Intracranial Pressure Monitoring Flashcards
If a needle were going to pass through the skull to the brain, what layers would it pass through on its way?
Dura mater
Arachnoid mater
Subarachnoid space
Pia mater
What is the function of the ventricles in the brain?
Production, transport and removal of cerebrospinal fluid
How many ventricles are present in the brain
4
Which ventricles are the largest and where are they located?
Lateral ventricles
One in each cerebral hemisphere
Where is the third ventricle located?
Midbrain
Smallest
Where is the 4th ventricle located?
Dorsal pons and midbrain
What cells filter the blood entering the ventricular spaces?
Ephithelial
How much CSF is produced in adults?
Adults generally produce 400-600 ml/day
Describe CSF
Clear watery fluid that surrounds brain and spinal cord
What are the functions of CSF?
Shock absorber
Nutrient supply
Waste elimination
Intracranial pressure regulation
Describe the ion concentration of CSF
Higher concentration of sodium, magnesium, and chloride
Lower concentrations of potassium and calcium
Whos is hydrocephalus most common in?
Infants
What is hydrocephalus
Build up of fluid in the ventricles of the brain
What causes hydrocephalus?
Caused by an imbalance in how much CSF is produced and how much is absorbed in the bloodstream
What are the 4 types of head bleeds?
Subdural
Epidural
Intracerebral
Subarachnoid
What are the clinical manifestations of increased ICP?
Drop in GCS
Projectile vomiting
Eye edema
Nonreactive pupils
How can we measure ICP?
Ventriculostomy
Catheter placed in right ventricle to monitor pressure
What is the cushing reflex?
Increase in blood pressure
Decrease in heart rate
Irregular breathing pattern
What is a normal ICP?
5-15 mmHg
What does a normal ICP waveform look like?
3 distinct peaks, each decreasing in amplitude
What is the purpose of a ventriculostomy?
Monitor ICP
Drain excess CSF to reduce pressure
Is variation in ICP with each cardiac cycle normal?
Yes
What do A-waves look like?
Shark fin
What do A-waves in ICP pressure indicate?
Poor compliance within the brain
What do B-waves in ICP pressure indicate?
Poor compliance within the brain
What do B-waves look like?
Sharp peaks
Which is worse, A-waves or B-waves?
A waves, awful
Describe cerebral blood flows relationship to MAP
CBF is independent from MAP
CBF is kept constant by autoregulation of cerebrovascular resistance
How is cerebral autoregulation achieved?
vasoconstriction/vasodilation of cerebral blood vessels
Sphincter like mechanisms in the precapillary arteriole
When is cerebral blood flow compromised?
When MAP is too low
When ICP is too high
What is cerebral autoregulation very sensitive to?
Changes in PCO2 and pH
How is cerebral perfusion pressure measured?
CPP=MAP-ICP
What is the critical range for CPP?
20-40 mmHg
What is the normal range for cerebral perfusion pressure?
60-100 mmHg
What happens to cerebral arterioles when MAP falls below 60?
Cerebral arterioles are maximally dilated
Brain is at risk for ischemia
What cerebral perfusion pressure should be targeting in ICU patients?
70-90 mmHg
What happens to cerebral arterioles when MAP is greater than 150 mmHg?
Cerebral arterioles are maximally constricted
Any further increase in pressure may cause excess CBF that may result in increased ICP
What is the minimum CPP require for adequate brain perfusion?
50 mmHg
What happens when CPP is less than 30 mmHg?
Brain death
What happens when CPP is greater than 150 mmHg?
Hyperemia
Excess blood in vascular system
What does the P1 wave in an ICP pressure wave represent?
percussion wave due to arterial pulsation
What does the P2 wave represent in an ICP waveform?
tidal wave, represents brain compliance
What does the P3 wave represent in an ICP waveform?
dicrotic wave, represents aortic valve closure
