Patients who have undergone heart valve replacement or repair surgery require warfarin for a period or lifetime of anticoagulation to prevent blood clots from forming in the body. However, some patients lack a proper understanding of warfarin anticoagulation therapy, which affects the effectiveness and safety of the entire treatment process. This article addresses some common clinical questions, hoping to help patients have a comprehensive and correct understanding of warfarin anticoagulation therapy. Patients taking warfarin should develop the habit of taking the medication regularly, usually 2 hours after dinner. If a missed dose occurs, it should be made up as soon as possible if it is not far from the scheduled time, but do not superimpose the missed dose on the next dose. Patients should not stop or reduce the dosage at will, and should not change products of different manufacturers at will. When taking multiple drugs at the same time, warfarin should be taken half an hour before the other drugs. Monitoring of prothrombin time Patients taking warfarin for postoperative anticoagulation are monitored for prothrombin time (PT value for short) to determine whether anticoagulation is adequate and to increase or decrease the dose based on this. Since the values measured vary from hospital to hospital, it is important to establish a normal control value (the PT value of a normal person measured with that reagent). A certain anticoagulation range needs to be achieved with warfarin, usually 1.5 to 2.0 times the normal control PT value for patients with valve replacement. For example, if the normal control value of PT in a hospital is 12 seconds, then the anticoagulation range that the patient needs to achieve is 18 to 24 seconds. Currently, most major hospitals in China and abroad use the International Normalized Ratio (INR value for short) as a measure of anticoagulation effectiveness. the INR is calculated from the PT value and the International Sensitivity Index (ISI) of the assay reagent. By excluding the influence of different reagents, it makes the INR value more comparable and facilitates the unification of medication standards. Therefore, INR values can be considered as standardized PT values, both of which reflect prothrombin time. Usually, the anticoagulation range required for INR values in patients undergoing valve replacement is 2 to 3. This value is constant, i.e., the INR value measured should be within this range regardless of the hospital where the patient is seen. How often blood tests are needed For one month after surgery, patients are advised to have their blood tested once a week to ensure safety, as the prothrombin time is not yet stable. When the prothrombin time is stable, it can be extended to once a month. However, once the patient has symptoms such as large petechiae on the skin all over the body, nosebleeds, and gastrointestinal bleeding, he should go to the hospital for examination and determination of prothrombin time to rule out the possibility of warfarin overdose to avoid further serious intracranial bleeding. What factors affect the anticoagulation effect Some studies have shown that the patient’s age, genetics, physical and dietary conditions, as well as certain drugs and foods, can have an effect on the anticoagulation effect of warfarin. Older people over 60 years of age have a reduced ability to clear warfarin and may reduce the dose appropriately. Genetic factors can lead to changes in certain enzymes in liver metabolism as well as changes in their own coagulation factors, all of which can affect the anticoagulant effect of warfarin. Patients with poor liver function, biliary tract pathology, poor diet, and chronic alcohol consumption can cause enhanced anticoagulant effects of warfarin. Drugs that enhance the anticoagulant effect of warfarin include: broad-spectrum antibiotics, antiplatelet agents, chloral hydrate, hydroxyproteasone, methylsulfonylurea, quinidine, salicylates, promethazine, metronidazole, cimetidine, steroids, etc. Drugs that weaken the anticoagulant effect of warfarin include: barbiturates, phenytoin sodium, carbamazepine, rifampin, oral contraceptives, vitamin K1, vitamin K3, estrogen, and sleeping pills. Foods that enhance the anticoagulant effect of warfarin include: grapefruit, fish oil, mangoes, etc. Foods that weaken the anticoagulant effect of warfarin include: green leafy vegetables, egg yolk, pork liver, green tea, etc. (mainly rich in vitamin K) as well as seaweed, avocado, soy milk, etc. How to use the medication for other surgeries If you have other diseases that require surgery while taking warfarin anticoagulation, you are usually in a dilemma if you stop taking the medication because of the risk of embolism and if you continue to take the medication because of the possibility of complications of intraoperative and postoperative hemorrhage. The correct approach is to discontinue warfarin 3 days prior to surgery and switch to low molecular heparin 5000 units subcutaneously twice daily until 12 hours prior to surgery. Fertility and Warfarin Anticoagulation Warfarin penetrates the placental barrier and has teratogenic effects on fetuses less than 3 months of age, and also has adverse effects on fetuses older than 3 months of age that cause central nervous system abnormalities and hemorrhage. Therefore, in the past, it was usually recommended that women of childbearing age taking warfarin should prefer not to have children. In recent years, it has been reported in China and abroad that when a single low-dose warfarin anticoagulation (<5 mg/day) is given during pregnancy, the fetal teratogenicity rate is less than 5%. Therefore, women of childbearing age who have undergone valve replacement surgery should complete the entire pregnancy and delivery process under the close observation and treatment of a specialist after their cardiac function has recovered to grade 1 or higher 2 years after surgery if they wish to have children. The use of low-molecular heparin (which does not cross the placental barrier) as an alternative to warfarin for anticoagulation has not been authoritatively evaluated in terms of risk to mother and child and cannot be promoted as standard therapy. Warfarin is rarely secreted from breast milk, so it can be used without interruption in breastfeeding women.