Modern
thinking about ICP:
George Kellie & Alexander Monro, Worked in Edinburgh, Beginning of 19th century.
Monro-Kellie hypothesis
1. Sum of intra cranial volumes of blood, brain, CSF, & other components (tumour, haematoma) is constant, and that an increase in any one of these must be offset by an equal decrease in another, or else pressure will rise.
2. These volumes are contained in an inelastic, completely closed skull.
3. Pressure is distributed evenly through out intracranial compartment
Monitoring
of ICP:
1911- Quinke described LP of relief of 'Brain pressure'.
1951- Guillaume & Janny measured ICP continuously.
1960- Lundberg A described ICP waves.
Physiology of ICP:
a) Calvarium is non distensible.
b) Brain is 1400ml.
c) Blood-75ml.
d) CSF- 75ml.
e) Normal range- 0-10mmhg.
f) Upper limit-15mmhg.
CPP:
Cerebral perfusion pressure = mean arterial pressure-Intracranial pressure (CPP = MAP-ICP).
Pathology:
a) Brain herniation.
b) Decrease in CBF.
c) increase in CPP.
d) Arterial hypertension.
e) Bradycardia.
f) Respiratory changes.
g) Neurogenic pulmonary oedema.
Mechanism:
a) MASSES- haematoma, abscess, tumours.
b) CSF - hydrocephalus.
c) CEREBRAL OEDEMA - vasogenic, cytotoxic, hydrostatic, hyposmolar, interstitial.
Brain herniation due to mass effect-causes:
a) Head injury.
b) Cerebrovascular.
c) Hydrocephalus.
d) Craniocerebral disproportion.
e) Benign ICP.
f) Metabolic.
g) Status epilepticus.
Symptoms:
a) Headache.
b) Vomiting.
c) Blurring vision, diplopia.
d) Drowsiness.
e) Loss of higher intellectual functions.
Signs:
1. Papilloedema
2. 6th n palsy.
3. Loss of higher intellectual function.
4. Localising neurological deficits.
Investigations in raised ICP:
a) X-rays.
b) CT scan.
c) MRI.
d) Cerebral Angiogram.
e) LP.
f) EEG.
Investigations - X-rays:
Children- sutural separation, silver beaten appearance.
Adults- Thinning of anterior wall of sella, sellar floor, dorsum sella, clinoids, Increased vascular marking.
Investigation - CT Scan:
a) Study of choice.
b) Readily available.
c) Takes less than 10 mins.
d) Non - invasive.
e) Life supporting equipment compatible.
f) Good for parenchymal & bony pathology-Tumor, Congenital ,Infection- cerebral abscess.
Investigation - MRI:
1a) Visualization of soft tissue better, Posterior fosse better visualized, Takes longer
time, Costlier, not compatible with serious patients.
Investigation - Angio:
Invasive, only for vascular pathology.
Investigation - LP:
a) Rules out infections.
b) CSF manometry.
c) Subarachnoid hemorrhage.
Treatment - Principles:
a) Decrease the ICP.
b) Adequate CPP.
c) Manage systemic BP.
d) Prevent ischemia.
e) Reverse the brain shift.
Decrease ICP.
Mannitol, Steroids, Diuretics, hyperventilation, Head position, CSF drainage, Decompression/lesion removal.
Hypertonic solutions:
a. Osmolality of brain ,CSF and blood is 275- 300 m osmol /lt.
b. Osmotic diuretic should not easily cross blood brain barrier.
c. Defective BBB limits usefulness.
d. Osmotic gradient should build up between plasma and brain to drain fluid from brain.
e. CSF production is reduced.
Rebound phenomenon:
a) Gradients between brain and plasma reduces after some time.
b) Active solute enters the brain cells.
c) Draws water into the cell.
d) Reaches equilibrium in CSF.
e) Disappearance from CSF is slower than in blood.
f) So fluid accumulation occurs in brain.
Mannitol:
a) Wise and Chater first reported the use of mannitol in ICP in 1962.
b) Rebound is less frequent.
c) I gram/kg BW is given in 10 minutes.
d) Raise in s osmolality occurs of 20 to 30 m osmol/lt.
e) Sustains for 3 hrs.
f) Reduces brain volume.
g) Increases cardiac output.
i) Increases CPP.
j) Decreases blood viscosity.
k) Decreases RBC size.
l) Dose- 1 gm/ kg BW.
Steroids:
a) Introduced to neurosurgery in 1960.
b) CSF production reduced by 43%.
c) Normal permeability restored in endothelial cells.
d) Neuronal membrane stabilization.
e) Inhibition of edema producing polyunsaturated fatty acids and suppression of lyosomal activity.
f) Facilitates bulk flow reabsorption through ventricular system.
g) CSF circulation improved where the cause is due to inflammation of subarachnoid region and a.villi.
h) Restores blood brain barrier.
i) Tumor growth inhibition - gliomas and metastatic tumours.
j) Cerebro- protective.
k) Dosage 4mg qid- 20 times more than endogenous production.
Diuretics:
a) Furasamide (lasix).
b) Acetazolamide (diamox).
Hypothermia:
a) Temp- 27 to 32 0c.
b) Reduces metabolism.
c) Cerebroprotective.
d) Reduces ICP.
e) Below 27 degrees has deleterious effect on heart and electrolyte imbalance.
Artificial ventilation:
a) Control ICP and pulmonary support.
b) Pco2 (30- 35 mm hg).
c) Avoid- over ventilation.
d) excessive rate.
e) excessive TV.
f) Avoid high peep.
Head position:
Head elevation 300 (traditional).
a) Causes ischemia.
b) Decreases CPP.
c) Increases ischemia.
Best position:
a) Avoiding jugular compression.
b) Supine with head at the level of the heart.
Adequate CPP:
a) CPP = mean AP - ICP.
b) Decrease ICP.
c) Increase systemic BP.
d) Normal range is 50- 60 mmhg.
Prevention of ischemia:
a) PCV 30-35%.
b) Cerebro-protective agents.
c) Maintain systemic BP.
d) Avoid over hydration.
e) Substitute blood and colloids.
Cerebral protection:
O2, Carotenoids, Barbiturates, Etomidate, Calcium channel blockers, Vit
C, Vit E, Phenytoin, Glutamate, receptor antagonists, Sendai cocktail.
Brain shift:
a) Reduction of the mass effect.
b) Treating the hydrocephalus.
c) Removing the CSF obstruction.
d) Decompression.
e) Debridement.
f) Ventriculo-peritonial shunt.
g) Decompression and evacuation.
h) Surgical decompression.
i) Relieving a hydrocephalus.
Principles of surgery:
a) Care of already compromised brain.
b) Avoid surgical trauma & retraction.
c) Less operative time.
d) Good anesthesia.
e) Microscope.
f) Bipolar.
Neuro anesthesia:
a) Smooth induction.
b) Good relaxation.
c) Avoid raise of ICP.
d) Good BP control( prevents bleeding).
e) Smooth and rapid recovery.
Microscope:
a) Better illumination.
b) Magnification.
c) Active participation by assistant.
d) Video recording, less cerebral trauma, less morbidity.
Summary of management- CSF volume:
a) Furosemide.
b) Acetazolamide.
c) Steroids.
d) External ventricular drainage.
e) Internal drainage (shunts).
Summary of management- blood volume:
a) Hyperventilation.
b) Head elevation.
c) Barbiturates.
Summary of management- brain volume:
a) Cerebral perfusion pressure management.
b) Lund protocol.
c) Antihypertensives.
d) Fluid resuscitation.
e) Cortisteroids.
f) Barbiturates.
g) Osmotic agents.
h) Diuretics.
i) Hypothermia.
Summary of management- surgical:
a) Surgical evacuation.
b) Surgical decompression.
Points to remember:
a) Raised ICP can be caused by medical & surgical causes.
b) Early reorganisation & early intervention gives better results.
c) C T scan is investigation of choice.
d) Maintenance of CPP is crux of the treatment.
e) Microscope reduces the PO mortality & morbidity when surgery is required.
f) Attending GP holds the key to early recognisation.
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