1.The mechanism of action of warfarin Warfarin mainly affects the exogenous coagulation system and competes with vitamin K to inhibit the synthesis process of some coagulation factors, so that the synthesis of this part of coagulation factors is reduced, thus exerting an anticoagulant effect. 2.Anticoagulation standard: oral warfarin has been widely clinically proven as anticoagulation therapy after heart valve replacement to prevent thrombosis. The anticoagulant strength of warfarin is monitored by Prothrombin Time (PT) and International Normalized Ratio (INR). However, the anticoagulation criteria have not been fully standardized, but there is a wide range of criteria used in different valves, at different times, and in different patients, with an emphasis on dynamic observation of PT and INR changes followed by appropriate adjustments. For mechanical valve replacements, oral warfarin is given for life after surgery; for biological valve replacements, oral warfarin is given for six months after surgery. The current more consistent view is the low-intensity anticoagulation criteria, that is, PT should be in the range of 18-24s and INR should be in the range of 1,8-2,5 after taking the drug. The specific classification is as follows: if it is simple aortic valve replacement, the INR should be kept at 1,8-2,3; if it is simple mitral valve or aortic valve plus mitral valve replacement, the INR should be kept at 1,8-2,5; if there is a tricuspid prosthetic mechanical valve, the INR should be kept at 2,0-2,5. Patients with a bioprosthetic valve but combined with atrial fibrillation, or without valve disease simple atrial fibrillation, their INR should Patients without atrial fibrillation who use a bioprosthetic valve or have a valvuloplasty ring implanted in the mitral or tricuspid position must be treated with warfarin anticoagulation within six months of surgery, and the INR should be maintained at 1,5-2,0. Patients who undergo total cavopulmonary anastomosis should be treated with warfarin anticoagulation for the first three months after surgery, and the INR should be maintained at 1,8-2,3. 3. The dose of warfarin should be adjusted to 0, 625C1, 25 mg, and PT should be reviewed within one week after dosage adjustment, with special attention to the trend of PT and INR. If the assay value continues to rise or fall, the dose should be adjusted although it is still within the desired range. If the INR is greater than 3 or 0 or the PT is greater than 30 seconds, the drug must be stopped on the same day and the test continued the next day, and the dosage decided according to the PT value. The rule of thumb is that if the INR value differs significantly from the target value, be sure to test daily on subsequent days until your INR test value is at the required anticoagulation strength. Post-valve replacement patients are prone to complications of anticoagulation therapy with embolism or bleeding during the first two years of anticoagulation therapy, especially the first year of initiation. Early after the patient’s surgery, the surface of the foreign body in the heart is not yet fibrinous and does not cover the vascular endothelium, and the area of exposed foreign body that can trigger a coagulation response is relatively large. Patients start to detect anticoagulation therapy by themselves and are not experienced enough to detect the problem and adjust the warfarin dose in time. Therefore, early after surgery, patients must have more laboratory tests, pay attention to the adjustment of warfarin dose, and must consult more doctors with experience in anticoagulation therapy when they are not sure. 4, the main complications warfarin as a heart valve replacement after anticoagulation therapy its primary complication is bleeding. The most common site of bleeding is the skin mucosa, followed by the gastrointestinal tract, genitourinary tract and intracranial area. According to the degree of bleeding, it can be divided into mild and severe. Mild bleeding is skin petechiae, hematuria, nasal and gum bleeding, heavy menstrual flow, and tarry stools. Severe hemorrhage refers to intracranial hematoma, hemoptysis, etc. Most of the deaths caused by anticoagulated bleeding are intracranial. The cause of bleeding may be related to other factors besides the high intensity of anticoagulation: such as the patient’s history of bleeding disorders, history of hypertension, abnormal liver and kidney function, etc. Its management: treatment with appropriate amounts of vitamin K, and fresh plasma transfusion is recommended. Another important complication after bleeding is embolism, with an incidence of 0 to 4.2 G. Although embolism is rarely fatal, it is a major cause of death and disability in the long term after mechanical valve replacement. The factors associated with the occurrence of embolism are mainly the insufficient anticoagulation strength and other drug interactions. Drug interactions are an important but often overlooked problem in warfarin anticoagulation. Aspirin, amiodarone, cimetidine, tetracycline, quinolones, fluconazole, metronidazole, and many other drugs increase the anticoagulant effect of warfarin and the risk of bleeding. When combined with amiodarone, the maintenance dose of warfarin should be reduced by half. Barbiturates, carbamazepine, and rifampin reduce the anticoagulant effect of warfarin. In both cases, care should be taken to adjust the warfarin dose or avoid combination. Foods that enhance the anticoagulant effect of warfarin: grapefruit, grapefruit, grapefruit juice, grapefruit juice, mango, fish oil. Foods that weaken the anticoagulant effect of warfarin: spinach, cabbage, leek, coriander, lettuce, celery, watercress, carrot, tomato, broccoli, cauliflower, cabbage, lettuce, green pepper, chili pepper, garlic, onion, egg yolk, soybean oil, cod liver oil, seaweed, avocado, animal liver, black tea, green tea. In short, warfarin dose individual differences, narrow therapeutic window, complex interactions with other drugs, natural foods on its anticoagulant effect and influence, a long time to use the appropriate, maintain the ideal anticoagulation strength is not easy indeed. The most important thing to remember is that if you are taking warfarin, don’t take the drug blindly and always go to the hospital for PT and INR testing.