NPPB and Patent ductus arteriosus: In a separate analysis, levels of NTproBNP in infants having later PDA surgery after prior ibuprofen treatment were compared with infants treated with ibuprofen only and they had significantly higher levels of NTproBNP on day three, 33,500 ng/L (29,500–35,000 ng/L) vs. 14,600 ng/L (7740–28,100 ng/L), respectively p < 0.01.