Intracranial Pressure Monitoring

Question 1

If a needle were going to pass through the skull to the brain, what layers would it pass through on its way?

Answer 1

Dura mater
Arachnoid mater
Subarachnoid space
Pia mater

Question 2

What is the function of the ventricles in the brain?

Answer 2

Production, transport and removal of cerebrospinal fluid

Question 3

How many ventricles are present in the brain

Answer 3

4

Question 4

Which ventricles are the largest and where are they located?

Answer 4

Lateral ventricles
One in each cerebral hemisphere

Question 5

Where is the third ventricle located?

Answer 5

Midbrain
Smallest

Question 6

Where is the 4th ventricle located?

Answer 6

Dorsal pons and midbrain

Question 7

What cells filter the blood entering the ventricular spaces?

Answer 7

Ephithelial

Question 8

How much CSF is produced in adults?

Answer 8

Adults generally produce 400-600 ml/day

Question 9

Describe CSF

Answer 9

Clear watery fluid that surrounds brain and spinal cord

Question 9

What are the functions of CSF?

Answer 9

Shock absorber
Nutrient supply
Waste elimination
Intracranial pressure regulation

Question 10

Describe the ion concentration of CSF

Answer 10

Higher concentration of sodium, magnesium, and chloride
Lower concentrations of potassium and calcium

Question 11

Whos is hydrocephalus most common in?

Answer 11

Infants

Question 12

What is hydrocephalus

Answer 12

Build up of fluid in the ventricles of the brain

Question 13

What causes hydrocephalus?

Answer 13

Caused by an imbalance in how much CSF is produced and how much is absorbed in the bloodstream

Question 14

What are the 4 types of head bleeds?

Answer 14

Subdural
Epidural
Intracerebral
Subarachnoid

Question 15

What are the clinical manifestations of increased ICP?

Answer 15

Drop in GCS
Projectile vomiting
Eye edema
Nonreactive pupils

Question 16

How can we measure ICP?

Answer 16

Ventriculostomy
Catheter placed in right ventricle to monitor pressure

Question 16

What is the cushing reflex?

Answer 16

Increase in blood pressure
Decrease in heart rate
Irregular breathing pattern

Question 17

What is a normal ICP?

Answer 17

5-15 mmHg

Question 18

What does a normal ICP waveform look like?

Answer 18

3 distinct peaks, each decreasing in amplitude

Question 19

What is the purpose of a ventriculostomy?

Answer 19

Monitor ICP
Drain excess CSF to reduce pressure

Question 20

Is variation in ICP with each cardiac cycle normal?

Answer 20

Yes

Question 21

What do A-waves look like?

Answer 21

Shark fin

Question 22

What do A-waves in ICP pressure indicate?

Answer 22

Poor compliance within the brain

Question 23

What do B-waves in ICP pressure indicate?

Answer 23

Poor compliance within the brain

Question 24

What do B-waves look like?

Answer 24

Sharp peaks

Question 25

Which is worse, A-waves or B-waves?

Answer 25

A waves, awful

Question 26

Describe cerebral blood flows relationship to MAP

Answer 26

CBF is independent from MAP CBF is kept constant by autoregulation of cerebrovascular resistance

Question 27

How is cerebral autoregulation achieved?

Answer 27

vasoconstriction/vasodilation of cerebral blood vessels Sphincter like mechanisms in the precapillary arteriole

Question 27

When is cerebral blood flow compromised?

Answer 27

When MAP is too low When ICP is too high

Question 28

What is cerebral autoregulation very sensitive to?

Answer 28

Changes in PCO2 and pH

Question 29

How is cerebral perfusion pressure measured?

Answer 29

CPP=MAP-ICP

Question 30

What is the critical range for CPP?

Answer 30

20-40 mmHg

Question 30

What is the normal range for cerebral perfusion pressure?

Answer 30

60-100 mmHg

Question 31

What happens to cerebral arterioles when MAP falls below 60?

Answer 31

Cerebral arterioles are maximally dilated Brain is at risk for ischemia

Question 31

What cerebral perfusion pressure should be targeting in ICU patients?

Answer 31

70-90 mmHg

Question 32

What happens to cerebral arterioles when MAP is greater than 150 mmHg?

Answer 32

Cerebral arterioles are maximally constricted Any further increase in pressure may cause excess CBF that may result in increased ICP

Question 33

What is the minimum CPP require for adequate brain perfusion?

Answer 33

50 mmHg

Question 34

What happens when CPP is less than 30 mmHg?

Answer 34

Brain death

Question 35

What happens when CPP is greater than 150 mmHg?

Answer 35

Hyperemia Excess blood in vascular system

Question 36

What does the P1 wave in an ICP pressure wave represent?

Answer 36

percussion wave due to arterial pulsation

Question 37

What does the P2 wave represent in an ICP waveform?

Answer 37

tidal wave, represents brain compliance

Question 38

What does the P3 wave represent in an ICP waveform?

Answer 38

dicrotic wave, represents aortic valve closure