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Haematology > Abnormal blood clotting > Flashcards

Abnormal blood clotting Flashcards

1
Q

What is a thrombosis?

A

A solid mass in the circulation from the constituents of the blood formed during life

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2
Q

Compare arterial to venous circulation in terms of relevance to thrombosis

A 
• Arterial circulation
- High pressure
- Platelet rich
- Antiplatelet agents work here
• Venous circulation:
- Low pressure 
- Fibrin rich 
- Anticoagulants work here
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3
Q

What event might occur if there is a thrombus in the coronary circulation?

A

Myocardial infarction

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4
Q

What events might occur if there is a thrombus in the cerebral circulation?

A
  • Cerebral vascular accident (CVA)
  • Transient ischaemic attack (TIA)
  • Stroke
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5
Q

What event might occur if there is a thrombus in the peripheral circulation?

A

Peripheral vascular disease (PVD)

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6
Q

What is a precursor for an acute arterial thrombotic event?

A

Atherosclerosis

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7
Q

Give 7 risk factors for arterial thrombosis

A
  1. Smoking
  2. Hypertension
  3. Diabetes
  4. Hyperlipidaemia
  5. Obesity
  6. Sedentary lifestyle
  7. Stress/type A personality
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8
Q

How would you diagnose conditions caused by arterial thrombosis?

A
  • MI: history, ECG, cardiac enzymes
  • CVA: history, examination, CT/MRI scan
  • PVD: history, examination, ultrasound, angiogram
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9
Q

What antiplatelet agents can be used for arterial thrombosis prevention?

A
  • COX inhibitor e.g. aspirin
  • P2Y12 inhibitor e.g. clopidogrel
  • Dipyramidole
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10
Q

What antiplatelet agents can be used for MI from arterial thrombosis?

A

• Aspirin
• Thrombolytic therapy
- Streptokinase
- Tissue plasminogen activator

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11
Q

What antiplatelet agents can be used for stroke from arterial thrombosis?

A
  • Aspirin or clopidogrel
  • Tissue plasminogen activator
  • Treat risk factors
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12
Q

What diagnostic investigations might you use for a venous thrombosis?

A
  • DVT compression ultrasound with or without Doppler
  • PE: CT scan, CT pulmonary angiogram
  • V/Q or perfusion scan
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13
Q

Give some circumstantial causes for venous thrombosis

A
  • Surgery
  • Immobilisation
  • Oestrogens e.g. HRT, OCP
  • Malignancy
  • Long haul flights
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14
Q

Give some common but low risk genetic causes for venous thrombosis

A
  • Factor V Leiden

* PT20210A

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15
Q

Give some rare but high risk genetic causes for venous thrombosis

A
  • Anti-thrombin deficiency

* Protein C or Protein S deficiency

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16
Q

Give some acquired causes for venous thrombosis

A
  • Anti-phospholipid syndrome
  • Lupus anticoagulant
  • Hyperhomocysteinaemia
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17
Q

What is the initial treatment for a venous thrombosis?

A

Low molecular weight heparin

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18
Q

What is the later treatment for a venous thrombosis?

A

(Either)
• Oral warfarin for 3-6 months
(Or)
• DOAC for 3-6 months

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19
Q

What is a deep vein thrombosis (DVT)?

A

A blood clot in the blood vessel of the lower limb

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20
Q

Give some signs and sypmtoms of a DVT

A
  • Swelling
  • Pain on walking
  • Tenderness
  • Warmth
  • Discolouration
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21
Q

How might you investigate a DVT?

A
  • D-dimer test

* Ultrasound compression test on proximal veins

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22
Q

What is the D-dimer test?

A
  • A blood test
  • A marker of endogenous fibrinolysis
  • A +ve D-dimer indicates the abnormally high levels of cross-linked fibrin degradation products
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23
Q

What does ‘high sensitivity, low specificity’ mean in relation to the D-dimer test?

A

A normal (-ve) test excludes diagnosis but a +ve test doesn’t confirm diagnosis

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24
Q

What can cause an increased D-dimer level?

A
  • DVT
  • Infection/spesis
  • Inflammation
  • Malignancy
  • Trauma/recent surgery
  • Haemorrhage
25
Q

How might you treat a DVT?

A
  • LMW heparin (SC OD, minimum 5 days)
  • Oral warfarin (INR 2-3, 6 months)
  • Direct acting oral anticoagulant (DOAC)
  • Compression stockings
  • Treat underlying cause e.g. malignancy, thrombophilia
26
Q

What are some risk factors for DVT?

A
  • Surgery, immobility, leg fracture
  • Synthetic oestrogen e.g. OCP, HRT
  • Long haul flights/travel (rare)
  • Inherited thrombophilia
  • Spontaneous DVTs are more likely to reoccur
27
Q

What mechanical methods can be used to prevent a DVT?

A
  • Hydration
  • Early mobilisation
  • Compression stockings
  • Foot pumps
28
Q

What chemical methods can be used to prevent a DVT?

A

Low molecular weight heparin

29
Q

What would be classified as ‘low risk’ and not require thromboprophylaxis for DVT?

A
  • <40yrs old
  • Surgery <30mins
  • Early mobilisation
  • Hydration
30
Q

What would be classified as ‘high risk’ and requires thromboprophylaxis for DVT?

A
  • Not in the low risk category
  • Hip and knee or pelvic surgery
  • Malignancy
  • Risk factors
  • Prolonged immobility
31
Q

What is the Wells’ score?

A

A criteria to predict DVT risk

32
Q

What is classified as ‘low risk’ by the Wells’ criteria?

A

A score <2

33
Q

Give the 9 points/criteria of the Wells’ score

A
  1. Active cancer
  2. Bedridden recently >3 days or major surgery within 4 weeks
  3. Calf swelling >3cm compared to other leg
  4. Collateral (non-varicose) superficial veins present
  5. Entire leg swollen
  6. Localised tenderness along deep venous system
  7. Pitting oedema, greater in symptomatic leg
  8. Paralysis, paresis, or recent plaster immobilisation of the lower extremity
  9. Previously documented DVT
34
Q

What is a pulmonary embolism (PE)?

A

A clot from leg that breaks off and travels to the heart and blocks the pulmonary arteries

35
Q

What problems can PEs lead to?

A
  • Hypotension
  • Cyanosis
  • Severe dyspnoea
  • R heart strain or failure
36
Q

What are the 3 key common presentations of PEs?

A
  • Chest pain (usually pleuritic)
  • Shortness of breath
  • Signs and symptoms of a DVT
37
Q

Give 3 signs of a PE

A
  • Tachycardia
  • Tachypnoea
  • Pleural rubs
38
Q

What might blood gases indicate in a PE?

A

Decreased O2 and CO2 = type 1 respiratory failure

39
Q

What might a chest x-ray show in a PE?

A

CXRs are usually normal in PEs and clots probably wouldn’t be seen

40
Q

What might an ECG show in a PE?

A

Usually show sinus tachycardia

41
Q

What further investigations might you do for a PE?

A
  • D-dimer
  • V/Q scan: mismatch defects
  • CT pulmonary angiogram spiral CT with contrast
42
Q

How would you treat a PE?

A
  • Same as for DVT
  • Ensure normal Hb, platelets, renal function, baseline clotting
  • LMW heparin, warfarin, DOAC
  • Tend to treat for 6 months rather than the 3 months for a DVT
  • Treat any underlying causes if possible
  • Consider IVC filter if anticoagulation is contraindicated
43
Q

How does warfarin work?

A

Works in the liver as an indirect anticoagulantby preventing synthesis of active factors II, VII, IX and X

44
Q

What is warfarin an antagonist of?

A

Vitamin K

45
Q

How long is the half-life of warfarin?

A

36hrs

46
Q

What is the usual target range for INR?

A

2-3

47
Q

What does DOAC stand for?

A

Direct oral anticoagulant

48
Q

Is warfarin orally active?

A

Yes

49
Q

Are DOACs orally active?

A

Yes

50
Q

How do DOACs work?

A

Direct action on factor II or X clotting factors

51
Q

Do DOACs have a longer or shorter half-life than warfarin?

A

Shorter

52
Q

What type of molecule is heparin?

A

A glycosaminoglycan

53
Q

How does heparin work?

A

It is an indirect thrombin inhibitor by binding to antithrombin and increasing its activity

54
Q

Is heparin orally active?

A

No

55
Q

What is low molecular weight heparin (LMWH)?

A

A smaller molecule of heparin with less dose variation and not very negatively charged

56
Q

How is low molecular weight heparin given?

A

Subcutaneously in a weight adjusted dose

57
Q

How does low molecular weight heparin differ when used for prophylaxis rather than treatment?

A

The amount needed for prevention(prophylaxis) is much smaller than the treatment dose

58
Q

How does aspirin work?

A
  • It inhibits cyclo-oxygenase irreversibly

* It inhibits thromboxane formation and consequently inhibits platelet aggregation

Haematology (5 decks)

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