Ischaemia, Infarction and Shock Flashcards
What is the name given to any state of reduced tissue oxygen availability?
Hypoxia
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
Ischaemia results in …
hypoxia
In prolonged ischaemia, irreversible cell damage occurs. What is the process of cell death?
Cell death occurs by necrosis (infarction) in sustained ischaemia
When is therapeutic reperfusion effective in ischaemia?
Tissue perfusion is good if ischaemia is reversible. (short duration of ischaemia)
what is reperfusion injury?
generation of reactive oxygen species by inflammatory cells causes further damage when reperfusing ischaemic tissues.
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
What is ischaemic necrosis caused by occlusion of the arterial supply or venous drainage?
Infarction
What are the main causes of Infarction?
- thrombosis
- embolism
- Vasospasm
- compression of vessel
- Vaculitis
- rupture of vascular supply (AAA)
What shape are most infarctions?
wedge shaped
where does colliquative necrosis normally occur?
brain
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
What organs have a single blood supply which makes them vulnerable to infarction?
1) Kidneys
2) Spleen
3) Testis ect.
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)
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.
What organ requires 15% of cardiac output and 20% of body oxygen?
Brain
What is the name given to any abnormality of the brain caused by pathological process involving the blood vessels?
Cerebrovascular disease
Give an example of a cerebrovascular accident?
Stroke
what causes an ischaemic stroke?
- thrombosis secondary to atheroscelrosis
- embolism
What causes haemorrhagic stroke?
- intracerebral haemorrhage (hypertensive)
- Ruptures aneurysm in the circle of willis»_space;>subarachnoid haemorrhage
What is the site of the thrombosis or embolism that causes ischaemic bowel disease?
Superior or Inferior mesenteric arteries
Infarction of entire portion of limb (organ)
Gangrene
what type of gangrene has ischaemic coagulative necrosis only?
Dry Gangrene
what is the characteristic feature of wet gangrene?
superimposed infection
what is the characteristic feature of gas gangrene?
superimposed infection with gas producing organism e.g. clostridium perfringens
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
What results in a critical imbalance between oxygen delivery and oxygen consumption?
Shock
impaired tissue perfusion and prolonged oxygen deprivation leads to ….?
cellular hypoxia
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»_space;>lactic acid
What are the systemic effects of shock?
1) alterations in the serum pH
2) Endothelial dysfunction»_space;> vascular leakage
3) Stimulation of inflammatory and anti-inflammatory cascades
4) end organ damage (ischaemia)
what is the sequential result of shock
- cell death
- end organ damage
- multi organ failure
- death
what are the different types of shock?
1) hypovolaemic
2) Cardiogenic
3) Distributive
- anaphylactic
- septic
- toxic shock syndrome
- neurogenic
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
How to compensate for hypovolaemic shock?
increase vasoconstriction
-this increases total peripheral resistance
What are the causes of hypocolaemic shock?
1) Haemorrhage
2) Non-haemorrhagic fluid loss e.g. diarrhoea, vomiting
Reduces circulation volume
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)
What kind of shock is caused my MI, right ventricular infarction, stunned myocardium?
Myopathic cardiogenic shock
what causes vasodilation in septic shock?
increased cytokines and mediators released by the immune reaction
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
What happens in neurogenic shock?
1) spinal injury leads to
2) loss of sympathetic vascular tone
3) Vasodilation
4) Hypovolaemia
5) Shock
What organisms release exotoxins that causes Toxic Shock syndrome?
Staph Aureus
Staph Pyogenes
