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EMS - Mechanisms Of Disease > Ischaemia, Infarction and Shock > Flashcards

Ischaemia, Infarction and Shock Flashcards

1
Q

What is the name given to any state of reduced tissue oxygen availability?

A

Hypoxia

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2
Q

What is the name given to the pathological reduction in blood flow to tissues .
(usually as a result of obstruction to arterial flow by thrombosis/ embolism)

A

Ischaemia

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3
Q

Ischaemia results in …

A

hypoxia

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4
Q

In prolonged ischaemia, irreversible cell damage occurs. What is the process of cell death?

A

Cell death occurs by necrosis (infarction) in sustained ischaemia

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5
Q

When is therapeutic reperfusion effective in ischaemia?

A

Tissue perfusion is good if ischaemia is reversible. (short duration of ischaemia)

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6
Q

what is reperfusion injury?

A

generation of reactive oxygen species by inflammatory cells causes further damage when reperfusing ischaemic tissues.

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7
Q

what is the name given to the tissue damage caused when blood supply returns to the tissue after a period of ischemia or lack of oxygen (anoxia, hypoxia).

A

reperfusion injury

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8
Q

What is ischaemic necrosis caused by occlusion of the arterial supply or venous drainage?

A

Infarction

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9
Q

What are the main causes of Infarction?

A
  • thrombosis
  • embolism
  • Vasospasm
  • compression of vessel
  • Vaculitis
  • rupture of vascular supply (AAA)
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10
Q

What shape are most infarctions?

A

wedge shaped

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11
Q

where does colliquative necrosis normally occur?

A

brain

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12
Q

What factors influence the degree of ischaemic damage?

A

1) nature of blood supply
2) rate of occlusion
3) Tissue vulnerability to hypoxia
4) Blood oxygen content

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13
Q

What organs have a single blood supply which makes them vulnerable to infarction?

A

1) Kidneys
2) Spleen
3) Testis ect.

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14
Q

What organs have an alternative blood supply which maked them less prone to infarction via ischaemia?

A

1) Lungs (pulmonary and bronchial arteries)
2) Liver (hepatic artery and portal vein)
3) Hand (Radial and ulnar artery)

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15
Q

Slow developing occulsions are………………likely to infarct tissues

A

LESS

Slow developing occlusions are less likely to infarct tissues because:
-it allows time for development of alternative (collateral) perfusion pathways.

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16
Q

What organ requires 15% of cardiac output and 20% of body oxygen?

A

Brain

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17
Q

What is the name given to any abnormality of the brain caused by pathological process involving the blood vessels?

A

Cerebrovascular disease

18
Q

Give an example of a cerebrovascular accident?

A

Stroke

19
Q

what causes an ischaemic stroke?

A
  • thrombosis secondary to atheroscelrosis

- embolism

20
Q

What causes haemorrhagic stroke?

A
  • intracerebral haemorrhage (hypertensive)

- Ruptures aneurysm in the circle of willis&raquo_space;>subarachnoid haemorrhage

21
Q

What is the site of the thrombosis or embolism that causes ischaemic bowel disease?

A

Superior or Inferior mesenteric arteries

22
Q

Infarction of entire portion of limb (organ)

A

Gangrene

23
Q

what type of gangrene has ischaemic coagulative necrosis only?

A

Dry Gangrene

24
Q

what is the characteristic feature of wet gangrene?

A

superimposed infection

25
Q

what is the characteristic feature of gas gangrene?

A

superimposed infection with gas producing organism e.g. clostridium perfringens

26
Q

what is the name given to the physiological state characterised by a significant reduction of systemic tissue perfusion (SEVERE HYPOTENSION), resulting in DECREASED OXYGEN DELIVERY TO TISSUES

A

Shock

=hypotension and decreased oxygen delivery

27
Q

What results in a critical imbalance between oxygen delivery and oxygen consumption?

A

Shock

28
Q

impaired tissue perfusion and prolonged oxygen deprivation leads to ….?

A

cellular hypoxia

29
Q

What are the cellular effects of shock?

A

1) membrane ion pump dysfunction
2) Intracellular swelling
3) leakage of intracellular contents into extracellular space
4) inadequate regulation of intracellular pH
5) Anaerobic respiration&raquo_space;>lactic acid

30
Q

What are the systemic effects of shock?

A

1) alterations in the serum pH
2) Endothelial dysfunction&raquo_space;> vascular leakage
3) Stimulation of inflammatory and anti-inflammatory cascades
4) end organ damage (ischaemia)

31
Q

what is the sequential result of shock

A
  • cell death
  • end organ damage
  • multi organ failure
  • death
32
Q

what are the different types of shock?

A

1) hypovolaemic
2) Cardiogenic
3) Distributive
- anaphylactic
- septic
- toxic shock syndrome
- neurogenic

33
Q

What kind of shock can be attributable to :

  • intravacular fluid loss (blood,plasma)
  • decreased venous return to heart (ie. decreased pre-load)
  • therfore decreased stroke vol and decreased cardiac output.
A

Hypovolaemic shock

34
Q

How to compensate for hypovolaemic shock?

A

increase vasoconstriction

-this increases total peripheral resistance

35
Q

What are the causes of hypocolaemic shock?

A

1) Haemorrhage
2) Non-haemorrhagic fluid loss e.g. diarrhoea, vomiting

Reduces circulation volume

36
Q

what are the causes of cardiogenic shock?

A

1) Myopathic (heart muscle failure)
2) Arrythmia-related (abnormal electrical activity)
3) Mechanical
4) Extra cardiac (obstruction to blood outflow)

37
Q

What kind of shock is caused my MI, right ventricular infarction, stunned myocardium?

A

Myopathic cardiogenic shock

38
Q

what causes vasodilation in septic shock?

A

increased cytokines and mediators released by the immune reaction

39
Q

What happens in anaphylactic shock?

A

1) sensitised individuals exposed to stimulus
2) IgE mediated
3) Mast cell degranulation leads to histamine release
4) vasodilation
5) contraction of bronchioles
6) laryngeal oedema

40
Q

What happens in neurogenic shock?

A

1) spinal injury leads to
2) loss of sympathetic vascular tone
3) Vasodilation
4) Hypovolaemia
5) Shock

41
Q

What organisms release exotoxins that causes Toxic Shock syndrome?

A

Staph Aureus

Staph Pyogenes

EMS - Mechanisms Of Disease (18 decks)

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