Raised Intracranial Pressure

Question 1

What makes up the contents of the skull?

Answer 1

CSF
Blood
Brain parenchyma

Question 2

What proportion and volume makes up the CSF?

Answer 2

150ml (10%)

Question 3

What proportion and volume make up the blood volume?

Answer 3

120ml (10%)

Question 4

What proportion and volume make up the brain parenchyma>

Answer 4

1400ml (80%)

Question 5

What is the normal CSF pressure within ICP in adults?

Answer 5

<10-15 mmHg

Question 6

What is the normal CSF pressure within ICP in children?

Answer 6

3-7 mmHg

Question 7

What are some methods of measuring ICP?

Answer 7

Subarachnoid ICP monitor
Intraventricular ICP monitor
Transcranial doppler
Subdural ICP monitor
Intraparenchymal PBO2 monitor
Intraparenchymal ICP monitor
Epidural ICP monitor
NIRS sensors

Question 8

WHat is NIRS?

Answer 8

A non-invasive method

Near Infrareed Spectroscopy

Question 9

WHat is NIRS dependant on?

Answer 9

The relative transparency of tissue for light in the NIR range
The O2 dependant light absorbance of Hb

Question 10

When is ICP measured?

Answer 10

Mainly in trauma
Continuous ICP monitoring
Goal directed treatment to reduce ICP

Question 11

When is it ICP measurement used in acute cases?

Answer 11

In overall brain resuscitation

Question 12

Describe the normal Time, ICP graph

Answer 12

Three waves:

P1-P3

Question 13

What doe each of the ICP waveform changes represent?

Answer 13

P1- arterial pulsation
P2- brain tissue compliance
P3- dicrotic wave (aortic valve closure)

Question 14

What happens to the graph in acute brain injury and why?

Answer 14

Acute brain injury compliance starts decreasing resulting in reversal of P1:P2 ratio and P2>P1

Question 15

What are the Lundberg wave changes that occur in increased ICP?

Answer 15

A wave- Plateau
B wave- Rhythmic oscillation every 1-2 mins
C wave- oscillation every 4-8 months

Question 16

What is the Monroe-Kellie Doctrine?

Answer 16

The brain has compensatory mechanisms for a mass in the brain

Question 17

What are the immediate compensatory mechanisms of the brain?

Answer 17

Decrease in CSF volume by movement of fluid into lumbar area
Reduced CSF production
Decrease in the blood volume by squeezing the blood out of the sinuses

Question 18

What are the delayed compensatory mechanisms of the brain?

Answer 18

Decrease in extracellular fluid

Question 19

How does anoxic changes occur in the brain?

Answer 19

Pressures exceed arterial supply –> increased blood supply –> Anoxic changes

Question 20

What are the volume pressure relations of Monro-Kellie doctrine?

Answer 20

The sum of the intracranial volumes within blood brain and CSF and other components is constant
Non-linear association between volumes and pressure

Question 21

Describe the graph of Monro-Kellie doctrine?

Answer 21

Sudden acceleration of intracranial volume, there is a point at which there’s acceleration of pressure therefore brains pushed through foraman magnum

Question 22

Why is ICP important?

Answer 22

Leads to death or disability most acute cerebral conditions and there major consequences are:
Brain shifts
Brain ischaemia

Question 23

What is cerebral perfusion pressure?

Answer 23

The calculated difference between the mean arterial pressure and the ICP

Question 24

What are the symptoms of raised ICP?

Answer 24

Headache
Nausea and vomiting
Double vision
Other neurological symtpoms

Question 25

What are the signs of raised ICP?

Answer 25

``` Bradycardia Systolic hypertension Irregular respirations Cheyne Stokes respirations Decreased mental abilities Confusion Non-reactive pupils Loss of consciousness Papilloedema ```

Question 26

What are the features of Cushing Reflex?

Answer 26

Bradycardia Sytolic hypertension Irregular breathing

Question 27

Describe the Cushing Reflex?

Answer 27

Increased ICP Decreased cerebral blood flow Increase in CO2, stimulating the vasomotor centre of the brain Sympathetic response leads to vasoconstriction= Inc. MAP to inc. CPP Baroreceptors in aortic arch and carotid arteries Reflex bradycardia HIGH BP LOW HR

Question 28

What can the causes of ICP be split into?

Answer 28

Stuff from blood e.g. haemotoma, injury and haemorrhage CSF- hydrocephalus Brain- tumult pr acute brain oedema

Question 29

What is Craniosynostosis?

Answer 29

Sutures that are fused and so no space for the expanding brain in babies

Question 30

What is the sequelae of extradural haemorrhage?

Answer 30

Loss of consciousness on initial injury Transient recovery with headache known as lexus interval in many As haemotoma enlarges, ICP will increase causing compression of the brain and rapidly deteriorating consciousness Cranial nerve palsies can be found

Question 31

When should an urgent head CT be ordered?

Answer 31

``` GCS below 13 Focal neuro deficit Seizure Loss of consciousness within older people, coagulopathy, dangerous mechanism of injury, amnesia Skull fracture ```

Question 32

What is the image on a CT of an extradural haemorrhage?

Answer 32

Like a lemon No lateral ventricles Midline shift No sulci

Question 33

Where is an extradural haemorrhage found? Thus which artery is severed?

Answer 33

Collection of blood between inner surface of skull and periosteal dura mater Middle meningeal artery

Question 34

What are 4 sites of brain herniation?

Answer 34

Subfalcine Transtentorial Uncal Tonsillar (coning, involving midbrain)

Question 35

What does an acute subdural haemorrhage look like on a CT?

Answer 35

Banana

Question 36

Who is most affected by subdural haemorrhage and why?

Answer 36

Older people because it is usually a haemorrhage of the bridging veins that are stretched due to shrinking of the brain

Question 37

WHat is the difference in CT scan between acute and chronic subdural haemorrhages?

Answer 37

Chronic is more dark than acute | There is also less midline shift which means neurological abnormalities may not be present immediately

Question 38

WHat are the treatments of subdural haemorrhages?

Answer 38

Burr hole | Craniotomy

Question 39

What is tier 0 in the treatment of rICP

Answer 39

``` Airway Ventilation Blood pressure Fluids Sedation Fever Glucocorticoids Facilitate cerebral venous drainage Bed elevation Nursing care ```

Question 40

What is tier 1 in treatment of rICP?

Answer 40

General physiological homeostasis CSF drainage Osmotic therapy works by reducing brain water Mannitol, hyperosmolar therapy as cells swell Diuretics Neuromuscular blockade Hyperventilation

Question 41

What is tier 3 in treatment of rICP?

Answer 41

Barbiturate coma Optimised hyperventilation Hypothermia Decompressive craniotomy

Question 42

Describe communicating hydrocephalus?

Answer 42

Impaired CSF reabsorption in the absence of any obstruction | Functional impairment of the arachnoid granulations

Question 43

Describe non-communicating hydrocephalus?

Answer 43

Foramen of Monro- blockage of lateral ventricles Aqueduct of sylvia's 4th ventricle obstruction --> dilation of the aqueduct and the other ventricles (chiari) Congenitral malformation leading to blockage of Lusaka and Magendie

Question 44

Describe cerebral oedema?

Answer 44

Grey matter blends imperceptibly into white matter Loss of grey-white discrimination Lateral borders of both ventricles displaced medially Sign of central herniation begins to funnel through central opening in tentorium

Question 45

Describe the pathophysiology of anoxic brain injury?

Answer 45

``` Decreased cerebral blood flow Decreased O2 Failure of ATP driven ion pump in brain cell Efflux of K from cell Influx of Na into cell Depolarisation of neurones Water follows Na into cell and causes Odrma Activated NOS--> NO Toxic O2 radicals produced ```

Question 46

What is given for brain resuscitation?

Answer 46

``` Barbiturates SO dismutase calcium channel antagonist glutamate antagonist NO syntheses inhibitors Hypothermia ```