Coagulation- Normal and Abnormal

Question 1

Define the term haemostasis

Answer 1

The halting of blood

Originates from the Trojan war, approx 1250 BCE

Question 2

What is the ideal coagulation system designed to do?

Answer 2

Allow blood to flow through vessels, cope with leaks, and repair mechanism to dissolve clots

Question 3

What are the main constituents of coagulation?

Answer 3

• Vessel wall lined by endothelium
• Platelets
• Coagulation factors in pre-activated state
• Inhibitors of coagulation
• Fibrinolytic system and inhibitors

Question 4

What role do endothelial cells play in coagulation?

Answer 4

Line blood vessels and form a barrier, produce thrombomodulin and heparin sulphate, and reduce platelet adhesion

Question 5

What stimulates platelet production?

Answer 5

Thrombopoetin (TPO) derived from the liver

Question 6

How long do platelets circulate in the bloodstream?

Answer 6

5-10 days with approximately 30% stored in the spleen

Question 7

What is the function of thromboxane A2 and serotonin released from platelets?

Answer 7

Cause vasoconstriction

Question 8

What are the two pathways that activate the coagulation cascade?

Answer 8

• Intrinsic pathway (endothelial collagen)
• Extrinsic pathway (tissue factor)

Question 9

What are coagulation inhibitors?

Answer 9

Proteins that regulate coagulation, such as Protein C and Antithrombin

Question 10

What activates plasminogen in the fibrinolytic system?

Answer 10

Tissue plasminogen activator (tPA) from endothelial cells

Question 11

What is measured as a product of fibrinolysis?

Answer 11

Fibrin degradation products including D Dimers

Question 12

What is the reference range for platelet count?

Answer 12

150-400 x 10^9/L

Question 13

What does a bleeding time test assess?

Answer 13

Overall clotting, mainly platelet function

Question 14

What is the purpose of Prothrombin time (PT) testing?

Answer 14

Measures time until clot forms in extrinsic and common pathways

Question 15

What does the Activated Partial Thromboplastin Test (APTT) measure?

Answer 15

Intrinsic and common pathway of coagulation

Question 16

What is the final substrate for making fibrin?

Answer 16

Fibrinogen

Question 17

What is the inheritance pattern of Haemophilia A and B?

Answer 17

X-linked defect

Question 18

What is Von Willebrand disease characterized by?

Answer 18

Defect in platelet adhesion and binding of VIII

Question 19

What are common causes of acquired coagulation disease?

Answer 19

• Liver disease
• Disseminated Intravascular Coagulation (DIC)

Question 20

What triggers Disseminated Intravascular Coagulation (DIC)?

Answer 20

• Trauma
• Malignancy
• Sepsis
• Amniotic fluid embolism

Question 21

What is thrombocytopenia?

Answer 21

Low platelet count

Question 22

What can cause thrombocytopenia?

Answer 22

• Under-production
• Increased use
• Abnormal distribution

Question 23

What is the role of Protein C in coagulation?

Answer 23

Activated by thrombomodulin-thrombin complex to degrade coagulation factors Va and VIIIa

Question 24

What is the significance of the INR?

Answer 24

Expresses the ratio of the patient’s PT time over the control PT time

Question 25

What is the effect of Warfarin on coagulation factors?

Answer 25

Reduces factors II, VII, IX, and X

Question 26

What is a common inherited defect that leads to increased clotting?

Answer 26

Factor V Leiden

Question 27

What are the components of Virchow’s triad?

Answer 27

• Abnormal vessel wall
• Abnormal flow
• Abnormal blood component

Question 28

What can lead to abnormal blood component?

Answer 28

• Increased hemoglobin/red cell count
• Increased WBC or platelet count
• Increased viscosity of plasma