Thrombosis, embolism & shock Flashcards Preview

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Flashcards in Thrombosis, embolism & shock Deck (24)
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1

Why is clotting a positive?

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

2

What are the 3 steps of normal haemostasis?

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

3

How di we limit coagulation

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

4

Define thrombosis

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

5

Define embolism

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

6

What are the 3 factors promoting coagulation

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

7

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

myocardial infarction and rheumatoid endocarditis

8

Abnormalities of blood flow can cause:

Atrial fibrillation and aneurysms

9

Factors that promote thrombosis

Abnormalities in the vessel wall eg atheroma, inflammation
Abnormalities of blood flow eg. aneurysms, plaques, spasm causing turbulence

10

Venous thrombosis

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

11

Fate of thrombi

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

12

Thrombi (emboli)

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

13

Fat (emboli)

eg. petechial haemorrhage in brain due to fat emboli

14

Tumour (emboli)

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

15

Atheroma (emboli)

eg. fragments of plaque may break off

16

What is shock?

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

17

Clinical features of shock

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

18

3 stages of shock

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

19

Hypovolaemic shock

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

20

Cardiogenic shock

large acute myocardial infarction/other acute cardiac disease

21

Septic shock

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

22

Anaphylactic shock

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

23

Neurogenic shock

spinal chord trauma/damage
regional anaesthesia

24

Obstructive shock

cardiac tamponade
massive pulmonary embolism
tension pheumothorax