Deep vein thrombosis (DVT) is a disease caused by abnormal clotting of blood in deep veins, which mostly occurs in the lower limbs and is a more common complication of spinal cord injury, and dislodgment of thrombus can cause pulmonaryembolism (PE), which has a very high mortality rate, so this disease should be taken seriously. The main causes of DVT are venous wall damage, slow blood flow and hypercoagulable state of blood. The latter two are high-risk factors for the formation of blood clots.Clinical manifestations of DVT: 1. Symptoms: Swelling and pain in the affected limb, aggravated by activity, improved by elevation of the affected limb. Occasionally, there is fever and accelerated heart rate.2. Symptoms: swelling of the distal limb or the whole limb of the thrombus is the main feature, the skin is normal or mildly bruised, and the skin temperature is higher than that of the normal limb. Severe cases can be cyanosis, skin temperature is reduced. If the arteries are affected, the distal arterial pulsations may be weakened or absent. If the thrombus occurs in the venous plexus of the calf muscle, pressure pain at the site of the thrombus (positive Homans and Neuhof’s disease) can occur: Positive Homans’s disease: when the affected limb is straightened and the ankle joint is dorsiflexed, the diseased veins in the calf muscle are stimulated by passive pulling of the gastrocnemius muscle and the piriformis muscle, which causes deep pain in the calf muscle; positive Neuhof’s disease (i.e., gastrocnemius muscle pressure test): the diseased veins in the calf muscle are stimulated, which causes pain in the deep part of the calf muscle. Positive Neuhof’s disease (i.e., gastrocnemius muscle compression test): stimulation of diseased veins within the calf muscle, causing deep calf muscle pain. Later thrombus mechanization, often left with venous insufficiency, superficial varicose veins, hyperpigmentation, ulceration, swelling, etc., known as post-DVT syndrome (postthrombosissyndrome, PTS). Thrombus dislodgement can cause the manifestation of pulmonary artery embolism.Auxiliary examination of DVT 1, impedance volume tracing measurement: for symptomatic proximal DVT has high sensitivity and specificity, and operation is simple, low cost. However, for asymptomatic DVT, the sensitivity is poor and the positive rate is low.2. Plasma D-dimer assay: detected by enzyme-linked immunosorbent assay (ELISA), with high sensitivity. Acute DVT, D dimer 500ug/L has important reference value. Since patients are almost always positive for D dimer in the short-term postoperative period, it is of little value for the diagnosis or differential diagnosis of DVT, but it can be used for preoperative screening of patients at high risk of DVT. In addition, it is not specific for the diagnosis of venous thromboembolism, such as tumors, inflammation, infection, necrosis and many other conditions that can produce fibrin, D dimer can also be 500ug/L, so the predictive value is low, and can not be based on the diagnosis of DVT. the specificity of this test is low for the elderly patients over 80 years of age, and it is not appropriate to be used in these populations. 3, color Doppler ultrasonography: it has high sensitivity, high accuracy, and it is a non-invasive test for patients with high risk of DVT. It is a non-invasive examination and is suitable for screening and monitoring of patients. Careful non-interventional human vascular ultrasound can keep the sensitivity at up to 93~97% and specificity at 94~99%;. Highly suspicious individuals should be reviewed daily if negative. In conjunction with the presence or absence of thrombotic favorability, patients can be categorized as having a high, moderate, or low likelihood of DVT before performing ultrasound. If two consecutive ultrasound examinations are negative, patients with low possibility can be observed clinically, patients with medium and high possibility can be given anticoagulant therapy, and patients with high morbidity group should be considered to undergo venography if the second scan is still negative.4. Radionuclide angiography: utilizing nuclides to increase the concentration of nuclides in the lower extremity deep vein blood flow or blood clots, which is visualized by scanning, is a valuable non-invasive examination for DVT diagnosis. 5, spiral CT venography (computedtomo-venography, CTV): is a new diagnostic method of DVT in recent years, which can simultaneously check the situation of deep veins of the abdomen, pelvis and lower limbs. 6, venography: it is the “gold standard” for the diagnosis of DVT. Treatment of DVT I. Early DVT treatment Anticoagulation is the standard treatment for venous thromboembolism, and a large number of clinical randomized controlled experiments have confirmed that anticoagulation can inhibit the spread of thrombus, reduce the incidence of pulmonary embolism and death rate, as well as recurrence.Early anticoagulation of DVT can be injected with low molecular heparin and heparin (refers to ordinary heparin, hereinafter the same) subcutaneously. Depending on the needs of the disease, coapplication of vitamin K antagonists can be started on the first day of treatment, and heparin is discontinued after the INR is stabilized and greater than 2.0. Individual variability in heparin dosage for the application of regular heparin is large, so intravenous administration of heparin must be monitored to ensure efficacy and safety. Currently, the commonly used monitoring is the activated partial thromboplastin time (aPTT), and the therapeutic effect of heparin should be achieved and maintained as soon as possible at 1,5 to 2,5 times the pre-anticoagulation level. However, the aPTT does not always reliably reflect plasma heparin levels or heparin antithrombotic activity. The laboratory can determine the therapeutic range of aPTT in this laboratory based on anti-factor X activity equivalent to plasma heparin levels of 0, 30, and 7 IU/mL as measured by amide hydrolysis. Dosage adjustments can be made by direct assay of heparin levels in hospitals where available, and in heparin-resistant patients who require high daily doses of heparin and do not reach the therapeutic range of aPTT, the dose of heparin can be adjusted based on the determination of anti-factor Xa. Intermittent intravenous heparin has a higher risk of bleeding than continuous intravenous administration. Usage of heparin in the treatment of DVT (for reference): the starting dose of heparin can be given as a single dose of 6250 U, with subsequent adjustment of the heparin dose based on the aPTT results. The recommendation is to use subcutaneous low molecular heparin or intravenous and subcutaneous heparin for patients who have an objective basis for a confirmed diagnosis of DVT. For patients with high clinical suspicion of DVT, if not contraindicated, anticoagulation may be considered while awaiting test results, with the decision to continue anticoagulation based on the confirmed diagnosis. The combination of a vitamin K antagonist and low molecular heparin or heparin is recommended to be started on the first day of treatment and discontinued after the INR reaches 2.0. In patients with acute DVT subcutaneous heparin can be used as an alternative to intravenous heparin. Application of low-molecular heparin Low-molecular heparin has better predictability of pharmacokinetics and biological effects than heparin. Laboratory monitoring is not required in most patients if the dose of low molecular heparin subcutaneous injection is adjusted for body weight once or twice daily. Use with caution in renal insufficiency or pregnant women. Recent studies have shown statistically non-significant differences in the risk of recurrent venous thrombosis, pulmonary embolism, and hemorrhage between low molecular heparin and regular heparin, with the same results for both. Survival with low molecular heparin is better than heparin in patients with malignant tumors. There were no significant differences in safety and efficacy between different low molecular heparins. The efficacy and risks of low molecular heparin are comparable to those of heparin. The main advantage of low molecular heparin is that it is easy to use and mostly does not require monitoring. A 12-hourly subcutaneous injection of low-molecular heparin is recommended for patients with acute DVT; in patients with severe renal failure, intravenous heparin is recommended, and low-molecular heparin should be considered with caution. Thrombolytic therapy in theory, the use of thrombolytic drugs to dissolve venous thrombus, rapid relief of vascular obstruction can be used as one of the treatment measures for patients with DVT. Early thrombolytic therapy is effective, but thrombolytic therapy may increase the risk of bleeding. It is not certain that thrombolytic therapy for early DVT reduces the incidence of PTS. Recommended Treatment Severe iliofemoral vein thrombosis in the acute phase may be considered for thrombolysis with appropriate anticoagulation. Catheter thrombolysis Catheter thrombolysis has some advantages over systemic thrombolysis, but catheter thrombolysis has been reported to be associated with local and systemic bleeding and requires careful evaluation of benefit/risk in comparison with conventional anticoagulation before it is indicated in patients. There are national controlled clinical studies of systemic and catheter thrombolysis that conclude that catheter thrombolysis is associated with higher efficacy, shorter duration of therapy, and fewer complications than conventional drug therapy. There are small samples of case reports supporting the local application of thrombolytic drugs. In view of the lack of sufficient evidence-based medical evidence in China, catheter thrombolysis still needs to be strictly controlled for the indications at present. Recommendations The use of catheter thrombolysis should be limited to certain selective patients, such as patients with more severe iliofemoral vein thrombosis. Surgical thrombolysis Surgical venous thrombolysis is mainly used for early proximal DVT, and the usual complication of surgical thrombolysis is thrombus recurrence. However, its long-term efficacy such as PTS and patency rate remains uncertain. Therefore, it can be considered to be applied in severe patients, such as certain severe iliofemoral vein thrombosis and femoral cyanosis patients. There are no clinical randomized controlled trials of surgery versus non-surgery in China. There are clinical controlled trials showing that surgery is beneficial in reducing the incidence of post-thrombotic syndrome. There are only a few results from small randomized controlled trials abroad that confirm that surgery reduces pulmonary embolism and recurrence of early thrombosis as well as valvular function with good long-term efficacy. For long-term efficacy, the majority of these are currently observational case studies. It is recommended that embolization be considered in certain selective patients, such as more severe iliofemoral vein thrombosis. Inferior vena cava filtersInferior vena cava filters can prevent and minimize the occurrence of pulmonary embolism. The indications for placing an inferior vena cava filter are patients with proximal DVT in whom anticoagulation is contraindicated or complicated, recurrent thromboembolism in the setting of adequate anticoagulation, heparin-induced thrombocytopenia syndrome, recurrent pulmonary embolic episodes in combination with pulmonary hypertension, and concomitant surgical thrombolysis of the pulmonary arteries with endothelial debridement. Immediately after filter placement, anticoagulation should be performed. Although placing an inferior vena cava filter on the basis of anticoagulation reduces the incidence of pulmonary embolism, it does not improve the early and late survival of patients with first-ever VTE. However, with the prolongation of time, there is a higher tendency of recurrence of deep vein thrombosis in patients with placed filters. Foreign data show that the incidence of fatal pulmonary embolism can be below 1% after adequate anticoagulation. Therefore inferior vena cava filters are indicated for patients at high risk of pulmonary embolism. It is recommended that for most patients with DVT, it is recommended that vena cava filters not be routinely applied; for patients in whom anticoagulation is contraindicated or has complications, or in whom recurrent thromboembolism occurs despite adequate anticoagulation, it is recommended that inferior vena cava filters be placed. Postural therapy in patients with early DVT is recommended along with anticoagulation for a period of strict bed rest to prevent dislodgment of thrombus resulting in pulmonary embolism. However, in patients with chronic DVT, the rate of pain and swelling resolution is significantly faster in patients with exercise and leg compression than in patients on bed rest. Therefore, bed rest is not strictly required. It is recommended that patients with early DVT should mainly rest in bed with the affected limbs elevated. Long-term treatment of DVT Patients with DVT require long-term anticoagulation to prevent the development of symptomatic thrombosis and/or recurrent venous thrombotic events. The optimal course of long-term anticoagulant therapy for patients with DVT can be categorized into five grades based on observation. The grades are as follows: (1) first-episode DVT secondary to transient risk factors; (2) DVT with cancer and first-episode DVT; (3) first-episode spontaneous DVT (defined as DVT occurring in the absence of known risk factors); and (4) first-episode DVT with prothrombinogen genes and prognostic hallmarks associated with an elevated risk of recurrent thromboembolism (including anticoagulation factor III, protein C or protein S deficiency, prothrombinogen gene mutations such as factor VLeiden or coagulation rmaseogen 20210 gene mutations), patients with antiphospholipid antibodies, hypercysteinemia, or levels of factor VIII higher than 90% of normal, or persistent residual thrombus as confirmed by ultrasound on recurrent examinations; and (5) recurrent episodes of DVT (two or more episodes of VTE). Vitamin K antagonists in the long-term treatment of DVT Adjusted doses of vitamin K antagonists such as warfarin are very effective in preventing recurrent VTE. The criteria for detecting the anticoagulant effect of vitamin K antagonists are the prothrombin time and the INR.Anticoagulation intensityThe intensity of anticoagulation therapy with vitamin K antagonists has been demonstrated abroad by randomized trials. Low standard intensity (INRl,5~1,9) treatment is poor and does not reduce the incidence of concomitant bleeding. Therefore high-intensity warfarin therapy (INR3,1 to 4,0) does not provide better antithrombotic therapy. High-intensity therapy has also been shown to be associated with a clinically high risk (20%) of severe bleeding. Only small samples of observations have been reported in this country, and strong evidence is lacking. Recommendations Recommendations Vitamin K antagonists should maintain the INR at 2,0 to 3,0 throughout the course of treatment, requiring regular monitoring. Long-term treatment regimens Randomized trials and prospective cohort studies have shown that three months of treatment in patients with first-episode DVT secondary to transient risk factors has been sufficient to reduce recurrence of VTE. A randomized trial of the risk-benefit ratio of an extended course of anticoagulation therapy in patients with primary DVT compared with a control group of patients treated conventionally for 3 to 6 months found that an extended course of therapy was very effective in reducing the incidence of recurrent VTE, but that there was an increased risk of hemorrhage during the course of therapy, and that the benefits and drawbacks of an extended course of anticoagulation for patients with primary DVT should be fully considered before deciding whether or not to proceed. treatment in patients with primary DVT should be decided after full consideration of the advantages and disadvantages. The coronary risk of VTE recurrence is higher in patients with a propensity for thrombosis. These include protein C, protein S, factor VLeiden and prothrombin 20210A mutations, increased levels of coagulation factor VIII, elevated homocysteine levels and the presence of positive antiphospholipid antibodies. Stratified analyses of randomized trials and studies of non-randomized clinical trials have demonstrated the benefit of prolonging the course of warfarin. Vitamin K antagonists are recommended for at least 3 months in patients with a first episode of DVT secondary to a transient hazard. For patients with a first episode of idiopathic DVT, anticoagulation with a vitamin K antagonist for at least 6 to 12 months or longer is recommended. For patients with two or more episodes of DVT, long-term therapy is recommended. For patients on long-term anticoagulation therapy, periodic risk-benefit assessments should be performed to determine whether to continue treatment. Post-Thrombotic Syndrome (PTS) Post-Thrombotic Syndrome (PTS) is defined as a cluster of symptoms and signs in patients who have had a previous episode of venous thrombosis, and the incidence of PTS is approximately 20% to 50%. It is usually associated with chronic venous insufficiency. The predominant symptoms are chronic postural swelling, pain, or localized discomfort. The severity of symptoms varies over time, with the most severe manifestation being a venous ulcer at the ankle. Usually the symptoms are non-acute and the need for treatment is determined by the degree of self-consciousness of the patient. Randomized trials have confirmed that wearing compression stockings is effective for PTS. Physical therapy for post-thrombotic syndrome is currently limited to a small sample of controlled trials showing that intermittent pneumatic compression therapy and compression stockings help to reduce symptoms. Compression stockings are recommended for patients with mild lower extremity edema due to PTS. Intermittent compression therapy is recommended for patients with severe lower extremity edema due to PTS. Attachment: Clinical staging of DVT Acute stage: within 7 days of onset; subacute stage: from day 8 to 30 (1 month) of onset; chronic stage: after 30 days of onset; the early stage referred to in this guideline includes both the acute and subacute stages.