Haemostasis

Question 1

Haemostasis defintion?

Answer 1

stopping of bleeding AND maintenance of vascular patency

Question 2

Requirements for Haemostasis? (4)

Answer 2

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

Question 3

Normal haemostatic system components?

Answer 3

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

Question 4

What is primary haemostasis ?

Answer 4

formation of platelet plug

Question 5

What is secondary haemostasis?

Answer 5

formation of fibrin clot

Question 6

Why does fibrinolysis happen?

Answer 6

To keep vascular patency so basically blood clots then unclots

Question 7

Where & how do platelets form?

Answer 7

budding from cytoplasm of megakaryocytes in the bone marrow

Question 8

Platelets have a nucleus. T/F?

Answer 8

False - don’t have

Question 9

Life span of platelets?

Answer 9

7-10days

Question 10

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

Answer 10

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)

Question 11

Vascular cause of failure of platelet plug formation

Answer 11

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

Question 12

Commonest inherited bleeding disorder?

Answer 12

von willebrand

Question 13

Consequences of failure of platelet plug formation (4)

Answer 13

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

Question 14

Screening tests for primary Haemostasis?

Answer 14

platelet count,

no simple screening tests for other causes

Question 15

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

Answer 15

True

Question 16

Outline formation of fibrin clot

Answer 16

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

Question 17

Positive feedback loop in formation of fibrin clot

Answer 17

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

Question 18

What is intiation phase of fibrin clot formation?

Answer 18

tissue factor and VIIa

Question 19

What is amplification phase of fibrin clot formation?

Answer 19

thrombin activating VIII and IXa

Question 20

What is propagation phase?

Answer 20

Generation of fibrin clot

Question 21

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

Answer 21

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

Question 22

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

Answer 22

single clotting factor deficiency - usually hereditary,

multiple clotting factor deficiency - usually acquired

Question 23

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

Answer 23

Plasmin

Question 24

What is plasmin formed by and from what?

Answer 24

Formed by Tissue Plasminogen Activator (tPA) from plasminogen

Question 25

FDPs can be measured in blood how?

Answer 25

D-dimers

Question 26

Consequences of failure of fibrin clot formation?

Answer 26

no clinical syndrome, | pattern depends on single/multiple abnormalities and the clotting factors involved

Question 27

Pattern of bleeding in haemophilia?

Answer 27

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

Question 28

Pattern of bleeding in DIC

Answer 28

general bleeding tendency into abdominal etc basically all over

Question 29

Screening tests for fibrin clot formation? (2)

Answer 29

``` Prothrombin time (PT), activated partial thromboplastin time (APTT) ```

Question 30

What factors does PT test?

Answer 30

``` VIIa, V, Xa, Prothrombin, fibrinogen ```

Question 31

What factors does APTT test?

Answer 31

``` VIII, IXa, V, Xa, prothrombin, fibrinogen ```

Question 32

Deficient VIIa which test normal which delayed

Answer 32

PT delayed, | APTT normal

Question 33

Primary Haemostasis patterns of bleeding (2)

Answer 33

purpura, | mucosal

Question 34

Secondary Haemostasis patterns of bleeding (2)

Answer 34

joint bleeds, | muscle bleeds

Question 35

Deficient VIII or IXa which test normal which delayed

Answer 35

PT normal, | APTT delayed

Question 36

History in bleeding disorders important questions (3)

Answer 36

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

Question 37

what drug history important?

Answer 37

aspirin, anti-inflammatories

Question 38

Naturally occurring anticoagulants

Answer 38

serine protease inhibitors, | protein C and protein S,

Question 39

What do serine protease inhibitors do?

Answer 39

makes anti-thrombin which switches off thrombin

Question 40

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

Answer 40

bind to V, Xa, VIII and IXa

Question 41

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

Answer 41

thrombomodulin

Question 42

What is thrombophilia?

Answer 42

deficiency of naturally occurring anticoagulants

Question 43

Which part of coagulation cascade is the extrinsic pathway?

Answer 43

TF and VII

Question 44

Which part of coagulation cascade is the intrinsic pathway?

Answer 44

VIII, IX, XI, XII

Question 45

Which part of coagulation cascade is in final common pathway?

Answer 45

V and X

Question 46

What tests constitute basic coagulation screen?

Answer 46

FBC, PT, ATPP

Question 47

PT measures which pathway?

Answer 47

Intrinsic

Question 48

APTT measures which pathway?

Answer 48

extrinsic