Acute renal failure (ARF) is a complication associated with cardiac surgery with cardiopulmonary bypass (CPB) with an impact on morbidity and mortality.To identify risk factors associated with postoperative IRA according to pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease scale in children undergoing cardiac surgery with CPB.A nested case-control study was conducted. We included children under 16 years of age attended postoperative for CBP in a pediatric intensive care unit over a period of 18 months. The cases were those who developed ARF according to the classification pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease scale during their stay in the pediatric intensive care unit. Controls were those who did not develop this complication. Logistic regression analysis was performed and adjusted odds ratio (OR) and confidence intervals at 95% (95% CI) were calculated.91 patients (31 cases and 60 controls) with a median age of 20 months and predominance of males (53.8%) were analyzed. Independent risk factors for ARF were the intraoperative lactate level > 6 mmol/l (OR = 4.91; 95% CI 1.26-19.05; p = .02) and cyanotic heart disease (OR = 3.62; 95% CI 1.11-11.63; p = .03).This study identified that pediatric patients with lactate levels >6 mmol/l during CPB and those with cyanotic congenital heart disease are a subgroup of high risk to develop ARF after heart surgery and should be closely monitored to prevent, detect and/or treat this complication timely manner.