Coagulation Physiology & Disorders Flashcards
What happens in primary haemostatsis?
Platelets bind to breach
Forms platelet plug
What initiates coagulation?
Damage to vessel wall
What happens in secondary haemostatsis?
Fibrin clot forms
Stabilises platelet plug
What prevents clots in intact vessels?
Endothelial cells
What acts as a bridge between vessel wall & platelet?
VWF
What makes the fibrin clot?
Coagulation factors
What are the 2 main features of prothrombin (coagulation factor)?
Enzyme site
Glutamic acid tail
What does vitamin K do to the Glutamic acid tail of prothrombin?
It converts it into a negatively charged gamma carboxylated Glutamic acid (which can stick to surface of platelets)
What converts Vitamin K epoxide back to Vitamin K?
Vitamin K reductase
What enzyme does Warfarin inhibit in order to thin the blood?
Vitamin K reductase
What is produced locally at vessel damage that thickens blood?
Thrombin
What does thrombin cleave?
Fibrinogen —> fibrin
Fibrin spontaneously polymerises to form clot
What process breaks down the fibrin clot?
Fibrinolysis
What happens in fibrinolysis?
Plasminogen binds to fibrin & it is activated
Plasminogen—>plasmin
Plasmin cleaves fibrin & breaks down clot
What converts plasminogen —> plasmin?
Tissue plasminogen activator
What deficiency is seen in Haemophilia A?
Factor 8 deficiency
What deficiency is seen in Haemophilia B?
Factor 9 deficiency
How is Haemophilia inherited?
X linked recessive
Mother gives to son
Name a common place of bleeding in haemophilia & what this causes
Joint & muscle
Chronic joint damage & disability
Is Von Willebrand disease more or less common than haemophilia?
More common
What can’t form in VW disease?
The platelet plug
⬇️ platelet vessel wall adhesion
⬇️ platelet aggregation
⬇️ factor 8
What can’t form in haemophilia?
The fibrin clot
What 2 tests do you do for a bleeding patient?
FBC
- (low platelets, Hb, MCV)
Coagulation screen
- (PT, aPTT, TCT, Fibrinogen level)
What is measured to see how we’ll warfarin is working?
INR
What is the target INR?
2-3 or 3-4
Depending on bleeding risk
What converts
Fibrinogen ➡️ fibrin
Thrombin
What causes Vitamin K deficiency?
Warfarin New borns Critically ill Obstructive jaundice Malabsorption
Causes of DIC (abnormal clotting & bleeding, life threatening)
Infection (meningococcus) Malignancy Obstetric (placental abruption, eclampsia, amniotic fluid embolism) Shock ABO mismatch Venom (snake, spider)
Thrombocytopenia means…
Low platelet count
What is seen clinically in DIC
Generalised oozing (bento puncture sites)
What is seen in blood test if DIC patient?
Prolonged PT, aPTT, TT
Thrombocytopenia
Low fibrinogen
Raised D-dimer
What test tells you if a prolonged thrombin time is due to heparin?
A reptilase time
