RAISED ICP

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RAISED ICP

• Atandrila Das

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Monro-Kellie Doctrine

• Cranial cavity is a rigid sphere
• Filled to capacity with non compressible contents
• Increase in the volume of one of the constituents
  will lead to a rise in pressure

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Intracranial pressure-volume relationship
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Cerebral blood flow

• CBF (CAP JVP) / CVR
• CBF is normally maintained at a relatively
  constant level by autoregulation of CVR over a
  wide range of BP
• In the setting of raised ICP, CBF can be reduced
• CPP is a clinical surrogate for the adequacy of
  cerebral perfusion.
• CPP MAP ICP
• CPP becomes dependent on MAP when autoregulation
  compromised
• To maintain CPP in the setting of raised ICP,
  systemic BP needs to be elevated.

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Contents

• Brain 80
• Blood 10
• CSF 10

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Causes of raised ICP

• Increased volume of normal contents
• Brain oedema, benign intracranial HTN
• CSF hydrocephalus
• Blood vasodilatation, venous thrombosis
• Space occupying lesions
• Tumour
• Abscess
• Intracranial heamorrhage

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Symptoms/signs

• DROWSINESS
• Headache
• Nausea/vomiting
• Papilloedema
• Cushings triad

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Normal fundus
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Papilloedema
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Cerebral herniation

• Can occur depending on cause of raised ICP
• 3 major types
• Transtentotial
• Foramen magnum
• subfalcine

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Transtentorial

• Displacement of brain and herniation of uncus of
  temporal lobe through the tentorial hiatus
• Causes compression of
• midbrain contralateral hemiparesis (usually),
  Cushing response, , respiratory failure
  (cheyne-stokes)
• CN III dilatation of ipsilateral pupil
  initially
• Posterior cerebral artery hemianopia

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Foramen magnum (coning)

• Progressively increasing ICP causes further
  downward herniation of the brainstem into foramen
  magnum or coning.
• This results in shearing of the perforators
  supplying the brainstem and haemorrhage within
  (Duret heamorrhage).
• Traction damage to pituitary stalk resulting in
  DI.
• With progressive herniation pupils change from
  dilated and fixed to midsize and unreactive.
• Signifying irreversible events leading to
  brainstem death.

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Subfalcine

• Cingulate gyrus herniates under falx.
• Usually asymptomatic unless ACA kinks and
  occludes causing bifrontal infarction.

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ICP monitoring

• Indications
• Head injury
• Following major intracranial surgery
• Assessment of benign intracranial HTN
• Normal ICP 10-15mmHg
• Can be recorded from ventricle, brain substance,
  subdural or extradural space
• Risks CNS infection and intracranial haemorrhage

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A waves
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Management

• Definitive treatment treat underlying patholgy
• To control raised ICP
• Head elevation
• Controlled ventilation maintain PaCO2 at 30-35
  mmHg. Reduction of CO2 will reduce cerebral
  vasodilatation
• Sedation/paralysis decrease metabolic demand
• If ventricular catheter in situ, drain CSF
• Diuretic therapy mannitol osmotic diuretic,
  increases serum osm and draws water out of the
  brain. Usual dose 0.5-1.0g/kg. monitor serum osm
• Hypertonic saline
• Barbiturate therapy thiopentone when given as a
  bolus dose can be helpful in temporarily reducing
  ICP.

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Bibliography

• Essential Neurosurgery. Prof. A Kaye. Third
  edition
• Handbook of neurosurgery. M. Greenberg. Sixth
  edition
• Uptodate Evaluation and management of elevated
  intracranial pressure in adults. E.Smith
• http//www.millerneurosurgery.com/index.php/proced
  ures