Intracranial Pressure and Cerebral Blood Flow

Question 1

What is intracranial pressure?

Answer 1

Pressure within skull

Question 2

Where is it easiest to do pressure monitoring in brain?

Answer 2

Intraparenchymal space of brain

Question 3

What is normal intracranial pressure?

Answer 3

5=10mmHg

Question 4

Equation for perfusion pressure

Answer 4

Mean arterial pressure- central venous pressure

Question 5

Equation for cerebral perfusion pressure

Answer 5

Mean arterial pressure- intracranial pressure

Question 6

What is the Monro-Kellie Hypothesis?

Answer 6

Idea that contents of cranium- brain, CSF, blood are incompressible
Increase in one cause decrease in otehr

Question 7

Composition of CSF similar to what?

Answer 7

Interstitial fluid

No proteins

Question 8

If ICP increases where does CSF move?

Answer 8

CSF move to spinal space to decrease ICP

Question 9

Volume of CSF changes dependent on ICP

how does this occur?

Answer 9

Rate of reabsorption changes

Rate increases as ICP increases

Question 10

Where is CSF produced?

Answer 10

Produced mainly by choroid plexus in lateral and 3rd ventricle

Question 11

What connects lateral and 3rd ventricles?

Answer 11

Foramina of monro

Question 12

What connects 3rd to 4th ventricle?

Answer 12

Aqueduct of sylvius

Question 13

Hoace?w is CSF reabsorbed on brain surf

Answer 13

By arachnoid granulations

Question 14

What is communicating hydrocephalus?

Answer 14

Blocked CSF reabsorption at arachnoid granulations or too much CSF produced

Question 15

What is non-communicating CSF circulation?

Answer 15

Blocked CSF circulation
Commonly at aqueduct
Tumour or haemorrhage

Question 16

Treatment of hydrocephalus

Answer 16

Shunt

Redirected fluid into peritoneal cavity

Question 17

What is hypovolaemia

Answer 17

Abnormally low extracellular level of fluid in body

Question 18

Equation for blood flow

Answer 18

Perfusion pressure/ vascular resistance

Question 19

STEPS to increase blood flow to brain when fall in blood pressure

Answer 19

Fall in blood pressure
Cerebral blood flow decrease
Inadequate perfusion 
Low O2 pressure High CO2 pressure
Vasodilation lead to increase in local blood flow to brain
Cerebral blood flow restored

Question 20

Does high CO2 increase CBF or decrease?

Answer 20

High CO2= vasodilation= high CBF

Question 21

Does increasing cerebral metabolism increase or decrease CBF?

Answer 21

Cerebral metabolism means greater production of metabolites (like CO2)

Increases ICP

Question 22

What is the equation for cerebral perfusion pressure?

Answer 22

MAP-ICP

Question 23

Higher ICP sensed by which ventricle?

Answer 23

4th

Question 24

Which clinical features guide management with head injruy?

Answer 24

Observations of bp/heart rate/ SaO2
Focal signs: pupils, sensory
Global function: level of conciousness: GCS

Question 25

How does Glasgow Coma Scale work?

Answer 25

Cannot score 0
8 is when you do something
Minimum is 3

Question 26

What is Coning?

Answer 26

Continual rise in ICP forces cerebella tonsils pushed down into foramen magnum
Pressure of brainstem to rise, cranial nerves compressed,
Brain stem pushed through foramen magnum and blood flow ceases
Brain stem death

Question 27

Coning symptoms

Answer 27

Hypothalamic failure- no control of temperature regulation (hypothermia)
Pituitary failure- no ADH secretion
Respiratory arrest- no breathing
Coma
High BP

Question 28

What does body do to prevent secondary injury?

Answer 28

Prevent rises in ICP

Maintain normal/high arteriole BP