Cerebral Perfusion and Intracranial Pressure

Question 1

Define cerebral perfusion

Answer 1

CPP is effectively the blood pressure gradient across the brain

Question 2

What effect does increased ICP have on CPP ?

Answer 2

CPP = MAP - ICP

so increased ICP decreases CPP

Question 3

Name 3 factors which regulates cerebral blood flow

Answer 3

CPP
Conc. of arterial CO2
Arterial PO2

Question 4

At what pressure would the brain be in a hypertensive crisis ?

Answer 4

150mmHg

Question 5

What does cerebral edema do to ICP

Answer 5

Increases ICP can cause intracranial hypertension

Question 6

What form do the capillaries within the blood brain barrier take ?

Answer 6

The are fenestrated with astrocytic foot processes which wrap around the capillary

Question 7

What are the 2 ways in which substances/molecules can pass through the BBB ?

Answer 7

If they are:
Lipid soluble
Amino acids & sugars are passed through by specific carrier mediated mechanisms

Question 8

How does the rigid skull and brain compensate for a change in volume i.e. a brain mass or lesion

Answer 8

Decreases the venous blood or CSF within the brain, this is called compliance

Question 9

What is elastance ?

Answer 9

The opposite of compliance where a change in pressure is observed for a given change in volume

Question 10

When the CSF is displaced within the brain where does it go ?

Answer 10

Through the ventricular system to the foramina of luschka and Magendie into the spinal subarachnoid space

Question 11

What is Cushing’s reflex ?

Answer 11

A vasopressor response which causes hypertension, irregular breathing and bradycardia