Flashcards in Hydrocephalus and increased ICP Deck (38)
Which structures exert pressure onto the brain?
Intracranial circulating blood volume
What can physiologically cause the ICP to fluctuate?
What is a normal ICP?
What are the bodies immediate compensatory mechanisms for increased ICP?
Decrease CSF by moving it out of the foramen magnum
Decrease in blood volume by increasing venous outflow via the sinuses
What are the delayed compensatory mechanisms for increased ICP?
Decrease in ECF; brain swelling
How is cerebral perfusion pressure calculated?
MAP - ICP
What occurs to CPP in hypotension?
CPP will fall
What CPP is compatible with consciousness?
20; below this and you will be comatose
How is cerebral blood flow autoregulated?
Pressure; arterioles dilate or constrict in response to changes in BP or ICP
Metabolic; arterioles dilate in response to chemicals such as lactic acid or Co2
What is the action of CO2 on cerebral blood flow?
Increased Co2 or increased BP = vasodilation
Decreased CO2 or hypotensive = vasoconstriction
What is a short term mechanism for decreasing ICP?
Hyperventilation, blow off Co2 and therefor vasoconstrict the blood vessels
What can cause an increased ICP?
What can cause a mass effect within the brain?
What can cause swelling within the brain?
Acute liver failure
What can cause increased CVP?
Venous sinus thrombosis
Obstruction of jugular veins
High abdo pressure (ICP tends to be higher in pregnancy)
What can cause non-communicating (obstructive) hydrocephalus?
Chiari Syndrome (ectopia of cerebellar tonsils)
Increased production; choroid plexus papilloma
What can cause communicating hydrocephalus?
Malignant meningeal disease
What are the early signs of increased ICP?
Pupillary dysfunction +/- papilloedema
Changes in vision; decreased visual acuity, tunnel vision
What are the late signs of increased ICP?
Fixed, dilated pupil
Bradycardia; cushing's reflex
Hyperthermia; dysfunctional hypothalamus
Increased urinary output
What are the goals of therapy in managing patients with raised ICP?
Prevent ischaemia and brain compression
What is the management for increased ICP?
Maintain head in midline to facilitate maximal venous outflow
Loosen tube ties, cervical collars
HoB 30-45 degrees elevation
Avoid gagging, coughing etc
Decrease environmental stimuli
Maintain fluid balance and normal electrolytes
Maintain normocarbia; short term can hyperventilate to decrease ICP and increase CPP
What is the medical management for an increased ICP?
Diuretics; mannitol, hypertonic saline, furosemide, urea
Barbiturate coma; phenobarb
What surgical treatment can be performed to decreased ICP?
Remove mass lesion; if abscess evacuate within 24 hours
CSF diversion; VP shunt
What is communicating hydrocephalus?
Dilatation of ventricles throughout all the ventricular systems within the brain
What is non-communicating hydrocephalus?
Obstructive; commonly at the cerebral aqueduct
What are the different types of congenital hydrocephalus?
What are the hallmarks of normal pressure hydrocephalus?
Hakim's triad: abnormal gait (wide based, shuffling gait_, urinary incontinence (lack of frontal disinhibition), dementia
What are the differential diagnosis of normal pressure hydrocephalus?
All other forms of dementia
All urinary problems
What can be seen on the scans of those with normal pressure hydrocephalus?
Large sylvian fissures
Disproportionately large subarachnoid spaces
Angle between ventricles less than 90 degrees