inter cranial pressure and cerebral blood flow

Question 1

what is ICP

Answer 1

pressure of the tissues inside the cranial cavity , exerted by fluids such as CSF

Question 2

normal ICP

Answer 2

5-10mmHg

Question 3

cerebral perfusion pressure = (equation)

Answer 3

mean arterial pressure - ICP
so raised ICp will reduce cerebral perfusion pressure , narrow arteries
important or will have an ischemia

Question 4

definition of Cerebral perfusion pressure

Answer 4

amount of pressure needed to maintain blood flow to the Brain

Question 5

whats is Cerebral spinal fluid

Answer 5

cushions brain
regulates ICP
transfer medium for nutrients

Question 6

where do you Carry out a lumber puncture

Answer 6

L3-4

Question 7

why do you get a headache from a lumbar puncture

Answer 7

because CSF escapes so Brain sags and pulls on meningeal attachments - effect of less CSf circulation

Question 8

when shouldn’t you o a lumbar puncture

Answer 8

when raised ICP because Brain will be pulled down foramen magnum - coning

Question 9

How does the body respond to raised ICP ( cerebral vasodilation) - short term

Answer 9

pressure onto ventricles moves CSF to spinal spaces lowering ICP

Question 10

what hypothesis states that the volume of the cranium is fixed, blood csf and brain are all incompressible so any increase in one needs to be decrease by another. (Contents of cranium > brain, CSF, Blood are incompressible. )

Answer 10

Monro-Kellie hypothesis

Question 11

How does the body respond to raised ICP - long term

Answer 11

Volume of CSF balanced between
Production
- constant rate of about 500mL a day
- Energy-dependent (Na+/K+ ATPase)

Reabsorption
- variable
- rate Increases as ICP rises
(CSF replenished 3-4 x per day)

Question 12

what is hydrocephalus

Answer 12

Abnormal expansion of brain caused by accumulation of Cerebrospinal fluid - blockage of the movement of CSF

CSF blockage causes a rise in ICP.

Question 13

what are the two types of hydrocephalus

Answer 13

communicating

non communicating

Question 14

what is communicating hydrocephalus

Answer 14

blocked CSF is absorbed at arachnoid granulations , circulation is normal (blocked reabsorption)

Question 15

what Is non-communicating hydrocephalus
caused by what
and causes an increase in what

Answer 15

blocked CSF circulation,

caused by a tumour or haemorrhage - most common at the aqueduct causing increased ICP

Question 16

hypovolemia

Answer 16

decrease in the volume of blood in your body

Question 17

Normal cerebral blood flow

Answer 17

50-60ml/min- body will maintain CPP at expense of parts of circulations during shock or hypovlolemia

Question 18

Blood flow =

Answer 18

perfusion pressure/vascualr resistance

Q=P/R

Question 19

how is cerebral blood flow maintained

Answer 19

myogenic

metabolism - increase activity more metabolites leading to vasodilation keeping ICP down

Question 20

do normla response mechanisms have an effect on the vasculature i.e. humoral (renin)(angiotensin) and neurological ( nerves ANS)

Answer 20

no

Question 21

what local mechanisms can take place

Answer 21

vasodilation and vasoconstriction

Question 22

what is Cushings response

Answer 22

If ICP rises and is sensed in the fourth ventricle generating an increase in MAP to restore CPP
rise in ICP drop in CPP
associated with reflex bradcardia

Question 23

in an subarachnoid haemorrhage blood spreads widely through the CSF - little lines. This causes symptoms such as ; vomting, collapse, seizures and coma and can
Cause: berry aneurysm rupture. What is major symptom left out of this list

Answer 23

Thunderclap headache

Question 24

in an extradural heamatoma , you have Deteriorating consciousness after head injury and originally there can ben no loss of conciseness. Can get confusion, brisk reflexes and hemiparesis too. What are the 3 signs of a extradural heamatoma on a scan.

Answer 24

lemon/ lens shaped bleed - white
ventricle compressed
mid line distorted

Question 25

in a chronic subdural haematoma. The mid line of the Bain is slightly distorted . Fluctuating consciousness, evolving stroke esp. if on anticoagulants. Intellectual slowing, sleepiness, personality changes and unsteadiness. what appearance does this type of bleed give on an MRI

Answer 25

Crescent shaped collection of blood over 1 hemisphere

Question 26

what is an epidural haematoma typically caused by a blow to what area damaging what artery

Answer 26

typically caused by a blow to the pterion which will damage the middle meningeal artery, resulting in a bleed outside of the meninges, compressing the brain. Lemon shape on CT – defined outlines of blood

Question 27

Which bleed has a less defined outline of blood on the CT epidural or subdural?

Answer 27

Subdural haematoma - bleeds into subdural space - usually caused by tears of the bridging veins across the subdural space - significant midline shift and distortion of the ventricles seen on CT scan - outline of blood is not as defined as in an epidural bleed CT scan

Question 28

how can you confirm a subarachnoid haematoma

Answer 28

- confirmed using a lumbar puncture as blood is seen in the CSF. - Usually caused by a ruptured brain aneurism but also caused by a severe brain injury

Question 29

an intracerebral bleed can occur after a brain injury , where does the bleeding often take place

Answer 29

- Bleeding often into the ventricles

Question 30

what things are good to do in head injuries with raised intracranial pressure

Answer 30

``` prevent hypotension (low blood pressure) avoid hypoxia use hypotonic (low pressure) saline tilting the patients head up ```

Question 31

What is harmful in head injuries with raised intracranial pressure

Answer 31

maintaing mild hypercarbia ( high co2 in blood)

Question 32

using the Glasgow coma scale below what number does action need to be taken

Answer 32

3

Question 33

what is coning | is the brainstem affected

Answer 33

Caused by an increase in Intra cranial pressure (ICP) - Brain(cerebellar tonsils) is pushed down through the foramen magnum. Affects brainstem and causes particular type of shallow, sporadic breathing as the breathing centre is affected. Nerves compressed ICP>BP systolic blood flow ceases