Coagulation

Question 1

What two opposing systems does the body balance in haemostasis?

Answer 1

Coagulation → forms clots to stop bleeding<br></br>Fibrinolysis → breaks clots to maintain blood flow

Question 2

What is the final product of the coagulation cascade?

Answer 2

Fibrin – a mesh stabilising the platelet plug

Question 3

Difference between white and red thrombus?

Answer 3

White thrombus: arterial, platelet‑rich, treated with antiplatelets<br></br>Red thrombus: venous, fibrin + RBCs, treated with anticoagulants

Question 4

What conditions are examples of arterial thrombosis?

Answer 4

Myocardial infarction and ischaemic stroke

Question 5

What conditions are examples of venous thrombosis?

Answer 5

Deep vein thrombosis (DVT) and pulmonary embolism (PE)

Question 6

Why are venous clots dangerous?

Answer 6

They can detach → travel to lungs → pulmonary embolism

Question 7

What is VTE?

Answer 7

Venous thromboembolism = DVT + PE

Question 8

What happens during normal haemostasis after vessel injury?

Answer 8

↓ NO and prostacyclin from endothelium<br></br>Platelet activation (Ca²⁺ dependent)<br></br>Coagulation cascade activation<br></br>Fibrin stabilises clot

Question 9

What two pathways start the coagulation cascade?

Answer 9

Extrinsic (tissue factor) and intrinsic (collagen exposure)

Question 10

Why is calcium essential for clotting?

Answer 10

Allows clotting factors to bind platelet phospholipid surfaces

Question 11

Why are EDTA tubes used in lab blood samples?

Answer 11

They chelate calcium and prevent clotting

Question 12

What is the most important reaction in coagulation?

Answer 12

Prothrombin → thrombin → fibrinogen → fibrin

Question 13

What is the thrombin burst?

Answer 13

Thrombin activates V, VIII, XI and platelets → rapid amplification of clotting

Question 14

How does healthy endothelium prevent clotting?

Answer 14

Releases nitric oxide and prostacyclin and activates natural anticoagulants

Question 15

Key natural anticoagulants in the body?

Answer 15

Antithrombin III and Protein C

Question 16

What is fibrinolysis?

Answer 16

Plasmin breaks down fibrin

Question 17

Which drugs are fibrinolytics?

Answer 17

Alteplase, reteplase, tenecteplase, streptokinase

Question 18

What does tranexamic acid do?

Answer 18

Blocks plasmin formation → prevents clot breakdown

Question 19

Main uses of anticoagulants?

Answer 19

DVT, PE, atrial fibrillation, surgical prophylaxis

Question 20

Do anticoagulants dissolve clots?

Answer 20

No – they prevent new clots and extension

Question 21

Direct thrombin inhibitor DOAC?

Answer 21

Dabigatran

Question 22

Antidote to dabigatran?

Answer 22

Idarucizumab

Question 23

Factor Xa inhibitor DOACs?

Answer 23

Apixaban, rivaroxaban, edoxaban

Question 24

Antidote to Factor Xa inhibitors?

Answer 24

Andexanet alfa

Question 25

Why DOACs are preferred?

Answer 25

Predictable effect
No routine monitoring
Few food interactions

Question 26

What is fondaparinux?

Answer 26

Indirect Factor Xa inhibitor given subcutaneously

Question 27

Mechanism of unfractionated heparin?

Answer 27

Enhances antithrombin III → inhibits thrombin (IIa) and Factor Xa

Question 28

Heparin monitoring test?

Answer 28

APTT

Question 29

Heparin antidote?

Answer 29

Protamine sulfate

Question 30

What is HIT?

Answer 30

Heparin + PF4 antibodies activate platelets → thrombosis despite low platelets

Question 31

Advantages of LMWH over UFH?

Answer 31

Longer half‑life
Predictable effect
Less monitoring
Less protein binding

Question 32

Mechanism of warfarin?

Answer 32

Inhibits vitamin K epoxide reductase → reduces activation of II, VII, IX, X

Question 33

Warfarin monitoring test?

Answer 33

PT/INR

Question 34

Warfarin antidote?

Answer 34

Vitamin K

Question 35

Why is heparin bridging used with warfarin?

Answer 35

Warfarin blocks new factor synthesis → slow onset

Question 36

Why warfarin dose varies?

Answer 36

CYP2C9 polymorphisms and vitamin K reductase gene variation

Question 37

What lab test measures intrinsic pathway?

Answer 37

APTT

Question 38

What lab test measures extrinsic pathway?

Answer 38

PT

Question 39

What is INR used for?

Answer 39

Monitoring warfarin effect

Question 40

When are fibrinolytics used?

Answer 40

Massive PE, acute MI, ischaemic stroke

Question 41

How does oestrogen increase clot risk?

Answer 41

Increases clotting factors and decreases antithrombin

Question 42

Which therapies increase VTE risk?

Answer 42

Combined oral contraceptives and HRT

Question 43

General VTE risk factors?

Answer 43

Age, obesity, cancer, pregnancy, surgery, smoking, heart failure, IBD, previous VTE

Question 44

How is DVT treated?

Answer 44

Anticoagulant (usually DOAC)

Question 45

How is PE treated?

Answer 45

Anticoagulant; fibrinolytic if life‑threatening

Question 46

Key treatment rule?

Answer 46

Arterial clot → antiplatelet
Venous clot → anticoagulant
Massive PE → fibrinolytic