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Haematology > Haemostasis and thrombosis > Flashcards

Haemostasis and thrombosis Flashcards

1
Q

What are the stages of haemostasis?

A

Vessel injury
Endothelial constriction
Platlets adhere, activate and aggregate to form plt plug
Coagulation cascade activated to for fibrin clot

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2
Q

Given some examples of circulating clotting inhibitors?

A

Antithrombin (AT) - neutralises thrombin (IIa)
Tissue factor pathway inhibitor - inhibits TF
Protein C, Protein S

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3
Q

How do Protein C and S work?

A

protein C is split into APC which forms a complex with protein S.
- This complex then binds to VIIIa in the intrinsic Xase complex leading to inhibition
- This complex also binds to Va in the prothrombinase complex resulting in inhibition

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4
Q

How is a fibrin clot broken down / degraded?

A

Plasminogen is activated by tissue plasminogen activator (tPA) and urokinase (uPA) to form plasmin
- Plasmin degrades the fibrin clot forming fibrin degradation products

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5
Q

What endogenously inhibitions tPA and urokinase?

A

Plasminogen activator inhibitor 1 and 2

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6
Q

How does tranexaminc acid work?

A

It inhibitors the conversion of plasminogen to plasmin
this promotes clotting

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7
Q

Broadly speaking, what are the differentials of a bleeding disorder?

A

Platlet abnormalities
- inadequate numbers (low production or increased destruction)
- Abnormal funciton

Genetics (rare)
Aquired (drugs, renal disease)

Clotting factor abnormalities
- Inadequate amount
- Abnormal function

Genetic - haemophilia A (factor VIII def), haemophilia B (factor IX def), Von Willebrand’s disease (def vWF which carries factor VIII)
Aquired - liver disease, malnutrition -> Vit K def

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8
Q

Are inhibitors to administered replacement factors more common in haemophilia A or B?

A

Haemophilia A

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9
Q

Can HIV be transmited via administered factors replacments for hemophilia?

A

No
most of the administered factors are no recontaminate rather than plt derived

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10
Q

What is Hades syndrome?

A

Multi system disorder characterized by aortic stenosis, GI bleeding from angioectasia/dysplasia, and vWF deficiency

pts with vWF def get angiodysplasia as vWF has an anti-angiogenic function

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11
Q

What is the most common bleeding disorder?

A

Von Wilibrands disease

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12
Q

What blood group is vWFd most common in?

A

Group O blood

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13
Q

is vWFd more common in men or women?

A

Women

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14
Q

Does TXA increase risk of VTE?

A

No

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15
Q

In what situation would you dose adjust TXA?

A

Renal impairment
- Nil need to adjust in liver impairment

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16
Q

What are teh two main types of congenital platlet disorders?

A

Bernard-Soulier syndrome, Glanzmann thrombasthenia

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17
Q

What is the main complication of platlet transfusion in congenital thrombocytopenias?

A

Alloimunisation causing refracroiness

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18
Q

How does refractoriness develop to platlet transfusion in congenital thrombocytopenias?

A

Patient develops anti HLA anitbodies to infused platlets

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19
Q

What are common sites of bleeding in pts with platlet defects?
What are common sites of bleeding in pts with clotting factors defects?

A

Wet and dry purpura
Bleeding from mouth, nose of GI system

Joint bleeding
Eccymosis

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20
Q

How is hemophilia treated generally speaking?

A

Factor replacement (mainstay)
Non factor related treatments

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21
Q

What is emicizumab and how does it work?

A

Emisizumab is a bispecifc activating MAB that binds to IXa and X and activates X by cross linking these factors

It is only used in haemophilia A (ie it requires factor IX to be present, so would not work in haemophilia B)

22
Q

What are some common downsides to long term management of haemophilia pts with factors replacement?

A

Requires IV replacment to be given - regular transfusions

There are peaks and troughs in action as they are metabolised

Cannot be used in pts with inhibitors - therefore pts can become refractory

23
Q

What are some advantages of emicizumab compared to factor VIII infusions for haemophilia A?

A

stable effect (nil peraks and troughs)
Can be given SC as opposed to IV
can be used in pts with inhibitors

24
Q

What is Fitusiran and how does it work? Which pts is this used in?

A

Fitusiran is a siRNA therapeutic agent which lowers levels of antithrombin

Used in pts with haemophilia A and B
Can be used in pts with or without inhibitors
No peaks or troughs in action
SC dosing

25
Q

What is Concizumab and how does it work?

A

This is a anti- tissue factor pathway inhibitor MAB that works by maintaining an augemented extrinsic pathway response to tissue da mage. This augmented response compensates for the decreased intrinisc pathway action in pts with haem A and B

Used in Haem A and B

26
Q

Why is INR used to measure the effect of warfarin?

A

All vitamin K factors are affected by warfarin (2,7,9,10)
however the effect is most pronounced in the extrinsic pathway (7), therefore INR is used

APTT will also be effected

27
Q

What antibodies are implicated in Heparin induced thrombocytopenia?

A

antiplatlets factor 4 antibodies

28
Q

Can HIT occurs after exposure to LMWH?

A

Yes, but at approximately 10x less rate then the rate following exposure to heparin

29
Q

What are the test involved in the diagnosis of APS?

A

Lupus anticoagulant
Anti cardiolipin antibodies
Beta 2 glycoprotien 1 antibodies (NOT microglubulin)

30
Q

What tests are involved in a thrombophilia screen?

A

genetic / congenital thrombophilia screen:
- FBE
- fV leiden
- Promthrombin gene mutation 20210A
- Protein C, S
- Antithrombin

Aquired thrombophilia screen:
- lupus anticoagulant
- beta 2 glycoprotein 1(IgM, IgG)
- anti cardiolipin antibodies (IgM, IgG)

31
Q

What are some common coingenital thrombophilias?

A

Antithrombin III deficiency
Protein C deficiency
Protein S deficiency
Factor V leiden
Prothrombin 20210

32
Q

What is the most common aquired thrombophilia?

A

APS

33
Q

What is APS?

A

This is an acquired thrombophilia characterised by thrombosis in associated with persistent antiphospholipid antibodies.
These antibodies activate a number of antibodies including platlets, monocytes and endothelial cells causing thrombosis as well as other events (miscarriages)

34
Q

ASP is commonly associated with another condition. What is this condition?

A

SLE

35
Q

How is APS diagnosed?

A

At least 1 clinical criteria
- Venous, arterial or small vessel thrombosis
- Pregnancy related morbidity:
- >/=1 unexplained death of a morphologically normal fetus >10 weeks gestation
- >/= 1 premature birth of morphologically normal fetus <34 weeks gestation due to pre-eclampsia, placental insufficiency
- >/=3 unexplained spontaneous abortions at <10 weeks with other causes excluded

Lab criteria: >/=1 present on 2 occasions 12 weeks apart (persistent)
- Cardiolipin
- Beta 2 glycoprotein 1
- Lupus anticoagulant

36
Q

What is Libman-Sacks endocarditis and what diseases is it associated with?

A

sterile, non bacterial endocarditis
Associated with SLE, APS and malignancy

Usually mitral or aortic valves effected

37
Q

Psychophysiology of HIT briefly?

A

Exposure to heparin (UF or LMWH)
development of autoantibody directed against endogenous platlets factor 4 in complex with heparin. This antibody with therefore called anti-platlet factor 4 antibody.

This autoantibody results in plt activation causing catastrophic venous and arterial thrombosis

38
Q

How long after heparin exposure does HIT develop?

A

Onsets day 5-10 following exposure

39
Q

What heparin agent is used in pts with HIT?

A

Danaparoid, fondaparinux
- cant used LMWH or UF
- Cant use warfarin until plt normalised

40
Q

What is the management of unprovoked cerebral vein thrombosis?

A

NOAC 3-6 months
- most dont recur so can stop at this time

41
Q

What anticoagulent would you used: preg with DVT?

A

LMWH
- Cant use NOAC in breast feeding or preg

42
Q

What anticoagulent would you used: Breast feeding with DVT / PE

A

LMWH / warfarin
- Cant use NOAC in breast feeding or preg

43
Q

What anticoagulent would you used: Morbid obese pt with PE?

A

NOAC

44
Q

What anticoagulent would you used: Pt with end stage RF?

A

Warfarin / heparin
- increasing number of trials for use of NOAC in poor renal function

45
Q

What anticoagulent would you used: mechanical valve?

A

Warfarin
- bridge with LMWH for any required surgery

46
Q

What anticoagulent would you used: urogenital bleeding?

A

LMWH
- NOACs increase risk or urogenital bleeding

47
Q

Approach to management of breakthrough VTE (ie VTE if already on anticoagulation)?

A

Is the pt taking the drug?
- If yes: is the dosing appropriate?
- If yes: then need to investigate for factors that could affect the drug (ie drug drug interaction etc)
- For pts on Heparin, need to check for antithrombin deficiency
- for pts on Warfarin, need to chack for drug interaction (abs, antiepileptics etc), increased vit K intake
- For pts on NOAC, ned to check for inappropriate dose redution, CYP3A4 inducer, morbidly obese, compliance

If there is no issue with the dose, then look for underlying conditions (most commonly cancer)

48
Q

Management of breakthrough VTE?

A

If pt on NOAC, VKA, or subtheraputic LMWH
- Switch to LMWH

If pt on theraputic LMWH
- consider 125% dose LMWH for short period

If pt stable following switch to LMWH after 6 months then can consider transition back to original agent (as long as there is no cancer)

49
Q

How does aspirin work as an antiplatlet?

A

inhibits COX (cyclooxygenase) dependent formation of thromboxane A2

50
Q

What factors does prothrombinex contain?

A

II, IX, X and very small amounts VII

51
Q

What is the dose of prothrombinex for intracranial haemorhage?

A

The dose is 50U/kg (maximum dose)
- this does not depend on the anticoagulant the pt was on prior to the bleed

52
Q

What is the antidote for dabigatran?

A

Idarucizumab

Haematology (5 decks)

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