What is the purpose of neurointensive care?
Prevent further damage (secondary injury) to the brain and allow best possible recovery from primary insult
What is the physiological basis for neurointensive care?
Monro-Kellie doctrine
How does the Monro-Kellie doctrine see the head?
As a ‘rigid box’ with a fixed volume
What is the fixed volume of the head made up of?
- Brain
- CSF
- Arterial and venous blood
What can cause expansion of the brain volume?
- Cerebral oedema
- ‘New matter’ occupying space
What ‘new matter’ can occupy space in the brain?
- Expanding haematoma
- Tumour
- Obstructive hydrocephalus
How can raised pressure in the head be compensated for?
Reduction in amount of CSF or venous blood
How good is the compensation mechanism of reduction in amount of CSF or venous blood?
Limited capacity for compensation, and will still be some increased in ICP towards 20mmHg
What is the normal ICP?
5-10mmHg
What happens when the capacity of the head to compensate for increased pressure fails?
The system becomes non-compliant and further small increases in volume will produce rapid rises in pressure
What is required due to the rapid increase in ICP when compensation mechanisms fail?
Rapid management
What management might be used in raised ICP?
- Osmotherapy
- Definitive surgery
What is the timeframe for performing definitive therapy to manage raised ICP?
Within 4-6 hours
What is the aim of definitive surgery to manage raised ICP?
Remove expanding intracranial mass lesions, e.g. haematoma
What happens once ICP exceeds mean arterial pressure (MAP)?
Cerebral perfusion becomes critically impaired, and hypoxic-brain injury may occur
What can further increases in ICP past MAP lead to?
- Transtentorial herniation
- Uncus or cerebellar tonsillar herniation
What part of the brain is affected in transtentorial herniation?
The innermost part of the temporal lobe
What does the uncus or cerebellar tonsillar herniation occur through?
The foramen magnum
What does brain herniation (transtentorial, uncus, or cerebellar tonsillar) lead to?
Brainstem compression and ultimately brain death
What is tonsillar herniation also known as?
Coning
What happens in tonsillar herniation?
The cerebellar tonsils move downward through the foramen magnum, causing compression of the lower brainstem and upper cervical spinal cord
What does increased pressure on the brainstem result in?
Dysfunction of the centres responsible for controlling respiratory and cardiac function
What investigation is required in all patients with encephalopathy?
Neuroimaging
Why do all patients with encephalopathy require neuroimaging?
To make an assessment of ICP
What monitoring should be considered in patients with encephalopathy?
ICP monitoring
How is ICP monitoring usually done?
Neurosurgical insertion of a fine bore catheter into the substance of the brain through a small burr hole
When is ICP monitoring the standard of care?
In traumatic brain injury requiring neurointensive care
What is the advantage of ICP monitoring?
Allows accurate assessment of cerebral perfusion pressure (CPP)
How is CPP calculated?
MAP - ICP
Why is control of CPP important?
To prevent cerebral ischaemia
What is the normal CPP in an infant?
> 50mmHg
What is the normal CPP in a child?
> 60mmHg
What is the normal CPP in an adolescent?
> 70mmHg
What feature of the cerebral vessels does blood flow depend on?
Diameter
What is the diameter of cerebral blood vessels affected by?
PaCO2
What effect does PaCO2 have on blood vessels?
Low levels cause vasoconstriction
High levels cause vasodilation
What is the result of PaCO2 having an effect on the diameter of cerebral blood vessels therefore on cerebral blood flow?
Maintenance of normocapnia is of critical importance
How should normocapnia be maintained in an intubated patient?
Once the patient is intubated, a formal blood gas should be measured to determine PaCO2. This should be correlated to end-tidal CO2 measurement, allowing adjustment of the ventilation constantly to avoid hyperventilation or hypoventilation
What can hyperventilation lead to in a ventilated patient?
Can induce ischaemia
What can hypoventilation lead to in an intubated patient?
Can lead to increased cerebral blood flow and exacerbation of raised ICP
What is the result of CPP being dependent on arterial pressure?
It is often necessary to maintain BP at above normal levels
What may be required to maintain BP at higher than normal levels?
Inotropes
What is important for maintaining adequate oxygen delivery in neurointensive care?
Ensuring physiologic haemoglobin levels, with transfusion if needed
How can cerebral oxygen demand be reduced?
- Sedation
- Seizure control
What is the role of hypothermia in reducing cerebral oxygen demand?
May have a role, but no definitive trial evidence to support use in children
Are steroids used in the treatment of raised ICP?
No - limited evidence of beneficial effects, although may have role in meningitis or tumours
What is used for osmotherapy in raised ICP?
3% saline or mannitol
What is the benefit of osmotherapy in raised ICP?
May reduce intracranial cellular oedema
Should osmotherapy be used in traumatic brain injury?
Only on advice of a neurosurgeon
What are the other strategies for reducing ICP?
- Fluid restriction
- Maintaining head tilt at 30 degrees upright in midline
How does maintaining the head at tilt 30degrees upright help in raised ICP?
Improves venous return
What are all treatments of raised ICP aimed at?
Trying to decrease or limit cerebral oedema, and acutely dropping the ICP by creating more space, hence limiting or preventing secondary brain injury
What does uncal herniation commonly cause compression of?
Cranial nerve III
Where does CN III originate?
In anterior aspect of midbrain
What does CN III compression result in?
Q- Parasympathetic paralysis and pupillary dilation of the eye on the affected side
- Loss of innervation of all ocular motility muscles except for lateral rectus and superior oblique, resulting in deviation of eye to ‘down and out’ position
What often presents first in CN III compression?
Pupillary dilatation
Why does pupillary dilatation often precede the somatic motor effects of CN III compression?
Because the parasympathetic fibres surround the motor fibres of the nerve, and so are compressed first
Is the pupillary dilatation unilateral or bilateral in uncal herniation?
Initially ipsilateral to side of lesion, but as ICP continues to rise, contralateral CN III is also compressed and bilaterally ‘fixed and dilated’ pupils seen
What is acute encephalopathy defined as?
A sudden onset of diffuse brain dysfunction, with or without an associated change in level of consciousness
Are encephalopathies convulsive or non-convulsive?
Can be either
What is convulsive status epilepticus (CSE) defined as?
Generalised convulsion lasting 30 minutes or longer, or repeated tonic-clonic convulsions occurring over a 30 minute period without recovery of consciousness between each convulsion
How might children with non-convulsive acute encephalitis present?
- Reduced conscious level
- Psychosis
- Confusion
How serious is CSE in childhood?
Life threatening condition with serious risk of neurological sequelae
What can cause neurological sequelae in CSE?
- Hypoxia due to airway obstruction and hypoventilation
- Neuronal damage due to unmet increased cerebral metabolic demands
What is the mortality of CSE in children?
Up to 4%
What are the neurological sequelae of CSE?
- Epilepsy
- Motor deficits
- Learning difficulties
- Behavioural problems
Are neurological sequelae common in CSE?
No, they are rare
What is the most common cause of CSE in paediatrics?
Uncontrolled epilepsy with underlying seizure disorder, or febrile convulsion
What age can febrile convulsions occur?
Children 6months - 6 years
What should be considered when CSE presents in a febrile child?
Infective meningoencephalitis
What are the most common bacteria causing infective meningoencephalitis?
Meningococcus and pneumococcus
What are the most common viruses causing infective meningoencephalitis?
Herpes simplex
Enteroviridae
What causes should be considered in all cases of acute encephalopathy?
- Space occupying lesions
- Autoimmune disease
- Vascular occlusion or bleeding
- Metabolic disorders
- Poisons and trauma, including NAI
What autoimmune diseases can cause acute encephalopathy?
- Acute disseminated encephalomyelitis (ADEM)
- Anti-NMDA receptor antibody encephalitis
What should be done in acute resuscitation and stabilisation in CSE?
- High flow oxygen
- Measure BM
- Brief history and clinical examination
- Stabilise airway, breathing, and circulation
- Assess conscious level (GCS/AVPU)
What is the disadvantage of artificial ventilation in acute resuscitation and stabilisation in CSE?
Reduces ability to monitor conscious level
What anti-microbial management is required in CSE?
Until a confirmed microbiological diagnosis has been made, patients should be started on high-dose antibiotic and anti-viral treatment
What antimicrobials are often used empirically in CSE?
- Third generation cephalosporin
- Macrolide
- Aciclovir
What needs to be done prior to taking CSF samples in CSE?
Exclude raised ICP
Why is it important to exclude raised ICP before taking CSF samples?
Because of the risk of coning
What will seizures lead to in CSE unless effectively controlled?
Further hypoxia and ischaemia
Why do seizures lead to further hypoxia and ischaemia in CSE?
Due to combination of airway obstruction and neuronal secondary energy failure
How can seizure activity be identified in CSE?
- Clinically
- EEG
How can brief seizures in CSE be managed?
Benzodiazepines, e.g. lorazepam
What management is often required for prolonged seizures in CSE?
- IV anticonvulsants, e.g. phenytoin
- Barbiturate infusions, e.g. phenobarbitone, thiopentone
When should rapid sequence induction be used in CSE?
If 20 mins after IV phenytoin or phenobarbitone has commenced, the child remains in CSE, or if the airway is not protected because of reduced conscious level
What should be used for rapid sequence induction in CSE?
Thiopentoner
What kind of agents should be used if neuromuscular paralysis is used in CSE?
Short acting
Why should neuromuscular paralysis be short acting if used in CSE?
To not mask the clinical signs of a convulsion
