Ischaemia, Infarction and Shock Flashcards Preview

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Flashcards in Ischaemia, Infarction and Shock Deck (41):
1

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

Hypoxia

2

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)

Ischaemia

3

Ischaemia results in ...

hypoxia

4

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

Cell death occurs by necrosis (infarction) in sustained ischaemia

5

When is therapeutic reperfusion effective in ischaemia?

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

6

what is reperfusion injury?

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

7

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).

reperfusion injury

8

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

Infarction

9

What are the main causes of Infarction?

-thrombosis
-embolism
-Vasospasm
-compression of vessel
-Vaculitis
-rupture of vascular supply (AAA)

10

What shape are most infarctions?

wedge shaped

11

where does colliquative necrosis normally occur?

brain

12

What factors influence the degree of ischaemic damage?

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

13

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

1) Kidneys
2) Spleen
3) Testis ect.

14

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

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

15

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

LESS

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

16

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

Brain

17

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

Cerebrovascular disease

18

Give an example of a cerebrovascular accident?

Stroke

19

what causes an ischaemic stroke?

-thrombosis secondary to atheroscelrosis
-embolism

20

What causes haemorrhagic stroke?

-intracerebral haemorrhage (hypertensive)
-Ruptures aneurysm in the circle of willis >>>subarachnoid haemorrhage

21

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

Superior or Inferior mesenteric arteries

22

Infarction of entire portion of limb (organ)

Gangrene

23

what type of gangrene has ischaemic coagulative necrosis only?

Dry Gangrene

24

what is the characteristic feature of wet gangrene?

superimposed infection

25

what is the characteristic feature of gas gangrene?

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

26

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

Shock

=hypotension and decreased oxygen delivery

27

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

Shock

28

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

cellular hypoxia

29

What are the cellular effects of shock?

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 >>>lactic acid

30

What are the systemic effects of shock?

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

31

what is the sequential result of shock

-cell death
-end organ damage
-multi organ failure
-death

32

what are the different types of shock?

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

33

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.

Hypovolaemic shock

34

How to compensate for hypovolaemic shock?

increase vasoconstriction
-this increases total peripheral resistance

35

What are the causes of hypocolaemic shock?

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

Reduces circulation volume

36

what are the causes of cardiogenic shock?

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

37

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

Myopathic cardiogenic shock

38

what causes vasodilation in septic shock?

increased cytokines and mediators released by the immune reaction

39

What happens in anaphylactic shock?

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

What happens in neurogenic shock?

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

41

What organisms release exotoxins that causes Toxic Shock syndrome?

Staph Aureus
Staph Pyogenes