Pathophysiology Of Raised Intracranial Pressure Flashcards

1
Q

Intracranial pressure range in adults

A

5-15mmHg

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2
Q

Intracranial pressure range in children

A

5-7mmHg

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3
Q

Intracranial pressure range in term infants

A

1.5-6mmHg

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4
Q

What is intracranial pressure determined by?

A

Volume of blood
CSF
Brain

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5
Q

What is Monro-Kellie doctrine hypothesis?

A

Any increase in the volume of one of the intracranial constitutes must be compensated by a decrease in the volume of one of the others

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6
Q

What are the first components to be pushed out of the intracranial space when there is an intracranial mass?

A

CSF
Venous blood

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7
Q

Cerebral perfusion pressure calculation

A

CPP = mean arterial pressure - ICP

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8
Q

What can cause raised ICP?

A

Too much CSF, blood or brain

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9
Q

What is hydrocephalus?

A

Build up of CSF within the brain

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10
Q

Management of hydrocephalus

A
  • acutely by tapping fontanelle with needle
  • medium term drainage by external ventricular drain
  • long term by ventricular shunts: tube between ventricular system + peritoneum or right atrium
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11
Q

Clinical signs of hydrocephalus

A
  • bulging head with head circumference increasing faster than expected
  • sunsetting eyes
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12
Q

Acquired causes of hydrocephalus

A
  • meningitis
  • trauma
  • haemorrhage e.g. post subarachnoid haemorrhage
  • tumours e.g. compressing cerebral aqueduct
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13
Q

What is cerebral blood flow dependent on?
When can it not be maintained?

A

Cerebral perfusion pressure
If CPP <50mmHg

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14
Q

Outline cerebral auto regulation in regards to mean arterial pressure + ICP

A
  • if MAP increases > CPP increases > triggers cerebral autoregulation > vasoconstriction of cerebral arterioles
  • if ICP increases > CPP decreases > triggers cerebral auto regulation > vasodilation of cerebral arterioles
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15
Q

Outline Cushing’s triad/response/reflex

A
  • rise in ICP > hypertension as body increases MAP to maintain CPP
  • increase in MAP > detected by baroreceptors > bradycardia via increased vagal stimulation
  • continuing compression of brain steam leads to damage to respiratory centres > irregular breathing
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16
Q

Four major pathophysiologies of cerebral oedema

A
  • vasogenic
  • cytotoxic
  • osmotic
  • interstitial
    ***
17
Q

Clinical features of raised ICP

A
  • constant headache which worsens on bending/straining + in morning
  • N + V
  • double vision
  • visual field defects
  • papilloedema
  • seizures
  • reducing GCS - confusion, drowsiness, unconscious
  • focal neurological signs
18
Q

Epidemiology idiopathic intracranial hypertension

A

obese middle aged females

19
Q

Diagnosis of idiopathic intracranial hypertension

A

Confirmed by raised opening pressure on lumbar puncture

20
Q

Treatment of idiopathic intracranial hypertension

A

Weight loss
Blood pressure control

21
Q

Types of brain herniation

A
  • tonsillar herniation (coning)
  • uncl herniation
  • subfalcine hernation
  • central downward herniation
  • external herniation
22
Q

Outline tonsillar herniation (coning)

A

Cerebellar tonsils herniate through foramen magnum > compression of medulla

23
Q

Outline subfalcine herniation

A

Cingulate gyrus herniates under free edge of Falx cerebri > compression of anterior cerebral artery as it loops over corpus callosum

24
Q

What is vulnerable in a subfalcine herniation?

A

Anteior cerebral artery as it loops over corpus callosum

25
Q

Outline uncl herniation

A
  • Uncus of temporal lobe herniates through tentorial notch > compresses adjacent midbrain
  • can cause oculomotor nerve palsy + blown pupil
  • can cause contralateral hemiparesis due to compression of cerebral peduncle
26
Q

Outline central downward herniation

A

Medial temporal lobe + other midline structures pushed down through tentorial notch

27
Q

Outline external herniation

A

Brain herniation through skull fracture or therapeutic craniectomy

28
Q

What is Cushing’s triad?

A

Hypertension
Bradycardia
Irregular breathing

29
Q

Management of a patient with acutely raised ICP

A
  • maintain O2 + remove CO2
  • maintain MAP > maintains CPP
  • sedation, analgesia + paralysis: decreases metabolic demand + prevents coughing + shivering that might increase ICP more
  • elevate head of bed 10-15°: maximises cerebral venous return
  • prevent hyperthermia
  • anticonvulsants
30
Q

Ongoing management of raised ICP

A
  • osmotic diuresis: e.g. mannitol or hypertonic saline
  • regular re-evaluation + monitoring
  • surgical intervention: evacuation of haemorrhage, ventricular drainage, evacuation of haemorrhage
31
Q

Examples of surgical intervention of raised ICP

A
  • evacuation of haemorrhage
  • ventricular drainage
  • decompressive craniectomy
32
Q

Generally what is classed as high ICP?

A

> 20mmHg

33
Q

If a patient has hypertension + raised ICP, why should you not attempt to lower it?

A

May be directly driving perfusion to ischaemic areas of brain

34
Q

Why can hydrocephalus cause sunsetting eyes?

A

Direct compression of orbits + oculomotor nerve as i exits midbrain