Raised intracranial pressure

Raised intracranial pressure
Cerebral blood flow
Brain edema
Dr. Sameer H. Aboud
The Intracranial Cavity
The contents of the
intracranial cavity
1: The brain about 1400 ml.
2: The blood 75-100 ml.
3: The CSF 75-100 ml.
All these three compartments are essentially
non compressible, and any change in the
volume of the brain, causes a reciprocal change
in the volume of one or both of the other two
compartments. This is called the Monro-Kellie
Obstruction to the flow of CSF at any point,
results in dilatation of the venticular system
proximal to the obstruction with profound
effect on intracranial pressure.
Indications for Access
& contraindications
1. CSF analysis: Bacteriological, Immunological , Cytology,
2. Measuring CSF pressure in cases of pseudotumor cerebri, and
normal pressure hydrocephalus.
3. The administration of antimicrobial and antineoplastic agents
normally excluded by the BBB.
4. Therapeutic CSF drainage. in cases of CSF fistula, pseudotumor
cerebri or communicating hydrocephalus.
Methods of access
1. Lumbar puncture
2. Cisternal puncture.
3. Ventricular puncture.
* Local inf.
* ^ICP. Due to SOL
* Blood dyscrasias.
Anticoaggualnt therapy.
BV= 75 ml
CBF: 50ml/100gm/min
Cerebral Autoregulation
Brain Volume
An increase in brain volume is produced either by a:
Edema: increase in brain water.
1. Vasogenic edema: extra cellular, disturbance of BBB.
localized around tumors, abscesses, hemorrhages and
localized cerebral contusions. It may lead to herniation.
2. Cytotoxic edema: intracellular, hypoxia (cardiac arrest),
Intoxication, sever hypothermia. It is usually generalized.
3. Osmotic edema: ECF, Abnormal ADH sec. Sever
hemodialysis, or excessive ingestion of water (Hysterical).
4. Hydrostatic Edema: ECF due to acute hypertension.
Elastance and Compliance
Compliance: Is that quality of distensibility available
within the intracranial contents, which enable them to
adapt to an expanding IC lesion.
Elastance: Is the resistance offered by the intracranial
contents to the expansion of an intracranial mass. It is
the inverse of compliance
Compliance is decreased by increased by:
1. Hypercarbia.
2. Hypoxia.
Hyperoxia (PaO2 >1000 mm Hg)
3. Sleep.
4. Anesthesia.
Intracranial pressure
Normal I.C.P. this is 50-200 mm. water (10 mm Hg.) it is pulsatile
owing mainly to I.C. arterial pulsation. It also shows fluctuations
reflecting the respiratory and cardiac cycles.
1. L.P: with the patient on his side, the L.P. needle is connected to
a manometer. This method is not accurate, can not be used for
monitoring and can be dangerous.
2. Ventricular cannulation: It is more accurate, can be used for long
periods, but may be complicated by infection.
3. Subdural sensor { These are the safest and most reliable, and
4. Extradural sensor{ and are usually used for monitoring.
Effects of increased ICP
A: Effects on vital signs:
These appear to be due to compression and distortion of the
brain stem. These effects are noticed in patients with critically
raised intracranial pressure, and in experimental animals.
1. Decrease in respiratory rate.
2. Bradycardia.
3. Cardiac arrhythmias.
4. Pupillary constriction, followed by unilateral pupillary dilatation
5. Increase in pulse pressure.
6. Increase in arterial blood pressure.
Effects of increased ICP
B: Effect on cerebral blood flow:
CBF = -------------------CVR
When ICP increases, cerebral blood flow remains constant by
auto regulation. the efficiency of this compensation depends on
the rate of expansion of the lesion, it's nature and site. And
also on the compliance of the intracranial contents.
CBF is increased in response to raised ICP, by cerebral
vasodilatation, However this causes increase in cerebral blood
volume and produces further brain swelling. When maximal
vasodilatation occurs, further increase in ICP causes
reduction in cerebral BF.
Effects of increased ICP
C: Clinical effects (symptoms and signs): Significant
raised intracranial pressure can be present with out
symptoms or signs.
1. Headache: Is typically maximal in the morning and is
relieved by vomiting. It is caused by distortion, stretching or
invasion of pain sensitive structures such as the bridging
veins, basal and meningeal arteries.
2. Vomiting: Usually associates headache and typically
occurs with out nausea.
3. Papilledema: This is the most reliable sign of raised ICP.
It's main features are:
Effects of increased ICP
D :Internal Brain herniation: resulting in strangulation, compression of
vital structures and blood vessels.
1. Cingulate herniation: compress the internal cerebral vein and the anterior
cerebral artery.
2. Central transtentorial herniation:
* Compression of the 3rd. nerve -------------> Dilated pupils .
* Compression of the post. cerebral art. ----> Hemianopia. Total blindness.
* Compression or ischemia of the brain stem.-> Decerebration. Coma.
* Distortion of the brain stem --------------> Hemorrhages.
3. Uncal herniation. compression of the mid-brain, 3rd nerve and the post.
cerebral art.
4. Tonsilar herniation: Occurs when the cerebellar tonsils,
herniate through the foramen magnum, resulting in compression of
medulla, Decerebration, coma, cardiovascular and respiratory
abnormalities (apnea).
1.Cingulate herniation
2.Central transtentorial
3.Uncal herniation
4.Tonsilar herniation
Medical Treatment of
raised intra cranial pressure.
1. Sedation, and positioning:
2. Hypertonic solutions:
* Manitol: 0.5- 1gm/ Kg body wt. over 30 min. bolus injection.
* Furosemide: is effective in reducing brain edema, and reducing CSF
40-120 mg daily.
* Glycerol: can be given orally as well as I.V. 0.5-2 gm/ Kg. every 4 hrs.
3. Steroids: Dexamethasone 4mg four times a day.
4. Hyperventilation:
5. Hyperbaric oxygen: (rarely used).
6. Hypothermia:
7. Induced barbiturate coma: Has been used to reduce intracranial pressure in
head injuries, and to increase brain tolerance to focal ischemia in aneurysm
surgery , strokes and SAH.

similar documents