Perfusion parameters during cardiopulmonary bypass as a predictor of acute kidney injury after aortic valve replacement

BACKGROUND: Acute kidney injury (AKI) is a major complication after cardiac surgery and significantly affects postoperative mortality and morbidity. This study was conducted to evaluate the association between target pump flow to achieve adequate oxygen delivery (DO(2)) and postoperative renal function after aortic valve replacement. METHODS: From January 2017 to May 2020, 281 patients (male:female, 160:121; mean age, 68±11 years) who underwent aortic valve replacement were retrospectively reviewed. Target pump flow was calculated based on DO(2) level of 280 mL/min/m(2). The primary endpoint was postoperative renal dysfunction, defined as the ratio of postoperative peak creatinine level to preoperative value. The ratio of the lowest actual pump flow to the ideal target pump flow, other hemodynamic variables related with cardiopulmonary bypass, intraoperative transfusion, and preoperative characteristics were analyzed to identify factors associated with the primary endpoint using a multivariable linear regression model. RESULTS: Preoperative and peak postoperative creatinine levels were 0.94±0.33 mg/dl and 1.15±0.56 mg/dl, respectively (ratio, 1.22±0.33). The ideal target pump flow was 4.70±0.59 L/min, whereas the lowest actual pump flow was 3.77±0.47 L/min (ratio, 0.81±0.13). The multivariable model showed that the ratio of the lowest pump flow to target pump flow (β±standard error, –0.405±0.162, P=0.013), as well as sex, stroke history, emergency operation, and transfusion of red blood cells were associated with the primary endpoint. CONCLUSIONS: Low actual nadir pump flow compared to the ideal target pump flow based on DO(2) is associated with the risk of AKI after aortic valve replacement.