Since the contact between the prosthetic valve and blood can easily cause platelet coagulation and the formation of thrombus, in serious cases, thrombus may be dislodged and cause vascular embolism in various organs, leading to hemiplegia, aphasia, arterial embolism of lower limbs, etc. It may even jam the prosthetic valve leaflet and prevent the valve from opening, leading to heart failure or sudden death. Therefore, a very important aspect after valve replacement is proper anticoagulation.
Insufficient anticoagulation can easily lead to thromboembolism and other evils, while excessive anticoagulation can lead to bleeding, mainly nasal bleeding, gum bleeding, stomach bleeding, hematuria, more than menstruation, and even intracranial bleeding, etc. Therefore, anticoagulation is a major life-related issue and must be handled in close cooperation with medical personnel.
1.Anticoagulants and their use
(1) At present, the main anticoagulants are Warfarin. Warfarin oral anticoagulation, 60 kg weight patients, generally need about 2.5 mg of warfarin once a day. However, the sensitivity of anticoagulants varies from patient to patient, so regular blood sampling for prothrombin time and activity is required.
(2) Warfarin is absorbed through the gastrointestinal tract, and more than 90% is bound to plasma proteins and metabolized by the liver, which starts to work 12 hours after taking the drug and reaches its peak effect in 48 hours, with a plasma half-life of 44 hours. Anticoagulants are taken once a day for 5-7 days to reach steady state, so the maintenance dose should be changed every 5-7 days. The prothrombin time returns to normal 5 to 6 days after discontinuation. In case of severe bleeding, vitamin K (VitaminK) can be used to counteract the effects of warfarin.
(3) Warfarin should be used for the first time 24 to 48 hours after removal of pericardial and mediastinal drains, and the dose should be adjusted according to the dynamic changes in prothrombin time and activity.
(4) The normal value of prothrombin time is 12 to 14 seconds, and the activity is above 80%. After valve replacement, the prothrombin time should be maintained at 1.5 to 2.0 times the normal value (generally at 19 to 24 seconds). The WHO (World Health Organization) now advocates an international standard for oral anticoagulant testing, the international normal ratio (INR). The INR should be controlled between 2 and 3 after valve replacement. the INR value overcomes the disadvantage of deviations in the measured values of each medical unit and can be used universally in each hospital. Chinese people are prone to bleeding tendencies, so anticoagulation should not be used in excessive amounts to avoid bleeding phenomena.
(5) If the prothrombin time is more than 2 times normal the dosage can be reduced by 1/4 or 1/8; if the prothrombin time is higher than 30 seconds, the dosage can be stopped once and adjusted after laboratory tests the next day. Prothrombin time or activity should be measured 4 to 5 days after each dose adjustment.
(6) If the dose is too high, pay attention to close observation. If epistaxis, gum bleeding, hematuria, black stool, intra-abdominal bleeding manifestation (abdominal pain), intracranial bleeding manifestation (coma) and other signs of bleeding appear, go to the hospital immediately for laboratory tests, reduce the dose or stop taking Warfarin, and if necessary, inject vitamin K against, or transfuse blood, plasma, platelets, etc.
(7) If there is blunted valve tone, heart failure, hemiplegia, aphasia, painful arterial embolism in the limbs, etc., review the prothrombin time and activity, and increase the anticoagulant dose if thrombosis is confirmed.
(8) The general maintenance dose of Warfarin is around 2.5mg, but there are great individual differences. If satisfactory anticoagulation effect cannot be achieved after using 5mg of Warfarin, it indicates that the patient is not sensitive to Warfarin, and other anticoagulants should be added, such as using aspirin, etc.
1 to 2 tablets should be added daily, while prothrombin time and activity should be monitored.
(9) During the patient’s hospitalization, prothrombin time or activity can be measured once a day, after a period of time to find the appropriate maintenance amount, can be changed to every other day; if the measurement is still stable after 3 to 4 times, can be changed to once a week; if the measurement is stable after 3 to 4 times, can be extended to once every half month. By analogy to 1 month. Even if the conditions are poor, it should be measured once every 3 months to prevent thromboembolism or bleeding. Once a month is recommended. If after adjusting the agent, it should be measured again in 4 to 5 days until it is stable, and then the interval of measurement should be extended appropriately.
2.The effect of food, drugs and other diseases on anticoagulation effect
(1) The effect of food
Foods rich in vitamin K can reduce the effect of anticoagulant drugs. The following foods are rich in vitamin K. The content of vitamin K (mg) per 100g of dry food is: spinach (4.4), cabbage (3.2), cauliflower (3.0), peas (2.8), carrots (0.8), tomatoes (0.6), potatoes (0.16), pig liver (0.8), and eggs (0.8). Although the above foods are rich in vitamin K, as long as a balanced diet, regular measurement of prothrombin time and activity, it is possible to adjust the dose of anticoagulants, no need to deliberately favor or prohibit a certain food.
(2) The influence of drugs
Drugs that enhance the effect of anticoagulant drugs are.
① Broad-spectrum antibiotics that reduce intestinal production of vitamin K.
(②Aspirin, Antomin, sulfonamides, and propofol can compete with warfarin for plasma protein binding sites, increasing the free blood concentration of the latter.
③Liquid paraffin can reduce the absorption of vitamin K.
④Chloramphenicol, metronidazole, metronidazole, and ethanol can inhibit the enzymes that degrade warfarin, resulting in a relative increase in warfarin concentration.
⑤ Phenytoin sodium, toluene, and sulfobutylurea have the same metabolic pathway.
(6) Aspirin and acetaminophen have anticoagulant synergistic effects.
(⑦Salicylates, botrytisine, chlorpromazine, and benadryl have the effect of interfering with platelet function.
(8) Quinidine, metformin, phenylephrine, and antomin have enhanced anticoagulant effects.
Drugs that reduce the anticoagulant effect.
①Decholamine can bind to anticoagulants in the intestine.
(ii) Hypnotics, rifampin, and ashwagandine have the effect of increasing the activity of enzymes in the liver and accelerating the metabolism of warfarin.
③Estrogens and oral contraceptives can increase the level of coagulation factors in the blood.