Acute Kidney Injury After Cardiac Surgery

Overview

Acute kidney injury (AKI) is common after cardiac surgery. The diagnosis is based on the criteria defined by the Kidney Disease Improving Global Outcomes (KDIGO) classification: oliguria and elevation of serum creatinine. However, oliguria is not specific of AKI and elevation of serum creatinine is too late. Therefore, new methods have been developed to earlier assess the risk of AKI. Among those methods, it has been shown that the increase of urinary dosage, in the hours following the surgery, of two proteins (Tissue Inhibitor of Metallo-Protease 2 (TIMP2) and Insulin Growth Factor Binding Protein 7 (IGFBP7)) is associated with an increased risk of occurrence of AKI in patients hospitalized in intensive care unit. The Nephrocheck® test combines the urinary dosage of those two proteins TIMP2 and IGFBP7. Insofar as post-surgery low cardiac output is one curable cause of AKI, the early detection of early kidney risk allows corrective measures to stabilize hemodynamic state and thus to reduce the risk of AKI.

The usual diagnostic markers of AKI are defaulted. Indeed, oliguria tends to overstate the impact of AKI, up to 40-50% of patients. Postoperative increased serum creatinine is a late marker for the AKI. Furthermore, perioperative hemodilution and serum creatinine kinetic delay the postoperative peak of serum creatinine from 48 to 72 h. Nephrocheck® test combines the urinary dosage of 2 proteins (TIMP2 and IGFBP7). These 2 proteins are excreted by the tubular cell in case of suffering whatever the origin, for example tissue hypoxia by low renal blood flow or a systemic inflammatory response. In a medical ICU, the test performed within 4 to 12 hours after kidney aggression can predict the onset of persistent AKI beyond 4 weeks. Until randomization, all patients are treated according to the standard of care for the center. This includes a blood test upon arrival in the intensive care unit and continuous monitoring of vital parameters.