Comparison of Diagnostic Criteria for Acute Kidney Injury in Cardiac Surgery

Background: There is considerable controversy regarding the diagnosis of Acute Kidney Injury (AKI), and there are over 30 different definitions. Objective: To evaluate the incidence and risk factors for the development of AKI following cardiac surgery according to the RIFLE, AKIN and KDIGO criteria, and compare the prognostic power of these criteria. Methods: Cross-sectional study that included 321 consecutive patients (median age 62 [53-71] years; 140 men) undergoing cardiac surgery between June 2011 and January 2012. The patients were followed for up to 30 days, for a composite outcome (mortality, need for dialysis and extended hospitalization). Results: The incidence of AKI ranged from 15% - 51%, accordingly to the diagnostic criterion adopted. While age was associated with risk of AKI in the three criteria, there were variations in the remaining risk factors. During follow-up, 89 patients developed the outcome and all criteria were associated with increased risk in the univariate Cox analysis and after adjustment for age, gender, diabetes, and type of surgery. However, after further adjustment for extracorporeal circulation and the presence of low cardiac output, only AKI diagnosed by the KDIGO criterion maintained this significant association (HR= 1.89 [95% CI: 1.18 - 3.06]). Conclusion: The incidence and risk factors for AKI after cardiac surgery vary significantly according to the diagnostic criteria used. In our analysis, the KDIGO criterion was superior to AKIN and RIFLE with regard its prognostic power.