Most patients with congenital heart disease will take diuretics to reduce the burden on the heart and maintain cardiac function. Since diuretics can lower potassium in the body and low potassium can lead to arrhythmias and other side effects, it is necessary to take potassium supplements at the same time as diuretics, which are usually prescribed together with diuretics when patients are discharged from the hospital. The principle of taking potassium supplements is “see urine to make up for potassium”. If children have ventricular premature beats and other arrhythmias, they should pay attention to them and take potassium supplements in time. 2, children with poor cardiac function may become resistant to diuretics after discharge due to long-term use of diuretics. If the daily dosage is taken and the daily intake and output are seriously high and low, it is necessary to add diuretics once or twice temporarily and pay attention to potassium supplementation when adding. 3.Some patients may experience the side effect of breast development after taking the diuretic spironolactone, if it occurs, the diuretic can be replaced. 4. The daily water intake of children in the early post-operative period after cardiac surgery is about 70ml-80ml/kg (not calculated in this way for adults), and then gradually additional according to the new function, and at the same time control the daily intake and output according to the discharge requirements.