Warfarin is a very important drug that is often applied after cardiac surgery. The proper use of this drug is extremely closely related to whether the treatment of the disease achieves its ultimate goal (prolonging life expectancy and improving quality of life). Below, common questions about anticoagulation therapy with warfarin are answered one by one in layman’s terms as concisely as possible. 1.Why warfarin anticoagulation therapy is needed Warfarin has anticoagulant effect, so it is used to prevent the formation of blood clots in human body. Under normal circumstances, blood flows smoothly and constantly in the heart and blood vessels, and the places where blood touches are covered by a layer of vascular endothelial cells, so there is no direct contact between blood and extravascular tissues, no direct contact between blood and foreign bodies, and no obstruction or stagnation of blood flow. When any one of these three “no’s” occurs, the clotting process is activated and a thrombus is formed. After cardiovascular surgery, direct contact of a foreign body with the blood, trauma, exposure of tissue without endothelial cell coverage in the lumen of the vessel or in the heart, atrial fibrillation or ventricular wall tumors resulting in slow or even stagnant local blood flow can lead to thrombosis in the heart or blood vessels. In addition, a hypercoagulable state of the blood due to physical causes or surgical stimulation can also lead to thrombosis. The following conditions commonly require warfarin treatment: implantation of mechanical heart valves, atrial fibrillation, deep vein thrombosis, pulmonary artery embolism, implantation of artificial vessels in the venous system (e.g., total vena cava-pulmonary artery anastomosis), implantation of artificial vessels in peripheral arteries, myocardial infarction combined with large ventricular wall tumors with intraventricular thrombosis, and antiphospholipid antibody syndrome. In cardiac surgery, warfarin is used most often in patients after valve surgery. Anticoagulation with aspirin alone in patients with persistent atrial fibrillation is less effective than with warfarin. If a patient is also equipped with a prosthetic heart valve, warfarin anticoagulation should be used regardless of whether it is a bioprosthetic valve or not. Patients who need to receive warfarin anticoagulation therapy should start taking warfarin orally as soon as the tracheal tube is removed and the patient is able to drink, with an initial dose of 5-6 mg. From then until discharge, the patient’s blood will be drawn daily during the postoperative recovery period to check the INR, and the doctor will adjust the warfarin dosage according to the daily test results in order to achieve the expected anticoagulation strength as soon as possible, and The warfarin dosage is adjusted by the physician based on the daily test results in order to achieve the desired anticoagulant strength as soon as possible and to bring the warfarin dosage to a relatively stable level before the patient is discharged. After discharge, the patient will need to start taking the warfarin dose on his or her own, based on the warfarin dose a day or two before discharge. We recommend that patients take their medication at night on a regular daily basis. There are two advantages to doing this. One is that the INR is checked in the morning and the results may be available by noon, so you may have to consult with your doctor if you have questions, and it is possible that the final decision on the dose will be made by afternoon. If you take the medication in the morning or morning, the dose is not appropriate, but has been taken, can only be adjusted the next day, inconvenient. Secondly, if you take the medication at a fixed time, you will develop a habit in the long run and will not miss a dose. When you are in the hospital, INR is checked every day, and when you are discharged from the hospital, the ward doctor will give the patient 3 lab sheets. These 3 lab sheets are to facilitate the patient’s post-operative review. Patients can also go to the hospital’s simple outpatient clinic to have their labs ordered. After discharge from the hospital, laboratory tests are usually performed once every 2-3 days. That anticoagulation record sheet from the discharge should come into play at this time. The patient should record the daily warfarin dose and the results of each INR on that anticoagulation sheet. If the INR is within the appropriate range, maintain the current dose, and if it is outside the range, adjust the medication.