negative [66.67%] predictive values and diagnostic accuracy [90%] in predicting extubation failure. BNP level variation during SBT may improve the predictive value of the trial on weaning outcome.