16 Raised Intracranial Pressure Flashcards
What are the normal CSF pressure ranges for: adults, children, term infants?
There are lots of ways for us to measure normal CSF pressure (including a lumbar puncture) . How do NIRS sensors work? (near-infrared spectroscopy)
Relies on:
- Relative tranaprency of tissue for light in NIR range
- Oxygenation dependent light absorbance of haemoglobin
Give some indications for ICP monitoring.
- ICP control in chronic cases
- Head injuries
The following image shows the wave form for Intracranial pressure. What do P1, P2 and P3 show?
P1- arterial pulsation
P2- brain tissue compliance
P3- Dicrotic wave (secondary upstroke in the descending part of a pulse tracing)
(P1>P2 normally- P2 may be greater than P1 in acute brain injury) )
What are the immediate and delayed compensatory mechanisms for raised ICP?
Immediate:
- Fluid moved to lumbar area
- Reduce CSF production
- Blood squeezed out of sinuses- reduced blood volume
Delayed:
- Decrease ECF
What does the Monro-Kellie doctrine show? (with relation to ICP)
Non-linear association between volumes and pressure in brain
What equation can we use to calculate cerebral perfusion pressure?
CPP= MAP-ICP
(Mean arterial pressure, intracranial pressure)
What are the 2 major consequences of increase intracranial pressure?
- Brain shifts
- Brain ischaemia
What are the signs and symptoms of raised intracranial pressure?
Signs
- Papilloedema
- Bradycardia
- Systolic hypertension
- Irregular respirations (eg Cheyne stokes respirations)
- Decreased GCS
- Confusion
- Non-reactive pupils
- LOC
Symptoms
- Headache
- Nausea and vomiting
- Double vision
- Neurological symptoms
**How does the cushing’s reflex work?
List some causes of raised ICP.
- Haematomas
- Depressed fractures
- Obstructive hydrocephalus
- Abscess
- Encephilitis
- Meningitis
- Water intoxication
What is craniosynostosis?
Birth defect in which the bones in a baby’s skull join together too early. This happens before the baby’s brain is fully formed. As the baby’s brain grows, the skull can become more misshapen
Explain why there might be a lucid interval with an extradural haemorrhage. (40% patients)
- LOC- due to impact of initial injury
- Haematoma enlarges
- ICP increases
- Compression of brain
- GCS decreases
- CN palsies if brain herniates
- GCS decreases
- Compression of brain
- ICP increases
What are the criteria for an urgent head CT?
GCS
- GCS <13 at any point
- GCS <14 2hrs+ after injruy
Neurological abnormality
- Focal neurological deficit
- Seizure
- LOC
- age greater than 65yrs
- Coagulopathy
- Injury
- Anterograde amnesia >30mins
- loss of the ability to create new memories after the event that caused amnesia
Other
- Suspected open/depressed skull fracture
- Signs of basal skull fracture
What are the 4 main sites of brain herniation?
The following CT scan shows a chronic subdural haemorrhage. How do we know it’s chronic and why is it that neurological abnormalities may not have been seen straight away?
Chronic because much darker than if acute bleed
Less midline shift- so neurological abnormalities may not have been seen straight away.
What should we do as a primary intervention for raised ICP? (Tier 0)
- Assess Airway, Breathing, Circulation
- Check cervical spine
- Elevate head, make sure nothing pressing on neck
- Control pain, fever, seizures (may need to give sedative- allow for intubation)
- Ventilation
- BP control
- Obtain non-contrast CT
- Consult neurosurgery- assess need for decompression
What is involved in the tier 1 management of raised ICP?
- CSF drainage
- Osmotic therapy (eg mannitol= osmotic diuretic)
- Diuretics
- Neuromuscular blockade
- facilitates mechanical ventilation
- helps if movement increased ICP
What management should we carry out tier 3 for raised intracranial pressure?
- Decompressive craniectomy/ clot evacuation
- Induce hypothermia
- Barbiturate coma
Differentiate between communicating and non-communicating hydrocephalus.
Communicating: impaired CSF reabsorption in absence of any obstruction
Non communicating: CSF-flow obstruction
- eg in:
- Foramen of Monro
- Aqueduct of sylvius
- eg in:
What is the Budd Chiari malformation?
Cerebellum= too big blocks off foramen magnum
What does the following CT image show?
DIFFUSE CEREBRAL OEDEMA
- Loss of grey/white discrimination
- Lateral borders of ventricles displaced medially
Outline the pathophysiology of an anoxic brain injury (when brain= deprived of oxygen).
How do we approach brain resuscitation? (6)
- Barbiturates
- Super oxide dismutase
- Nimodipine (CCB)
- Glutamate antagonists
- Nitric oxide synthesis inhibitors
- Hypothermia
