Raised Intacranial Pressure Flashcards
What is normal intra-cranial pressure?
Adult - 5-15mmHg
Children - 5-7mmHg
Tern infant - 1.5-6mmHg
What os the monro-Kellie doctrine?
Any increase in the volume of one of the cranial constituents must be compensated by a decrease in the volume of another.
How can too much blood cause raised ICP
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.
How does too much CSF cause raised ICP?
Hydrocephalus - congenital (obstruction to CSF outflow) or acquired (meningitis, trauma, hemorrage tumours)
What can cause congenital hydrocephalus?
Congenital obstruction to CSF flow caused by:
Neural tube defects
Aqueductal stenosis
Communicating hydrocephalus:
- Increased CSF production
- Decreased CSF absorption
How do you treat congenital hydrocephalus?
May be treated initially in babies by ‘tapping’ the fontanelle (inserting a needle to drain out CSF)
What is an EVD used for? Why is it good / bad?
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
What are the perminant solution to treating excess CSF?
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.
What is an omayya reservoir?
One way valve.
Measure pressure
Attach drain
What are the four types of cerebral oedema?
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
What else could cause raised ICP?
Tumour
Abscess
What is cerebral pressure qual to?
CPP = MAP - ICP
What are the three parts of cushing’s triad?
Increased MAP
Bradycardia
Irregular breathing
If these things happen then it means that there is imminent herniation of cerebellar tonsils throughout the brainstem.
What are the different types of herniation?
Tonsillar herniation
Sub-falcine herniation
Uncal herniation
Central downward herniation
External herniation through an open skull fracture
What are the early signs of RICP?
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
What is idiopathic intercranial hypertension?
Benign inter cranial hypertension.
Usually obese middle ages females.
Aetiology not well understood.
Improves with weight loss and blood pressure control
How do you monitor ICP?
ITU
Continuous ICP waveform
Allows you too see changes in ICP before Cushing’s reflex escalates.
How do you protect the brain?
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
How do you treat ICP?
Mannitol - 3% hypertonic saline.
External ventricular drain
Or, Decompressive Craniectomy
