Management of raised intracranial pressure

DR.MAZIN M.K. BOUJAN2011

Raised intracranial pressure is a major clinical feature of many neurological illnesses.

Physiology of normal intracranial pressure

• The normal supine intracranial pressure is 10–15 mmHg, measured at a position equal to the level of the foramen of Monro.

• The intracranial pressure is directly related to the volume of the intracranial contents within the skull.

the Monro–Kellie doctrine

• is that “the cranial cavity is a rigid sphere filled to capacity with noncompressible contents and that an increase in the volume of one of the constituents will lead to a rise in intracranial pressure”.

The intracranial contents

are: • BRAIN• CSF• BLOOD.

Causes of increased volume of normal intracranial constituents

• a space-occupying lesion: cerebral tumor, abscess, intracranial hematoma.

• cerebral edema: tumor, trauma.• benign intracranial hypertension:

(pseudo tumor cerebri).• hydrocephalus: due to any cause.• vasodilatation due to hypercapnia:

sleep, high altitude.

Volume of intracranial contents.essential neurosurgery textbook

blood 100-150ml CSF 100-150ml

ECF 100-150ml

GLIA 700-900ml

NEURONE 500-700 ml

volume to pressure relationship

is described in terms of compliance and elastance of the intracranial space.

• Compliance: is V/P, is the amount of ‘give 'available within the intracranial space.

• Elastance: is the inverse of compliance and is the ‘resistance’ offered to expansion of a mass or of the brain itself.

Cerebral blood flowCBF

• Autoregulation: the process whereby the brain adjusts the intracranial vascular resistance by altering vessel diameter and tone.

• cerebral blood flow is about 800 ml/min or 20% of the cardiac output.

Equations

1. CBF = CPP/CVR2. CPP = MAP – ICP• CBF: cerebral blood flow.• CPP: cerebral perfusion pressure. • CVP: cerebral vascular resistance.• MAP: mean arterial pressure.• ICP: intracranial pressure.

Neurological symptoms and signs of raised intracranial pressure

1. Headache: usually worse on waking in the morning and is relieved by vomiting.

2. Nausea and vomiting: usually worse in the morning.

3. Drowsiness: is the most important clinical feature of raised intracranial pressure.

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4. Papillodema: is due to transmission of the raised pressure along the subarachnoid sheath of the optic nerve.

5. Sixth nerve palsy, diplopia, false localizing sign.

6. Signs of brain herniation.7. In infants; tense, bulging fontanelle.

Systemic signs of raised ICP

Cushing triad of :

HYPERTENTION

RESPIRATORY IRREGULARITYBRADYCARDIA

TYPES OF BRAIN HERNIATION

1. Cingulate herniation(subfalcian herniation); the cingulate gyrus in one hemisphere is pushed under the falx towards the other hemisphere.

2. Uncal herniation(transtentorial herniation), the uncus and hippcampus pushed to the midline towards the tentorial edge causing the classical ipsilateral 3rd nerve palsy, hemiparesis (kernohan’s notch).

TYPES OF BRAIN HERNIATION

3. Central transtentorial herniation; downward movement of hemispheres and basal nuclei through the tentorail opining.

4. Upward transtentorial herniation ( the inverted pressure cone), is a variant of central herniation.

5. Cerebellar tonsils herniation through the foramen magnum.

MANAGEMNET OF INCREASED ICP

1. Head elevation: to 30 degrees, insure that there is no venous compression of internal jugular vein.

2. Hypertonic solutions: like mannitol, should be used for short period because of rebound phenomenon.

3. Diuretics: furosemide(frosemide), has the advantage of reducing ICP as well as reducing CSF production.

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4. hyperventilation: with sedation and intubation. The best method in reducing ICP and the effect is almost immediate. Hyperventilation causes hypocapnea (reduces CSF carbon dioxide which leads to CSF alkalosis and eventually cerebral vasoconstriction as well as cerebral blood flow and volume).

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5. hypothermia: has a limited use. Reduces cerebral oxygen demand, cerebral blood flow, and ICP.

Disadvantages are;1. Cardiac arrhythmias.2. seizure, drowsiness, and probably

coma during re-warming.

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6. Steroids; causes reduced CSF production and edema.

More effective in brain tumor, no important role in head trauma.

7. barbiturates: should be used only in intensive care units, as they cause hypotension and myocardial depression.

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Surgical interventions:8. Ventriculostomy, external drains and

shunt operations, CSF diversion procedures. To manage one of the intracranial contents, the CSF.

Can not be established in case of small ventricles like in benign intracranial hypertension.

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Craniotomy, craniectomy, lobectomy, and removal of the space occupying lesion, according to the cause of the raised ICP.

This could be a palliative or a definitive treatment.

Summary of Medical management of raised intracranial pressure

■ Position head up 30º.■ Avoid obstruction of venous drainage from

head.■ Sedation +/– muscle relaxant.■ Normocapnia 4.5–5.0 kPa.■ Diuretics: furosemide and mannitol.■ Seizure control.■ Normothermia.■ Sodium balance.■ Barbiturates.

Summary of Surgical management of raised intracranial pressure

■ Early evacuation of focal haematomas: EDH, ASDH

■ Cerebrospinal fluid drainage via ventriculostomy

■ Delayed evacuation of swelling contusions

■ Decompressive craniectomy

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