Abnormalities of haemostasis Flashcards
What are the main components of the haemostatic response?
Platelets
Von Willebrand factor
Clotting factors
What are the regulators of the haemostatic response?
Inhibitors of coagulation:
- Tissue Factor Pathway Inhibitor (TFPI)
- Protein C
- Protein S
- Antithrombin
Inhibitors of platelets:
- Prostcyclin
- Nitric oxide
How do platelets adhere to one another?
Gp1b receptors bind to the von willebrand factor that is exposed on the endothelium
GpIIbIIIa receptors then bind to the exposed von willbrand factor that is attached the the already bound platelets
How does Von Willebrand disease typically present?
Presents with mucocutaneous bleeding and with menorrhagia in women
What is thrombotic thrombocytopenic purpura?
Rare autoimmune disease in which many small thrombi form. Mainly treated through plasma exchange and transfusing platelets can make things worse.
What is the difference between primary and secondary haemostasis?
Primary haemostasis is the initial formation of a platelet plug
Secondary haemostasis is Formation of fibrin cross linking that stabalises the clot
Give some examples of problems with secondary haemostasis?
Due to low clotting factor levels or reduced clotting factor function
Haemophilia is an inherited form
Can be aquired through liver disease, Vit K deficiency and drugs
How does fibrinolysis take place?
Plasminogen and tissue plasminogen activator (tPA)
bind to fibrin
Plasmin breaks fibrin and fibrinogen down – formation of fibrin(ogen) degradation products (FDPs AKA Ddimers)
How does tranexamic acid work and what is it used for?
It inhibits fibrinolysis so helps to stop bleeding. Used in trauma and with bleeding risk
What does an isolated prolonged prothrombin time show?
Factor VII deficiency
What does an isolated prolonged partial thromboplastin time indicate?
Problem in the intrinsic or common pathways
What does a prolonged APTT and prothrombin time show?
Either a single factor deficiency in the common pathway or multiple factor deficiencies
