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Haematology > Introduction and overview to haemostasis > Flashcards

Introduction and overview to haemostasis Flashcards

1
Q

Define haemostasis

A

arrest of bleeding and maintenance of vascular patency

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2
Q

what are the requirements of haemostasis

A

it is ready at any time and immediate to act
acts at local site of injury
protection against unwanted thrombosis

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3
Q

what are components of a normal haemostatic system

A

primary haemostasis - platelet plug
secondary haemostasis - fibrin clot
fibrinolysis
anticoagulant defences

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4
Q

what kind of disorder do you have if your haematostatic system is underactive

A

bleeding disorder

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5
Q

what kind of disorder do you have if your haematostatic system is overactive

A

clotting disorder

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6
Q

what are megakaryocytes

A

large multinucleate cells found in the bone marrow only

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7
Q

how are platelets formed

A

budding off from megakaryocytes

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8
Q

what are platelets

A

small anucleate rings with a lifespan of 7-10days

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9
Q

how long should a patient stop antiplatelets prior to surgery

A

1 week

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10
Q

what is primary haemostasis

A

formation of platelet plug

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11
Q

is a platelet plug strong

A

no, it is weak

suitable for small injuries but not sufficient in greater damage

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12
Q

explain the process of primary haemostasis

A

Endothelial damage exposes collagen
Platelets and VWF bind to collagen
VWF helps platelets adhere to collagen and other platelets
Secretion of other chemicals help platelet aggregation

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13
Q

what are causes of failure of primary haemostasis

A

vascular: collagen deficiency
platelets: reduced number or function
VWF deficiency

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14
Q

what are symptoms and signs of primary haemostatic failure

A 
spontaneous bruising 
senile purpura 
purpura on legs 
mucosal bleeding: nose, conjunctiva, mouth, GI tract, menorrhagia 
intracranial haemorrhage
retinal haemorrhage - fundoscopy
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15
Q

what investigation can be done for primary haemostatic failure

A

platelet count

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16
Q

what is the term for high platelets

A

thrombocytosis

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17
Q

what is the term for low platelets

A

thrombocytopaenia

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18
Q

what is secondary haemostasis

A

formation of fibrin clot

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19
Q

is a fibrin clot strong

A

yes, fibrin strengthens the platelet plug

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20
Q

platelets are full of -ve phospholipids and Ca2+, true or false

A

true

21
Q

clotting factors are negatively/positively charged

A

negatively charged

22
Q

explain the process of secondary haemostasis

A

Tissue Factor activates factor 7
this complex activates factors 5+10
these then activate prothrombin to form thrombin
thrombin then converts fibrinogen to fibrin
fibrin is the final product
thrombin also acts in a positive feedback to activate factors 8+9
8+9 also activate factors 5+10
whole process is amplified

23
Q

list the main categories for failure of secondary haemostatic failure

A

single deficiency

multiple deficiencies

24
Q

features of single deficiency in secondary haemostatic failure

A

hereditary
rarer
eg haemophilia

25
Q

which clotting factor is deficient in haemophilia A

A

factor 8

26
Q

which clotting factor is deficient in haemophilia B

A

factor 9

27
Q

what is a cause of multiple deficiencies in secondary haemostatic failure

A

disseminated intravascular coagulation DIC

28
Q

list causes of DIC

A 
sepsis 
cancer 
ABO incompatibility 
RTA 
liver disease
29
Q

what is the pathophysiology behind DIC

A

increase in clot formation leading to widespread ischaemia

paradoxically there is also increased bleeding due to depletion of clotting factors

30
Q

what is fibrinolysis and what is its purpose

A

break down of fibrin clots
to maintain vascular patency
occurs when fibrin clot has formed and bleeding has stopped

31
Q

what is the process of fibrinolysis

A

tPA activates plasminogen into plasmin

plasmin breaks fibrin into FDPs

32
Q

what are d dimers

A

fibrin degradation products

33
Q

generally, failure of secondary haemostasis has characteristic symptoms, true or false

A

false

34
Q

what are symptoms of single deficiency secondary haemostatic failure

A

bleeding into joints and muscles

35
Q

what tests can be done to investigate fibrin clot formation as coagulation screen

A

prothrombin time PTT

activated partial thromboplastin time APTT

36
Q

what does prothrombin time measure

A

length of time taken for clot formation via extrinsic pathway

37
Q

prothrombin time measure extrinsic/intrinsic pathway

A

extrinsic

38
Q

which clotting factors can be tested in prothrombin time

A

TF/3, 7, 5, 10, PT

39
Q

clotting factors 8+9 are tested in prothrombin time, true or false

A

FALSE

40
Q

what does activated partial thromboplastin time (APTT) measure

A

length of time taken for clot formation via intrinsic pathway

41
Q

APTT measure extrinsic/intrinsic pathway

A

intrinsic

42
Q

which clotting factors are tested in APTT

A

8, 9, 5, 10, PT

43
Q

if there is a deficiency in factor 7, PT/APTT would be prolonged

A

PT

44
Q

if there is a deficiency in factor 8, PT/APTT would be prolonged

A

APTT

45
Q

list some naturally occurring anticoagulants

A

serine protease inhibitors eg anti thrombin

Protein C + S

46
Q

how does anti thrombin work

A

inhibits thrombin and so switches off haemostasis

47
Q

how do Protein C+S work

A

bind to factors 5+8 to switch off coagulation

48
Q

what would occur as a result of antithrombin/Protein C/S deficiency

A

excess clotting because you cant stop anticoagulation

49
Q

define thrombophilia

A

increased tendency to forming clots eg DVT, PE, VTE

Haematology (26 decks)

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