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Y2 MCD Haematology > haemostasis > Flashcards

haemostasis Flashcards

coagulopathy: compare the clinical features of bleeding due to different causes, and explain the principles of management of disorders of haemostasis

1
Q

elements of a significant bleeding history: epistaxis (nosebleeding)

A

epistaxis not stopped by 10 mins compression, or requiring medical attention/transfusion

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2
Q

elements of a significant bleeding history: cutaneous haemorrhage or bruising

A

cutaneous haemorrhage or bruising occur without apparent trauma (especially multiple or large)

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3
Q

elements of a significant bleeding history: prolonged bleeding

A

prolonged bleeding (>15 mins) from trivial wounds, or in oral cavity or recurring spontaneously in 7 days after wound (spontaneous GI bleeding leading to anaemia)

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4
Q

elements of a significant bleeding history: menorrhagia

A

menorrhagia requiring treatment or leading to anaemia, not due to structural lesions of the uterus

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5
Q

elements of a significant bleeding history: heavy, prolonged or recurrent bleeding

A

heavy, prolonged or recurrent bleeding after surgery or dental extractions

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6
Q

stages of haemostatic plug formation in response to injury

A

vessel constriction -> formation of unstable platelet plug (platelet adhesion and aggregation) -> stabilisation of plug with fibrin (blood coagulation) -> dissolution of clot and vessel repair (fibrinolysis)

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7
Q

2 general causes of abnormal haemostasis

A

lack of a specific factor, defective function of specific factor

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8
Q

2 causes of lack of a specific factor

A

failure of production (congenital or acquired), increased consumption or clearance

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9
Q

2 causes of a defective function of a specific factor

A

genetic defect, acquired defect (drugs, synthetic defect, inhibition)

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10
Q

what is exposed, triggering primary haemostasis, which isn’t normally; what binds and via what (platelet adhesion and aggregation)

A

collagen in subendothelium, which platelets (via GlpIa/vWF) and vWF bind to (platelet adhesion), causing exposure of GlpIIb/IIIa (platelets then aggregate and stick to each other)

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11
Q

what can be disordered in primary haemostasis

A

platelets, vWF, vessel wall

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12
Q

2 disorders of primary haemostasis associated with platelet adhesion and aggregation

A

thrombocytopenia (low platelet numbers presenting as petechiae (only if thrombocytopenia, not vWD)), impaired function of platelets

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13
Q

2 causes of thrombocytopenia

A

bone marrow failure (e.g. leukaemia, B12 deficiency (megaloblastic anaemia)), accelerated clearance (immune e.g. ITP, DIC)

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14
Q

describe process of auto-ITP (auto-immune thrombocytopenic purpura)

A

antiplatelet antibodies bind to sensitised platelet, which is then engulfed by a splenic macrophage

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15
Q

3 mechanisms and causes of thrombocytopenia

A

failure of platelet production by megakaryoctes, shortened half life of platelets, increased pooling of platelets in enlarged spleen (hypersplenism) and shortened half life

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16
Q

2 causes of impaired function of platelets

A

hereditary absence of glycoproteins or storage granules, acquired due to drugs e.g. aspirin, NSAIDs, copidogrel

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17
Q

what platelet surface glycoprotein is impaired by Glanzmann’s thrombasthenia

A

GpII/IIIa (recessive)

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18
Q

what platelet surface glycoprotein is impaired by Bernard Soulier syndrome

A

GpIb

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19
Q

what is impaired by storage pool disease

A

issue with contents or relase of dense granules, containing ADP, ATP, serotonin and Ca2+

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20
Q

cause of disorder of vWF

A

vW disease (autosomal; if severe, haemophoilia-like bleeding due to FVIII deficiency)

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21
Q

2 causes of vW disease

A

hereditary decrease of quantity and/or function (common), acquired due to antibody (rare)

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22
Q

2 functions of vWF in haemostasis

A

binding to collagen and capturing platelets, stabilising FVIII (FVIII may be low if vWF is very low)

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23
Q

3 types of hereditary vWF

A

type 1 or 3 (deficiency of vWF; type 1 not enough, type 3 (recessive) none at all), type 2 (vWF with abnormal function)

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24
Q

2 causes of disorder of vessel wall

A

inherited (rare), acquired

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25
Q

2 rare inherited conditions causing vessel wall disorder

A

hereditary haemorrhagic telangiectasia, Ehlers-Danlos syndrome, other connective tissue disorders

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26
Q

4 causes of acquired vessel wall disorders

A

scurvy, steroid therapy (thins connective tissue of small vessels, so more likely to bleed), ageing (senile purura), vasculitis

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27
Q

what type of bleeding is associated with disorders of primary haemostasis

A

immediate, prolonged, epistaxes, mucocutaneous, menorrhagia, easy bruising

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28
Q

4 tests for disorders of primary haemostasis

A

platelet count and morphology, bleeding time (not sensitive or specific so recreated as PFA100 in lab), assays of vWF, clinical observation

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29
Q

what is clotting factor I

A

fibrinogen

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30
Q

what is clotting factor II

A

prothrombin

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31
Q

what is clotting factor III

A

tissue factor (TF)

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32
Q

what is clotting factor IV

A

calcium ions (Ca2+)

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33
Q

what is clotting factor VI

A

activated factor V (Va)

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34
Q

what clotting factors require a post-translational vitamin K dependent modification

A

factors II, VII, IX and X

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35
Q

what clotting factors are not serine proteases

A

V, VIII, XIII

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36
Q

what factors are co-factors

A

V, VIII

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37
Q

what factor is a transglutamidase

A

XIII

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38
Q

where is phospholipid derived from

A

activated platelet membrane

39
Q

what does the fibrin mesh do

A

binds and stabilises platelet plug and other cells

40
Q

what is the instrinsic pathway of blood coagulation in secondary haemostasis

A

XII->XIIa, which activates XI->XIa, which activates IX->IXa, which, along with VIIIa, phospholipids and Ca2+, activates X->Xa

41
Q

what is the extrinsic pathway of blood coagulation in secondary haemostasis

A

tissue factor, released due to vessel damage, along with VIIa and Ca2+, activates IX->IXa (instrinsic pathway) or X->Xa

42
Q

what is the common pathway of blood coagulation in secondary haemostasis

A

Xa, along with Va, phospholipids and Ca2+, activates prothrombin->thrombin (IIa), which activates fibrinogen->fibrin. and XIII->XIIIa. XIIIa converts fibrin to crosslinked fibrin

43
Q

shape of normal thrombogram (thrombin generation over time by coagulation cascade)

A

TF trigger, before rapid rise in thrombin generation (minutes), before peaking and an equally rapid decline in generation, before rate slows

44
Q

shape of haemophilia A (FVIII) thrombogram (thrombin generation over time by coagulation cascade)

A

TF trigger, then very slow rise in thrombin levels, before peaking at a much lower level than normal after a longer period of time, followed by a slow decrease in thrombin levels

45
Q

what can be disordered in secondary haemostasis

A

any coagulation factor that results in failure of thrombin generation, and hence fibrin formation

46
Q

what vessels require secondary haemostasis

A

larger vessels, as a primary platelet plug would fall apart

47
Q

what is haemophilia

A

failure to generate fibrin to stabilise platelet plug

48
Q

2 causes of deficiency of coagulation factor production

A

hereditary, acquired

49
Q

2 hereditary haemophilias causing a deficiency of coagulation factor production, and corresponding coagulation factor

A

haemophilia A (FVIII), haemophilia B (FIX)

50
Q

what pathway do both haemophilia types affect

A

intrinsic pathway

51
Q

are all coagulation factor deficiencies the same

A

no

52
Q

compatibility with life and symptoms of haemophilia (FVIII and FIX deficiency)

A

severe but compatible with life; spontaneous joint and muscle bleeding (X-linked so affect males more)

53
Q

compatibility with life of prothrombin (FII) deficiency

A

lethal (die in utero)

54
Q

symptoms of FXI deficiency

A

bleed after trauma but not spontaneously

55
Q

symptoms of FXII deficiency

A

no excess bleeding at all

56
Q

3 causes of acquired coagulation disorder (much more common than hereditary)

A

liver disease, dilution, anticoagulant drugs (e.g. warfarin)

57
Q

why does liver failure lead to decreased production of coagulation factors

A

most coagulation factors are synthesised in the liver

58
Q

how does dilution occur, leading to an acquired coagulation disorder

A

red cell transfusions no longer contain plasma (major transfusions require plasma as well as erythrocytes and platelets)

59
Q

2 acquired causes of increased consumption of coagulation factors, leading to coagulation disorder

A

disseminated intravascular coagulation (DIC), immune (auto-antibodies)

60
Q

what activates disseminated intravascular coagulation (DIC), and what is consumed

A

generalised unregulated activation of coagulation by TF, consuming and depleting coagulation factors, platelets and fibrinogen (activates fibrinolysis as well); can’t be switched off but can treat underlying cause (e.g. deliver baby), or through replacement

61
Q

what is disseminated intravascular coagulation (DIC) associated with, and what does it lead to

A

associated with sepsis, major tissue damage and inflammation, with deposition of fibrin causing organ failure

62
Q

5 clinical symptoms of bleeding in coagulation disorders

A

superficial cuts do not bleed (platelets present), bruising is common but nosebleeds are rare, spontaneous bleeding is deep into muscles and joints, bleeding after trauma may be delayed and is prolonged, frequently restarts after stopping

63
Q

what is a hallmark of haemophilia

A

haemarthrosis (haemorrhage into joint space)

64
Q

what route of administration should be avoided in patients with coagulation disorders

A

intramuscular injections

65
Q

seriousness of haemophilia

A

very without treatment, as simply by cutting a lip someone could bleed to death

66
Q

platelet/vascular defect bleeding vs coagulation defect bleeding

A

platelet/vascular: superficial bleeding into skin and mucosal membranes, with bleeding immediately after injury; coagulation: bleeding into deep tissues, muscles and joints, with bleeding delayed, severe and prolonged after injury

67
Q

3 tests for coagulation disorders

A

screening tests (clotting screen), factor assays (e.g. for FVIII etc.), test for inhibitors

68
Q

3 screening tests for coagulation disorders

A

prothrombin time (PT), activated partial thromboplastin time (APTT), full blood count (platelets)

69
Q

what factor deficiencies are detected by prolonged APTT (activated partial thromboplastin time) in haemophilia (intrinsic pathway)

A

FXII, XI, VIII, IX (and V, X, II) until fibrin strand forms

70
Q

what factor deficiencies are detected by PT (prothrombin time) (extrinsic pathway)

A

FVIIa (and V, X, II) until fibrin strand forms; if high due to warfarin, treat with vitamin K injections

71
Q

8 bleeding disorders not detected by routine clotting tests, so history and screening tests important

A

mild factor deficiencies, vWF, FXIII deficiency (crosslinking), platelet disorders, excessive fibrinolysis, vessel wall disorders, metabolic disorders (e.g. uraemia), thrombotic disorders

72
Q

2 causes of fibrinolysis disorders

A

hereditary, acquired

73
Q

hereditary cause of fibrinolysis disorders

A

antiplasmin deficiency

74
Q

2 acquired causes of fibrinolysis disorders

A

drugs e.g. tPA (tissue plasminogen activator “clot buster”), disseminated intravascular coagulation (DIC)

75
Q

haemophilia inheritance pattern

A

sex-linked (X-linked) recessive disorder (affected males below normal range, carrier females vary due to lyonization); FVIII normal range is 0.5-1.5 iu/ml

76
Q

vWD inheritance pattern

A

autosomal dominant disorder (type 2, type 1 are autosomal dominant, type 3 is autosomal recessive)

77
Q

other common bleeding disorders (all the rest e.g. V deficiency, X deficiency etc.) inheritance pattern

A

autosomal recessive so much less common

78
Q

2 ways abnormal haemostasis due to failure of production/function is treated

A

replace missing factor/platelets, stop drugs

79
Q

2 ways to replace missing factor/platelets in abnormal haemostasis due to failure of production/function

A

prophylactic, therapeutic

80
Q

2 ways abnormal haemostasis due to immune destruction is treated

A

immunosuppression (prednisolone), splenectomy for ITP (immune thrombocytopenic purpura)

81
Q

2 ways abnormal haemostasis by increased consumption is treated

A

treat cause (e.g. of DIC), replace as necessary

82
Q

4 factor replacement therapies

A

plasma, cryoprecipitate, factor concentrates, recombinant forms

83
Q

what coagulation factors does plasma contain

A

all

84
Q

what coagulation factors does cryoprecipitate contain

A

fibrinogen, FVIII, vWF, FXIII

85
Q

what factor concentrates are available

A

all but FV

86
Q

what coagulation factors are present in prothrombin complex concentrates (PCCs)

A

FII, VII, IX, X (used to reverse warfarin)

87
Q

what 2 coagulation factors have recombinant forms

A

FVIII, FIX

88
Q

what can gene therapy be used to treat

A

haemophilia (B>A)

89
Q

2 other treatments of haemostatic disorders causing bleeding

A

platelet replacement therapy (pooled platelet concentrates available), novel approaches (e.g. bispecific antibody, anti TFPI (tissue factor pathway inhibitor) antibody, antithrombin RNAi)

90
Q

3 additional haemostatic treatments

A

DDAVP (desmopressin), tranexamic acid, fibrin glue/spray

91
Q

how does desmopressin (DDAVP) work

A

vasopressin derivative, causing a 2-5 fold rise in vWF and FVIII (FVIII>vWF) by releasing endogenous stores, so only useful in mild disorders

92
Q

how does tranexamic acid work

A

inhibits fibrinolysis by competing with fibrin for binding of TPA (tissue plasminogen activator)

93
Q

distribution of tranexamic acid

A

wide as crosses placenta, but low concentration in breast milk

94
Q

treatment of vWD

A

intermediate purity vWF/FVIII concentrates, DDAVP, tranexamic acid

Y2 MCD Haematology (20 decks)

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