Thrombosis And Embolism

Question 1

Define thrombosis

Answer 1

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

Question 2

Why does thrombosis occur?

Answer 2

Abnormalities of the vessel wall: atheroma, direct injury, inflammation (e.g. vasculitis)

Abnormalities of blood flow: stagnation, turbulence

Abnormalities of blood components: smokers post-partum (after baby), post-op.

Question 3

What do arterial thrombi look like?

Answer 3

pale, granular, lines of Zahn, lower cell content

Question 4

What do venous thrombi look like?

Answer 4

Soft, Gelatinous, Deep red as higher cell content

Question 5

What are the outcomes of thrombosis?

Answer 5

Lysis

Propagation

Organisation

Recanalisation

Embolism

Question 6

Lysis of thrombus?

Answer 6

Complete dissolution of thrombus

Fibrinolytic system active

Bloodflow re-established

Most likely when thrombi are small

Question 7

Propagation of thrombosis?

Answer 7

Progressive spread (enlargement) of thrombosis

Distally in arteries (away from heart) and proximally in vein (towardsthe heart) because of direction of blood flow.

Question 8

Organisation of thrombosis?

Answer 8

Reparative process

Ingrowth of fibroblasts ad capillaries (similar to granulation tissue)

Lumen remains obstructed

Question 9

Recanalisation of thrombosis?

Answer 9

Bloodflow is partially reestablished.

One or more channels formed through organising thrombus.

Question 10

Embolism of thrombosis?

Answer 10

Part of thrombus breaks off

Travels through the bloodstream

Lodges at distant site

Question 11

What are the effects fo arterial thrombosis?

Answer 11

Ischaemia

Infarction (if end arteries but not if collateral circulation)

Depends on site and collateral circulation

Question 12

What are the effects of venous thrombosis?

Answer 12

Congestion (usually more than one way for blood to get back to heart but it slowed down).

Oedema

Ischaemia - when tissue pressure = venous pressure

Infarction

But, most not cause ischemia / infaction because of collateral circulation.

Question 13

Define embolism

Answer 13

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 emboli?

Answer 14

Air - from IV injections/ infusions (need 100ml to cause air embolus)

Amniotic fluid

Nitrogen - divers if not decompression appropriately

Medical Equipment - go into arteries instead of veins

Tumour Cells

Question 15

Where could the thrombus occur in thrombo-emboli?

Answer 15

From systemic veins to the lungs = pulmonary emboli

From the heart pass via the aorta to renal, mesenteric and other arteries

From atheromatous carotid arteries pass to the brain Fro atheromatous carotid arteries pass to the brain - can cause mini stroke.

From atheromatous abdominal aorta pass to arteries of the leg

Question 16

What are the predisposing factors for DVT?

Answer 16

Immobility / bed rest

Postoperative

Pregnancy and post-partum

Oral contraceptives

Cardiac failure

Severe burns

Disseminated cancer

Question 17

Can DVT be prevented?

Answer 17

Can reduce risk fo DVT rather than prevention.

• Heparrin to interfere with coagulation
• Compressing leg veins using TED stockings
• Flowtron boots during surgery
• Movement - bending legs

Question 18

Can DVT be treated?

Answer 18

Intravenous heparin type drugs

Oral warfarin

• not dissolve thrombus but prevent significant propagation.

Question 19

What are the effects of pulmonary embolism?

Answer 19

Massive PE >60% reduction in blood flow - rapidly fatal

Major PE - medium sized vessels blocked Patient short of breath +/- cough and blood stained sputum

Minor PE - small peripheral arteries blocked. Asymptomatic or minor shortness of breath

Recurrent minor PEs lead to pulmonary hypertension.

Question 20

Where else can embolisms occur?

Answer 20

Cerebral embolism

Iatrogenic embolism (caused by air during medical examination)

Fat embolism