DVT: A HIGH RISK THREAT TO LIFE
Wednesday,27 January 2010 14:40 |
In medicine, Deep Vein Thrombosis (usually abbreviated as DVT) is the formation of a blood clot in a deep vein. It is a form of inflammation of a vein with clot formation. Deep vein thrombosis commonly affects the leg veins (such as the femoral vein or the popliteal vein) or the deep veins of the pelvis. Occasionally the veins of the arm are affected (if spontaneous, this is known as Paget-Schrötter disease). A DVT can occur without symptoms, but in many cases the affected extremity will be painful, swollen, red, warm and the superficial veins may be engorged.
The most serious complication of a DVT is that the clot could dislodge and travel to the lungs, which is called a pulmonary embolism (PE). DVT is a medical emergency, present in the lower extremity there is 3% chance of a PE killing the patient.A late complication of DVT is the post-phlebitic syndrome, which can manifest itself as edema, pain or discomfort and skin problems.
Venous thrombosis occurs via three mechanisms: decreased flow rate of the blood, damage to the blood vessel wall and an increased tendency of the blood to clot (hypercoagulability). Several medical conditions can lead to DVT, such as compression of the veins, physical trauma, cancer, infections, certain inflammatory diseases and specific conditions such as stroke, heart failure or nephrotic syndrome. There are several factors which can increase a person's risk for DVT, including surgery, hospitalization, immobilization (such as when orthopedic casts are used, or during long-haul flights, leading to economy class syndrome), smoking, obesity, age, certain drugs (such as estrogen or erythropoietin) and inborn tendencies to form clots known as thrombophilia (for example, in carriers of factor V Leiden). Women have an increased risk during pregnancy and in the early postnatal period within 6 months of delivery.
The most commonly used tests for the diagnosis of DVT are a blood test called D-dimers and doppler ultrasound of the affected veins. Sometimes, further testing is required to find the cause of the DVT. In specific cases, an attempt can be made to break down the clot (using thrombolytic agents). To prevent further accrual and formation of new clots with a risk of pulmonary embolism, anticoagulation (blood thinners) is advised (if not possible, an inferior vena cava filter may be used). Prevention of DVT is advised in many medical and surgical inpatients using anticoagulants, graduated compression stockings (also known as thromboembolic deterrent stockings) or intermittent pneumatic compression devices.

Signs and symptoms:There may be no symptoms referable to the location of the DVT, but the classical symptoms of DVT include pain, swelling and redness of the leg and dilation of the surface veins. In up to 25% of all hospitalized patients, there may be some form of DVT, which often remains clinically inapparent (unless pulmonary embolism develops). There are several techniques during physical examination to increase the detection of DVT, such as measuring the circumference of the affected and the contralateral limb at a fixed point (to objectivate edema), and palpating the venous tract, which is often tender.Palpation is not encouraged as it could dislodge a clot to the lungs causing fatal pulmonary embolism. Physical examination is unreliable for excluding the diagnosis of deep vein thrombosis.In phlegmasia alba dolens, the leg is pale and cool with a diminished arterial pulse due to spasm. It usually results from acute occlusion of the iliac and femoral veins due to DVT.

Diagnosis: The gold standard is injecting a peripheral vein of the affected limb with a contrast agent and taking X-rays, to reveal whether the venous supply has been obstructed. Because of its invasiveness, this test is rarely performed.
Prevention: Clinical practice guidelines by the American College of Chest Physicians (ACCP) provide recommendations on DVT prophylaxis in hospitalized patients.
General medical inpatients: Regarding general medical inpatients the guidelines state, "In acutely ill medical patients who have been admitted to the hospital with congestive heart failure or severe respiratory disease, or who are confined to bed and have one or more additional risk factors, including active cancer, previous VTE, sepsis, acute neurologic disease, or inflammatory bowel disease, the American College of Chest Physicians (ACCP) recommend prophylaxis with low-dose unfractionated heparin-LDUH (Grade 1A) or LMWH (Grade 1A). Enoxaparin or unfractionated heparin may be used. LMWH may be more effective than UFH. If UFH heparin is used, 5000 U 3 times daily may be more effective.
Since publication of the ACCP guidelines, an additional randomized controlled trial and meta-analysis ;including the trial have been published. The meta-analysis concluded " Anticoagulant prophylaxis is effective in preventing symptomatic venous thromboembolism during anticoagulant prophylaxis in at-risk hospitalized medical patients. Chronic renal dialysis patients may be at increased risk of thromboembolism, but randomized controlled trials have not addressed the risk.
Surgery patients: In patients who have undergone surgery, low molecular weight heparins (LMWH) are routinely administered to prevent thrombosis. LMWH can only currently be administered subcutaneously by injection. Prophylaxis for pregnant women who have a history of thrombosis may be limited to LMWH injections or may not be necessary if their risk factors are mainly temporary.