ICP and blood flow

Question 1

Normal ICP

Answer 1

5-15cm of water

Question 2

What produces and absorbs csf

Answer 2

Produced by choroid plexus and absorbed by the arachnoid granulars

Question 3

Above what ICP is pathological

Answer 3

20cm water

Question 4

How do we compensate for a large extradural heaematoma?

Answer 4

1. reduction of venous blood in th ebrain,
2. reduction of CSF in brain (more in spinal chord)
3. reduction of CSF volume

Question 5

What are P1 P2 and P3 corrospond to?

Answer 5

They are the waves on the ICP graph that relate to the impulses in arterial blood from the heart (really small)

Question 6

Wht esle nturally increases and decreases icp?

Answer 6

resp rate - more gradual increase and decrease though than p1, p2 and p3

Question 7

What is MAP

Answer 7

Diastolic pressure plus 1/3 pulse pressure

Question 8

CPP?

Answer 8

Cerebral Perfusion pressure -> difference between MAP and ICP

Question 9

What is the range of cpp that the barin can autoregulate and ensure optimum prefusion

Answer 9

50-150mmHg

Question 10

What are the autoregulation in cerrebreal?

Answer 10

Autonomic (symp and parasymp)

myogenic (muscles around vessles)

endothelial mechanisms (detecting pressure etc)

Metabolic autoregulation (CO2 mainly, only O2 if dropped significantly)

Question 11

What factors can lead to significant secondry insult in injured brain?

Answer 11

In brain injury can lose ability to control icp effectivlly and compensate, so anything that will cause it to change, eg hypertension/hypotension, hypoxia/raised ICP

Question 12

When and why would you monitor ICP in head injur patients

Answer 12

See reasons above, to ensure there is a sufficient CPP (cranial perfusion pressure) t ensure that the brain is constantly getting enough perfusion.

Question 13

In what other conditions is ICP measured?

Answer 13

HYdrocephalus
Stroke
vennous outflow obstruction
tumours
brian haemorrhage