Influence of the definition of acute renal failure post-cardiac surgery on incidence, patient identification, and identification of risk factors

OBJECTIVE: Acute renal failure post-cardiac surgery (RF) is a major complication and is associated with increased postoperative morbidity and mortality. Early recognition and identification of risk factors for RF is therefore important. However, several definitions of RF are used. The intention of this study is to evaluate if the used definitions influence the incidence and the identification of risk factors for RF. METHODS: We identified, after exclusion of 13 patients with preoperative dialysis, 995 consecutive patients undergoing cardiac surgery at the UMC St. Radboud Medical Center between January 2009 and 15 February 2010 as our study cohort. Apart from the definition used by the Society of Thoracic Surgeons, we selected five major international studies concerning RF, each using a different RF definition. These six definitions were used to evaluate the incidence of and identification of risk factors for RF in our study cohort. RESULTS: There is not only a statistically significant difference in incidence (range 4.94-38.1%) of RF between the definitions (p < 0.001), but also, the patients identified with RF differ. Univariate analysis identified for each definition several common but also several different risk variables. Multivariate analysis identified also different independent predictors, with different odds ratios for RF for each definition. CONCLUSION: This study shows that the used definition of RF influences not only the incidence of RF, but also patient identification and the identification of risk variables.