Acute kidney injury in cardiac surgery.

INTRODUCTION: Acute kidney injury (AKI) associated with cardiac surgery is a common postoperative complication that increases the morbidity and mortality substantially. However, there is limited information of AKI after cardiac surgery in our institution.

MATERIAL AND METHODS: We conducted a prospective, observational, and longitudinal analysis of adult patients that underwent to cardiac surgery requiring cardiopulmonary bypass and aortic cross clamp. Patients with preoperative chronic renal insufficiency that were on dialysis, with AKI detected up to 24 h before the procedure, or that received contrast agents 72 h before surgery were excluded. AKI was defined by the AKIN classification. Patients were followed up to 7 days after surgery or before if discharged from the intensive care unit. We analyzed age, sex, body mass index (BMI), co-morbilities, previous cardiac surgery, left ventricular ejection fraction, New York Heart Association class, type of procedure, cardiopulmonary bypass time, cross clamp time and bleeding.

RESULTS: Our analysis included 164 patients submitted to cardiac surgery. In the follow up, 84% did not have AKI, 11% had AKIN 1 and 2 accompanied by increase in serum creatinine and 6% had AKIN 3. Patients with AKI were older, had a higher preoperative creatinine, plasma glucose level, and a lower left ventricular ejection fraction. All together patients with AKIN had a longer hospital stay and a higher mortality (p < 0.001). The preoperative use of insulin was associated with the development of AKI, and there was a higher number of patients with a New York Heart Association class III and IV for heart failure in the more sever forms of AKI (p = 0.01). The logistic regression analysis revealed that patients with a high preoperative blood urea nitrogen (> 20 mg/dL) creatinine level (> 1 mg/dL), uric acid (> 7 mg/dL) and lower albumin (< 4 g/dL) or lower intraoperative hemoglobin (< 8 g/dL) had a higher risk for postoperative AKI.

CONCLUSIONS: The prevalence of AKI in our Institute is of 17%. Patients with AKIN 2 and 3 had a higher mortality and a longer stay in the intensive care unit. The major risk factors for AKI development were identified.