Flashcards in Clinical Haemostasis and Thrombosis Deck (28):
what is primary homeostasis and what is required to form this?
It is the formation of an UNSTABLE PLATELET PLUG.
Von willebrand factor and collagen are required.
What clinical feature is common to all bleeding disorders?
A disease of primary haemostasis could affect what components of the unstable platelet plug?
Vessel wall - ageing and steroids can damage the endothelium
Von Willebrand factor - vWF disease means that you have no vWF
Platelets - warfarin and other drugs affect platelet activity.
Thrombocytopenia (decrease in the number of platelets in the blood)
What is a characteristic feature of thrombocytopenia?
Petechiae ( these are small spots which occur in people)
what are the defects of primary homeostasis?
-Bleeding after trauma/surgery
What is the main role of secondary homeostasis?
1. involves the generation of thrombin from prothrombin
2. Thrombin converts fibrinogen to fibrin which form the insoluble mesh around the platelets.
What do we use to visualise the process of coagulation?
-we can visualise by measuring thrombin generation over time- this is called thrombogram.
Why is there a lag between the administration of a tissue factor trigger and the thrombin burst?
This is when co-factors and clotting factors are synthesised. This is when the co-factors and anticoagulant enzymes are being generated then there is a burst of thrombin.
what happens in haemophilia?
In haemophilia, coagulation factor 8 is missing causing failure of the thrombin burst. There is a much slower increase in thrombin and not as much thrombin is produced, this means that you do not get much of a fibrin mesh formed so the clot does NOT become stabilised.
what are the defects of secondary heamostasis?
Deficiency or defect of coagulation Factor 1-13.
-haemophilia co factors 8 or 9.
-Liver disease (most coagulation factors are made in the liver)
-Drugs (warfarin- inhibits synthesis of coagulation factors)
-Dilution (results from volume replacement)
-Consumption (disseminated intravascular coagulation-acquired)
What is haemophilia defined as?
Failure to generate fibrin to stabilise the platelet plug
Describe the pattern of bleeding of defects in secondary haemostasis.
DELAYED - people with defects in secondary haemostasis are generally fine with small cuts. They bleed deeper into joints and muscles. Do NOT tend to bleed excessively from small cuts (because the primary haemostasis is fine)
What is the hallmark of haemophilia?
Haemarthrosis - bleeding into joints. This is a characteristic feature of severe haemophilia A and B. They bleed into joints and the pressure builds up and the joint becomes swollen and painful.
State some defects of clot stability.
Excess fibrinolytic (tPA)
Deficient antifibrinolytic (antiplasmin)
What is DIC?
Disseminated intravascular coagulation - widespread activation of the coagulation cascade
Leads to consumption of the clotting factors - that's why it's also called consumptive coagulopathy
what are the clinical features of secondary heamostasis?
-Deeper: joints and muscles
-Do not tend to get excessive bleeding from small cuts
-small vessels are generally ok
-Nosebleeds are rare
-bleeding after trauma/surgery
-bleeding after intramuscular injections
what does venous emboli and arterial emboli cause?
Venous emboli= Pulmonary embolism
Arterial embolism= usually from heart, may cause stroke or limb ischaemia.
What are the consequences of thromboembolism?
Thrombophlebitic syndrome= swelling and ulcers in the leg due to damage to valves leading to stasis.
what can increase the irsk of thrombosis?
-combined contraceptive pill
How does risk of thrombosis change with age?
What are the three components of Virchow's triad?
Hypercoagulability= dominant in venous thrombosis
Vessel wall injury = dominant in arterial thrombosis
Stasis= complex, contributes to both. the fater the blood flows, the more activated coagulation factors get swept away and the less chance of a thrombus forming
Why is pregnancy associated with an increase in the risk of thrombosis?
Pregnancy involved reduced mobility and reduced flow and a decrease in protein S meaning that blood becomes procoagulant
What is the only circumstance in which thrombolytic therapy is given? Why is it not given more often?
Because giving thrombolytic therapy increases the risk of bleeding.
What happens in haemophilia?
Deficiency of factor 8 or factor 9. Massively slows down the production of thrombin and so there is no real thrombin burst. Not much fibrin mesh is formed and so the clot is not stabilised.
What is abnormal bleeding?
Abnormal bleeding is characterised by being spontaneous, prolonged or out of proportion to the injury.
what is thrombosis
Thrombosis is inappropriate clot formation and occurs in an intact vessel
what type of embolism do most patients die from?
Venous thromboembolism is an important cause of death in hospital patients