Potassium in the blood is a very important electrolyte ion for maintaining the normal physiological function of all organs in the body, especially the heart. Too much or too little potassium in the blood can cause abnormalities in the rhythm and function of the heart, especially in patients who have undergone valve surgery. Potassium is mainly supplied through food. For example, meat, fruits, vegetables, and milk are all rich in potassium, so people who eat normally do not usually have low potassium. In the early stage after heart surgery, the patient’s gastrointestinal function has not yet fully recovered, and gastrointestinal reactions such as loss of appetite, poor appetite, nausea, etc. often occur, and the amount of food eaten is small. Valve replacement patients often take diuretics after surgery, which increases the amount of potassium excreted in the urine, all of which contribute to low potassium in post-surgical patients. In view of the importance of potassium to the heart, close monitoring of blood potassium is required in the early postoperative period. If potassium is low (blood potassium <3.5 mmol/L), oral or intravenous supplementation is required to avoid arrhythmias caused by low potassium. Excessive potassium is also not good. Patients taking oral potassium-preserving diuretics and potassium chloride extended-release tablets may have high potassium (blood potassium value >5.5 mmol/L) if they are further complicated by renal insufficiency, low urine output or taking other related medications that affect the potassium excretion from the urine, which is also detrimental to the heart. Ideal blood potassium range after cardiac surgery is 4.0-5.0mmol/L. Our recommended method: if the patient often has low potassium before discharge, need to take oral potassium citrate or potassium chloride extended-release tablets to supplement potassium (only supplement potassium when taking diuretics at the same time, remember not to take only potassium ion supplementation drugs, which will easily lead to the occurrence of severe hyperkalemia; not to take diuretics alone, to prevent the occurrence of hypokalemia), then try 2-3 days after discharge to supplement potassium. Then try to recheck blood potassium about 2-3 days after discharge. If the diet returns to normal and two consecutive rechecks of blood potassium are normal, the interval between checks can be prolonged to 1-2 weeks, and if it remains normal, then the frequency of laboratory tests can be reduced in the future. However, frequent checking is needed when there are special circumstances such as medication adjustment, diarrhea, and profuse sweating.