Cerebral perfusion & ICP

Question 1

How much of the CO does the brain receive?

Answer 1

15%

Question 2

What is the normal cerebral blood flow?

Answer 2

55 to 60 ml/100g

Question 3

At what blood flow will ischaemia be observed?

Answer 3

20ml/100g

Question 4

At what blood flow will permanent brain damage occur?

Answer 4

10ml/100g

Question 5

What if the effective blood pressure gradient across the brain?

Answer 5

Cerebral perfusion pressure (CPP)

Question 6

What is the equation which define CPP?

Answer 6

CPP = MAP -ICP

Question 7

Which an increased ICP what will happen to CPP?

Answer 7

Decrease

Question 8

What factors regulate cerebral blood flow?

Answer 8

CPP

Arterial O2 & CO2

Question 9

What is cerebral autoregulation?

Answer 9

The ability to maintain blood flow to the brain over a wide range of CPP (50-150mmHg)

Question 10

If CPP is low, what will happen to arterioles?

Answer 10

Dilate in order to maintain blood flow

Question 11

If CPP is high, what will happen to arterioles?

Answer 11

Constrict

Question 12

What does CO2 do to blood flow?

Answer 12

Cause dilation of vessels do increases

Question 13

What is a subacute to chronic cause of intracrainal hypertension?

Answer 13

Cerebral oedema

Question 14

What is the BBB composed of?

Answer 14

Astrocyte foot processes

Endothelial tight junctions

Question 15

What does the BB prevent?

Answer 15

Prevents toxic materials from reaching brain

Question 16

What substances are able to cross the BBB?

Answer 16

Lipid soluble substances

Question 17

According to what doctrine is the skull a rigid structure which contains 3 substances?

Answer 17

Monro-Kelly Doctrine

Question 18

What 3 substances does the skull contain which contribute to volume?

Answer 18

Brain tissue
Blood
CSF

Question 19

When there is a new intracranial mass, a compensatory change in volume has to occur which results in____

Answer 19

Decrease in venous blood OR CSF

Question 20

What is change in compliance?

Answer 20

Change in volume observed for a given change in pressure (dV/dP)

Question 21

What is elastance?

Answer 21

Change in pressure observed for a given change in volume (dP/dV)

Question 22

What are the compensatory homeostatic mechanisms the brain compensates for increased ICP?

Answer 22

Veins collapse & squeeze blood out

CSF is displaced from ventricular system to subarachnoid space

Question 23

At the critical volume, following compensatory homeostatic control, a small change in volume will produce____

Answer 23

large change in pressure

Question 24

What are the different Lundberg waves =?

Answer 24

ABC waves

Question 25

What is the Cushings Reflex?

Answer 25

Bradycardia Hypertension Irregular breathing (vasopressor response)

Question 26

If there is an increase in ICP what will happen to CBF?

Answer 26

Decrease - activation of sympathetic system

Question 27

What does sympathetic innervation do to CVS?

Answer 27

Vasoconstricts - hypertension | Tachycardia

Question 28

Why is bradycardia observed in Cushings reflex?

Answer 28

Mechanical distortion of brainstem - respiratory centre crushed. Aortic baroreceptors stimulate vagus nerve

Question 29

What is the management for increased ICP?

Answer 29

Raise bed - increase Venous return Mannitol or hypertonic saline Hyperventilation: decrease CBF Surgical decompression

Question 30

What is the average weight of human brain?

Answer 30

1400g