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Haematology Week 2 2018/19 > 1: Haemostasis > Flashcards

1: Haemostasis Flashcards

1
Q

What is haemostasis?

A

Arrest of bleeding while maintaining vascular patency

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2
Q

What is primary haemostasis?

A

Formation of a fibrin plug at a site of bleeding

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3
Q

Which protein is involved in secondary haemostasis?

A

Fibrin

forms a CLOT around the platelet plug

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4
Q

Which two processes keep haemostasis in check after the formation of the fibrin clot?

A

Fibrinolysis

Anticoagulation

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5
Q

Which blood cells form platelets?

A

Megakaryocytes

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6
Q

Are platelets cells?

A

No

Buds of cytoplasm from megakaryocytes

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7
Q

How long do platelets last for?

Why is this clinically relevant?

A

7 - 10 days

Anti-platelets e.g aspirin are stopped 7-10 days before surgery to avoid bleeding

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8
Q

What is the accumulation of platelets at a site of injury called?

A

Aggregation

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9
Q

Platelets ___ to form a plug in ___ haemostasis.

A

aggregate

primary haemostasis

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10
Q

Why do elderly patients bruise easily?

A

Express less collagen at sites of injury

Leading to less efficient haemostasis

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11
Q

What is Vitamin C required to produce?

What is Vitamin C deficiency called?

A

Collagen

Scurvy

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12
Q

What is a reduced number of platelets called?

A

Thrombocytopaenia

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13
Q

What proteins encourage platelet adhesion at the site of an injury?

A

Collagen

Von Willebrand factor

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14
Q

What is an autoimmune disease which causes a rash and thrombocytopaenia?

A

Immune thrombocytopaenic purpura

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15
Q

What symptoms may a patient have if they cannot form a platelet plug?

A

Bruising

Purpuric rash

Exaggerated bleeding

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16
Q

What diseases, causing platelet dysfunction, can cause abnormal bleeding?

A

Vitamin C deficiency (reduced collagen expression)

Autoimmune thrombocytopaenic purpura

Von Willebrand disease

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17
Q

Why do purpuric rashes often appear on the lower limbs?

A

Oncotic pressure due to gravity

Fluid (inc. blood) squeezed out of capillaries

Elderly / thrombocytopaenic patients cannot stop this “bleeding”

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18
Q

What is measured to diagnosed primary haemostasis?

A

Platelet count

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19
Q

What molecules are platelets made of?

A

Phosphoplipids

Which are negatively charged

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20
Q

Which ion is secreted by platelets?

A

Calcium

Ca2+, binds to -ve phospholipids

21
Q

Which proteins bind to Ca2+ ions, found on the platelet plug, to cause secondary haemostasis?

A

Clotting factors

22
Q

Which clotting factors initiate coagulation?

A

Tissue factor and Factor VIIa

23
Q

Which two clotting factors convert prothrombin to thrombin?

A

Factor V and Factor Xa

24
Q

___ ___ and factor ___ initiate clotting.

A

Tissue factor and Factor VIIa

25
Q

The factor V/Xa complex converts ___ to ___.

A

prothrombin to thrombin

26
Q

Thrombin converts ___ to ___, forming a clot.

A

fibrinogen to fibrin

27
Q

What converts fibrinogen to fibrin to form a clot?

A

Thrombin

which is produced from prothrombin by factors V/Xa

28
Q

Apart from converting fibrinogen to fibrin to form a clot, what else does thrombin activate during coagulation?

A

Factors VIII/IXa

Which reactivates Factor V/Xa

Which converts more prothrombin to thrombin…

29
Q

Which protein, generated midway through the clotting cascade, activates other clotting factors?

A

Thrombin

30
Q

What is the end product of the clotting cascade?

A

Fibrin

forming a clot

31
Q

What is the first clotting factor which binds to the platelet plug?

A

Tissue factor <=> VIIa

32
Q

What diseases are caused by a deficiency of

a) Factor VIII
b) Factor IX?

A

a) Haemophilia A

b) Haemophilia B

33
Q

Which clotting factors are deficient in

a) Haemophilia A
b) Haemophilia B?

A

a) Factor VIII (haemophilia A)
b) Factor IX (haemophilia B)

34
Q

Why might a patient with an increased reticulocyte count (e.g haemorrhage, haemolysis) also have thrombocytosis?

A

Red blood cells and megakaryocytes are derived from the same progenitor cells

So when you get an increase in red cell production, you get an increase in platelets

35
Q

What is disseminated intravascular coagulation?

How is it related to clotting factors?

What triggers it?

A

Widespread clotting

Depletes clotting factors and platelets, thereby causing widespread bleeding

Trauma, sepsis, complicated pregnancy, malignancy, autoimmune disease…

i.e in anyone with widespread bleeding and thrombocytopaenia consider DIC

36
Q

Which protein breaks down fibrin?

A

Plasmin

37
Q

What is a notable fibrin breakdown product?

A

D dimer

38
Q

Which protein converts plasminogen to plasmin?

A

Tissue plasminogen activator (tPA)

39
Q

Where can blood escape in haemophilia?

A

Epistaxis, menorrhagia, malaena etc…

Into muscles

Into joints (haemarthrosis)

40
Q

What is the mode of inheritance of haemophilia A and B?

A

X linked recessive

41
Q

Which blood tests measure time taken for action of

a) tissue factor / factor VIIa?
b) factor VIII / IXa?

A

a) Prothrombin time (PT or INR)

b) Activated partial thromboplastin time (APTT)

42
Q

Which clotting times are useful for

a) warfarin monitoring
b) heparin monitoring?

A

a) Warfarin monitoring - prothrombin time (factor VII)

b) Heparin monitoring - APTT (factor VIII/IXa)

43
Q

What should you look at specifically on examination of someone with a suspected bleeding disorder?

A

Lower limbs - purpura

Mouth - the same

Eyes - retinal haemorrhage

Bleeding into muscles and joints

44
Q

Which naturally occurring anticoagulant acts on thrombin?

A

Anti-thrombin III

45
Q

Which anticoagulants act on clotting factors?

A

Protein C

(aided by protein S)

46
Q

Which protein does thrombin use to switch functions and inhibit (instead of promote) coagulation?

A

Thrombomodulin

switches on Protein C and S

47
Q

Which inherited disorder causes a tendency for venous thrombosis?

A

Thrombophilia

48
Q

What is the most common type of inherited thrombophilia?

A

Factor V Leiden

Haematology Week 2 2018/19 (7 decks)

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