10.2 raised Intracranial pressure Flashcards
what does cranial pressure have to be over to be considered high?
> 20 mmHg
if ICP is high, how will is show in a lumbar puncture?
CSF will pump out with heart beat
what can cause raised ICP?
- raised arterial pressure
- raised venous pressure e.g SVC obstruction
- haemorrhage (most common)
- hydrocephalus = congenital or acquired e.g meningitis, trauma, haemorrhage, tumour (too much CSF)
- cerebral oedema (too much brain)
- tumour
- abscess
what are some congenital obstructions to CSF flow?
- neural tube defects e.g spina bifida
- aqueduct stenosis
communicating hydrocephalus
- increased CSF production
- decreased CSF absorption
why is congenital hydrocephalus not bad in babies?
as fontanelles can move apart and make space for increased CSF so pressure doesn’t go up as quickly like it would in an adult
what is a external ventricular drain and what are the advantages and disadvantages?
allows short-medium term drainage of lateral ventricles and continuous pressure monitoring
disadvantages are its a direct pathway for bacteria from the skin into the brain, chamber must be at the same hight as the ventricles and is not a good long term solution
what is a ventricle peritoneal shunt?
shunts fluid from ventricles to peritoneum
easy to place but prone to infections and can kink, block or displace
what are the 4 types of cerebral oedema?
vasogenic - breakdown of tight endothelial junctions at BBB
interstitial - rupture of BBB = csf spreads to interstitial spaces
osmotic - higher osmolality in brain compared to serum
cytotoxic - intracellular retention of sodium and water
how can you calculate cerebral perfusion pressure?
CPP = MAP - ICP
cerebral perfusion pressure =
mean arterial pressure - intracranial pressure
what are the steps of cushings triad?
occurs in steps:
1) raised mean arterial pressure
2) bradycardia - increased in BP is sensed so HR is lowered is lowered by baroreceptors
(can get a bushings ulcer alongside)
3) irregular breathing - herniation of cerebellar tonsils due to raised ICP via foramen magnum = impinge on breathing nuclei centres on brainstem.
what are the early signs of raised ICP?
Headache - present on waking, worse on bending and coughing. constant
nausea and vomiting
difficulty concentrating or drowsiness, confusion
double vision - worse eyesight and papilloedema
focal neurological signs
seizures - may be experienced as blackouts
what can you use to treat raised ICP?
mannitol - a sugar. will draw fluid out of brain into bloodstream. also a diuretic so you’ll wee it out (3% hypertonic saline does the same, just salt)
also, an external ventricular drain
if all else fails, a decompressive craniotomy
what are the types of brain herniation?
1) cerebellar herniation
2) sub falcon herniation - beneath faux cerebri
3) unveil herniation
4) central downwards herniation
5) external herniation through open skull fracture
