Flashcards in Haemostasis Deck (23):
what is haemostasis?
Make a clot
Control the clotting
Breaking the clot down
What is the role of platelets in clotting?
Platelets are produced by megakaryocytes in the bone marrow.
They adhere to the vessel wall when it is damaged and there is exposure of underlying tissues.
Platelets adhere to collagen via von willebrand factor
Platelets then activate each other by secreting ADP and thromboxane. This also activates the clotting cascade
The result of this is to form a platelet plug.
What is the role of thrombin and fibrin in blood clotting?
Amplification system of precursor proteins generates thrombin
Thrombin converts soluble fibrinogen into insoluble fibrin
This enmeshes the platelet plug to make a stable clot
What is the role of thrombin inhibitors in blood clotting?
Stop excessive clotting.
Anticoagulation factors are: protein C, protein S, antithrombin, tissue factor pathway inhibitor
What is APTT?
Measures extrinsic pathway- injury to blood vessel from external force
What is PT?
Measures intrinsic pathway- damage to blood vessel from internal force eg atheroma.
Which clotting factors influence PT?
Which clotting factors influence APTT?
What are the 3 major reasons why you might develop thrombocytopenia?
Trapping of platelets
What might cause decreased production of platelets?
Heavy alcohol consumption
Why might platelets become trapped in the spleen?
In cases of splenomegaly eg portal hypertension/ viral infections/ EBV
What might cause increased destruction of platelets?
Immune thrombocytopenia (lupus and RA), bacteremia, thrombotic thrombocytopenic purpura
Medications- such as heparin
Which clotting factor are haemophilia A patients deficient in?
What clotting factor are haemophilia B patients deficient in?
How is haemophilia inherited?
X linked recessive
How will patients with haemophilia present?
Bleeding into muscles and joints
How is haemophilia treated?
With recombinant clotting factor that is missing.
What is the mode of inheritance of von willebrand disease?
What is von willebrand disease?
Abnormal platelet adhesion to vessel wall which causes skin and mucous membrane bleeding.
What is hereditary haemorrhagic telangiectasia?
Autosomal dominant condition which is characterised by microvascular swellings. GI haemorrhage can lead to iron deficiency anaemia.
What is DIC?
Disseminated intravascular coagulation
Its a type of microangiopathic haemolytic anaemia
Pathological activation of coagulation, numerous mimcrothrombi are formed in circulation, this uses up clotting factors and platelets
What will you expect in the blood results of A. DIC patient?
Prolonged INR, APTT, low fibrinogen, raised D dimers.