Thrombosis, embolism & shock

Question 1

Why is clotting a positive?

Answer 1

Normal haemostasis
Maintain blood fluid in normal vessels
Able to induce rapid and localised haemostatic plug at site if vascular injury

Question 2

What are the 3 steps of normal haemostasis?

Answer 2

Straight after injury - reflex vasoconstriction of arterioles
Endothelium injury exposes highly thrombogenic ECM
Platelets adhere and are activated, leading to the release of chemokines and the recruitment of additional platelets forming a haemostatic plug

Question 3

How di we limit coagulation

Answer 3

It is important to limit coagulation to site of injury
Anticoagulant mechanisms:
- anti-thrombin
- plasmin activation = breaks down fibrin

Question 4

Define thrombosis

Answer 4

Inappropriate activation of blood clotting in the vessels leading to a solid/semi-solid mass from the constituents of blood during life
Can form in heart, arteries, veins, capillaries
Arterial - due to injury/foreign material
Venous - at sites of stasis

Question 5

Define embolism

Answer 5

An embolus is a detached intravascular solid/liquid/gas that is carried by the blood stream to a distant site to its point of origin
Caused by thrombus, fat, tumour, infection, foreign body

Question 6

What are the 3 factors promoting coagulation

Answer 6

1. abnormalities of blood vessel wall due to endothelial injury
2. abnormalities of blood flow
3. abnormalities of blood’s constituents eg pregnancy, tumours, contraception, trauma

Question 7

Abnormalities of blood vessel wall and altered blood flow can cause:

Answer 7

myocardial infarction and rheumatoid endocarditis

Question 8

Abnormalities of blood flow can cause:

Answer 8

Atrial fibrillation and aneurysms

Question 9

Factors that promote thrombosis

Answer 9

Abnormalities in the vessel wall eg atheroma, inflammation

Abnormalities of blood flow eg. aneurysms, plaques, spasm causing turbulence

Question 10

Venous thrombosis

Answer 10

Stasis = alters normal laminar flow of blood
Immobility due to loss of function, post-op etc.
Direct compression of veins eg ovarian tumours compressing on pelvic veins

Question 11

Fate of thrombi

Answer 11

1. Resolution - fibrinolysis
2. Organisation -
   incorporation into a scar by macrophages and fibroblasts
   vessel lumen remains narrowed
   cell proliferation, capillary invasion & recanalisation, vessel become patent again
3. Detachment - thromboembolism

Question 12

Thrombi (emboli)

Answer 12

eg. massive fatal pulmonary thromboembolism lodged in major branch of pulmonary artery

Question 13

Fat (emboli)

Answer 13

eg. petechial haemorrhage in brain due to fat emboli

Question 14

Tumour (emboli)

Answer 14

When tumour penetrates blood vessel parts of tumour may break off and metastasise

Question 15

Atheroma (emboli)

Answer 15

eg. fragments of plaque may break off

Question 16

What is shock?

Answer 16

when organs and tissues of the body are not receiving an adequate flow of blood, depriving them of oxygen and allows build up of waste products
can cause serious damage and death

Question 17

Clinical features of shock

Answer 17

low systolic BP (<110)
tachycardia (>90bpm)
resp rate <7 >29 breaths/min
low urine output
metabolic acidosis
hypoxia
anxiety, legarthy

Question 18

3 stages of shock

Answer 18

1. Compensated = non-progressive, blood volume loss 15-25%
2. Non-compensated = progressive, blood volume loss over 25%
3. Irreversible = failure to restore circulation, critical organ damage

Question 19

Hypovolaemic shock

Answer 19

internal/external haemorrhage
high output fistulae (intestinal failure)
severe burns

Question 20

Cardiogenic shock

Answer 20

large acute myocardial infarction/other acute cardiac disease

Question 21

Septic shock

Answer 21

endotoxins from Gram negative bacteria
exotoxins from gram positive bacteria
shock sequence of dilation of blood vessels
bowel infarction/limb ischaemia

Question 22

Anaphylactic shock

Answer 22

severe form of allergic reaction to food, antibiotics, insect sting etc.

Question 23

Neurogenic shock

Answer 23

spinal chord trauma/damage

regional anaesthesia

Question 24

Obstructive shock

Answer 24

cardiac tamponade
massive pulmonary embolism
tension pheumothorax