Prognostic role of BNP in children undergoing surgery for congenital heart disease: analysis of prediction models incorporating standard risk factors

Background: The routine use of brain natriuretic peptide (BNP) in pediatric cardiac surgery remains controversial. Our aim was to test whether BNP adds information to predict risk in pediatric cardiac surgery. Methods: In all, 587 children undergoing cardiac surgery (median age 6.3 months; 1.2-35.9 months) were prospectively enrolled at a single institution. BNP was measured pre-operatively, on every post-operative day in the intensive care unit, and before discharge. The primary outcome was major complications and length ventilator stay >15 days. A first risk prediction model was fitted using Cox proportional hazards model with age, body surface area and Aristotle score as continuous predictors. A second model was built adding cardiopulmonary bypass time and arterial lactate at the end of operation to the first model. Then, peak post-operative log-BNP was added to both models. Analysis to test discrimination, calibration, and reclassification were performed. Results: BNP increased after surgery (p<0.001), peaking at a mean of 63.7 h (median 36 h, interquartile range 12-84 h) post-operatively and decreased thereafter. The hazard ratios (HR) for peak-BNP were highly significant (first model HR=1.40, p=0.006, second model HR=1.44, p=0.008), and the log-likelihood improved with the addition of BNP at 12 h (p=0.006; p=0.009). The adjunction of peak-BNP significantly improved the area under the ROC curve (first model p<0.001; second model p<0.001). The adjunction of peak-BNP also resulted in a net gain in reclassification proportion (first model NRI=0.089, p<0.001; second model NRI=0.139, p=0.003). Conclusions: Our data indicates that BNP may improve the risk prediction in pediatric cardiac surgery, supporting its routine use in this setting.