venous%20thromboembolism%20-%20prevention
VENOUS THROMBOEMBOLISM - PREVENTION
Venous thromboembolism is comprised of pulmonary embolism and deep venous thrombosis and is associated with significant morbidity and mortality.
All patients admitted for major trauma, surgery or acute medical illness should be assessed for risk of venous thromboembolism and bleeding before starting prophylaxis for venous thromboembolism.
Decision on which type of prophylaxis to be given must be individualized for each patient.

Venous%20thromboembolism%20-%20prevention Signs and Symptoms

Introduction

Venous Thromboembolism (VTE)

  • Most commonly manifested as pulmonary embolism (PE) and deep venous thrombosis (DVT), and is associated with significant morbidity and mortality
    • 1/3 of patients present with symptoms of DVT and 2/3 with PE
    • Also manifests as superficial vein thrombosis (SVT), a less severe form of DVT
  • One of the most common life-threatening cardiovascular diseases in the US and with increasing incidence and mortality rates in Asia

Risk Factors

  • All patients admitted for major trauma, surgery or acute medical illness should be assessed for risk of VTE and bleeding before starting prophylaxis of VTE
    • Balance the risk of VTE against bleeding as the medicines used for VTE prevention are associated with an increased bleeding risk 
    • Studies show that appropriate VTE prophylaxis should be given to surgical patients in Asia who are at risk for VTE
  • Assess critically ill patients more frequently for VTE and bleeding risk

Assessment of Individual Risk Should Include:

Personal Risk Factors for Venous Thromboembolism (VTE) 

  • Increasing age
    • There is exponential increase in risk with increasing age (>60 years) 
  • Marked obesity - Body mass index (BMI) ≥30 kg/m2
  • Varicose veins, venous compression caused by tumor, arterial abnormality or hematoma
  • Previous PE or DVT, or 1st-degree relative with VTE history
  • Pregnancy or puerperium (within 6 weeks)
    • Preexisting acquired thrombophilia (antiphospholipid syndrome) 
  • Hormone therapy
    • Oral combined contraceptives, estrogen-containing contraceptives, hormone replacement therapy (HRT), Raloxifene, Tamoxifen (increased risk by 3x)
    • High-dose progestins (increased risk by 6x) 
  • Thrombophilias (inherited or acquired)
    • Phospholipid antibody syndrome, deficiencies in antithrombin III, protein S, protein C, factor V Leiden mutation, prothrombin gene mutation 
  • Malignancy (active or occult)
    • Especially pelvic, abdominal or metastatic
  • Myeloproliferative disorders
    • Polycythemia, paraproteinemia 
  • Immobility (bed rest >3-4 days), lower extremity paresis
  • Smoking

Risk Factors Related to Trauma, Surgical Procedure, Severe Infection or Acute Medical Illness

  • Trauma
    • Especially spinal cord injury, multiple trauma or pelvis, hip or lower limb fractures
  • Surgery
    • Risk will depend on site, technique, duration of the procedure, type of anesthetic, presence of infection and duration of post-operative immobilization
      • Hip and knee replacement surgery have a higher risk of VTE 
      • Duration of surgery and anesthesia >90 minutes or 60 minutes if it involves the pelvis or lower limb
      • General anesthesia has higher risk of VTE than spinal/epidural
  • Cancer therapy
    • Chemotherapy, angiogenesis inhibitors, radiotherapy
  • Behcet’s disease/paroxysmal nocturnal hemoglobinuria 
  • Erythropoiesis-stimulating agents
  • Cardiac dysfunction
    • Uncompensated congestive heart failure (CHF), recent myocardial infection (MI)/stroke
  • Nephrotic syndrome
  • Inflammatory bowel disease
  • Central venous catheterization
  • Acute respiratory failure
  • Chronic renal disease
  • Critical care admission

Risk Factors for Bleeding 

  • Personal or family history of bleeding disorders
  • Active or recent (within the week) bleeding
  • Acute hemorrhagic stroke
  • Ulcerative gastrointestinal disease, eg active peptic ulcer
  • Platelet count <50,000 µ/L
  • Medications used, eg NSAIDs, antiplatelets, anticoagulants, thrombolytics 
  • Liver disease or abnormal renal function
  • Uncontrolled hypertension
  • Procedures with critical bleeding consequences, eg epidural or spinal anesthesia, lumbar puncture, intracranial or neurosurgery, head and neck surgery or orthopedic surgery

Pathogenesis

  • Virchow’s triad theorizes 3 factors contributing to the development of VTE: Hypercoagulability, endothelial damage, and stasis
  • Hypercoagulability has been associated with factor V Leiden mutation and prothrombin gene mutation
    • Cancer also produces a hypercoagulable state due to the procoagulant activity produced by malignant cells and also secondary to effects of chemotherapeutic agents
  • Major contributing risk factors include history of trauma, surgical procedures, spinal cord injury, long bone fractures, and previous VTE
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