7. Bleeding And Thrombosis Flashcards
What do you need to make a blood clot
Plasma and coagulation factor
Platelets and Von wilibrands factor (vWf)
They need to be activated
Natural anticoagulants-confines clot
Fibrinolytic system- removes clot after enough time
Discuss the epithelium
It’s a non stick surface, things don’t want to stick to it,
It produces nitric oxide, heparins, thrombomodulin, prostacyclins
What activates clots?
Abnormal surface- e.g. subendothelial collagen
and physiological activator e.g. tissue factor
Discuss how platelets are involved in clotting?
Platelets contains lots of receptors to things that want to stick to it such a vWF, fibrinogen or things that sense damage e.g. epinephrine. This makes platelets activated and sticky
How do platelets do it’s job?
They contain granules and factors that help the platelet do there job. Alpha and dense granules. The platelets role is to become a clumpy clot and allows for fibrinogen clots
What is the role of platelets?
3 A’s
Adhere
Activate
Aggregation
Provide phospholipid activation for coagulation
What is adhered in platelets?
vFW, fibrinogen
What is activated in platelets
Pathways are activated
Cyclase oxigenase promotes aggregation, aspirin inhibits this
ADP/P2Y12 pathway- clipidogrel inhibits this pathway
How do platelets aggregate?
Form thromboxane, shrink down and clump together.
What is Von wilibrands factor?
A big sticky molecule. Need to have it at sites of vessel damage or else you bleed. Most common bleeding disorder is Von wilibrands disease.
Why do we need vWF
Binding sites for collagen, platelet binding sites, binding sites for factor 8
What consists of a platelet plug?
Platelets
Fibrinogen
vWF- binds platelets to collagen
What do we need to form a permenant clot?
A fibrin clot
How do we form a fibrin clot?
A set of coagulation factors. Like dominoes
They act like dominoes and if they all activate each other then bleeding stops
Why would haemophilia occur?
Coagulation factor deficiency or a factor is excessively inhibited
What are the extrinsic factors that cause clot
Tissue factor (3)—> 7—> 10 —> prothrombin and thrombin
How does the intrinsic pathway occur
Activated by prothrombin
12–>11->9+8–>10+5–> prothrombin (2) + thrombin (1)
What is a natural coagulation factor
Factors that switch off the process of natural clot formation
Tissue factor inhibitor
Activated tissue protein C and S
Antithrombin
What happens if natural anti coagulation factors are absent?
Fibrin and red cells- red clot found in arteries
Platelets- white clot found found in veins
When a clot fixes itself it’s a thrombus.
When a clot flies off it’s an embolis
How does activated protein C and S disinhibit clots?
Inactivates factor 8?
How does antithrombin stop clotting
Inhibits coagulation factor 10 and thrombin
How does tissue inhibiting factor stop clotting
Inhibits clotting factor 10, reducing thrombin production
What is involved in the fibrinolytic system?
They disregard clots. They produce the activaters of plasminogen. (TPA)
What do plasminogens do?
TPA cleaves plasminogen into plasmin.
Plasmin degrades clots and causes pain fibrinogen degradation products such a D-dimmers
How do antiplatlet drugs work?
Aspirin inhibits the COX pathway in platelets
Clipidogrel inhibits the ADP pathway.
Tirofiban inhibits the GP IIb/III pathway
What are high risk bleeding situations?
Spinal surgery
Neuro surgery
Retinal surgery
How do anticoagulants drugs work?
Warfarin inhibits the post translational factors factors to inhibit the production of thrombin and fibrin
Heparin- binds to antithrombin and kills activated activated protease
Direct inhibitors of tenase- apixiaban, rivaroxaban, dabigatran
How do you assess someone’s PT time?
Blood is extracted and calcified to stop immediate clotting factors. Separated by centrifuge. Plasma is added to tissue clotting factor. Blood is re calcified and it is timed how long to clot
Intrinsic pathway
How do you assess someone’s APTT
tests the extrinsic coagulation pathway, normal clotting is around 35s
