This retrospective observational study aims to identify risk factors for postoperative complications in children undergoing cardiac surgery at a tertiary hospital in Brazil. By analyzing both electronic and physical medical records, researchers will examine demographic, clinical, surgical, and laboratory data, focusing on variables such as cardiopulmonary bypass (CPB) time, use of vasoactive drugs, and the occurrence of complications such as arrhythmias, acute kidney injury, and infections. Statistical analysis will include both descriptive and inferential methods, with multivariate logistic regression used to identify predictors of adverse outcomes. The study will be conducted between 2025 and 2027 with an estimated budget of R$1,000. Its goal is to inform preventive strategies and optimize perioperative care, ultimately improving patient outcomes and reducing hospital costs.