DVT Flashcards
What is DVT?
Formation of a thrombus in a large vein of the body
What are the signs and symptoms of DVT?
- Calf warmth
- Swelling
- Tenderness
- Erythema
- Mild fever
- Pitting oedema
Possible signs and symptoms of heart failure if thrombus embolizes
What is the differential diagnosis of DVT?
- Bakers cyst
- Cellulitis
- Synthetic oestrogen
- Lymphoedema
- Chronic venous insufficiency
- Arterial Aneurysm
- Enlarged lymph nodes compressing veins
What are the risk factors of DVT
- Age
- Trauma
- Immobility
- Pregnancy (levels of clotting proteins increase in pregnancy)
- Surgery
- Cancer
- Obesity
- Thrombophilia
What are the investigations in suspected DVT?
=> Wells score
=> D-dimer
=> Ultrasound of leg
How are the Wells score, D Dimer and ultrasound scanning used in the diagnosis of DVT
If WELLS score is ≤ 1 and D Dimer is -ve, DVT excluded
If D Dimer is +ve, proceed to ultrasound:
+ve ultrasound = DVT
-ve ultrasound = DVT EXCLUDED
If WELLS score is ≥ 2, do D Dimer and Ultrasound:
-ve D Dimer and -ve ultrasound = DVT excluded
-ve D Dimer and +ve ultrasound = treat as DVT
+ve D Dimer and -ve ultrasound = repeat scan after a week
What is the WELLS score criteria for DVT?
FEATURES
Active cancer treatment -1
Paralysis, paresis, or recent plaster immobilisation of leg - 1
Local tenderness - 1
Entire swollen leg -1
Calf swelling > 3cm compared to unaffected limb - 1
Pitting oedema - 1
Collateral superficial veins - 1
Previous DVT - 1
Alternative diagnosis as least as likely as DVT - (-2)
WELLS score ≤ 1 means DVT unlikely
WELLS score ≥ 2 DVT likely
What is the MOA of Heparin?
- Reduces the likelihood of clots forming by inactivating cofactors, e.g. factors II, IX, X, XI
- LMWH is preferred to unfractionated heparin
- Unfractionated heparin acts on antithrombin as opposed to factor Xa. It forms a complex with antithrobmin which catalyses the inhibition of several cofactors
What are the major side affects of heparin?
- Easy bleeding and bruising
- Pain, redness, warm or irritation of injection site
What is the MOA of Wafarin?
- Inhibits reductase enzyme responsible for regenerating vitamin K
- Vitamin K is responsible for conversion of cofactors into their activated form
What are the major side affects of Wafarin?
- Severe bleeding
- Red or brown urine
- Black or bloody stools
- Severe headache or stomach pain
What is the difference between a thrombus and a clot?
THROMBUS:
- Made of RBCs, fibrin and platelets
- Forms within the CVS
- Forms in flowing blood
CLOT:
- Made of RBCs and fibrin. NO PLATELETS
- Forms outside CVS (e.g. in a test tube)
- Forms in stationary blood
What is the most important risk factor of arterial thrombosis?
Atherosclerosis
What is the most important risk factor of venous thrombosis?
Stasis and Hypercoagubility
What are the possible pathways a thrombus can take?
- Propagation
- Organisation
- Recanalisation
- Embolism
- Resolution
What are the prophylactic measures against DVT?
- Compression stockings
- Single dose LMWH subcut
What is the treatment for DVT?
- LMWH or Fondaparinux given immediately after diagnosis
- Warfarin given within 24 hours of diagnosis
- LMWH or Fondaparinux continued for 5 days or when the INR ≥ 2.0 for at least 24 hours, at which point they are stopped and patient is only on Warfarin
- Warfarin should be continued for 3 month at which point doctors decide whether to continue or not
- In practice, may be given for 6 months, and defo given for 6 months if patient has cancer
