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Haematology > Haemostasis + Anti-coagulation > Flashcards

Haemostasis + Anti-coagulation Flashcards

1
Q

What does endothelium that lines blood vessels produce to stop clots and encourage flow

A 
Heparins
TFPI - natural anti-coagulant
Thrombomodulin
NO 
Prostacylin - prevent aggregation
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2
Q

What flows in the blood and has potential to form clots

A

Platelet
Red cell
Coagulation factors

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3
Q

What is the process of primary haemastasis when there is vessel damage

A

Vasconstriction
vWF released from damaged endothelium and binds to collagen
Platelets aggregate as exposed to sub endothelial collagen
Platelet activation by ADP receptor
GIIB/11A receptors now exposed and can bind fibrinogen
Primary platelet plug = weak
Tissue factor produced from tissue e.g. damaged vessel (physiological activator of coagulation) - extrinsic
or
Activated by sub endothelial collagen (intrinsic)
Activates coagulation proteins
Work to produce a fibrin clot - secondary haemostasis

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4
Q

What is on surface of platelets to help binding

A

GPIIb/IIa receptor

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5
Q

What do platelets bind to

A

Fibrinogen
Collagen
VWf

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6
Q

What are platelets activated by

A

P2y12 / ADP pathway

COX pathway

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7
Q

What does COX pathway produce

A

Converts arachidonic acid ->Thromboxane A2 which aids aggregation of platelets + provides surface for coagulation proteins to be activated

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8
Q

What forms stable fibrin clot (secondary haemostasis)

A

Coagulation cascade
Coagulation proteins - factor XI / IV / VII activated
Intrinsic pathway
Extrinsic pathway
Activate pro-thrombin which activates thrombin
Thrombin converts fibrinogen to fibrin to form clot

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9
Q

What happens if coagulation proteins are deficient

A

Fibrin clot won’t form

Anti-coagulants inhibit these proteins as well

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10
Q

What are natural anti-coagulants in the blood that tell clot to stop forming

A

Anti-thrombin - most important
TFPI
Protein C and S

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11
Q

What coagulation factors does anti-thrombin act on

A

Factor 10

Thrombin

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12
Q

What is fibrinolysis

A

Removal of clot

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13
Q

What endothelial cells activate plasminogen

A

t-PA

u-PA

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14
Q

What does activated plasminogen do

A

Converts to plasmin to break down clots

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15
Q

What is left after clots broken down

A

Fibrin degradation product

e.g. D-dimer

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16
Q

What are anti-thrombotic / coagulant durgs and when are they indicated

A

Warfarin
Heparin
DOAC’s - Rivaroxaban / Edozaban / Dalbigatran

AF
VTE
Post surgery
Immobilisation
Valvular heart disease
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17
Q

What are anti-platelets

A

Clopidogrel / Prasugrel / Ticagrelor
Aspirin
Abciximab

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18
Q

What does aspirin do

A

Inhibits COX so stops production of thromboxane A2

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19
Q

What does abciximab do

A

Prevents GP IIB/ IIA from binding fibrinogen

Used less often

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20
Q

What does clopidogrel etc do

A

Prevents ADP pathway

Use in combination with aspirin

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21
Q

Who is put on antiplatelet

A 
Angina
MI
Stroke
Obesity
DM
FH
SMoking
Risk of abnormal clot
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22
Q

What is warfarin and what factors affected

A

Vitamin K antagonist so stops coagulation factors being produced
Hepatic metabolism by p450
1972 - 10, 9,7,2

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23
Q

How do you reverse warfarin and when

A

Vitamin K

Prothrombin complex to activate coagulation proteins if major bleed = rapid

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24
Q

What is indication for warfarin and what is the target INR and when is it used over DOAC

A

Artificial heart valves

  • Aortic 2-3
  • Mitral 2.5-3.5

VTE
- 2.5-3.5 (higher if recurrent)
AF
- 2-3

Artificial valve / Mitral stenosis / obesity and renal failure <30

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25
Q

What does warfarin require and what do you do if too low

A

Weekly INR check as narrow therapeutic range with dose adjustment

If INR <2
Cover with LMWH and increase dose

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26
Q

When is warfarin CI and SE

A 
Unreliable to get INR check 
Peptic ulcer
Bleeding disorder
Severe hypertension
Liver disease 
Pregnancy as teratogenic but CAN breastfeed

SE
Haemorrhage
Teratogenic so CI in pregnancy
Necrosis / purple toes

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27
Q

What do you do if INR 5-8, no bleed

A

Withhold dose

Start at lower dose

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28
Q

What do you do if INR 5-8, minor bleed

A

Stop warfarin
Admit for IV vit K 1-3mg
Restart when INR <5

29
Q

What do you do if INR >8, no bleed

A

Stop warfarin + haematology
Don’t give IV K
Oral vit K
Restart when INR <5

30
Q

What do you do if INR >8, minor bleed

A

Stop warfarin
Admit urgently for IV vit K 1-3mg
Restart when <5

31
Q

What do you do if major bleed on warfarin regardless of INR

A 
Stop warfarin
Fluid and blood transfusion
Treat cause 
Prothrombin complex = rapid
IV Vit K 5mg
Can give FFP if prothrombin not available 
Consider platelet replacement
32
Q

What are benefits of DOAC and how do you treat bleed

A

Do not require monitoring
Annual blood test

DOAC

  • Add charcoal to slow absorption if recent dose
  • Consider specific antitode
  • Can give prothrombin or FFP if severe and no antitode to reverse
33
Q

When are DOAC indicated

A

Prevention of VTE / stroke
Preferred except in mechanical heart valves or severe MS or severe obesity
Work instantly so don’t require with LMWH like warfarin

34
Q

How does rivoraxaban / abixaban work and how is it excreted

A

Direct factor Xa (10) inhibitor
Liver
No reversal agent

35
Q

How does dapigatran work and how is it excreted

A

Direct thrombin inhibitor
Renal
Monoclonal Ab to reverse

36
Q

When are DOAC contraindicated

A

Severe renal / liver
Bleeding

PT / APTT insensitive but gives a rough idea

37
Q

What are options for heparin

A

LMWH
Unfractioned heparin
All activate anti-thrombin

38
Q

What is treatment of choice for VTE

A

LMWH - dalteparin / anaxoparin

Also used if post op or immobile as high risk of VTE as prophylaxis as quick onset and to cover till INR target

39
Q

How does LMWH work and how can it be given

A

SC
Inhibits factor XA only by activating anti-thrombin
Monitor factor XA but not required
Long action

40
Q

How does unfractioned heparin work and how is it given

A

Inhibits thrombin and factor XII by activating anti-thrombin III
SC or IV
Rapid onset and short duration
Used if high risk of bleed as can be terminated rapidly

41
Q

How do you monitor unfractioned heparin and reverse

A

APTT

Protamine sulphate

42
Q

What are SE of heparin

A

Bleeding
Thrombocytopenia - don’t give if platelets low e.g. <50
Osteoprosis
Hyperkalaemia

43
Q

What are CI to heparin

A 
Bleeding disorder
Low platelet  - <50 
Peptic ulcer
Haemorrhage
Severe hypertension
Renal failure
44
Q

What is used instead of heparin If CI due to renal and how does it work

A

Fondaparinux - inhibits factor XA

45
Q

What does transexamic acid do

A

Binds to plasminogen and prevents conversion to plasmin

46
Q

What blood tests are used to monitor coagulation

A

FBC - for platlet
LFT - for liver function and albumin for synthetic
D-dimer

Coag 
PT
APTT
Bleeding time 
Fibrinogen
47
Q

What does PT look at

  • Put onto paper for OSCE
A

Tests factors involved in extrinsic pathway (play tennis outside)

  • Fibrinogen
  • Thrombin
  • 2,7,9, 10, (vit K dependent)
48
Q

How is PT reported as and what should values be

A

INR - 0.8-1.2
PT - 12-13s
Use to measure clotting on a regular basis as good measure of overall clotting (as factors rarely in deficiency)

49
Q

When is INR prolonged / affected

A

Warfarin as more strongly affects extrinsic pathway
Vit K deficiency
Liver disease
DIC

50
Q

What does APTT look at

A

Tests factors involved in intrinsic pathway

  • Fibrinogen
  • Thrombin
  • 5,8, 10, 11, 12
51
Q

What is normal APTT

A

30-40s

52
Q

When is APTT increased / affected

A

Will be affected by overall clotting so anything that affects PT can affect APTT
Also indicates issues with certain factors
Factor defieincy
Haemophilia A and B / acquired
vWF
Anti-phospholipid
DIC

53
Q

When is bleeding time prolonged

- Should be 1-6 minutes

A 
Platelet issues will increase the time 
Thrombocytopenia
Uraemia 
Aspirin use
VWF deficiency as can't make plug
TTP / ITP / HUS / DIC
54
Q

What factors affect coagulation

A

pH
Temp - hypothermia
Calcium

55
Q

How much platelets do you need for major surgery

A

100 - required for plug

56
Q

When would you get purpura

A

<30

57
Q

When would you get spontaneous bleeding

A

<10

58
Q

Coag values warfarin / vit K deficiency

A

PT - prolonged
APTT - normal (increased in vit K deficiency)
Bleeding - Normal
Platelet - normal

59
Q

Coag values aspirin

A

PT - normal
APTT - normal
Bleeding - prolonged as stops platelet aggregating but does not affect coag so everything else normal
Platelet - normal

60
Q

Coag values heparin / NOAC

A

PT - normal / prolonged
APTT - Prolonged as factors in extrinsic pathway
Bleeding - Normal
Platelet - normal

61
Q

Coag values DIC

A

PT - prolonged
APTT - prolnged
Bleeding - prolonged
Platelet - low

Require platelet and clotting factors

62
Q

Coag values Haemophilia

A

PT - normal
APTT - prolonged as factors
Bleeding - normal
Platelet - normal

63
Q

Coag values vWF

A

PT normal as to do with platelet not able to adhese
APTT - prolonged as to do with VIII in intrinsic pathway
Bleed - prolonged
Platelets - normal

64
Q

Coag values HUS / TTP / ITP

A

PT -normal
APTT - normal
Bleeding - prolonged
Platelet - low

Normal PT / APTT good differentiator form DIC
NEVER give platelets

65
Q

What do you do if any bleeding on anti-coagulant

A 
Compress 
Assess haemodynaic status
- BP
- Basic coag bloods
- FBC / U+E
Get Hx of when got last dose
66
Q

Surgery on warfarin

A

Stop 5 days before and when INR <1.5
If emergency reverse with prothrombin
Restart as soon as you can

67
Q

What drugs may increase warfarin

A 
p450 inhibitor as can't break down Liver disease
Anti-fungal
Macrolide
Ciprofloxacin
Amiadarone
SSRI
Acute alcohol
Sodium valrpoate 
NSAID - platelet function
Sulphonamide
68
Q

What drugs may decrease

A 
p450 inducer
Vit K
Barbiturates
Phenytoin
Carbamazepine 
Cholestrolamine
Rifampicin
St Jon's wort
Chronic alcohol
Smoking

Haematology (13 decks)

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