Raised Intacranial Pressure

Question 1

What is normal intra-cranial pressure?

Answer 1

Adult - 5-15mmHg
Children - 5-7mmHg
Tern infant - 1.5-6mmHg

Question 2

What os the monro-Kellie doctrine?

Answer 2

Any increase in the volume of one of the cranial constituents must be compensated by a decrease in the volume of another.

Question 3

How can too much blood cause raised ICP

Answer 3

Haemorrhage - most common. As the bridging veins shear and cause a bleed. (Subdural, Extra-dural, stroke)

Also:
Raised arterial pressure (‘malignant hypertension)
Raised venous pressure - SVC obstruction
BUT, both these things are rare.

Question 4

How does too much CSF cause raised ICP?

Answer 4

Hydrocephalus - congenital (obstruction to CSF outflow) or acquired (meningitis, trauma, hemorrage tumours)

Question 5

What can cause congenital hydrocephalus?

Answer 5

Congenital obstruction to CSF flow caused by:
Neural tube defects
Aqueductal stenosis

Communicating hydrocephalus:

• Increased CSF production
• Decreased CSF absorption

Question 6

How do you treat congenital hydrocephalus?

Answer 6

May be treated initially in babies by ‘tapping’ the fontanelle (inserting a needle to drain out CSF)

Question 7

What is an EVD used for? Why is it good / bad?

Answer 7

Allows:
Short-medium term drainage of CSF
Continuous pressure monitoring

Disadvantages:
Direct pathway for bacteria from skin into brain
Chamber must be kept at same height as ventricles
Not a good long term solution

Question 8

What are the perminant solution to treating excess CSF?

Answer 8

Ventricular shunts

Ventricular-peritoneal shunts:
Easier to place - more common
Prone to infection
Can kink, block or displace

Ventriculo-atrial shunt:
Less common as children grow as will need replacing.

Question 9

What is an omayya reservoir?

Answer 9

One way valve.
Measure pressure
Attach drain

Question 10

What are the four types of cerebral oedema?

Answer 10

Vasogenic - Breakdown of tight endothelial junctions at blood brain barrier. -Vasoactive, substance.

Cytotoxic - Intracellular retention of sodium and water - toxins.

Osmotic -High osmolality in brain compared to serum - SIADH excessive H2P intake

Interstitial - Rupture of BBB - CSF spreads to interstitial spaces - Hydrocephalus Trauma

Question 11

What else could cause raised ICP?

Answer 11

Tumour

Abscess

Question 12

What is cerebral pressure qual to?

Answer 12

CPP = MAP - ICP

Question 13

What are the three parts of cushing’s triad?

Answer 13

Increased MAP
Bradycardia
Irregular breathing

If these things happen then it means that there is imminent herniation of cerebellar tonsils throughout the brainstem.

Question 14

What are the different types of herniation?

Answer 14

Tonsillar herniation

Sub-falcine herniation

Uncal herniation

Central downward herniation

External herniation through an open skull fracture

Question 15

What are the early signs of RICP?

Answer 15

Headache - present on walking, worse on bending coughing. Constant

Nausea and vomiting

Difficulty concentrating or drowsiness

Confusion - subtle, difficult with daily activities

Double vision - difficultly accommodating, worsening eyesight, visual field defects, papilloedema

Focal neurological signs - cerebral cortex, cerebellum, brainstem

Seizures - may be blackouts, collateral history important

Question 16

What is idiopathic intercranial hypertension?

Answer 16

Benign inter cranial hypertension.

Usually obese middle ages females.

Aetiology not well understood.

Improves with weight loss and blood pressure control

Question 17

How do you monitor ICP?

Answer 17

ITU

Continuous ICP waveform

Allows you too see changes in ICP before Cushing’s reflex escalates.

Question 18

How do you protect the brain?

Answer 18

Airway control and ventilation - ensures optimal oxygenation and ventilation

Circulatory support - maintains a MAP to allow adequate CPP

Sedation, analgesia and paralysis - Decrease cerebral metabolic demand. Prevents cough, shivering, posturing

Head up (15-30) position - Improves cerebral venous drainage. Take off C-Spine collar

Temperature - Avoid high temperature as increases metabolic demand. Some units advocate cooling

Anticonvulsants - Prevents seizures, reduce metabolic demand

Nutrition and PPI - Improved heading of injuries. Prevention of Cushing’s ulcer

Question 19

How do you treat ICP?

Answer 19

Mannitol - 3% hypertonic saline.

External ventricular drain

Or, Decompressive Craniectomy