Increased Pressure inside the Cranium

The pressure normally exerted by the cerebrospinal fluid is known as intracranial pressure. Cerebrospinal fluid (CSF) is generated in the cerebral ventricles and it circulates around the brain and spinal cord. The human skull contains brain matter, blood supplying nutrients and oxygen to the brain and cerebrospinal fluid which protects the brain. Monroe Kelly hypothesis states that the volume of these components is in dynamic equilibrium.

The normal intracranial pressure ranges from 0 to 10 mm of Hg although 15 mm of Hg is considered the upper limit of normal. If the intracranial pressure increases due to any reason, the body will try to bring it back to normal by some compensatory mechanisms like displacing CSF to the spinal and perioptic subarachnoid space, compressing the venous system, decreasing the production of CSF and vasoconstriction of the cerebral vasculature

A sustained elevation of Intra Cranial Pressure beyond 15 mm of Hg or higher is known as intracranial hypertension

Conditions that increase the brain volume like brain tumors, cerebral edema due to different reasons.

Conditions that increase blood volume like obstruction to venous outflow from brain, increased arterial blood supply to the brain as in infections and increase in the level of CO₂ in the arterial blood.

Conditions that increase the production of CSF like tumors of the choroid plexus, communicating hydrocephalus and subarachnoid hemorrhage.

Decreased Cerebral Blood Flow

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Decreased Cerebral Perfusion Pressure

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Increased CO₂

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Decreased O₂

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Increased acidosis

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Vasodilatation

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Increased Cerebral Blood Flow

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Increased Cerebral Blood Volume

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Increased Intra Cranial Pressure

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Impairment of auto regulation

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Cerebral herniation and death

Transient pressure signs include

Decreased level of consciousness: The person may become drowsy or not oriented to time, place or person.

Pupillary abnormalities: Normally pupils constrict briskly on flashing bright light. This response may be delayed or impaired in people with intracranial hypertension.

Visual disturbances, motor dysfunction, headache, vomiting, aphasia, changes in respiratory pattern and changes in vital signs are other signs.

This is a compensatory response of the body in an attempt to provide adequate cerebral perfusion pressure [(Mean arterial pressure (MAP) – Intracranial pressure (ICP)] in the presence of rising intra cranial pressure. It is indicated by a rising systolic pressure, a widening pulse pressure and bradycardia

Neurological assessment should be done frequently i.e., every 15 mins to 1 hr.

It includes assessment of the level of consciousness using Glasgow Coma Scale (GCS). GCS assesses the response of the patient to call, touch and painful stimulation in terms of eye opening, verbal response and motor response.

Pupillary size and reaction to direct light are assessed to detect the early signs of increasing intracranial pressure and its effect on the optic nerve.

Assessment of respiratory pattern, pulse and blood pressure are done on a regular basis.

Elevation of the head of the bed to 30⁰ will help in improving the venous drainage.

Hyperventilation (increasing the respiratory rate will help in reducing hypercapnoea and thereby reducing intracranial pressure.

Blood pressure is maintained above 90 mm of Hg and below 150 mm of Hg at all times to maintain an effective cerebral perfusion pressure.

CSF drained using a tube put into the cerebral ventricles (ventriculostomy) can be used as a temporary method to reduce intracranial pressure.

Drugs like Mannitol, corticosteroids and diuretics help in reducing intracranial pressure.

Fluid management aims at preventing hypotension and maintaining serum osmolality and electrolyte levels.

Hyperthermia should be treated aggressively because it can increase the cerebral blood flow and result in increased intracranial pressure.

Seizures should be prevented by giving anticonvulsants as it will increase intracranial pressure.