Haemostasis Flashcards
Define Haemostasis and state 2 functions
What are the 3 steps in Haemostasis
The stopping of bleeding
Prevents bleeding
Prevents unnecessary coagulation
Make clot
Control clotting
Breakdown of clot (Fibrinolysis)
What 5 things are essential for Haemostasis
Keep blood moving Blood vessels Platelets Coagulation factors Anticoagulant factors
Compare primary and secondary Haemostasis
Primary: Platelets aggregate to form a plug at the vessel hole
Secondary: Plug strengthened with fibrin filaments
Describe Platelet Adhesion
- Damage to vessel wall
- Exposure of underlying tissues
- Platelets adhere to collagen via vWF receptor
Describe platelet activation
- Platelets secrete ADP and other substances to become activated and activate other platelets
- Involved in activation of clotting cascade
- Secrete coagulation factors from internal stores
Describe Platelet Aggregation
Cross linking of platelets to form a platelet plug
Identify 7 mediating factors that stimulate clotting
Platelet receptors- Glycoprotein complexes Von willebrands factor Fibrinogen Collagen surfaces ADP Thrombin Thromboxane
Outline the clotting cascade mechanism to make fibrin
- Intrinsic and extrinsic pathways activate Factor X
- Factor Xa activates Prothrombin II-> Thrombin IIa
- Thrombin IIa activates Fibrinogen 1-> Fibrin Ia
What are 2 ways that coagulation is controlled
- Natural anticoagulants inhibit activation of clotting cascade
- Clot destroying proteins, which are activated by the clotting cascade
Name 4 Natural Anticoagulants
Protein C
Protein S
Antithrombin
Tissue factor pathway inhibitor
What are Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT)
PT: A diagnostic test used to evaluate the extrinsic and common pathway
APTT: A diagnostic test used to evaluate the intrinsic and common pathways
A problem with which factors cause Prolonged PT
Which pathways are each factor in
7- Extrinsic
5,10,Prothrombin, Fibrinogen- Common
A problem with which factors cause Prolonged APPT
Which pathways are each factor in
8,9,11,12- Intrinsic pathway
5,10, Prothrombin, Fibrinogen- Common Pathway
What are D dimers
Fibrin degradation products
What does Von Willebrand Factor do
Involved in;
- Platelet aggregation
- Platelet adhesion
- Carries factor 8
What are 3 functions of the vessel wall
- Vasoconstriction
- Production of Von Willebrand’s Factor
- Exposure of collagen and tissue factor, initiating activation of clotting factors
Outline fibrinolysis
Plasminogen activator activates PLASMIN from PLASMINOGEN
Plasmin breaks down FIBRIN to D-Dimers
What are 3 causes of bleeding disorders and what are the 2 types
Inherited and acquired
Abnormalities in;
- Vessel wall
- Platelets
- Coagulation factors
What are 2 types of Coagulative Disorders
Congenital and acquired
Identify 3 congenital coagulation factor disorders
Identify 3 acquired coagulation factor disorders
Haemophilia A ( Deficiency in factor 8) Haemophilia B (Deficiency in factor 9) Von Willebrand’s disease
Liver disease
Vit K deficiency (Causes more bleeding)
Anticoagulants
Identify 4 signs of Coagulation factor disorders
- Intercerebral haemorrhage
- Severe post op, post traumatic bleeding
- Joint pain and deformity
- Prolonged bleeding after dental extraction
What is the inheritance pattern for Haemophilia
How does it present
How is it treated
X-linked recessive
Bleeding into muscles and joints, and post-operatively
Treated with recombinant factor 8 or DDAVP (releases factor 8 from vessels)
What is the inheritance pattern for Von Willebrand’s Disease
Identify 2 signs
What is the main genetic defect
Autosomal dominant
- Abnormal platelet adhesion to vessel wall
- Reduced Factor 8 amount/ activity
Main: Reduced vWF production
What are 3 clinical signs of von Willebrand’s Disease
Skin and mucous membrane bleeding
Prolonged bleeding after trauma
Spontaneous joint/ muscle bleeds (Rare)
Name 2 vessel wall abnormalities
Where do these occur
Easy bruising
Spontaneous bleeding from small vessels
Mainly skin but can be from mucous membranes
How does Disseminated Intravascular Coagulopathy affect;
PT
APTT
Fibrinogen count
D dimer count
What must happen for DIC to occur
Raised PT
Raised APTT
Low fibrinogen
Raised D dimers
Must be a trigger
Identify 5 triggers for DIC
Malignancy Massive tissue Injury Infections Massive haemorrhage and transfusion ABO transfusion reaction
What are Thrombophilias
How common are these? Do patients with these develop clots
Acquired/ congenital defects of haemostasis
Rare conditions, not unless patients have additional risk factors
What are the Congenital and Acquired causes of Thrombophilias
Congenital causes include deficiency in Natural Anticoagulants and an Abnormal Factor 5
Acquired causes include Antiphospholipid syndrome
