Raised ICP Flashcards
What are the normal intracranial pressures (CSF pressure) for Adults, children and term infants?
- Adults: <10-15 mmHg
- Children: 3-7 mmHg
- Term infants: 1.5-6 mmHg
How can you measure ICP?
- Lumbar puncture
- Subdural ICP monitor
- Subarachnoid ICP monitor
- Epidural ICP monitor
- many more…
What is NIRS?
Near Infra-Red Spectroscopy
- Meaures ICP indirectly by measuring cerebral perfusion
- Relies on the transparency of tissue for light int he NIR range and O2 dependent light absorbance of Hb
What is the normal ICP wave? What kind of things will increase ICP normally?
Usually P1> P2
Normally increased by; cough, respiration, valsalvar manouvre
How can the ICP wave change in acute brain injury?
A change in brain injury compliance causes the reversal of P1:P2 and P2> P1
What are some of the immediate compensatory mechanisms that kick in when ICP is raised?
- Decrease in CSF volume → fluid moves into lumbar area
- Reduced CSF production
- Decreased blood volume → blood squuezed out of the sinuses
What delayed mechanism acts to reduce raised intracranial pressure?
Decrease in extracellular fluid
What is the Monro-Kellie doctrine?
The sum of intracranial volumes within brain and CSF and other components (tumour, haemaotoma) is constant
Intracranial volume rises gradually then rapidly to the point where the brain can b squeezed out of the foramen magnum
How does ICP relate to cerebral perfusion?
Cerebral perfusion pressure = MAP - ICP
What are the 2 major consequences of increased ICP?
- Brain shifts
- Brain ischemia
What are some of the symptoms and signs of rICP?
Symptoms
- Headache
- Nausea and vomting
- Double vision
- Neurological symptoms
Signs
- Bradycardia
- Systolic hypertension
- Irregular respiration
- Cheyne Stokes respirations
- Decreased mental abilities
- Confusion
- Non-reactive pupils
- Loss of conciousness
- Pappiloedema
What is Cushing’s reflex?
What is craniosynotosis?
Early fusion of the sutres of the skull → not enough rough for the expanding brain
What should you not do to patients who have raised ICP?
Do not push in lots of fluids!
Explain what happens due to ICP in extradural haemorrhage?
- Patient presents with loss of conciousness on initial injury
- followed by transient recovery‘lucid interval’ (in 40% patients)
- As haematoma enlarged, ICP rises compressing the brain → deteriorating conciousness
- May see cranial nerve palsies as brain structures start to herniate