[Acute renal failure after cardiac surgery: evaluation of the RIFLE criteria]

Introduction: Acute renal failure is a common complication is a common complication in cardiac surgery under cardiopulmonary bypass. It is associated with increased morbidity and mortality. Acute kidney injury (AKI) is a clinical entity encompassing the entire spectrum of acute renal failure, since minor alterations to the need for renal replacement therapy. The RIFLE criteria have been proposed for defining and classifying AKI. The aim of our study was to apply the RIFLE to a population of patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and to assess its relevance in terms of risk factor for hospital mortality compared to other risk factors.

Methods: In this prospective observational study, we included patients who were operated for programmed cardiac surgery. The assay of blood creatinine was performed at admission, after surgery and daily for 5 days post-surgery. The AKI was evaluated according to the criteria of classification RIFLE. The patients were divided into three levels of severity based on plasmatic creatinine (R: Risk=creatinine×1.5; I: Injury=creatinine×2; F: Failure=creatinine×3). We have analyzed the different perioperative parameters and we sought associations with the occurrence of AKI. We also studied the impact of AKI on length of stay in ICU and mortality early and late.

Results: One hundred and thirty-six patients were included. AKI was diagnosed in 17.6% of patients (RIFLE-R: 8.8%, RIFLE-I: 5.9% and RIFLE-F: 2.9%). AKI significantly prolongs the duration of ICU stay (7±3.8 versus 5±2.3 days; P=0.02). RIFLE-R patients had a mortality of 8.3%, compared to 12.5% for I and 50% for F. Patients without PORD had a mortality of 1.8%. In univariate analysis, age, the EURO score, preoperative renal dysfunction, duration of aortic clamping, duration of CPB and C-reactive protein (CRP) were significantly associated with the occurrence of AKI. In multivariate analysis only preoperative renal dysfunction (clearance less than 63 mL/min) and CRP greater than 158 mg/L were found as independent factors of occurrence of AKI.

Conclusion: RIFLE classification seems to be a reliable way to detect acute renal failure and to classify its severity. The AKI is a common complication and is associated with increased morbidity and mortality. Identifying the risk factors allows a better prevention strategy.