ICP Flashcards
kellie Monroe doctrine?
3 components contributing to ICP
- brain tissue
- CSF
- intracranial circulating volume
normal ICP?
7-15 mmHg at rest
can be negative in vertical position
immediate compensation for raised ICP?
decrease CSF volume by moving it out of FM
decrease blood volume by squeezing sinuses
delayed compensation?
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cerebral perfusion pressure (CPP) is equal to what?
MAP - ICP
CPP in hypotension?
low
cushings response?
opposite to shock response
- BP increases to compensate for lower ICP
cerebral blood flow equals what?
cerebral perfusion pressure / cerebrovascular resistance
in a healthy brain, cerebral blood flow is constant over wide range of pressure, what happens in abnormal brain?
cant autoregulate
blood flow varies
types of autoregulation of CBF?
pressure autoregulation (dilation/constriction in response to BP) metabolic autoregulation (dilation in response to chemicals - lactic acid, CO2 etc) CO2 is a potent dilator (increased CO2 = dilation vice versa)
causes of raised ICP?
mass effect (tumour, infarct, abscess, haematoma etc) brain swelling (encephalopathy, ischaemia, liver failure, IIH, hypercarbia) - decreased CPP but don't really cause any brain tissue shift/herniation increased central venous pressure (venous sinus thrombosis, heart failure, jugular vein obstruction) problems with CSF flow
what can cause CSF flow problems?
obstruction (0bstructive/non-communicative) - masses - chiari syndrome increased CSF production (choroid plexus tumour) decreased absorption (communicating) - SAH - meningitis - malignant meningeal disease
early signs of raised ICP?
reduced conscious level headache pupillary dysfunction +/- papilloedema changes in vision nausea and vomiting
later signs of raised ICP?
coma fixed, dilated pupils hemiplegia bradycardia > cushings triad hyperthermia increased urine output (compensates for raised ICP via changing BP)
interventions for raised ICP?
maintain head in midline to facilitate blood flow
loosen tube ties, collars etc to maximise venous return
HoB 30-45 degrees elevation
avoid gagging, coughing etc which could increase ICP
decrease environmental stimuli which could increase ICP
treat hyperthermia
maintain fluid balance and normal electrolytes
maintain normocarbia
point of decompensation?
point where brain cant compensate for volume of mass (hydrocephalus, bleed etc) any longer and ICP suddenly and rapidly increases, quickly causing damage and herniation etc
medical management of raised ICP?
diuretics - mannitol, hypertonic saline, furosemide, urea) barbiturate coma (late down line) antiepileptics surgical decompression - remove mass lesion - CSF diversion (drain, shunt etc) - hemicraniectomy
communicating vs non-communicating?
communicating
- dilation of CSF throughout all ventricles in the brain
- meningitis, post subarachnoid haemorrhage
- all ventricles enlarged on imaging
non-communicating/obstructive
- obstruction occurs before CSF flows out into spinal spaces
- usually between 3rd and 4th ventricles
- stenosis, tumours etc
VP shunt?
between ventricles and peritoneum
features of normal pressure hydrocephalus?
disease of elderly hakims triad - abnormal gait - urinary incontinence - dementia
differential diagnoses of normal pressure hydrocephalus?
other dementias cervical myelopathy urinary problems parkinsons depression
features on imaging of NPH?
enlarged ventricles
wide sulci
normal brain at top (pressure pushes brain up to top)
90 degree angle between lateral ventricles
how is NPH investigated?
LP
lumbar drain test
lumbar infusion studies
how is NPH managed?
VP shunt using medium-low or low pressure valve
- can be better to use a variable valve
features of IIH?
raised ICP of no known cause
never have ventricular dilation
normal imaging
who usuall gets IIH?
women of child bearing age
mainly western civilisations
overweight
signs and symptoms of IIH?
headache diplopia visual blurring visual field defects progressing to tunnel vision tinnitus radicular pain papilloedema - 25% of people end up with severe/permanent visual loss
how is IIH managed?
weight loss
- potentially bariatric surgery
CA inhibitors (acetazolamide, topiramate)
diuretics
CSF diversion
interventional radiology (venous sinus plasty/stenting)
ONSF
IIH differentials?
any other headache
cervical radiculopathy
any other reason for ICP
investigations in IIH?
LP
CT/MRI head
CTV/MRV
fundoscopy +/-ophthalmology review
