16. Ischaemia and Infarction Flashcards
What is ischaemia?
Lack of blood supply
Leads to lack O2 and nutrition and build up of waste
What factors determine how susceptible a tissue is to ischaemia?
Poor blood supply
Collateral circulation (is there a bypass)
Metabolic rate
‘Watershed’ areas
Which organs have good collateral circulation?
Liver
Lung
Bowel
Brain
Which organs don’t have collateral circulation?
Kidney
Spleen
Heart
What areas of the body are considered watershed areas?
Splenic flexure of the colon
Anterior/middle cerebral
Deep myocardium
What is reperfusion injury?
Blood supply restoration after a loss can cause an increase of tissue damage
What mechanisms cause reperfusion injury?
Free radicals are formed
Ca++ ATPase failure increases Ca++ in cytosol (cell death)
What drugs are given after cerebral and myocardial infarcts to prevent reperfusion injury?
Ca++ channel blockers
What is infarction?
Area of ischaemic necrosis caused by occlusion of an artery or vein
What are the causes of ischaemia and infarction?
Shock Obstruction to a vessel Vasculitis Compression or torsion of a vessel Local vasospasm
What is a thrombosis?
Solid mass in flowing blood
What is an embolus?
Solid/liquid/gas that moves from one part of circulation to another
What is the presentation of stercoral ulceration of retrosigmoid colon?
Chronic constipation
Faeces closes off blood vessels in bowel wall
How does an area of infarct look early on?
Irregular
Hyperaemia at edges due to inflammation
How does late infarct look like in solid organs?
White due to low haemosiderin pigment
Pale and defined
