MOD 14 - Ischaemia & hypoxic injury

Question 1

what is hypoxic injury

Answer 1

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

Question 2

what is ischaemia

Answer 2

pathological reduction in blood flow to tissue

Question 3

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

Answer 3

generation of reactive oxygen species by inflammatory cells causes further damage

Question 4

what is infarction

Answer 4

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

Question 5

what is the most common cause of infarction

Answer 5

thrombosis and embolism - most commonly within arteries

Question 6

what does red infarction indicate?

Answer 6

haemorrhagic - dual blood supply/venous infarction

Question 7

what does white infarction mean?

Answer 7

single blood supply hence totally cut off

Question 8

what are the factors influence the degree of ischaemic damage

Answer 8

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

Question 9

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

Answer 9

3 to 4 minutes

Question 10

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

Answer 10

20 to 30 minutes

Question 11

what is cerebrovascular disease

Answer 11

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

Question 12

what are the causes of haemorrhagic stroke

Answer 12

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

Question 13

what are cerebrovascular accidents

Answer 13

ischaemic stroke

Question 14

what are some examples of some ischaemia around the body

Answer 14

heart - ischaemic haert disease (angina)

brain - cerebrovascular disease (TIA/CVA)

intestines - ischaemic bowel

extremities - peripheral vascular disease/gangrene

Question 15

what are ischaemic bowel disease

Answer 15

• usually caused by thrombosis or embolism in the superior or inferior mesenteric arteries,
• presents with abdominal pain

Question 16

what is shock?

Answer 16

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

Question 17

what are the consequences of shock?

Answer 17

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

Question 18

what are the effect of shock at a cellular level

Answer 18

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

Question 19

what are the systemic effects of shock

Answer 19

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

Question 20

what are the different types of shock?

Answer 20

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

Question 21

what is hypovolaemic shock

Answer 21

intra-vascular fluid loss (blood, plasma etc)

decreased venous return to heart AKA ‘pre-load’

decreased stroke volume - decreased cardiac output

Question 22

what can compensate for hypovolaemic shock

Answer 22

increase systemic vascular return (vasoconstrict)

Question 23

what are the cause of hypovolaemic shock

Answer 23

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

Question 24

what is third spacing

Answer 24

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

Question 25

what is cardiogenic shock

Answer 25

cardiac pump failure decrease cardiac output

Question 26

how can you compensate for cardiogenic shock

Answer 26

increase systemic venous return (vasocontrict)

Question 27

what are the causes of cardiogenic shock

Answer 27

1 - myopathic (heart muscle failure) 2 - arrythmia-related (abnormal electrical activity) 3- mechanical 4 - extra-cardiac (obstruction to blood outflow)

Question 28

what can be some examples of myopathic cardiogenic shock

Answer 28

MI, Right ventricular infarction, dilated cariomyopathies

Question 29

what can be some examples of arrhythmia-related cardiogenic shock

Answer 29

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

Question 30

what can be some examples of mechanical cardiogenic shock

Answer 30

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

Question 31

what can be some examples of extra-cardiac cardiogenic shock

Answer 31

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

Question 32

what is distributive shock

Answer 32

- decreased systemic venous return due to severe vasodilation

Question 33

how can you compensate for distributive shock

Answer 33

increase cardiac output - flushed/bounding heart

Question 34

what is septic distributive shock

Answer 34

severe, over-wheming systemic infections

Question 35

what can cause septic distributive shock

Answer 35

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

Question 36

what can anaphylactic distributive shock

Answer 36

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

Question 37

how does anaphylactic distributive shock work

Answer 37

- 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

Question 38

how does neurogenic shock cause problem?

Answer 38

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

Question 39

how is toxic shock syndrome caused

Answer 39

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