Ischaemia, Infarction and Shock

Question 1

what is hypoxia and what is it caused by

Answer 1

stat of reduced O2 availability causing cell injury due to lack of aerobic respiration

inadequate blood O2 such as low O2 in atm, decreased O2 carrying capacity (anaemia or CO poisoning)

Question 2

what is ischaemia

what are some common causes

Answer 2

localised tissue hypoxia resulting from reduction in blood flow

obstruction of arterial supply eg from atherosclerosis, thrombosis or embolism

Question 3

what is a short duration of ischaemia called and why can sudden reperfusion be dangerous

Answer 3

reversible cell injury

sudden reperfusion = ischaemic reperfusion injury and tissue damage

Question 4

what can prolonged ischaemia lead to

Answer 4

irreversible cell injury which leads to infarction and necrosis

Question 5

what are the most common/rare causes of infarction

Answer 5

thrombosis/ rupture of atherosclerotic plaque, embolism

rare - vasospasm, tumour, twisting of vessels

Question 6

why is venous occlusion rare to cause infarction (which tissues can it occur in)

Answer 6

collateral circulation in venous circulation

excluding kidneys, spleen, ovaries which are vulnerable to venous infarction

Question 7

what is infarction classified by

Answer 7

colour
red - haemorrhagic - venous infarction still supply reaching area but not enough

white - anaemic - single blood supply cut off

Question 8

why are most infarcts wedge shaped

Answer 8

blood supply gives off branches

Question 9

describe the histology of an infarction

Answer 9

coagulative necrosis (if in brain colliquative necrosis) 
acute and chronic inflammation = scar tissue

Question 10

what is low flow infarction

Answer 10

infarction due to diminished blood flow - watershed area

Question 11

define shock

Answer 11

reduced systematic tissue perfusion resulting in decreased o2 to muscles

Question 12

how can shock lead to death

Answer 12

cellular hypoxia, end-organ damage - multiple organ failure - death

(can be reversed if quick enough)

Question 13

what are the 3 types of shock

Answer 13

cardiogenic
hypovolaemic
distributive

Question 14

what is cardiogenic shock and its subtypes

Answer 14

cardiac pump failure - deacreased CO 
subtypes:
myopathic 
arrhythmia 
mechanical 
extra cardiac

Question 15

what is hypovolaemic shock

how can you identify this in a patient

Answer 15

intra-vascular fluid loss

vasoconstriction and increased HR
cool and clammy

2 subtypes: haemorrhage, non-haemorrhage (diarrhoea)

Question 16

what is distributive shock

how do you identify this and what are some sub types

Answer 16

severe vasodilation compensated by increased HR

flushed, warm

subtypes: septic shock, anaphylactic shock, neurogenic shock
toxic shock syndrome

Question 17

what are some combination of shock types

Answer 17

septic shock

mix of distributive - vasodilation
hypovolumic component - diarrhoea and vomiting
cardiogenic component - sepsis relation myocardial dysfunction

Question 18

what is the mortality of shock

Answer 18

septic shock - 35-60%

cardiogenic - 60 - 90%