Monitoring of anticoagulation and thrombolytic therapy Anticoagulation and thrombolytic therapy should be carried out under standardized and scientific monitoring, neither insufficient dose to achieve the desired effect, nor too large a dose to issue blood. (1) APTT (activated partial thromboplastin time): 1.5~2.5 times longer than the normal control group (people can be controlled at 1.5~2.0 times) to achieve the best anticoagulation effect with minimal risk of bleeding. 1.5 times the APTT is said to be the threshold of heparin effect, APTT should be tested every 6h. (2) ACT (activated clotting time): the normal reference value is 74~125s, maintained at 360~450s under extracorporeal circulation. when >500s or bleeding occurs, it can be neutralized with fisetin to reach 80~120s. (3) PT (prothrombin time): normal is 11~13s, and should be maintained within 25s during treatment. (4) International normalized ratio (INR): In 1992, the World Health Organization established a unified standard for monitoring oral anticoagulation therapy: INR= (patient PT/average normal PT) ISI, ISI is the international sensitivity index. For national population, INR should be controlled at 2.0~2.5, when INR is 4.0, the risk of bleeding increases significantly, when INR is 5.0, the patient is at risk of bleeding. Some scholars divided 364 patients with DVT into two groups, who were given oral warfarin for 6 months. Group 1: 192 patients (52.7%), INR 1.9-2.5. Group 2: 172 patients (47.3%), INR 2.6-3.5. Results: Small bleeding: 1.04% in group 1, 4.06% in group 2. For larger bleeding: 1.04% in group 1 and 6.03% in group 2. The difference between the two was significant (small bleeding: epistaxis, subcutaneous bleeding. Major bleeding: gastrointestinal bleeding, joint hemorrhage, etc.) [10]. There are 3 ways to reduce INR: ① Discontinuation of anticoagulants: INR must be reduced from 2~3 d to normal in 4~5 d after discontinuation. ② Oral vitamin K11?0~2?5 mg/d can reduce 95% of patients with INR between 4~10 within 24 h. ③In the case of severe warfarin overdose or more serious bleeding, the most rapid and effective method is transfusion of fresh plasma or prothrombin complex. (5) antithrombin activity (AT:A) measurement: the anticoagulant effect of heparin mainly depends on AT (antithrombin), normal plasma AT:A is 80% ~120%. When AT:A is lower than 60%, the effect of heparin is reduced, and when it is lower than 30%, heparin almost loses its anticoagulant effect. Therefore, during the application of heparin, it is important to keep the AT:A around 80%, if it is less than 60%, it should be supplemented with plasma or antithrombin in a timely manner He, Department of General Surgery, Huashan Hospital, Fudan University