Venous Thrombosis & Anticoagulants Flashcards
Describe how veins move blood back to the heart
Rely on muscles surrounding to pump the blood
Valves help to move blood towards the heart
Low pressure system - only activates the coagulation cascade
State Virchow’s triad
Stasis
Hypercoagulation
Vessel wall
How will a DVT present?
Hot, swollen, tender, pitting oedema
How will a PE present?
Pulmonary infarction, pleuritic chest pain, collapse, hypoxia, right heart strain
Name the risk factors for venous thrombosis
Age Obesity Pregnancy & Puerperium Previous DVT/PE Trauma/surgery Malignancy Paralysis Oestrogen therapy Infection Thrombophilia
What is thrombophilia?
Inherited condition that increases the chances of having blood clots - increased fibrin clot formation and decreased anticoagulation
What is factor V leiden?
Change in factor V meaning it is not switched off as efficiently as normal factor V
Name the types of hereditary thrombophilia
Factor V leiden Prothrombin 20210 Antithrombin deficiency Protein C deficiency Protein S deficiency
What signs would increase you suspicious of hereditary thrombophilia?
Venous thrombosis <45 years old
Recurrent venous thrombosis
Unusual sites
Family history
Describe the management for thrombophilia
Short term prophylaxis around events of known risk
Anticoagulation to treat thrombotic event
Long term anticoagulation if recurrent
What signs would suggest long term anticoagulation is required?
History of previous thrombosis
Spontaneous thrombosis
Family history
Thrombophilia screening results
What is the main cause of acquired thrombophilia?
Antiphospholipid antibody syndrome
State the three main clinical features of anti-phospholipid antibody syndrome
Recurrent thrombosis
Recurrent foetal loss
Mild thrombocytopenia
Describe the pathology in anti-phospholipid antibody syndrome
Antibodies bind to B2 glycoprotein 1 causing conformation change and activation of primary and secondary haemostasis
What happens to APTT in anti-phospholipid antibody syndrome?
Prolong due to artefacts with assay - lupus anticoagulants
What conditions are associated with anti-phospholipid antibody?
Autoimmune
Lymphoproliferative
Viral
Drugs
How is anti-phospholipid antibody syndrome managed?
Aspirin - arterial
Warfarin - venous
Name the two indications for anticoagulants
Venous thrombosis
AF
What is the target of anticoagulants?
Fibrin clot
Coagulation cascade
How does heparin work?
Potentiates antithrombin and has an immediate effect
How is heparin administered?
IV or SC
What are the two forms of heparin?
Unfractionated
Low molecular weight
Describe the mechanism of action of heparin
Binds to antithrombin to keep it bound to thrombin/Xa leading to inactivation of coagulation
What is the predominant action of the two forms of heparin?
Unfractionated - thrombin binding
LMWH - Xa binding
How is heparin monitored?
APTT is sensitive for unfractionated
Anti-Xa assay can be used for LMWH
What are the complications of heparin?
Bleeding
Heparin induced thrombocytopenia
Osteoporosis
Describe heparin induced thrombocytopenia
Antibodies cause platelets to stick together (HITT)
Which type of heparin is HITT more common in?
Unfractionated
How do you reverse heparin?
Stop heparin
Protamine sulphate in severe bleeding
How does protamine sulphate work?
Reverses antithrombin effect and complete reversal for unfractionated and partial for LMWH
Name the coumarin anticoagulants
Warfarin, phenindione, acenocaoumarin, phenprocoumarin
How do coumarin anticoagulants work?
Inhibition of vitamin K
What depends on vitamin K?
Clotting factors II, VII, IX and X
Protein C and S
What must be done at the start of warfarin therapy?
Heparin should be prescribed as initially increased risk of clot due to protein C and S decreased
Describe the action of vitamin K
Carboxylation of glutamic acid residues allowing the clotting factors to bind to the platelet
Why must warfarin be closely monitored?
Narrow therapeutic index
How is warfarin monitored?
INR - mathematical correction using prothrombin time to allow for differences in lab techniques
What is the INR aim for patients on warfarin?
2-3
How can you reverse warfarin?
Stop therapy
Oral vit K if INR >8
Administer clotting factors - blood components
How long does vitamin K take to work in comparison to clotting factors?
Vit K - 6 hours
Clotting factors - immediate
Name the two types of new anticoagulant
Oral direct thrombin inhibitor
Oral Xa inhibitor
Give an example of an oral direct thrombin inhibitor and what is the problem with it?
Dabigatran
Excreted via kidneys and minor insult can lead to complications
What are the Xa inhibitors?
Edoxaban, rivaroxaban, apixaban
What are the indications for the new anticoagulants?
Prophylaxis
DVT/PE
Stroke prevention in AF
