Raised Intracranial Pressure Flashcards
What makes up the contents of the skull?
CSF
Blood
Brain parenchyma
What proportion and volume makes up the CSF?
150ml (10%)
What proportion and volume make up the blood volume?
120ml (10%)
What proportion and volume make up the brain parenchyma>
1400ml (80%)
What is the normal CSF pressure within ICP in adults?
<10-15 mmHg
What is the normal CSF pressure within ICP in children?
3-7 mmHg
What are some methods of measuring ICP?
Subarachnoid ICP monitor Intraventricular ICP monitor Transcranial doppler Subdural ICP monitor Intraparenchymal PBO2 monitor Intraparenchymal ICP monitor Epidural ICP monitor NIRS sensors
WHat is NIRS?
A non-invasive method
Near Infrareed Spectroscopy
WHat is NIRS dependant on?
The relative transparency of tissue for light in the NIR range
The O2 dependant light absorbance of Hb
When is ICP measured?
Mainly in trauma
Continuous ICP monitoring
Goal directed treatment to reduce ICP
When is it ICP measurement used in acute cases?
In overall brain resuscitation
Describe the normal Time, ICP graph
Three waves:
P1-P3
What doe each of the ICP waveform changes represent?
P1- arterial pulsation
P2- brain tissue compliance
P3- dicrotic wave (aortic valve closure)
What happens to the graph in acute brain injury and why?
Acute brain injury compliance starts decreasing resulting in reversal of P1:P2 ratio and P2>P1
What are the Lundberg wave changes that occur in increased ICP?
A wave- Plateau
B wave- Rhythmic oscillation every 1-2 mins
C wave- oscillation every 4-8 months
What is the Monroe-Kellie Doctrine?
The brain has compensatory mechanisms for a mass in the brain
What are the immediate compensatory mechanisms of the brain?
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
What are the delayed compensatory mechanisms of the brain?
Decrease in extracellular fluid
How does anoxic changes occur in the brain?
Pressures exceed arterial supply –> increased blood supply –> Anoxic changes
What are the volume pressure relations of Monro-Kellie doctrine?
The sum of the intracranial volumes within blood brain and CSF and other components is constant
Non-linear association between volumes and pressure
Describe the graph of Monro-Kellie doctrine?
Sudden acceleration of intracranial volume, there is a point at which there’s acceleration of pressure therefore brains pushed through foraman magnum
Why is ICP important?
Leads to death or disability most acute cerebral conditions and there major consequences are:
Brain shifts
Brain ischaemia
What is cerebral perfusion pressure?
The calculated difference between the mean arterial pressure and the ICP
What are the symptoms of raised ICP?
Headache
Nausea and vomiting
Double vision
Other neurological symtpoms
What are the signs of raised ICP?
Bradycardia Systolic hypertension Irregular respirations Cheyne Stokes respirations Decreased mental abilities Confusion Non-reactive pupils Loss of consciousness Papilloedema
What are the features of Cushing Reflex?
Bradycardia
Sytolic hypertension
Irregular breathing
Describe the Cushing Reflex?
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
What can the causes of ICP be split into?
Stuff from blood e.g. haemotoma, injury and haemorrhage
CSF- hydrocephalus
Brain- tumult pr acute brain oedema
What is Craniosynostosis?
Sutures that are fused and so no space for the expanding brain in babies
What is the sequelae of extradural haemorrhage?
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
When should an urgent head CT be ordered?
GCS below 13 Focal neuro deficit Seizure Loss of consciousness within older people, coagulopathy, dangerous mechanism of injury, amnesia Skull fracture
What is the image on a CT of an extradural haemorrhage?
Like a lemon
No lateral ventricles
Midline shift
No sulci
Where is an extradural haemorrhage found? Thus which artery is severed?
Collection of blood between inner surface of skull and periosteal dura mater
Middle meningeal artery
What are 4 sites of brain herniation?
Subfalcine
Transtentorial
Uncal
Tonsillar (coning, involving midbrain)
What does an acute subdural haemorrhage look like on a CT?
Banana
Who is most affected by subdural haemorrhage and why?
Older people because it is usually a haemorrhage of the bridging veins that are stretched due to shrinking of the brain
WHat is the difference in CT scan between acute and chronic subdural haemorrhages?
Chronic is more dark than acute
There is also less midline shift which means neurological abnormalities may not be present immediately
WHat are the treatments of subdural haemorrhages?
Burr hole
Craniotomy
What is tier 0 in the treatment of rICP
Airway Ventilation Blood pressure Fluids Sedation Fever Glucocorticoids Facilitate cerebral venous drainage Bed elevation Nursing care
What is tier 1 in treatment of rICP?
General physiological homeostasis
CSF drainage
Osmotic therapy works by reducing brain water
Mannitol, hyperosmolar therapy as cells swell
Diuretics
Neuromuscular blockade
Hyperventilation
What is tier 3 in treatment of rICP?
Barbiturate coma
Optimised hyperventilation
Hypothermia
Decompressive craniotomy
Describe communicating hydrocephalus?
Impaired CSF reabsorption in the absence of any obstruction
Functional impairment of the arachnoid granulations
Describe non-communicating hydrocephalus?
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
Describe cerebral oedema?
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
Describe the pathophysiology of anoxic brain injury?
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
What is given for brain resuscitation?
Barbiturates SO dismutase calcium channel antagonist glutamate antagonist NO syntheses inhibitors Hypothermia
