Haemostasis Thrombosis And Embolism

Question 1

What is a thrombosis

Answer 1

Thrombosis is the formation of a solid mass of blood within the circulatory system in life

Question 2

What is the difference between a thrombosis and a clot?

Answer 2

Thrombosis is always pathological, clot is phisiological

Thrombosis occurs in the vessels

Question 3

Why does thrombosis occur?

Answer 3

• Abnormalities of the vessel wall
– atheroma/atherosclerosis - innapropriate activation of clotting
– direct injury
– inflammation eg vasculitis

• Abnormalities of blood flow
– stagnation
– turbulence

• Abnormalities of blood components
– smokers - hyper coagulative blood
– post-partum - physiologically useful to have haemostatic mechanism to stop bleeding where placenta detached
– post-op

Question 4

Describe the appearcene of arterial thrombi

Answer 4

Pale, granular, lower cell content, lines of Zahn (fibrin rich cell poor pale line and cell rich fibrin poor dark line)

Question 5

Describe the apparent end of venous thrombi

Answer 5

Soft, gelatinous, deep red, higher cell content - moor red cells trapped in

Question 6

What are the outcomes of thrombosis?

Answer 6

Lysis, propagation, organisation, recanalisation, embolism

Question 7

What is lysis?

Answer 7

• Lysis
– complete dissolution of thrombus
– fibrinolytic system active
– bloodflow re-established
– most likely when thrombi are small

Question 8

What is propagation?

Answer 8

• Propagation
– progressive spread/enlargement of thrombosis
– distally in arteries
– proximally in veins (veins get progressively larger towards heart)

Question 9

What is organisation?

Answer 9

• Organisation
– reparative process
– ingrowth of fibroblasts and capillaries (similar to granulation tissue)
– lumen remains obstructed- do not restore blood flora when there is organisation of a thrombus

Question 10

What is recanalisation?

Answer 10

• Recanalisation
– bloodflow re- established but usually incompletely
– one or more channels formed through organising thrombus
- allows some passage of blood but no where near as much as normal

Question 11

What is emboslim?

Answer 11

• Embolism
– part of thrombus breaks off
– travels through bloodstream
– lodges at distant site

Question 12

What are the effects of thrombosis?

Answer 12

Arterial

• ischaemia
• infarction- if you block an end artery - you get infarction - cell death - due to oxygen lack
• depends on site and collateral circulation - Some tissues have collateral blood supply - blocking one artery wont cause cell death

Venous

• congestion
• oedema - hydrostatic pressure increased by connection so fluid forced out, as oedema develops the pressure in the tissue increases and becomes equal to arterial pressure so no flow in, runs the risk o ischaemia or infarction
• ischaemia
• infarction
• most dont cause ischaemia/infarction as blood is able to return through unblocked veins

Question 13

Define embolism

Answer 13

• Definition
Embolism is the blockage of a blood vessel by solid, liquid or gas at a site distant from its origin.
>90% of emboli are thrombo-emboli

Question 14

What are other types of embolism other than thromboemoboli?

Answer 14

• Other types
– air eg from intravenous injection 
– amniotic fluid - relatively infrequent 
– nitrogen
– medical equipment
– tumour cells

Rewatch

Question 15

Where can thrombosis-emboli end up?

Answer 15

• from systemic veins pass to the lungs = pulmonary emboli - goes first towards the heart, keep encountering progressively lager veins and gets bigger, next time they encounter a smaller vessel eg in lungs they get stopped
• from the heart pass via the aorta to renal, mesenteric, and other arteries
• from atheromatous carotid arteries pass to the brain
• from atheromatous abdominal aorta pass to arteries of the legs

Question 16

What are predisposing factors of DVT?

Answer 16

• predisposing factors
– immobility/bed rest
– post-operative
– pregnancy and post- partum 
– oral contraceptives 
– severe burns 
– cardiac failure 
– disseminated cancer

Question 17

Can dvt be prevented?

Answer 17

Rewatch

Question 18

Can DVT be treated>

Answer 18

• intravenous heparin/other anticoagulant type drugs
• oral warfarin
- compression stocking
- flowtron boots - intermittent calm compression - shifting blood from veins

• when thrombus gets to iliofemoral vein it can get really big - if this breaks off it can form big embolism - treatment mainly aimed at stopping propagation

Question 19

What are the effects of pulmonary embolism

Answer 19

Pulmonary embolism - effects
• massive PE >60% reduction in bloodflow rapidly fatal
• major PE - medium sized vessels blocked. Patients short of breath +/- cough and blood stained sputum
• minor PE - small peripheral pulmonary arteries blocked. Asymptomatic or minor shortness of breath
• recurrent minor PEs lead to pulmonary hypertension

If reduce output form RHS for heart 0 no return - heart stops.- if large pulmonary emobilsm but not so big that it stops the heart,
minor - nothing very much

Question 20

What is a cerebral embolism?

Answer 20

Rewatch
Can use agents to reduce risk of arterial thrombi
aspirin most common - reduce risk of arterial thrombus. Primary or secondary preventative measure
carotid artery disease - most likely explanation = cerebral embolism

Question 21

.What is an iatrogenic emobolism?

Answer 21

See slide andrwatch

Question 22

What is a fat embolism ?

Answer 22

Rewatch