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VENOUS THROMBOEMBOLISM - PREVENTION
Venous thromboembolism is comprised of pulmonary embolism and deep venous thrombosis and is associated with significant morbidity and mortality.
Decision on which type of prophylaxis to be given must be individualized for each patient.
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.
Early mobilization and leg exercises for any patient recently immobilized are recommended. Immobilized patients should also be adequately hydrated.
Intermittent pneumatic compression devices periodically compress calf and/or thighs and stimulate fibrinolysis. It has been shown to be effective in prophylaxis of asymptomatic deep venous thrombosis in surgical patients.
Graduated compression stockings may be used for deep venous thrombosis prophylaxis in surgical patients with no contraindication for use.

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
  • 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 
    • Studies show that appropriate VTE prophylaxis should be given to surgical patients in Asia who are at risk for VTE

Risk Factors

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 Surgical Procedure, Trauma, 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
      • 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
  • Erythropoiesis-stimulating agents
  • Cardiac dysfunction
    • Uncompensated congestive heart failure (CHF), recent myocardial infection (MI)/stroke
  • Nephrotic syndrome
  • Inflammatory bowel disease
  • Behcet’s disease/paroxysmal nocturnal hemoglobinuria
  • Central venous catheterization
  • Acute respiratory failure
  • Chronic renal disease
  • Critical care admission

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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