Haemostasis Flashcards

Question

Where are clotting factors synthesised?

Answer 1

Mostly in the liver and except VIII and VWF (made in endothelial cells)

Answer 2

Factors II (prothrombin), VII, IX and X are dependent on Vitamin K for gamma carboxylation of their glutamic acid residues, which is essential for the function of these clotting factors.

Answer 3

-Protein C and protein S (co-factor) thrombin binds to thrombomodulin on endothelial cell surface causing protein C to become APC (activated protein C) in the presence of S inactivates 8a and 5a -antithrombin inactivates thrombin and 10a the action of antithrombin is made more potent by heparin released from macrophages

Answer 4

-Heparin Potentiates action of antithrombin => inactivates 10a and 2a (thrombin) Administered IV or SC -Warfarin Vit K antagonist => interferes with protein carboxylation Reduces synthesis of Factors 2, 7, 9, 10 in the liver Administered orally, takes several days to take effect as it deals with synthesis of new factors Needs to be monitored by regular blood testing DOACs (Direct Oral Anticoagulants) Directly inhibits thrombin or 10a (without the involvement of antithrombin)

Answer 5

Mechanism to lyse clots- primary fibrinolytic enzyme - Plasmin circulates as plasminogen it is activated by tissue plasminogen activator (t-PA) however this only happens when it comes together on lysine residues on fibrin

Answer 6

Fibrin degradation products Also breaks down other plasma proteins ie factors 5 and 8 and fibrinogen inhibited by anti-plasmin (which circulates in blood) and alpha 2 macroglobulin

Answer 7

Recombinant t-PA (using bacteria to make it) administered intravenously to selected patients presenting with ischaemic stroke. time-dependent and so t-PA needs to be given to eligible patients as quickly as possible There is a high risk of bleeding associated with its use. Thrombolytic therapy can also be given to patients with life threatening pulmonary emboli

Answer 8

Tranexamic Acid => synthetic derivative of lysine, binds plasminogen Prevents activation of plasminogen Used to treat bleeding in trauma, surgery and for inherited bleeding disorders

Answer 9

Prothrombin Time (PT) Test It measures primarily the clotting ability of factors 1, 2, 5, 7, 10 If any of these factors are too low, it takes longer than normal for the blood to clot. The results of this test will be normal among most people with haemophilia A and B. Extrinsic Pathway

Answer 10

It measures the clotting ability of factors 8, 9, 11, 12. The results of this test will show a longer clotting time among people with haemophilia A (VIII) or B (IX) and XI deficiency. Intrinsic pathway

Answer 11

1. Reduction in platelet number or function Primary haemostasis –platelet plug 2. Reduction in coagulation factors Secondary haemostasis – fibrin clot 3. Increased fibrinolysis

Answer 12

Reduced anticoagulant proteins Reduced fibrinolytic actvity e.g. pregnancy Increased clotting factors Factor 8 in pregnancy Factor V Leiden (thrombophilia) Myeloproliferative disorders

Answer 13

- allow the stimulation of blood clotting processes following injury, where blood changes from its liquid state (coagulation) - Limit the extent of the response to the area to prevent excessive or generalised clotting (thrombosis) - Start the process leading to breakdown of the clot as part of the healing process (fibrinolysis)

Answer 14

II- prothrombin - essential VII - essential IX - essential X - essential 2+7=9 and 10

Answer 15

endothelial cells can synthesise more COX where non nuclear platelets cannot

Answer 16

TP-α platelet adhesion and aggregation TP-β vasoconstriction

Answer 17

Calcium ions play an important role in the binding of activated clotting factors to the phospholipid surfaces of platelets.

Answer 18

The three contributory factors to pathological clotting or thrombosis. * Blood: dominant in venous thrombosis * Vessel wall: dominant in arterial thrombosis * Blood flow: complex, contributes to both arterial and venous thrombosis

Answer 19

Failure of production - drugs/viruses, bone marrow infiltration Shortened survival - immune thrombocytopenia, increased splenic pooling Reduction in function- inherited causes or aspirin (antiplatelet drugs

Answer 20

Congenital VWD haemophilia A - Factor VIII deficiency haemophillia B - Factor XI deficiency Acquired liver Anticoagulant drugs DIC -disseminated intravascular coagulation - condition in which blood clots form throughout the body, blocking small blood vessels) Tx: Replacement with recombinant factors

Answer 21

Increased fibrinolysis | DIC, due to thrombolytic therapy tPA

Answer 22

• Reduced levels of anticoagulant proteins • Reduced fibrinolytic activity - pregnancy where there is an inhibition of plasminogen • Increased levels of clotting factors or platelets - Levels of VIII rising in pregnancy - The activity of factor V is increased by a mutation - Factor V Leiden makes factor V more resistant to inactivation by protein C - inherited thrombophilia - Platelets are increased in number in some myeloproliferative disorders, where the bone marrow output is increased.

Haemostasis Flashcards

(46 cards)