A 3-month-old female infant was found to have a large amount of pericardial effusion by cardiac ultrasound due to restlessness, rapid breathing, and increased heart rate on the 18th day after atrial septal defect and ventricular septal defect repair surgery. She was scheduled for an emergency pericardiotomy. A large amount of pericardial effusion can compress the heart, which restricts the ventricular diastolic filling, reduces the venous return, and decreases the cardiac output and blood pressure. In severe cases, it can lead to pericardial tamponade and acute circulatory failure. Cardiac compression symptoms can be effectively alleviated by effusion draining. The goal of anesthetic management for children with large amounts of pericardial effusion is to maintain sufficient cardiac output by avoiding the occurrence of bradycardia, hypotension, hypovolemia, and myocardial suppression. Due to the sharp increase of blood return to the heart after pericardial decompression, the risk of congestive heart failure is significantly increased. Therefore, the anesthesiologist should be particularly vigilant for the possible occurrence of congestive heart failure.