PP 5 Thrombosis + Embolism Flashcards by Emily Stephens

Thrombosis defintion

Formation of solid mass of blood within the circulatory system

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Thrombus definition

Solid mass of blood within circulatory system

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Clot defintion

Mass of blood outside vessel wall

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Thrombus vs clot

Thrombus is within circulatory system
Clot is outside circulatory system

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What is Virchow’s triad?

Thrombus form when there’s abnormalities in:
- vascular wall
- blood flow
- blood components

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What can cause damage to vascular system?

Atheroma
Inflammation - vasculitis
Direct injury
Damage to heart

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Atheroma definition

Degeneration of arteries due to fatty deposition

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What causes change to blood flow?

Stasis
Turbulent blood flow

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Stasis in blood meaning

Slowing of blood

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Causes of blood stasis

Narrowing of vessels
Low BP
Immobility

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Causes of turbulent blood flow

Defects in walls + heart valves
Atrial fibrillation

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Hypercoagulable state of blood meaning

Sticky blood

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Who is at risk of hypercoagulable blood?

Smokers
Pregnancy + post-partum
Trauma + burns
Post-operative patients
Genetic diseases e.g anti thrombin III deficiency

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Appearance of an atrial thrombus

Pale
Granular
Lower cell content
Lines of Zahn

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Appearance of a venous thrombus

Deep red
Soft
Gelatinous
Higher cell content

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Why are lines of Zahn present in arterial thrombi but not venous?

There is a degree of shielding by valves in veins

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Describe the formation of thrombus

1- platelets are activated
2- platelets aggregate + bind together by fibrin
3- RBCs get trapped
4- thrombus formed

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Role of plasmin

Degrades fibrin
Dissolves thrombus

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What is a breakdown product of fibrin?

D-dimers

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What can D-diners be detected in the blood for?

Indicate clotting occurring

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What converts plasminogen to plasmin/

tPA tissue plasminogen activator

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What breaksdown fibrin?

Plasmin

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List possible outcomes of thrombosis

Lysis
Propagation
Organisation
Recanalisation
Embolism

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What process restores complete blood flow after thrombosis?

Lysis

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What is lysis of thrombosis?

Breakdown of thrombus

What type thrombi does lysis occur to?

Small ones

What is propagation of thrombus?

Spread of thrombosis

What is organisation of thrombus?

In growth of fibroblasts + capillaries Lumen remains obstructed

What is recanalisation of thrombus?

Channel formation through an organised thrombus

What process restores partial blood flow after a thrombus?

Recanalisation

What is embolism of a thrombus?

Part of thrombus breaks off Travels in bloodstream Lodges at distant site

Effects of venous thrombosis

Congestion Oedema Ischaemia Infarction

Common locations of venous thrombosis

Cavernous sinus Subclavian vein Inferior vena cava Uteroplacental Deep vein thrombosis

Effects of arterial thrombosis

Ischaemia Infarction Dependent on site + collateral blood supply

Common locations of arterial thrombosis

Cerebral artery Carotid artery Coronary artery Mesenteric + renal artery Femoral, iliac + popliteal artery

What can thrombosis in cerebral artery cause?

Ischaemic stroke

What can thrombosis in coronary artery cause?

Myocardial infarction

Embolism definition

Blockage of blood vessel by **solid, liquid or gas** at distant site room organ

Examples of embolisms

Thrombus Air Amniotic fluid Nitrogen Medical equipment Fat Tumour cells

List come predisposing factors to DVT

Immobility/bed rest Post-operative Pregnancy + post-partum Oral contraceptives Severe burns Cardiac failure Disseminated cancer Superficial thrombophlebitis Obesity Old age Previous/family history of DVT

What is Superficial thrombophlebitis?

Inflammation in superficial vein of leg

What can you do to prevent thromboembolism caused by bed rest?

Identify patients at high risk Mobilise early + decrease bed rest +/- aspirin Low molecular weight heparin subcutaneously Leg compression during surgery e.g. *TED stockings + ‘flowtron boots’*

Different types of pulmonary thromboembolisms + their effects

- massive coiled embolus in main PA - **death** - small embolus lodges in peripheral PA - *pulmonary infarct* - multiple repeated small emboli - *pulmonary hypertension*

What can be used to identify DVT in leg?

Ultrasound

What can be used to identify an embolism?

CT pulmonary angiogram

Why are NOAC/DOACs better than oral warfarin

Easier to manage - no tests needed Warfarin requires many tests Easy to accidentally overdose on warfarin

What does NOAC/DOAC stand for?

**N**oval/**D**irect **O**ral **A**nti**C**oagulant

Examples of NOAC/DOACs

Rivaroxaban Apixaban Dabigatron

Treatments of thrombosis

Clot busters/thrombolysis Low molecular weight heparin Oral warfarin NOAC/DOAC Embolectomy Filters in IVc Aspirin

Examples of clot busters

Streptokinase Ateplase

How has warfarin work?

Inhibits synthesis of vitamin K dependent clotting factors

What drug increases PT and is monitored by regular INR measurements?

Warfarin

Conditions for which warfarin is used

DVT Pulmonary embolism Cardiac arrhythmias After cardiac valve replacement

What tests are needed if you are in warfarin?

PT/INR test

What effect would a paracetamol overdose have on clotting tests? Why?

PT raised Paracetamol toxicity > liver failure Prothrombin isn’t produced by the liver

What is prothrombin a test on?

Extrinsic pathway Clotting factors made by the liver

What effect would a paracetamol overdose have on blood tests?

Raised PT Raised ALT

What effect would a paracetamol overdose have on ALT tests? Why?

Increased ALT Hepatocytes die due to paracetamol toxicity ALT leaks out of the damaged cell membranes

What is a paracetamol overdose treated with?

N-acetylcysteine

Why are pregnant women predisposed to DVT?

- Pregnancy blood is hypercoagulable - The baby can compress venous outflow from legs and cause venous stasis

Why is low molecular weight heparin favoured over warfarin?

LMW heparins effective immediately Warfarin takes a few days to become effective

What type of inhibitor is aspirin?

Non-competitive

What does aspirin do?

- Irreversible inhibits cylcooxygenase (enzyme for prostaglandin synthesis) - platelets can’t produce thromboxane A2 - reduced platelet aggregation

What inhibits cyclooxgenase?

Aspirin - non competitively Ibuprofen - competitively

What does low molecular weight heparin do?

Irreversible complexes with and activates antithrombin III

Bleeding time in aspirin

Prolonged

What does cyclooxgenase cataylse?

Prostaglandin synthesis

Where do the of thrombi that cause majority of pulmonary emboli arise from?

Deep veins of thigh + popliteal vein

What is most likely cause of thrombi occurring in veins

Blood stasis

What type of thrombi usually occur at site of endothelial injury?

Atrial and cardiac thrombi

PP 5 Thrombosis + Embolism Flashcards

(70 cards)