As early as 1859, the German scholar Virchow proposed three major factors for venous thrombosis: stagnant venous blood flow, venous wall damage, and hypercoagulable blood. This is the classic cause of venous thrombosis. Stagnant venous blood flow means that venous blood flow is slowed down because of venous stenosis, extra-venous occupancy, high abdominal pressure, sedentary standing, etc., which makes venous thrombosis easier; damage to the venous wall means that the venous lining is damaged because of smoking, infection, tumor implantation, etc., which makes venous thrombosis easier; hypercoagulable blood means that the blood is easily coagulated because of dehydration, platelet hyperfunction, leukemia, etc., which makes venous thrombosis easier. This makes the formation of venous thrombosis easy. However, among the above three factors, any single factor is often not enough to cause the disease, but often a combination of factors.
From this, we deduce that the people at risk for lower extremity DVT are bedridden elderly, obese people, smokers, tumor patients, post-surgical patients, dehydrated people and pregnant women, and patients with blood disorders. This has been repeatedly confirmed in clinical work.
Here, we can also infer that the main approaches to prevent lower limb DVT are regular activity of lower limbs, smoking cessation, weight loss, use of elastic stockings during pregnancy, moderate water intake, anticoagulation especially needed for patients after surgery, tumors, hematological diseases, etc.
What are the manifestations of patients with lower limb deep vein thrombosis?
Mainly self-conscious soreness and swelling, pain in calf gastrocnemius muscle when hooking the back of the foot; often can see swelling of lower limbs, ankle edema; also can not have any symptoms and signs, but only the performance of pulmonary infarction; into the chronic stage (after 30 days), then can have the performance of lower limb deep vein thrombosis sequelae, such as varicose veins, hyperpigmentation, mossy skin, and even venous ulcers.
According to the composition of thrombus, venous thrombosis is divided into three types.
1.Red thrombus, the most common, is more uniform in composition, with platelets and leukocytes scattered within a gelatinous mass of red blood cells and fibrin;
2.White thrombus, basically composed of fibrin, leukocytes and lamellar platelets, only a very small number of red blood cells;
3.Mixed thrombus, consisting of white thrombus as the head, lamellar red thrombus and white thrombus as the body, and red thrombus or lamellar thrombus as the tail.
According to the site of thrombus, the lower limb venous thrombosis is also divided into three types.
1.Peripheral type, i.e. thrombosis of the muscular plexus of the lower leg, which is a good site for deep vein thrombosis after surgery.
2, central type, that is, iliofemoral vein thrombosis, which is more common on the left side (Cockett syndrome), may be related to the right common iliac artery crossing the left common iliac vein, which has some compression on the left common iliac vein. If the thrombus is dislodged, pulmonary embolism can be formed.
3.Mixed type, regardless of the retrograde spread of iliofemoral vein thrombosis or the prograde expansion of calf muscle plexus thrombosis, as long as the whole lower limb deep vein system is involved, it is mixed type.
According to the time of thrombosis, the lower extremity venous thrombosis can be divided into three types.
1.Acute phase, where the thrombosis occurs within 7 days;
2.Sub-acute phase, where the thrombosis occurs within 8 to 30 days;
3. Chronic phase, where the thrombosis has occurred for more than 30 days.
According to the typical symptoms and signs, it is certainly not difficult to diagnose lower extremity deep vein thrombosis, but the clinical manifestations are often very different, so it is necessary to cooperate with some auxiliary examinations to make the diagnosis. Practical and convenient lower extremity deep vein ultrasound, which can diagnose most of the lower extremity venous thrombosis, in addition to radioisotope examination, electrical impedance volume tracing examination, venous manometry, D-2 aggregation measurement, etc.. In some difficult cases, invasive phlebography is sometimes required.
The acute danger of lower extremity venous thrombosis is localized swelling and pain, ankle edema, lower extremity infection, and most dangerously, fatal pulmonary infarction. The late danger, that is, the danger of sequelae, is deep vein valve insufficiency in the lower extremities, manifesting soreness and swelling of the lower extremities after walking, venous stasis dermatitis, secondary varicose veins, recurrence of venous thrombosis, and even venous ulcers.
For treatment, firstly, account for the condition, use postural therapy, bed rest for 1 to 2 weeks, avoid activities and straining to defecate, which may cause thrombus dislodgement. Elevate the foot of the bed 20-25cm, so that the lower limbs are higher than the heart level, which can improve venous return and reduce edema and pain.
When starting to get out of bed, elastic stockings or elastic bandages need to be worn, and the duration of use varies according to the embolism site: 1 to 2 weeks for calf muscle plexus thrombosis; no more than 6 weeks for N vein thrombosis; 3 to 6 months for iliofemoral vein thrombosis.
At the same time, anticoagulation therapy is required, which is the basic treatment as well as postural therapy. Heparin or low-molecular heparin is used in the acute phase, with a gradual transition to the coumarin derivative warfarin, and attention is paid to monitoring coagulation tests, especially to monitoring the internationalized standard ratio, preferably ensuring that it is between 1.5 and 2.0. For first episodes, vitamin K antagonists should be applied for at least 3 months, while in patients with first episodes of idiopathic DVT, indefinite anticoagulation therapy should be considered.
This can be combined with thrombolysis and de-agglomeration therapy. Urokinase is commonly used for thrombolysis. Urokinase is extracted from human urine and has fewer side effects than streptokinase. The first dose is 3000-4000 IU/Kg, which is administered intravenously within 10-30 minutes, and the maintenance dose is 2500-4000 IU/Kg/hour, and the duration of treatment is usually 12-72 hours.
Pay attention to monitoring fibrinogen and euglobulin dissolution time. If fibrinogen is lower than 2g/L or euglobulin dissolution time is less than 70 minutes, it is necessary to suspend the drug for one time, and the application can be continued for 7-10 days. Thrombolysis can also use fibrinolytic enzymes (fibrinase, plasma enzymes). Low-molecular dextran is commonly used to remove aggregates.
For most patients with DVT, vena cava filters are not routinely used. An inferior vena cava filter is recommended only in patients with recurrent thromboembolism despite contraindications or complications of anticoagulation therapy or adequate anticoagulation.
There is no cure for the sequelae of deep vein thrombosis, which are more or less common after a single episode. For the treatment of the sequelae of lower extremity DVT, it is recommended to use elastic stockings with ankle pressure of 30-40 mmHg for 2 years after the DVT, while intermittent pneumatic compression therapy can be used in patients with severe edema of the lower extremities due to post DVT syndrome. In patients with mild edema of the lower extremities due to post DVT syndrome, compression stockings can be used, and rutin and horse chestnut seed extract can be taken to reduce symptoms.