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RAISED ICP

RAISED ICP. Atandrila Das. 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. Intracranial pressure-volume relationship. Cerebral blood flow.

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RAISED ICP

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  1. RAISED ICP Atandrila Das

  2. 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

  3. Intracranial pressure-volume relationship

  4. 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.

  5. Contents • Brain – 80% • Blood – 10% • CSF – 10%

  6. 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

  7. Symptoms/signs • DROWSINESS • Headache • Nausea/vomiting • Papilloedema • Cushing’s triad

  8. Normal fundus

  9. Papilloedema

  10. Cerebral herniation • Can occur depending on cause of raised ICP • 3 major types: • Transtentotial • Foramen magnum • subfalcine

  11. 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

  12. 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.

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

  14. 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

  15. A waves

  16. 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.

  17. 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/procedures

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