Intracranial Pressure and Hydrocephalus Flashcards
What 3 intracranial components make up the Monroe-Kellie Doctrine?
Brain
Blood
CSF
What does the Monroe-Kellie Doctrine say about the 3 intrcrania components and their relationship to ICP
All 3 components have pressure exerted on them
If the pressure exerted in any of the 3 increase OR if a 4th component is introduced (tumour, bleed etc) then this can cause a raise in ICP
What physiological functions can increase ICP?
Coughing/sneezing
Going to the toilet
(can also be elicited by valsalva maneouvres)
What is a normal ICP at rest?
7-15mmHg
ICP can be negative. TRUE/FALSE?
TRUE - if patient is in vertical position OR if under general anaesthetic
Also very often negative in babies
How do we immediately compensate for an acute rise in ICP?
- CSF pushed out of foramen magnum
- decreased blood volume to the brain
Roughly how much CSF is made per day?
around 1 pint
How is the cerebral perfusion pressure calculated?
Mean arterial blood pressure (MAP) - ICP = CPP
Cerebral perfusion pressure is the same as cerebral blood flow. TRUE/FALSE?
FALSE
CPP = net pressure gradient causing cerebral blood flow to the brain
(narrow limit as too little blood means ischaemia and too much raises ICP)
Cushing’s Triad is the OPPOSITE of a shock response from the body. What symptoms are experienced?
Hypertension
Bradycardia
Irregular breathing
What is meant by the term “autoregulation” of cerebral blood flow?
Means that cerebral blood flow remains constant over a variety of blood pressures
When would autoregulation of cerebral blood flow be lost?
Post brain injury
How can ICP be decreased by the patient themselves?
Hyperventilation
- Decreases CO2
- Decreases BP => causes vasoconstriction of blood vessels in body
- Decreases cerebral blood flow
- Decreases ICP
What non-CSF related causes are there for raised ICP?
Mass - tumour, infarct
Brain swelling - ischaemia, encephalopathy
Increased Central Venous Pressure - venous sinus thrombosis, heart failure
What problems with CSF flow can lead to a raised ICP?
Obstruction:
- masses (colloid cyst, tumour at midbrain)
- chiari (cerebellar tonsils herniate through foramen magnum)
Increased production - e.g. choroid plexus papilloma
Decreased Absorption:
- Subarachnoid haemorrhage
- After meningitis
What are the early signs of a raised ICP?
- Decreased conscious level
- headache
- pupil dysfunction/ change in vision
- Nausea and Vomiting (due to midbrain distortion)
What late signs present in raised ICP?
- Coma
- fixed dilated pupil
- hemiplegia
- Cushing’s triad
- Hyperthermia
- Increased urinary output
What are the aims of intervention in raised ICP?
- Maintain cerebral perfusion pressure
- prevent ischaemia
How should blood flow to the head be promoted through intervention?
- ensure head is in midline/neutral position
- loosen any collars/ jewellery that could impair blood flow
- put Head of Bed between 30-45 degrees to maximise blood flow
How should spikes in ICP be avoided through intervention?
decrease any environmental stimuli that could cause patient to gag/cough/sneeze etc
Why is it important to intervene when patients GCS can still be at 15?
Rapid decompensation of brain after prolonged period of compensating
- if any suspicion patient is about to decompensate, then they require surgery before herniation of brain
What medicinal treatments can be used in raised ICP?
- diuretics (mannitol, hypertonic saline, furosemide)
- Barbiturate coma (phenobarbitone used to subdue all but basic brain functions)
- Anti-epileptic drugs sometimes used
What is the difference between a Communicating and Non-communicating hydrocephalus?
Communicating = ALL ventricles dilated Non-communicating = Not all ventricles dilated (depends on point of obstruction - usually between 3rd/4th ventricle => triventricular enlargement)
What is meant by the buzzword “sun-setting” eyes?
Compression of the midbrain in hydrocephalus causes problems moving eyes upwards
