Clinical Aspects of Cerebral Perfusion and ICP Flashcards
What percentage of cardiac output goes to the brain?
15%
What is the perfusion of the brain in ml/100g/min?
55-60ml/100g brain tissue per minute
How does grey matter and white matter blood flow differ?
Grey matter blood flow is 75ml/100g/min, white matter is around 45ml/100g/min
At what perfusion does ischaemia occur?
Ischaemia occurs at 20ml/100g/min
At what perfusion does permanent damage occur?
Permanent damage results when the blood flow drops below 10ml/100g/min
What is the most significant factor that determines cerebral blood flow?
Most significant factor that determines cerebral blood flow at any given time is cerebral perfusion pressure (CPP):
- Is the effective blood pressure gradient across the brain
What does CPP stand for?
Cerebral perfusion pressure
What formula describes cerebral perfusion pressure?
CPP = MAP – ICP
How does increased ICP impact CPP?
Increased ICP causes decreased CPP
What are some factors that regulate cerebral blood flow under physiological conditions?
- CPP
- Concentration of arterial CO2
- Arterial PO2
What is cerebral autoregulation?
Ability to maintain constant blood flow to the brain over a wide range of CPP (50-150mmHg)
Over what range of mmHg does cerebral autoregulation work?
50-150mmHg
What happens when CPP is low for cerebral autoregulation?
- Cerebral arterioles dilate to allow adequate flow at the decreased pressure
What happens when CPP is high for cerebral autoregulation?
- Cerebral arterioles constrict
Under certain pathological conditions, cerebral blood flow cannot always be autoregulated. What are some examples?
- Hypertension
- If CPP exceeds 150mmHg such as in hypertensive crises the autoregulatory system fails
- Exudation of fluid from the vascular system with resultant vasogenic oedema
- Toxins such as CO2 can cause diffuse cerebrovascular dilation and inhibit proper autoregulation
- During first 4 to 5 days of head trauma many patients experience a disruption in cerebral autoregulation
Cerebral oedema is a prominent cause of what?
Subacute to chronic intracranial hypertension
What is cerebral oedema?
State of increased brain volume as a result of an increase in water content
What are he different kinds of cerebral oedema?
- Vasogenic oedema (extracellular oedema)
- Cytotoxic oedema (intracellular oedema)
- Interstitial oedema
![](https://s3.amazonaws.com/brainscape-prod/system/cm/330/759/999/a_image_thumb.png?1584383170)
What is vasogenic oedema also called?
Extracellular oedema
What is cytotoxic oedema also called?
Intracellular oedema
Compare and contrast the pathogenesis of each type of cerebral oedema?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/330/760/002/a_image_thumb.png?1584383190)
Compare and contrast the location of each type of cerebral oedema?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/330/760/003/a_image_thumb.png?1584383198)