Thrombosis, embolism, infarction and shock

Question 1

Haemostasis

Answer 1

He maintenance of blood levels - preventing bleeding and blood clot formation in normal circulation

Question 2

What are the three components involved in haemostasis?

Answer 2

Vascular wall, platelets and coagulation cascade

Question 3

Importance of vascular wall in haemostasis

Answer 3

Provides contraction and a small cat to close the gap on the broken side and prevent blood from leaking out

Question 4

Importance of platelets in haemostasis

Answer 4

Form small plaques that cover holes in blood vessels to prevent bleeding

Question 5

Importance of coagulation cascade in haemostasis

Answer 5

Activated when the cut is too large or severe and involves a variety of enzymes that cause a clot to form

Question 6

Thrombosis

Answer 6

A solid mass formed within the vascular system usually due to overactive haemostatic processes. Prone to fragmentation

Question 7

What are the three predisposing factors of thrombosis?

Answer 7

Endothelial injury (most important), stasis and turbulence of bloodflow and blood hypercoagulability (thrombophilia)

Question 8

Endothelial injury

Answer 8

Exposes the extracellular matrix due to a loss of cell integrity. Collagen and tissue factors are then able to activate platelets and clotting factors to cause adhesion

Question 9

Stasis of blood flow

Answer 9

Stagnant bloodflow leads to accumulation of clotting factors and platelets promotes coagulation. Contribute to venous thrombosis

Question 10

Turbulence of bloodflow

Answer 10

Causes damage to endothelial cells which then promotes thrombosis. Contributes to arterial and cardiac thrombosis

Question 11

Stages of arterial thrombosis

Answer 11

Atheroma, ulceration, platelet adherence and thrombus formation

Question 12

Atheroma

Answer 12

A bulge filled with lipids forms in the collagen layer underneath epithelial cells. A plaque forms on top of the epithelial cells. Causes mechanical disruption and damage

Question 13

Ulceration

Answer 13

Loss of endothelial cells which exposes collagen

Question 14

Platelet adherence

Answer 14

Clotting factors and platelets are activated I did hear to the blood vessel wall where the endothelial cells were lost

Question 15

Thrombus formation

Answer 15

Alternating layers of fibrin, platelets and red blood cells that forms a platform for other clotting factors to cause hypercoagulation

Question 16

Risk factors for thrombosis

Answer 16

Prolonged bedrest or immobilisation, myocardial infarction, arterial fibrillation, prosthetic cardiac valves, tissue injury, cancer and increased age

Question 17

Common sites of arterial thrombosis

Answer 17

Coronary, cerebral and femoral arteries. Due to turbulence

Question 18

Common sites of Venous thrombosis

Answer 18

Superficially on deep veins of the leg. Due to stasis at valves. Causes pulmonary infarction after metastasis

Question 19

Embolisation

Answer 19

A solid mass travelling in the bloodstream often due to dislodging of the thrombus

Question 20

What are the fates of a thrombus?

Answer 20

Propagation (growing bigger), embolisation, dissolution and organisation/recanalisation

Question 21

Dissolution

Answer 21

Result of fibrinolysis (breakdown of fibrin)

Question 22

Recanalisation

Answer 22

Blood vessel Newmans are restored by forming new channels after occlusion

Question 23

Organisation of thrombuses

Answer 23

Formation of scar and connective tissue by the invasion of macrophages. Prevents risk of embolism but bloodflow is now lost

Question 24

Complications of venous thrombosis

Answer 24

Blood and extracellular fluid accumulates locally causing oedema due to impaired drainage. Embolism after better stasis and dislodging. Pulmonary embolism and infarction due to less bloodflow to the left ventricle of the heart

Question 25

Sources of emboli

Answer 25

Dislodged thrombus or blood clot, infected lesions, gas bubbles (oxygen or nitrogen, from injections or divers moving from high to low pressures), fat deposits, bone marrow and fractions, tumour cells and amniotic fluid during labour

Question 26

Complications of pulmonary embolism

Answer 26

Most are clinically silent but symptoms can be right heart failure, cardiovascular collapse or even sudden death

Question 27

Gangrene

Answer 27

Dead and necrotic tissue turned black due to ischaemia

Question 28

Infarct

Answer 28

An area of ischaemic necrosis caused by occlusion of either the arterial supply or the venous drainage in a tissue. Only arises if the cause is blood vessel occlusions – otherwise simply called necrosis

Question 29

Other causes of infarction

Answer 29

Vasospasms, haemorrhage into plaques, vessel compression by tumours and traumatic rupture due to hyperoxia

Question 30

Shape of infarcts

Answer 30

Wedge - in lungs, triangular - in kidney, scarred - in spleen

Question 31

How are infarcts classified?

Answer 31

Based on their colour (reflects haemorrhage) and any microbial infection

Question 32

White infarcts

Answer 32

Anaemic. In solid organ is with end arterial circulation

Question 33

Red infarcts

Answer 33

Haemorrhagic. Mainly in the brain

Question 34

Septic infarcts

Answer 34

Infected

Question 35

Bland infarcts

Answer 35

Non-infected

Question 36

Factors that influence infarction outcomes

Answer 36

Availability of alternative blood supply, rates of occlusion development, vulnerability to hyperoxia and is normal oxygen content of the blood

Question 37

What and when are the first visible signs of infarction?

Answer 37

After 24hrs, pallor seen and inflammation at the edge

Question 38

Shock

Answer 38

Inadequate tissue perfusion

Question 39

What is shock characterised by?

Answer 39

Systemic hypotension due to reduced cardiac output and circulating blood flow

Question 40

Cardiogenic shock

Answer 40

Results from low cardiac output due to heart failure and poor myocardial contractility

Question 41

Extravasation

Answer 41

Blood leaking out into the tissues

Question 42

Hypovolaemic shock

Answer 42

Results from low cardiac output due to the loss of blood plasma volume

Question 43

Causes of blood loss

Answer 43

Haemorrhage, vomiting and diarrhoea, increased diuresis, burns and diabetes insipidus

Question 44

Septic shock

Answer 44

Results from vasodilation and peripheral pooling of blood as part of a systemic immune reaction to infection

Question 45

Symptoms of shock

Answer 45

Confusion, restlessness, excessive thirst, weak and rapid pulse, pale cool moist skin