Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Deep Venous Thrombosis

Basics
Description
  • DVT is a blood clot in the deep venous plexus of the legs.
  • Venous thrombus may embolize and result in fatal PE.
  • Classification:
    • DVTs are classified by location using ultrasound.
      • Thrombi below the popliteal fossa usually do not embolize.
      • 50% of thrombi at or above the popliteal fossa will embolize.
General Prevention
  • Pharmacologic prophylaxis
  • Pneumatic compression
  • Early mobilization
Epidemiology
Incidence
  • The DVT rate in orthopaedic patients without prophylaxis is:
    • 15-25% after total hip arthroplasty
    • As high as 50% after total knee arthroplasty
    • 20-60% after pelvic, acetabular, or hip fracture
    • 0.3-26% after spinal surgery
    • 0.25% after foot and ankle surgery
  • Affects males and females equally
Risk Factors
  • Age >60 years
  • Prolonged immobility or paralysis
  • History of DVT or PE
  • Family history of DVT or PE
  • Cancer
  • Obesity
  • Varicose veins
  • Congestive heart failure
  • Myocardial infarction
  • Stroke
  • Major lower extremity trauma, including fractures of the pelvis and hip
  • Hypercoagulable states
  • Sepsis
  • Hormone therapy
  • Inherited thrombophilia
  • Smoking
  • Pregnancy and giving birth
Genetics
  • The risk of DVT is increased by inherited thrombophilia, including the presence of:
    • Protein C and S deficiency
    • Heparin cofactor II deficiency
    • G20210A prothrombin gene polymorphism
    • Dysfibrinogenemia
    • Factor V Leiden deficiency
Etiology
The Virchow triad (endothelial injury, blood injury, and clotting abnormalities) can result in venous thromboembolism.
 
Diagnosis
Signs and Symptoms
  • DVT and PE manifest few specific symptoms; the clinical diagnosis is neither sensitive nor reliable .
    • DVT:
      • Pain and swelling in the leg and thigh
      • Possible phlebitis
      • Fever
    • PE:
      • Dyspnea
      • Pleuritic chest pain
      • Hemoptysis
      • Tachypnea
      • Acute right ventricular strain
      • Rubs or cackles in the lung fields
      • Tachycardia
History
A history of risk factors should be obtained to risk-stratify the patient.
 
Physical Exam
  • Calf pain
  • Swelling of the calf (may be measured and compared with the other side)
  • Tachypnea and hypoxia
  • Tachycardia
Tests
  • Electrocardiography:
    • Classic findings after massive PE are S waves in lead I, and a Q wave with T-wave inversion in lead III.
    • In less severe PE, sinus tachycardia and new arrhythmias may be present.
Lab
  • DVT: None
  • PE:
    • Arterial blood gas
    • D-dimer
Imaging
  • DVT:
    • Doppler ultrasonography:
      • Sensitive for detection of DVT
      • Sensitivity decreases in the upper thigh and pelvic veins.
      • Operator-dependent
    • Venography:
      • 100% sensitive and specific
      • Provides visualization of the entire deep venous system
      • Expensive and invasive
    • Magnetic resonance venography:
      • May be difficult to interpret and is operator-dependent
      • Visualizes pelvic thrombi
  • PE:
    • Chest radiography:
      • Results generally are normal, but a pleural effusion or wedge-shaped pulmonary infarction may be noted.
    • Ventilation-perfusion scan:
      • A normal ventilation-perfusion scan excludes PE.
      • An abnormal scan showing perfusion defects does not confirm PE.
    • Pulmonary angiography:
      • 100% sensitive and specific, but expensive and invasive.
    • Spiral chest CT:
      • Sensitive and specific for PE detection
      • Replaced pulmonary angiography
Pathological Findings
  • A clot develops in the lower extremity veins and enlarges proximally.
  • The clot can embolize and fill the pulmonary arteries.
Differential Diagnosis
  • Lower leg thrombosis:
    • Phlebitis
    • Cellulitis
    • Deep or superficial wound infection
    • Ruptured Baker cyst
  • PE:
    • Acute myocardial infarction
    • Congestive heart failure
    • Pneumonia
    • Fat emboli syndrome
Treatment
All patients undergoing major orthopaedic surgery (e.g., hip/knee arthroplasty) or who have had pelvic fractures or major lower extremity trauma should be placed on routine prophylaxis.
 
General Measures
  • Prophylaxis:
    • Anticoagulants are effective in reducing DVT incidence.
    • Pneumatic compression devices applied intraoperatively and postoperatively are effective.
    • Vena cava filter may be used for high-risk patients in whom anticoagulation is contraindicated.
  • DVT above the popliteal fossa:
    • Patients should be anticoagulated immediately.
    • Bleeding risks should be considered, especially if the patient is within several days of surgery, because wound hematoma or uncontrolled bleeding may occur.
    • Patients should be placed on bed rest to decrease the chance of embolization.
  • DVT below the popliteal fossa:
    • Blood clots may resolve over time without treatment.
    • Prophylactic doses of anticoagulant should be continued, and clots should be followed with Doppler ultrasonography to rule out propagation.
Activity
To decrease the risk of embolization, patients with above-the-knee clots should be placed on bed rest until anticoagulation is achieved.
 
Medication (Drugs)
First Line
  • Prophylaxis:
    • Patients at risk of DVT should be treated with prophylaxis.
    • Guidelines for prophylaxis were published in Chest and are widely followed.
    • Patients should be risk-stratified according to their risk factors and the type of surgery.
  • For patients at high risk of DVT, the following treatments are thought to have the highest evidence for use:
    • Low molecular weight heparin:
      • Enoxaparin, 30 mg subcutaneously every 12 hours
      • Dalteparin, 5,000 IU subcutaneously every 24 hours
    • Warfarin:
      • Dose given nightly after surgery
      • Goal: Prothrombin time INR of 2.0-3.0
    • Pentasaccharides:
      • Approved for use after hip fracture
      • Fondaparinux sodium, 2.5 mg subcutaneously every 24 hours
  • Duration of prophylaxis:
    • Should be continued for at least 2 weeks after surgery for high-risk patients
    • Should be continued for at least 4 weeks for patients at very high risk of DVT
  • Treatment of DVT or PE:
    • Enoxaparin, 1 mg/kg subcutaneously every 24 hours
    • Warfarin:
      • Goal: Prothrombin time INR of 2.0-3.0
      • Length of treatment varies, but current recommendation is for at least 3 months.
    • Heparin, intravenous drip, dose-adjusted to an activated partial thromboplastin time of 2.0-3.0 times control values
Second Line
  • Evidence is not as substantial for DVT prophylaxis with aspirin or with mechanical devices, such as sequential compression devices.
  • Sequential compression devices and graded compression stockings may be useful in the early period after surgery before anticoagulants are given.
  • Compliance with these devices is difficult to enforce.
  • The use of these methods alone for DVT prophylaxis is not recommended by the Chest guidelines.
Follow-up
Complications
  • Increased risk of DVT in the future
  • Chronic venous stasis
  • PE
  • Death
Patient Monitoring
Monitoring varies, depending on the anticoagulant chosen.
 
Miscellaneous
Codes
ICD9-CM
  • 415.1 Pulmonary embolus
  • 453.9 Venous embolism and thrombosis, of unspecified site
Patient Teaching
  • Patients at risk are told the warning signs of DVT and PE, including:
    • Calf pain and calf and foot swelling that persist despite elevation
    • Chest pain, cough, and shortness of breath
  • Patients should be educated about early mobilization.
  • Medication teaching:
    • Low-molecular-weight heparin: Subcutaneous injection, side effects, bleeding precautions
    • Coumadin: Diet instructions, limiting vitamin K, bleeding precautions, importance of lab monitoring (INR)
Prevention
Patients should be risk-stratified and treated with prophylaxis according to the Chest guidelines.
 
FAQ
Q: Is immobility a risk for DVT?
A: Yes. Immobility, such as long travel in a car or plane or periods of bed rest or casting, place a patient at risk for DVT.

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