Cerebral Perfusion & ICP Flashcards
what does GCS stand for?
glasgow coma score
what are the three components of the GCS ?`
best eye response
best verbal response
best motor response
under which GCS is someone in a coma?
<8
on a CT scan how can you tell that a brain is swollen?
can’t see ventricles or they have a reduced size
can’t see sulci
what does brain swelling result in ?
increased intracranial pressure
what four pathophysiological processes result in brain swelling ?
- haemorrhage
- disruption of the BBB which increases extra cellular fluid
- membrane failure which results in an increase of Ca
- influx of inflammatory mediators
what is vasogenic oedema ?
when there is an increase in extra cellular fluid
what is cytotoxic oedema ?
when there is an increase of Ca ions and causes swelling of cells
state two secondary effects of raised intracranial pressure ?
- herniation syndromes
2. decreased cerebral perfusion
does decreases cerebral perfusion result in a higher or lower GCS ?
lower GCS
is there is fixed volume in adults and babies ?
in adults there is a fixed volume but in babies their sutures haven’t fuse yet so they don’t have a fixed volume
what three components make the fixed volume of the intracranial space?
brain
CSF
blood
what is the equation used to measure the volume of the intracranial space?
Monro-Kellie Doctrine
how can the intracranial space compensate for an increase of pressure ?
increase venous output
increase output of CSF to subarachnoid space
how is cerebral perfusion pressure calculated ?
mean arterial pressure - intracranial pressure = CPP
what should normal CPP be?
80mmHg
what should normal MAP be?
90mmHg
what should normal ICP be?
5-15mmHg
does the brain have a high or low metabolic requirement?
high requirement
can the brain use anaerobic respiration ?
no
what are the four components that regulate cerebral blood flow?
auto regulation
cerebral metabolism
CO2 and O2
neurohumoral factors
what is auto regulation ?
auto regulation is a myogenic mechanism when the smooth muscle constricts
when does auto regulation occur ?
when there is an increase in the wall tension
does the vessel diameter increase or decrease with increasing cerebral perfusion pressure?
decrease
what nucleus do the optic tract pass through before entering the optic radiation ?
lateral geniculate nucleus
what nucleus do the optic fibres pass through for the light reflex?
pretectal nucleus
what nucleus does the oculomotor nerve pass through to the ciliary ganglia ?
Edinger Westphal nucleus
what nerve causes constriction of the pupil?
oculomotor
what causes a fixed dilated pupil?
when there is an increased intracranial pressure and the brain herniates through the tenterium cerebelli and compresses the oculomotor nerve and prevents contraction of the sphincter pupillae
name three hernias that can occur in the brain ?
Subfalcine herniation
medial motor cortex
Uncal herniation
IIIrd CN, ipsilateral corticospinal tracts
Foramen magnum herniation
brain stem centres
what is it called when the
- pulse decreases
- resp. rate decreases
- diastolic decreases
cushings response
why does the pulse and resp. rate decrease with increased intracranial pressure ?
the cardiac centres and resp centres are being compressed
does an increase in CO2 partial pressure increase or decrease cerebral blood flow?
increase
does an decrease in O2 partial pressure increase or decrease cerebral blood flow?
increase
what is the normal CO2 partial pressure ?
35-45mmHg
what is the normal O2 partial pressure ?
80-100mmHg
when there is increased blood flow what occurs?
cerebral vasodilation and oedema
increased ICP
does increased cerebral pressure result in increased or decreased cerebral blood flow ?
decreased blood flow
what is hyperventilation ?
very slow deep breathes
does hyperventilation help with increased intracranial pressure ?
yes
- will decrease CO2 in blood and hence will reduce vasodilation
what drug is given to drain out the brain and reduce the intracranial pressure ?
mannitol
what type of drug is mannitol ?
diuretic
what instrument can be used to measure the intracranial pressure ?
ICP bolt
if the increased intracranial pressure doesn’t respond to medical treatment, what can be done ?
craniotomy and evacuation of clot
external ventricular drainage
decompressive craniectomy
what post ICP management may need to be done for a patient ?
- neuropsychology
- physio
- social work
- post traumatic counselling
