NPPB and acute kidney injury: The median overall preoperative NT-proBNP concentration was 76.36 pg ml−1 (interquartile range 39.86 to 178.47 pg ml−1), and the preoperative NT-proBNP concentrations were markedly higher in patients who developed AKI after surgery than among those who did not (median 163.10 versus 72.74 pg ml−1, P < 0.001, Table 1).