THE BLOG

Blood Clots, Deep Vein Thrombosis And Pulmonary Embolism

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What is Deep Vein Thrombosis (DVT)?

DVT is the formation of a blood clot (thrombus) within a deep vein. The deep veins pass through deep tissues and muscles. Muscle contractions (walking, running, activity, etc.) squeeze blood through the deep veins to the heart. The deep veins have valves which prevent blood from flowing back to the ankles and feet.

The majority of blood clots are small and are usually broken down or dissolved. Large clots may form and can block the vein causing the patient to complain of pain and swelling. Homan's sign is not very specific. High index of suspicion is necessary for diagnosis.

Virchow's Triad contributes to the development of deep venous thrombosis.
1. Endothelial Injury
2. Venous Stasis
3. Hypercoagulability

One triad may contribute more than others.

RISK FACTORS:
  • History of DVT (most important)
  • Tumor (malignancy)
-- Up to 20%
  • Oral contraceptive therapy.
  • Aging.
  • Obesity
  • Smoking
  • The Virchow's Triad:
  1. Venous Stasis
    • Immobilization (patient stays in bed)
    • Physical therapy is not available
    • Being on an airplane or in a car for a long period of time without movement
  • Intimal injury
    • Due to trauma, fracture dislocation or results from surgery.
    • Surgery itself is a risk factor because of the use of general anesthesia and stress of the surgery
  • Hypercoagulable State
    • Could be inherited/genetics (Factor V Leiden, Protein S deficiency, Protein C deficiency).
    Increased blood viscosity + immobilization + an intimal tear from trauma or surgery may lead to DVT.

    Once the condition is suspected, a Venous Doppler ultrasound examination is ordered to confirm the diagnosis. If the study is positive and the clot is above the knee, then DVT is treated with IV Heparin therapy followed by long term Coumadin therapy. Occasionally a vena cava filter is used.

    Where does Deep Vein Thrombosis (DVT) come from?

    DVT predominantly occurs within deep veins of the legs above the knee, it may also occur in the upper extremities.

    What conditions can cause DVT?
    • Spinal cord injury.
    • Total knee replacement - more DVT, less PE than total hip replacement.
    • Polytrauma patient.
    • Hip fractures.
    • Total hip replacement - less DVT and more PE than total knee replacement.
    Prophylaxis for DVT (chemical/mechanical prophylaxis):
    • Chemical methods will include anticoagulants such as aspirin, Lovenox, Coumadin, Heparin and others.
    • Each of these has their advantages and disadvantages.
    • Lovenox decreases the incidence of DVT, but does not decrease the rate of death from PE.
    • None of the anticoagulation agents including Lovenox provide absolute protection against DVT or PE.
    • Both the chest and orthopaedic surgeons' organizational guidelines are related to total joint arthroplasty and hip fractures.
    • Currently there are no guidelines for prophylaxis in trauma patients.
    • When giving prophylaxis, you must weigh the risk of complication (bleeding) versus the benefit of preventing DVT.
    • Mechanical prophylaxis should be used in the majority of patients or in all patients who need prophylaxis.
    • Mechanical compression is recommended by the American Academy of Orthopaedic Surgeons (AAOS) in low or high risk groups, especially if the patient is having a joint replacement.
    • Mechanical compression increases the venous return and endothelial-derived fibrinolysis.

    What is a pulmonary embolism (PE)?

    A PE is blockage of the pulmonary arteries in the lungs that can lead to death. Usually the pulmonary embolus can become lodged within the upper or lower portion of either lung (typically the lower portion of the lung). It is possible for the clot to become lodged in the middle where the pulmonary artery branches, this is known as a Saddle Embolus.

    The incidence of PE occurs in about 700,000 patients per year. 200,000 of these cases may be fatal. Early diagnosis and treatment are the most important factors for survival of the patient. According to the AAOS, the rate of DVT does not correlate with PE. DVT and PE can develop independently of each other and they are part of the hypercoagulable state. One does not need to have DVT in order to develop a PE. The origin of PE is debatable. One opinion is that a blood clot breaks off; it may travel to the heart. If a blood clot becomes lodged in the pulmonary arteries of the lung, this may be fatal. A blood clot may occur in the pulmonary artery itself, not originating from the leg.

    Where does the blood clot come from?

    According to the AAOS published guidelines, (page 32) "These results illustrate that the presence of a DVT may not reliably predict PE, and that the absence of a DVT does not seem to assure physicians and patients that the patient will not have a PE."

    It is best to advise the patient that a PE may occur even if they are on prophylaxis for DVT. Educate the patient on the symptoms of PE. For example, if symptoms occur in the chest (Dyspnea) after surgery on the hip, it is important to go to the emergency room immediately. Early diagnosis is very important for survival of the patients.

    Pulmonary embolism should be suspected in patients postoperatively with:
    • Acute chest pain
    • Tachypnea
    • Tachycardia
    • Syncope
    • Seizures

    Diagnosis is done with ventilation-perfusion (VQ) and helical chest CT scan. Treatment is done with IV Heparin followed by Coumadin. Occasionally a vena cava filter is used.

    Here is the link to my video on DVT and PE:

    For more videos, check out my YouTube:
    https://www.youtube.com/channel/UCOHfqHMhHvfQCYJDXfpSAiw