Preoperative n-terminal pro-b-type natriuretic peptide and postoperative acute kidney injury in cardiac surgery: a mediation analysis of intraoperative hypotension

Background: Preoperative N-terminal pro-B-type natriuretic peptide (NT-proBNP) and intraoperative hypotension (IOH) are associated with acute kidney injury (AKI) after cardiac surgery. However, the mediating role of IOH between preoperative NT-proBNP and AKI is unclear. Methods: This secondary analysis enrolled patients aged 18 yr or older undergoing cardiac surgery with general anesthesia. Increased NT-proBNP was defined as a preoperative NT-proBNP concentration > 900 pg/mL. IOH was defined as MAP less than 65 mm Hg and was characterized by the cumulative duration, area under the curve (AUC), and time-weighted average (TWA). Mediation analysis was used to estimate the relationships between NT-proBNP, IOH, and AKI. Results: Among 972 identified patients, 321 (33.0%) showed evidence of increased preoperative NT-proBNP. These patients had an increased occurrence of postoperative AKI (166 of 321 [51.7%] vs 164 of 651 [25.2%], P < 0.001). When IOH was characterized by the cumulative duration, AUC, and TWA, significant indirect associations with IOH were observed between increased preoperative NT-proBNP and postoperative AKI [(0.016; 95% CI, 0.005–0.029), (0.019; 95% CI, 0.007–0.034), and (0.019; 95% CI, 0.007–0.034)], respectively accounting for 13.9%, 16.4%, and 16.5% of the total effect. Conclusion: IOH mediates a statistically significant portion of the relationship between increased preoperative NT-proBNP and postoperative AKI in cardiac surgery patients. Further research is needed to investigate whether optimizing anesthesia management by alleviating intraoperative hypotension could reduce the risk of AKI in patients with increased preoperative NT-proBNP.