Thrombosis, embolism & shock Flashcards Preview

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Flashcards in Thrombosis, embolism & shock Deck (24)
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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


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


How di we limit coagulation

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


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


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


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


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

myocardial infarction and rheumatoid endocarditis


Abnormalities of blood flow can cause:

Atrial fibrillation and aneurysms


Factors that promote thrombosis

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


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


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


Thrombi (emboli)

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


Fat (emboli)

eg. petechial haemorrhage in brain due to fat emboli


Tumour (emboli)

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


Atheroma (emboli)

eg. fragments of plaque may break off


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


Clinical features of shock

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


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


Hypovolaemic shock

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


Cardiogenic shock

large acute myocardial infarction/other acute cardiac disease


Septic shock

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


Anaphylactic shock

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


Neurogenic shock

spinal chord trauma/damage
regional anaesthesia


Obstructive shock

cardiac tamponade
massive pulmonary embolism
tension pheumothorax