The daily physiological requirement for a normal infant of less than ten kilograms is Kg X 100ml/day; eg: an infant of 8Kg can be fed with 800ml/day of fluid. For children with simple precordial diseases such as atrioventricular defects and normal cardiac function after PDA, the physiological requirement can be multiplied by 100ml per kilogram of body weight. For children with slightly poor cardiac function, the amount can be reduced appropriately by giving 80%-90% of the physiological requirement; for complex precordial diseases, such as F4, transposition of the aorta, complete pulmonary vein ectopic drainage, complete endocardial cushion defect, etc., the amount of fluid intake should be limited in the early postoperative period, we should eat less and more, avoid overeating, and generally give 70%-80% of the physiological requirement, and observe the amount of urine, if there are swollen eyelids and large liver, it may be If there is swelling of the eyelids and large liver, it is possible that there is too much fluid or poor cardiac function, and it is necessary to consult a doctor in time. When the child has diarrhea, vomiting or fever, the amount of fluid can be released appropriately to replenish the lost water. If the child has excessive urination, sunken eyes, and thirst, fluid intake should be increased and oral diuretics should be adjusted to reduce the number of doses.