MOD 14 - Ischaemia & hypoxic injury Flashcards Preview

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Flashcards in MOD 14 - Ischaemia & hypoxic injury Deck (39):
1

what is hypoxic injury

any state of reduced tissue O2 availability (general & regional)

2

what is ischaemia

pathological reduction in blood flow to tissue

3

what will happen if reperfusion of non-infarcted but ischaemic tissues always good

generation of reactive oxygen species by inflammatory cells causes further damage

4

what is infarction

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

5

what is the most common cause of infarction

thrombosis and embolism - most commonly within arteries

6

what does red infarction indicate?

haemorrhagic - dual blood supply/venous infarction

7

what does white infarction mean?

single blood supply hence totally cut off

8

what are the factors influence the degree of ischaemic damage

nature of the blood supply, rate of occulsion, tissue vulnerability to hypoxia , blood oxygen content

9

how long will irreversible cell damage occur if brain tissue is deprived of oxygen

3 to 4 minutes

10

how long will irreversible cell damage occur if heart tissue is deprived of oxygen

20 to 30 minutes

11

what is cerebrovascular disease

any abnormality of the brain caused by a pathological process involving the blood vessels

12

what are the causes of haemorrhagic stroke

intracerebral harmorrhage (hypertensive), ruptured aneurysm in the circle of Willis (subarachnoid)

13

what are cerebrovascular accidents

ischaemic stroke

14

what are some examples of some ischaemia around the body

heart - ischaemic haert disease (angina)

brain - cerebrovascular disease (TIA/CVA)

intestines - ischaemic bowel

extremities - peripheral vascular disease/gangrene

15

what are ischaemic bowel disease

- usually caused by thrombosis or embolism in the superior or inferior mesenteric arteries,

-presents with abdominal pain

16

what is shock?

a physiological state characterised by a significant reduction of systemic tissue perfusion (severe hypotension) resulting in decreased oxygen delivery to the tissues

17

what are the consequences of shock?

shock result in a critical imbalance between oxygen deliver and oxygen consumption

impaired tissue perfusion and ultimately prolonged oxygen deprivation leads to cellular hypoxia and derangement of critical biochemical processes at first cellular and eventually systemic levels

18

what are the effect of shock at a cellular level

membrane ion pump dysfunction, intracellular swelling, leakage of intracellular contents into the extracellular space, inadequate regulation of intracellular pH
anaerobic respiration - lactic acid

19

what are the systemic effects of shock

Alterations in the serum pH (acidaemia)
Endothelial dysfunction vascular leakage
Stimulation of inflammatory and anti-inflammatory cascades
End-organ damage (ischaemia)

20

what are the different types of shock?

hypovolaemic, cardiogenic, distributive (anaphylactic, spetic, toxic shock syndrome, neurogenic)

21

what is hypovolaemic shock

intra-vascular fluid loss (blood, plasma etc)

decreased venous return to heart AKA 'pre-load'

decreased stroke volume - decreased cardiac output

22

what can compensate for hypovolaemic shock

increase systemic vascular return (vasoconstrict)

23

what are the cause of hypovolaemic shock

haemorrhage, non-haemorrhagic fluid loss - diarrhoea, vomiting, burns

24

what is third spacing

acute loss of fluid into internal body cavities - common postoperatively and in intestinal obstruction

25

what is cardiogenic shock

cardiac pump failure

decrease cardiac output

26

how can you compensate for cardiogenic shock

increase systemic venous return (vasocontrict)

27

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)

28

what can be some examples of myopathic cardiogenic shock

MI, Right ventricular infarction, dilated cariomyopathies

29

what can be some examples of arrhythmia-related cardiogenic shock

- atrial and ventricular arrhythmias
- AF - arrhythmia & disorientated filling and emptying
- ventricular tachycardia, bradyarrhythmias and complete heart block

30

what can be some examples of mechanical cardiogenic shock

valvular defect, ventricular septal defects, atrial myoxmas, ruptured ventricular free wall aneurysm

31

what can be some examples of extra-cardiac cardiogenic shock

Anything that impairs cardiac filling or ejection of blood from heart
Massive pulmonary embolism, tension pneumothorax,
Severe constrictive pericarditis, pericardial tamponade et

32

what is distributive shock

- decreased systemic venous return due to severe vasodilation

33

how can you compensate for distributive shock

increase cardiac output - flushed/bounding heart

34

what is septic distributive shock

severe, over-wheming systemic infections

35

what can cause septic distributive shock

increase cytokines/mediators - vasodilation & can also cause Disseminated Intravascular coagulation

36

what can anaphylactic distributive shock

severe type 1 hypersensitivity reaction - sensitised individuals, small doses of allergen - IgE cross-linking

37

how does anaphylactic distributive shock work

- Sensitized individuals
Hospital e.g. drugs (penicillin etc)
Community e.g. peanuts, shellfish, or insect toxins
Small doses of allergen

- IgE cross-linking

- massive mast cell degranulation

- vasodilation

- contraction of bronchioles/respiratory distress

- laryngeal oedema

- circulatory collapse

shock/death

38

how does neurogenic shock cause problem?

spinal injury/aesthetic accidents - loss of sympathetic vascular tone - vasodilation - shock

39

how is toxic shock syndrome caused

S. aureus/ S. pyogenes produce exotoxins - superantigens - non-specific binding of class II MHC to T cell receptors - widespread release of massive amounts of cytokines - decreased systemic venous return