Intracranial Pressure and Hydrocephalus Flashcards
what is intracranial pressure
pressure exerted by the cranium on the brain tissue, CSF and intracranial circulating blood volume
what is the monroe- kellie- doctrine
three components of intracranial pressure (brain tissue, CSF and circulating intracranial blood), have pressure exerted on them, if you increase the volume of any of these components you will increase in the intracranial pressure
what is normal ICP
7-15mmHg
can be negative when in vertical position
higher than 15/16 probably abnormal
what are the compensatory mechanisms for an expanding mass
immediate- decrease in CSF volume by moving out of FM, decrease in blood by squeezing sinuses
delayed- decrease in ECF
what is the formula for cerebral perfusion pressure
MAP - ICP = CPP
what does a CPP below 20 usually mean
coma
what is cushings response/ triad
response to increased ICP opposite of shock result: -increased BP -irregular breathing -bradycardia
what are the theories of autoregulation of cerebral blood flow
pressure- vessel constriction/ dilatation
-metabolic- arterioles dilate in response to CO2/ lactic acid etc
CO2 is a potent dilator:
- increase CO2/ increased BP = vasodilation
- decreased CO2/ decreased BP= vasoconstriction
what are the common causes of raised ICP
mass effects- distort surrounding brain brain swelling (ischaemia, anoxia, metabolic, acute liver failure, encephalopathy, IIH, hypercarbia) - decreased cerebral perfusion but minimal tissue shift increase in central venous pressure (venous sinus thrombosis, HF, obstruction of jugular veins) problems with CSF flow (obstruction - masses, chiari syndrome), (increased production- choroid plexus papilloma), (decreased absorption- communicating hydrocephalus = SAH, meningitis, malignant meningeal disease)
what is chiari syndrome
a structural defect in the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum
what are the early signs of raised ICP
decreased consciousness, HA, pupillary dysfunction +/- papilloedema, changes in vision, N&V
what are the later signs of raised ICP
coma, fixed dilates pupils, hemiplegia, bradycardia -> cushings triad, hyperthermia, increased urinary output
what is the intervention for raised ICP
goals= maintain CPP, prevent ischaemia and brain compression
- maintain head in midline to facilitate blood flow
- loosen tube ties, collars, jewellery etc
- head oh bed 30-45 degrees elevation
- avoid gagging/ coughing etc
- decrease environmental stimuli
- treat hyperthermia
- maintain fluid balance and normal electrolytes (watch urine output)
- maintain normocarbia (short term can hyperventilate patient to decrease CO2
what medical management exists for raised ICP
diuretics (mannitol, hypertonic saline, furosemide, urea)
barbiturate coma (later down the line, subdues the brain)
antiepileptics (prevent energy expendature that seizure would cause)
surgical decompression
other surgery- mass removal (abscesses have to removed within 24hrs) CSF diversion
what are the types of hydrocephalus
communicating (the dilatation of CSF is throughout the entire ventricular system) non communicating (obstruction occurs before the CSF floes out into the sagittal sinus, commonly at cerebral aqueduct)
can be congenital (aqueduct stenosis, choroid cyst, malformations, intraventricular haemorrhage)
or acquired
