ICP And Cerebral Blood Flow

Question 1

What is normal ICP volume

Answer 1

5 -15 cm
Anything over 20cm for prolonged period of time is pathological

Question 2

What is the monro-Kellie hypothesis

Answer 2

Intracranial volume is fixed due to non-compliant skull
The contents of the skull are non-compressible
Any change in volume of contents increases pressure unless reduction of other content

Question 3

What is the bodies response to raised ICP e.g. from extradural haematoma

Answer 3

Compensation:
- reduction of venous blood
-Displacement of CSF towards spine —> reduction of CSF volume

The brain has minimal compliance (cannot be compressed)

Question 4

What is the pathology of raised ICP

Answer 4

Localised shift of brain across compartments—> focal or global reduction of blood flow —> focal or global ischaemia —> reduced energy production —>pump failure on cell membrane—> cellular dysfunction—> increase in toxic metabolites —> membrane damage and cell death

Question 5

What is auto-regulation of brain pressure

Answer 5

Ability of brain to maintain constant blood flow over wide range of pressures
Brain also has ability to increase blood flow to specific regions in brain when they are active e.g. temporal lobe during speech

Question 6

Why is it autoregulation of CBF (cerebral blood flow) and ICP important

Answer 6

Brain tissue use glucose and ketones exclusively for metabolism
Brain tissue have no stored energy source
Impaired blood flow leads to mitochondrial energy production failure within seconds and cell death within minutes

Question 7

What is neuromonitoring

Answer 7

ICP measurements and maintenance of cerebral perfusion pressure as therapy