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Haematology > Haematology 5- Thrombosis: Aetiology and Management > Flashcards

Haematology 5- Thrombosis: Aetiology and Management Flashcards

1
Q

Consequences of Thromboembolism

A
  • Recurrence
  • Thrombophlebitic syndrome (recurrent pain, swelling and ulcers
  • Pulmonary hypertension
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2
Q
  • THREE contributory factors to thrombosis
A
  • Blood composition
    • (viscosity)
      • Haematocrit (high)
      • Protein/ paraprotein (high level- e.g. myeloma and paraprotein)
    • Platelet count
    • Coagulation – net excess of procoagulant activity
  • Vessel wall
  • Blood flow
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3
Q

procoagulant and antiocgulant factors

A
  • Coagulation factors push to produce thrombin and eventually fibrin
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4
Q

SBA 1: The risk of thrombosis is increased by:

  • Reduced prothrombin
  • Thrombocytopenia
  • Reduced Protein C
  • Elevated anti-thrombin
  • Increased fibrinolysis
A
  • Reduced prothrombin
  • Thrombocytopenia
  • Reduced Protein C
  • Elevated anti-thrombin
  • Increased fibrinolysis
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5
Q

The Vessel Wall is normally Antithrombotic- how?

A

expresses anticoagulant molecules

  • Thrombomodulin – help activate protein C
  • Endothelial Protein C receptor – help activate protein C
  • Tissue factor pathway inhibitor
  • Heparans- help antithrombin work
  • It does NOT express tissue factor
  • It secretes antiplatelet factors:
    • Prostacyclin (PGI2)
    • NO
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6
Q

what makes Vessel Wall Prothrombotic

A
  • Stimulus:
    • Infection
    • Malignancy
    • Vasculitis
    • Trauma
    • Hypoxia
  • Effects:
    • Anticoagulant molecules (e.g. thrombomodulin) are downregulated
    • Adhesion molecules upregulated
    • TF may be expressed
  • Prostacyclin production reduced

This becomes procoagulant which is how the vessel wall comes into play in thrombosis

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7
Q

Inflammation and Thrombosis: Malignancy

A

causes inflammation, leading to expression of tissue factor

+ can also cause obstruction

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8
Q

Blood Flow: Stasis promotes Thrombosis

A
  • Mechanism:
    • There is an accumulation of activated factors
    • This promotes platelet adhesion
    • This also promotes leukocyte adhesion and transmigration
    • Hypoxia produces inflammatory effect on endothelium
  • Causes of stasis:
    • Immobility- surgery, paraparesis, travel
    • Compression- tumour, pregnancy
    • Viscosity- polycythaemia, paraprotein
    • Congenital- vascular abnormalities
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9
Q

SBA 2: Which factor confers the highest risk of thrombosis?

  • Factor V Leiden
  • Antithrombin deficiency
  • FHx of thrombosis
  • Reduced Factor VIII level
  • 3 hour plane flight
A
  • Factor V Leiden
  • Antithrombin deficiency
  • FHx of thrombosis
  • Reduced Factor VIII level
  • 3 hour plane flight

Thrombotic risk factors can combine to cause a massively increased risk of thrombosis

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10
Q

Heparin - is it delayed use or immediate use?

disadvantages

MOA

example

A

Heparin– increase anticoagulant activity by potentiating anti-thrombin

LMWH (SC) + unfractionated heparin - IV

Long term disadvantages

  • SC injections
  • Risk of osteoporosis
  • Variable renal dependence
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11
Q
  • Direct Acting Anti-Xa and Anti-IIa (IIa- thrombin) –
  • is it delayed use or immediate use?

disadvantages

MOA

example

A

immediate use - peak in 2-4 hours

Inhibit the activation of coagulation factors

Take orally not SC like LMWH

unfractionated heparin

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12
Q

warfarin

  • is it delayed use or immediate use?

disadvantages

MOA

example

A
  • DELAYED- takes 2-3 days
  • Warfarin – reduce procoagulant activity
  • Vitamin K epoxide reductase inhibitor >>> inhibits coagulation factor proteins 2, 7, 9, 10
  • Also causes a reduction in Protein C and S
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13
Q

how is warfarin prophylactic + theraputic

A
  • HIGH dose= therapeutic
  • LOW dose= prophylactic
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14
Q

SBA 3: Which agent has a delayed anticoagulant effect?

  • Vitamin K
  • Unfractionated heparin
  • Warfarin
  • LMWH
  • Aspirin
A
  • Vitamin K
  • Unfractionated heparin
  • Warfarin
  • LMWH
  • Aspirin
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15
Q

Monitoring Heparin Therapy

A
  • LMWH- Reliable pharmacokinetics so not usually required to monitor
  • Unfractionated heparin
  • Always monitors therapeutic levels with APTT (activated partial thromboplastin time) or anti-Xa
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16
Q

examples of direct acting anticoagulants + do they require monitoring

A
  • Anti-Xa: Direct factor Xa inhibitor
    • Rivaroxaban, apixaban, edoxaban
  • Anti-IIa: Direct thrombin inhibitor
    • Dabigatran
  • No monitoring
17
Q

Delayed Anticoagulation- Long Term

warfarin- mode of adminstration

MOA + how can it be reversed

A
  • inhibits the synthesis of Vitamin K-dependent proteins (factors 2, 7, 9 and 10) >>> so delayed onset of action
  • also reduces amount of protein C and S

reversed with:

  • vitamin K - takes 12 hours
  • giving factors 2, 7, 9, 10- immediate response
18
Q

How does warfarin achieve an anticoagulant effect?

  • Reduce the production of Protein C and Protein S
  • Blocks phospholipid synthesis
  • Reduces plasma concentration of procoagulant factors
  • Acts as a cofactor for antithrombin
  • Inhibits Factors II, VII, IX, X
A
  • Reduce the production of Protein C and Protein S
  • Blocks phospholipid synthesis
  • Reduces plasma concentration of procoagulant factors
  • Acts as a cofactor for antithrombin
  • Inhibits Factors II, VII, IX, X
19
Q

Monitoring Warfarin

A
  • Measure of effect is the INR (International Normalised Ratio)-
  • Derived from prothrombin time
20
Q

can warfarin + heparin + DOAC be given in pregnancy

A
  • Teratogenic
21
Q

Summary of Different Anticoagulants used

A
22
Q

Patients at Increased risk of Thrombosis

A
  • Medical inpatients
    • Infection/ inflammation
    • immobility (including stroke)
    • age
  • Patients with cancer
    • Procoagulant molecules, inflammation, flow obstruction
  • Surgical inpatients
    • Immobility, trauma, inflammation
  • Previous VTE, FHx, genetic traits
  • Obese
  • Elderly
23
Q

Thromboprophylaxis + what is used

A

low dose anticoagulation to reduce the risk of clotting when in hospital or when going home

LMWH

  • E.g. tinzaparin 4500U OR Clexane 40mg OD
  • Not monitored

TED stockings (for surgery or if heparin is contraindicated)

Flotron (boot)- Intermittent compression (increases flow) – avoiding stasis component

Sometimes DOAC +/- aspirin (orthopaedics)

24
Q

when during hospital admission should thrombophylaxis be given

A

All admissions to hospital should be assessed for thrombotic risk and unless contraindication exists, receive heparin prophylaxis

25
Q

Risk Assessment for VTE

A
  • Patient
    • Age > 60 years
    • Previous VTE
    • Active cancer
    • Acute or chronic lung disease
    • Chronic heart failure
    • Lower limb paralysis (excluding acute CVA)
    • Acute infection
    • BMI > 30
  • Procedure
    • Hip or knee replacement
    • Hip fracture
    • Other major orthopaedic surgery
    • Surgery > 30 mins
    • Plaster cast immobilisation of lower limb
26
Q

Treatment for DVT/ PE

A

Need to be anticoagulated IMMEDIATELY

27
Q

Thrombolysis - when is its use

A
  • Thrombolysis is only used for life-threatening PE OR limb-threatening DVT

big increase in the risk of INTRACRANIAL HAEMORRHAGE (4%)

28
Q

factors for risk of recurrence of VTE and long term coagulation

A

need to assess risk of recurrence and bleeding when considering long term coagulation

risk of recurrence- factors:

  • If it occurred after surgery, it has LOW risk of recurrence
  • If it has occurred with a non-surgical risk (e.g. COCP, flight), it has a MODERATE risk of recurrence
  • If it was idiopathic, it has HIGH risk of recurrence
    • They will benefit from long term thromboprophylaxis
29
Q

which gender has higher risk of recurrence of DVT/PE

A
  • Men have a HIGHER risk of recurrence than women
30
Q

thrombosis in what part of body has higher reucrrence risk

A
  • Proximal thrombosis (i.e. pelvic or popliteal thrombosis) has a higher rate of recurrence than distal thrombosis (e.g. calf)
31
Q

when should patients be offered CT scan for thromembolic disease

A
  • All patients > 60 years old with idiopathic thromboembolic disease should be offered a CT scan to check for an underlying cause
32
Q

SBA 5: Which patient is most likely to benefit from long term anticoagulation after their DVT?

Circumstance of DVT:

  • 57 y/o man after flying from Kuala Lumpur
  • 27 y/o woman during pregnancy
  • 33 y/o woman on COCP
  • 77 y/o man after hip replacement
  • 30 y/o man after a long walk
A
  • 57 y/o man after flying from Kuala Lumpur
  • 27 y/o woman during pregnancy
  • 33 y/o woman on COCP
  • 77 y/o man after hip replacement
  • 30 y/o man after a long walk

remember men have higher risk of recurrence than women

long walk- had an unprecipitated/ idiopathic thrombosis- unlike long flight, pregnancy, COCP, surgery

33
Q
  • 32 y/o woman developed DVT after removal of ovarian cyst. Father and 2 brothers had DVT*
  • what should be the next step:*
  • Testing for antithrombin deficiency?
  • Recommend HRT?
  • Continue long term anticoagulation?
A
  • Testing for antithrombin deficiency?
  • Recommend HRT
  • Continue long term anticoagulation

There is a strong FHx so suggests something is inherited. Continuing longer term anticoagulation may be a good idea if the tests from the antithrombin deficiency come back as positive.

34
Q

29 y/o man, collapsed at work following PE. No family history

what should be done next

  • Test for Factor V Leiden?
  • Daily aspirin?
  • Continue long-term anticoagulation?
  • Heparin injections for long haul flights?
A
  • Test for Factor V Leiden?
  • Daily aspirin?
  • Continue long-term anticoagulation?
  • Heparin injections for long haul flights?

This man had an unprecipitated thrombosis and subsequent PE. Once you have had a PE once, you are likely to see it again. Long-term anticoagulation is the most important thing as this could recur.

Aspirin is popularly used as an anticoagulant, but it is NOT good at this.

35
Q

67 y/o man present with DVT and weight loss. Started on LMWH

what should be done next

  • Abdo-pelvic CT scan?
  • Switch to DOAC?
  • Switch to warfarin?
A
  • Abdo-pelvic CT scan?
  • Switch to DOAC?
  • Switch to warfarin?

Cancer is an inflammatory process that can precipitate a thrombosis.

36
Q

IMPORTANT: ANTICOAGULATION AND RECURRENCE AFTER FIRST VTE + need for long term coagulation

A
  • Very LOW after surgical precipitant
    • No need for long term anticoagulation
  • HIGH after idiopathic VTE (10-20% in 2 years)
    • Consider long term anticoagulation
  • After MINOR precipitants (COCP, flights, trauma)
    • Usually 3 months adequate
    • Longer duration may be dictated by presence of thrombotic and haemorrhagic risk factors
37
Q

summary

A
  • Heparin and warfarin are anticoagulants with complementary properties
  • Knowledge of risks allows appropriate use of thromboprophylaxis and duration of anticoagulant therapy

Haematology (16 decks)

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