Thrombosis Flashcards
(29 cards)
What is Virchow’s triad?
- Injury to vessel wall
- Altered blood flow
- Altered coagulability of blood
What do you use for white clots?
- Antiplatelet drugs
- Fibrinolysis
NB. White clots are platelet rich so used for atherosclerosis
What do you use for red clots?
- Warfarin
- Heparin
- Anti factor X
- Thrombin II inhibitors
NB. These used to anti-coagulate (fibrin rich clot) - usually formed in low flow systens such as veins (DVT) and atrial fibrillation
What is the coagulation system?
- Thrombin cleaves fibrin to fibrinogen
What does clopidogrel do?
- Blocks P2Y12 - used as antistroke along with aspirin :.
- Affects ADP pathway which leads to the expression of GPIib/IIIa receptors
- Thereby stopping platelet linkage by fibrinogen binding to GP receptors
What does streptokinase do?
- Activates plasminogen to form plasmin
- Plasmin degrades fibrin
What does tissue plasminogen activator do?
- Activates plasminogen to form plasmin
- Plasmin degrades fibrin
What does TXA (tranexamic acid) do?
Causes the expression of GPIib/IIIa receptors
What does Dipyridamole do?
- Inhibits the synthesis of TXA2 (inhibits cyclic endoperoxidase)
- Therevy stopping the expression of Iib/IIIa receptors
What is the mechanism of action of heparin?
- Low molecular weight heparin used in acute coronary syndrome only (inc. dalteparin and enoxaparin)
- Potentiates action of antithrombin III
- Binds to antithrombin
- Causes factor Xa to bind to this complex and be broken down
How does unfractioned heparin work?
- Binds to anti-thrombin
- Can bind to thrombin OR factor Xa
- Thereby stopping formation of thrombin and thrombin itself (factor Xa used to make thrombin)
What are the side effects of heparin?
- Bleeding - thins blood –> can cause intracranial, GI bleeding etc
- Osteoporosis with long term use
- Heparin induced thrombocytopaenia (potentiates bleeding because lowers platelet levels)
How do you reverse heparin?
- Unfractioned - protamine sulphate
- No reversal agent for LMWH - just need to stop taking it
How does dabigatran work?
Direct thrombin inhibitor
How does rivaroXaban work?
Inhibits factor Xa
How does warfarin work?
- Most commonly used
- Prolongs prothrombin time
- Acts on Vit K reductase
- If no Vit K reductase then cannot go through gamma carboxylation of factors 2, 9, 7 and 10
- Warfarin is loaded - dose based on genetic variability
What are the side effects of warfarin?
- Intacranial hemorrhage (ICH) due to very therapeutic window esp. if INR goes up too much
- Hemorrhage can be subdural
- Interacts with no. of medications (:. need to have regular blood tests to inhibit or potentiate effects)
- Warfarin is metabolised by CYP2C9 :. enzyme inhibitors potentiate the effects of warfarin and inducers reduce the effect
What is the advantage of warfarin?
- You can reverse it
- By giving vitamin K as this would reverse effects
What is heparin used for?
- Subcutaneous injection
- DVT, pulmonary embolism, prophylaxis, cancer patients to stop tumours from bleeding
How are direct thrombin inhibitors and anti-Xa’s administered?
- Orally
What are the side effects of DCOAs?
- Better efficacy than warfarin in terms of stroke, systemic embolism, ischaemia, heamorrhagic stroke
- Causes LESS intracranial bleeding than warfarin
- Causes same/less major bleeding than warfarin
- Causes more GI bleeding than warfarin
How are DCOAs in terms of vascular safety?
- Less MIs
- Less all cause mortality
- Less vascular mortality
How is warfarin administered?
Orally - needs to be monitored
What is bridging and what do you use to bridge?
- Bridging is when you give someone a short acting anticoagulant instead of a long acting one e.g. if someone with pulmonary embolism now then need to give LMWH immediately rather than loading
- It is also given when need to stop warfarin e.g. for surgery, so given before and after surgery to reduce risk of bleeding after surgery (as warfarin has high risk of bleeding)
