Medicine 5th year, 11th lecture/part one (Dr. Sabir)
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  • 1. Venous thrombosis By Dr. Sabir M. Ameen
  • 2. Predisposing factors
    • 1 . Patient : a) age: >40 b) obesity c) varicose veins d) previous DVT e) OCP f) pregnancy/puerperium g) dehydration
    • h) immobility
    • 2. Surgical : a) if >30 min duration b) abdominal or pelvic c) orthopedic to lower limb
  • 3. Pred. fact.
    • 3. Medical : a) MI/HF b) IBD c) malignancy d) Nephrotic syn e) pneumonia
    • 4. Hematological : a) PV b) ET c) PNH d) myelofibrosis
    • 5. Anticoagulant deficiency : a) antithrombin b) protein C c) protein S d) factor V Leiden e) prothrombin mutation.
    • 6. Antiphospholipid syndrome : a) lupus anticoagulant b) anticardiolipin Ab
  • 4. Venous thrombosis
    • VT: arise either because of damage to, or pressure on veins (e.g. varicose veins or pelvic tumor) , or as a result of changes in plasma or cellular elements of blood.
    • When thrombosis occur in an individual under 40 yr of age, particularly if there is a family history of thrombosis, investigations for a predisposing blood abnormality should be undertaken.
  • 5. Wells Criteria
  • 6. Wells
    • Low probability (-2-0) = 3-13%
    • Moderate probability (1-2) = 17-38%
    • High probability (>2)= 60-75%
  • 7. Special Investigations Test Advantages Disadvantages Contrast “ Gold standard” Invasive Venography Sensitivity ~ 100% Requires specialized equipment   Easily interpretable Rare, but serious side effects MRI Highly accurate Expensive   Safe during pregnancy Not readily available   Non-invasive   CT Non-invasive Limited data   Can diagnose pelvic DVT     Concurrently exclude PE   Ultrasonography Highly accurate Not accurate for calf or pelvic DVT   Non-invasive Complete study is time consuming D-Dimer Rapid laboratory study Only used to rule-out DVT   Can aide in exclusion of DVT  
  • 8. Management of thromboembolism
    • Indications for anticoagulation:
    • Heparin :
    • 1. Treatment & prevention of DVT
    • 2. Pulmonary embolism
    • 3. post-thrombolysis for MI
    • 4. unstable angina
    • 5. acute peripheral arterial occlusion
  • 9. Indications of warfarin Rx
    • prophylaxis against DVT
    • treatment of DVT & PE
    • arterial embolism
    • AF with stroke risk factors
    • mobile mural thrombus on echo post-MI
    • extensive anterior MI( all these INR= 2.5)
    • recurrent DVT
    • mechanical prosth heart valves( latter two INR=3.5)
  • 10. Contraindications to anticoagulation
    • 1. Recent surgery( esp. to eye or CNS)
    • 2. pre-existing hemorrhagic condition( e.g. liver disease, RF, hemophilia, thrombocytopenia)
    • 3. Peptic ulcer
    • 4.Recent cerebral hemorrhage
    • 5. Uncontrolled HT
    • 6. Dementia and frequent falls in old age
  • 11. Heparin
    • Standard (unfractionated) heparin (SH) produces its anticoagulant effect by potentiating the activity of antithrombin which inhibits the procoagulant enzymic activity of factors IIa, VIIa, IXa, Xa, and XIa.
    • Low-molecular weight heparin ( LMWH) augments antithrombin activity preferentially against factor Xa. LMWH does not prolong PTT( unlike SH), and injections need only be given once daily SC and no monitoring is required, many pts can be treated at home.
  • 12. Heparin…cont.
    • SH is reserved for treating pts with very severe, life-threatening TE e.g. major PE giving rise to hypoxia or hypotension.
    • Dose: loading dose of 5000 U i.v, followed by a continuous infusion of 20U/kg/hr initially. PTT done after 6 hr, and if satisfactory daily thereafter. The aim is to keep PTT 1.5-2.5 times the control time.
  • 13. Heparin…cont.
    • Half-life of heparin is 1 hr, and if pt bleeds, it is sufficient just to discontinue the infusion; however, if bleeding is severe , the excess can be neutralised with i.v protamine. Treatment with either SH or LMWH should continue for 6-8 days, and it is appropriate to start warfarin therapy at the same time as heparin, and heparin should be contiued until INR is >2.0 for 2 consecutive days.
  • 14. Warfarin
    • It inhibits vit. K-dependent carboxylation of factors II, VII, IX and X in the liver.
    • Dose: loading 10 mg orally on the first day, and subsequent daily doses depending on the INR. If single DVT it is given for 3-6 mon, if two or more it should be continued for life. Bleeding is the most common side effect of warfarin: 0.5-1.0%/yr. If INR is above therapeutic level stop warfarin and give a small dose of vit.k e.g. 5 mg orally or 2 mg by slow i.v inj. If the pt bleeds, give vit. K ¹ 1-5 mg slowly i.v, and
  • 15. Warfarin..cont.
    • If bleeding is serious , give coagulation concentrate containing factors II, VII, IX and X (50U/kg)or, if unavailable, FFP
  • 16. Prevention of venous thrombosis
    • Full-length graduated compression stockings
    • SH or LMWH
    • It should be started preop and continued until the pt is fully mobile
    • Conditions: A) moderate risk of DVT: 1. major surgery in pts >40yr or with other risk factors, 2. major medical illness: e.g HF, chest infection, malignancy, IBD
    • B) High risk of DVT: 1. hip or knee surgery, 2. major abdominal or pelvic surgery( for malignancy or with Hx of DVT or known thrombophilia)