Q: What are the high-risk factors for developing DVT?
A: Age: Deep vein thrombosis can be seen in people of any age, but the greater the age, the higher the incidence; patients over 40 years of age are usually considered to be at high risk.
Braking: Patients who are bedridden and braked for a long time have a significantly slower venous blood return due to a weakened calf muscle pump, which increases the risk of DVT.
History of venous thrombosis: 23% to 26% of patients with acute DVT have a previous history of venous thrombosis, and these newly formed thrombi often come from the original diseased vein. It has been found that the blood of patients with recurrent DVT is often in a hypercoagulable state.
Malignant tumors: Malignant tumors can release pro-coagulant substances and increase the activity of blood clotting factors, so patients with malignant tumors have a higher risk of DVT, and lung cancer is one of the most likely malignant tumors to cause DVT.
Surgery: perioperative braking, intraoperative and postoperative abnormalities of coagulation, anticoagulation and thrombolytic systems in vivo, and damage to venous vessels are the main factors for the high incidence of DVT in surgical patients.
Trauma: Blood is in a hypercoagulable state after trauma, and trauma resulting in lower limb fractures, spinal cord injury, venous vascular injury and the need for surgical treatment make trauma patients prone to DVT.
Primary hypercoagulable state: Patients with genetic mutations or inherited defects in anticoagulant substances that leave the blood in a hypercoagulable state. Primary blood hypercoagulation is responsible for 5-10% of all DVT patients.
Postpartum: The placenta produces a large amount of estrogen during pregnancy, which reaches its peak at full term. The amount of estriol in the body can increase to 1000 times that of non-pregnancy, and estrogen promotes the production of various coagulation factors by the liver, while the large increase of fibrinogen in the body at the end of pregnancy aggravates the hypercoagulable state and may lead to deep vein thrombosis.
Q: What is the Caprini individualized venous thrombosis risk assessment model?
A: It was created by Dr. Caprini of Glenbrook Hospital in 1988. By recording and scoring various factors related to the risk of venous thrombosis, he classified hospitalized patients into four levels: low risk, intermediate risk, high risk and very high risk, and individualized the venous thrombosis prevention program according to the patient’s venous thrombosis risk level.
Q: What are the clinical symptoms of deep vein thrombosis?
A: Swelling of the affected limb: It is the most common symptom after the formation of deep vein thrombosis in the lower limb. The affected limb has high tissue tone and non-depressed edema. The swelling is most severe on the second or third day after the onset of the disease, and then gradually decreases.
Pain and tenderness: tenderness is mainly confined to the site of the inflammatory response to the venous thrombosis, such as the femoral vein pathway or the calf. Calf gastrocnemius pressure pain is also known as a positive Homans sign. Because of the risk of dislodging the thrombus by squeezing the calf, excessive force should not be applied during the examination.
Superficial varicose veins: Superficial varicose veins are compensatory reactions, which are usually not obvious in the acute stage and are a manifestation of the sequelae of venous thrombosis in the lower limbs.
Femoral cyanosis: When the deep vein thrombosis of lower extremity extensively involves the intra-muscular plexus, because the iliofemoral vein and its lateral branches are all blocked by the thrombus, the tissue tension is extremely increased, resulting in arterial spasm of lower extremity, limb ischemia or even necrosis. Clinically, the pain is severe, the skin of the affected limb is shiny with blisters or blood blisters, and the skin color is blue-purple, which is called painful femoral cyanosis (Phlegmasia Cerulea Dolens). It is often accompanied by arterial spasm, weakened or absent arterial pulsations in the lower extremities, decreased skin temperature, and consequently a high degree of circulatory disturbance. The patient has a strong systemic reaction with hyperthermia and atrophy, and is prone to shock manifestations and wet gangrene of the lower extremities.
Femoral white swelling: In acute embolism of the deep veins of the lower extremities, the edema of the lower extremities reaches its highest level within a few hours, the swelling is concave and hypertonic, and the obstruction occurs mainly in the femoral venous system. When combined with infection, the stimulation of the artery continues to spasm, and swelling, skin pallor, and small subcutaneous reticular venous dilatation of the entire extremity are seen, called painful femoral bruising (Phlegmasia Alba Dolens).
Femoral cyanosis and femoral leukomalacia are less common and are an emergency condition that requires emergency surgery to remove the embolus in order to save the affected limb.
Q: What ancillary tests are available for deep vein thrombosis?
A: 1. Plasma D-dimer (DD) determination: D-dimer is a specific molecular marker representing coagulation activation and secondary fibrinolysis, which has a high sensitivity (>99%) and an important reference value for the diagnosis of acute deep vein thrombosis.
2.Color Doppler ultrasonography: with high sensitivity and accuracy, it is the preferred method for the diagnosis of deep vein thrombosis and is suitable for screening and monitoring of patients.
3.Spiral CT venous imaging: It has higher accuracy and can examine the abdomen, pelvis and deep veins of lower limbs at the same time.
4.Nuclear magnetic resonance venography: it can accurately show iliac, femoral and N vein thrombosis, but cannot satisfactorily show calf vein thrombosis without the use of contrast agent.
5.Venography: Accuracy is away, not only can effectively determine the presence or absence of thrombus, thrombus site, scope, formation time and collateral circulation, but also often used to identify the diagnostic value of other methods.
Q: What is the diagnostic process of deep vein thrombosis?
A: (1) Take medical history and perform risk assessment. (2) D-dimer assay for screening. (3) Color Doppler ultrasonography. (4) Venography if necessary.
Q: What diseases should be differentiated from deep vein thrombosis?
A: Lower extremity lymphedema: there is often a history of surgery, infection, radiation, parasites, etc. that damage the lymphatic vessels.
Localized hematoma of lower extremity: Most of them have history of trauma, and the swelling is limited, rarely involving the whole lower extremity, ultrasound examination can help to differentiate.
Gastrocnemius muscle laceration injury: mostly develops after trauma or strenuous activity.
Systemic diseases: congestive heart failure, chronic renal insufficiency, fluid overload, anemia, hypoproteinemia, and pelvic malignancy can cause lower extremity edema, but it is usually bilateral and symmetrical, and there is no superficial venous anger or skin color change.