Management of raised intracranial pressure DR.MAZIN M.K. BOUJAN 2011
Raised intracranial pressure is amajor clinical feature of manyneurological 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 contentsare:• 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 to pressure relationshipis 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.
Intracranial pressure monitoring• There are three ways to monitor pressure in the skull (intracranial pressure).
1.INTRAVENTRICULAR CATHETER.The intraventricular catheter is thought to be the most accurate method. A burr hole is drilled through the skull. The catheter is inserted through the brain into the lateral ventricle.
2.SUBDURAL SCREW.A subdural screw or bolt is a hollow screw that is inserted through a hole drilled in the skull. It is placed through the dura mater. This allows the sensor to record from inside the subdural space.
3.EPIDURAL SENSOR.an epidural sensor is inserted between the skull and dural tissue. Is placed through a burr hole drilled in the skull. This procedure is less invasive than other methods, but it cannot remove excess CSF.
Neurological symptoms and signs of raised intracranial pressure1. 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.
CONTINUE4. 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 ICPCushing triad of : HYPERTENTION RESPIRATORY BRADYCARDIA IRREGULARITY
TYPES OF BRAIN HERNIATION1. 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 HERNIATION3. Central transtentorial herniation; downward movement of hemispheres and basal nuclei through the tentorial 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 ICP1. 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
Continue…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).
Continue..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.
Continue..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.
Continue..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.
Continue..Craniotomy, craniectomy, lobectomy, a nd 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