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Haematology > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

Haemostasis defintion?

A

stopping of bleeding AND maintenance of vascular patency

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2
Q

Requirements for Haemostasis? (4)

A

permanently ready,
prompt response,
localised response,
protection against unwanted thrombosis

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3
Q

Normal haemostatic system components?

A

formation of platelet plug,
formation of fibrin clot,
fibrinolysis,
anticoagulant defences

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4
Q

What is primary haemostasis ?

A

formation of platelet plug

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5
Q

What is secondary haemostasis?

A

formation of fibrin clot

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6
Q

Why does fibrinolysis happen?

A

To keep vascular patency so basically blood clots then unclots

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7
Q

Where & how do platelets form?

A

budding from cytoplasm of megakaryocytes in the bone marrow

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8
Q

Platelets have a nucleus. T/F?

A

False - don’t have

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9
Q

Life span of platelets?

A

7-10days

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10
Q

What triggers platelet adhesion when an endothelial wall is damaged and what leads to aggregation?

A

endothelial damage exposes collagen, endothelial cells then release von willebrand factor and other proteins that platelets have receptors for. Then platelets secrete chemicals which leads to aggregation (i.e. platelets sticking together)

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11
Q

Vascular cause of failure of platelet plug formation

A

vascular: lacking collagen e.g. old or scurvy,
platelets: reduced number - thrombocytopenia,
reduced function e.g. aspirin,
von willebrand factor reduction

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12
Q

Commonest inherited bleeding disorder?

A

von willebrand

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13
Q

Consequences of failure of platelet plug formation (4)

A

spontaneous bruising and purpura,
mucosal bleeding e.g. epistaxes, gastrointestinal, conjunctival, menorrhagia,
intracranial haemorrhage (rare, only severe cases),
retinal haemorrhages

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14
Q

Screening tests for primary Haemostasis?

A

platelet count,

no simple screening tests for other causes

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15
Q

Minor injuries usually only require primary Haemostasis. T/F?

A

True

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16
Q

Outline formation of fibrin clot

A

negatively charged phospholipid in platelets release calcium so surface is positively charged, negatively charged clotting factors attracted and sit on surface.
tissue factor released from damaged endothelium binds to clotting factor VIIa and activates it,
these activate V and Xa which activate prothrombin forming thrombin.
Thrombin activates fibrinogen from fibrin and also activates clotting factors VIII and IXa which activate more V and Xa

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17
Q

Positive feedback loop in formation of fibrin clot

A

Thrombin activates fibrinogen from fibrin and also activates clotting factors VIII and IXa which activate more V and Xa

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18
Q

What is intiation phase of fibrin clot formation?

A

tissue factor and VIIa

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19
Q

What is amplification phase of fibrin clot formation?

A

thrombin activating VIII and IXa

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20
Q

What is propagation phase?

A

Generation of fibrin clot

21
Q

Causes of failure of fibrin clot formation? (give examples of each) (3)

A

single clotting factor deficiency e.g. haemophilia,
multiple clotting factor deficiencies e.g. DIC, liver disease,
increased fibrinolysis e.g. usually part of complex coagulopathy

22
Q

Single clotting factor deficiency is usually acquired/hereditary and multiple clotting factor deficiencies is usually acquried/hereditary

A

single clotting factor deficiency - usually hereditary,

multiple clotting factor deficiency - usually acquired

23
Q

Once bleeding stopped, fibrinolysis occurs to maintain vascular patency. What degrades fibrin into fibrin degredation products (FDP)?

A

Plasmin

24
Q

What is plasmin formed by and from what?

A

Formed by Tissue Plasminogen Activator (tPA) from plasminogen

25
Q

FDPs can be measured in blood how?

A

D-dimers

26
Q

Consequences of failure of fibrin clot formation?

A

no clinical syndrome,

pattern depends on single/multiple abnormalities and the clotting factors involved

27
Q

Pattern of bleeding in haemophilia?

A

Bleeding into load bearing joints e.g. ankles and knees

28
Q

Pattern of bleeding in DIC

A

general bleeding tendency into abdominal etc basically all over

29
Q

Screening tests for fibrin clot formation? (2)

A 
Prothrombin time (PT), 
activated partial thromboplastin time (APTT)
30
Q

What factors does PT test?

A 
VIIa, 
V, 
Xa, 
Prothrombin, 
fibrinogen
31
Q

What factors does APTT test?

A 
VIII, 
IXa,
V, 
Xa, 
prothrombin, 
fibrinogen
32
Q

Deficient VIIa which test normal which delayed

A

PT delayed,

APTT normal

33
Q

Primary Haemostasis patterns of bleeding (2)

A

purpura,

mucosal

34
Q

Secondary Haemostasis patterns of bleeding (2)

A

joint bleeds,

muscle bleeds

35
Q

Deficient VIII or IXa which test normal which delayed

A

PT normal,

APTT delayed

36
Q

History in bleeding disorders important questions (3)

A

bleeding/bruising,
duration (lifelong/short),
previous surgery/dental extractions

37
Q

what drug history important?

A

aspirin, anti-inflammatories

38
Q

Naturally occurring anticoagulants

A

serine protease inhibitors,

protein C and protein S,

39
Q

What do serine protease inhibitors do?

A

makes anti-thrombin which switches off thrombin

40
Q

Protein C and Protein S bind to what to switch them off?

A

bind to V, Xa, VIII and IXa

41
Q

What does thrombin bind to to switch on the proteins PC and PS?

A

thrombomodulin

42
Q

What is thrombophilia?

A

deficiency of naturally occurring anticoagulants

43
Q

Which part of coagulation cascade is the extrinsic pathway?

A

TF and VII

44
Q

Which part of coagulation cascade is the intrinsic pathway?

A

VIII, IX, XI, XII

45
Q

Which part of coagulation cascade is in final common pathway?

A

V and X

46
Q

What tests constitute basic coagulation screen?

A

FBC,
PT,
ATPP

47
Q

PT measures which pathway?

A

Intrinsic

48
Q

APTT measures which pathway?

A

extrinsic

Haematology (25 decks)

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