Head Injury Management: Application of physiological principles

Question 1

What is primary brain injury?

Answer 1

• Occurs at the moment of impact
• Pattern & extent of damage depends in nature of impact
• Not treatable

Question 2

What is secondary brain injury?

Answer 2

• Focus of medical intervention is to minimise secondary brain injury
• Optimise oxygenation
• Optimise cerebral perfusion
• Keep control of blood glucose
• Hypo / hypercapnia (CO2 manipulates cerebral perfusion)

Question 3

What secondary processes occur at the cell & molecular level to exacerbate neurological damage?

Answer 3

• Neurotransmitter release (glutamate)
• Free radical generation
• Calcium mediated damage
• Inflammatory response
• Mitochondrial dysfunction
• Early gene activation

Question 4

Describe the Monroe-Kellie doctrine.

Answer 4

A pressure-volume relationship (between ICP, volume of CSF, blood, and brain tissue, and cerebral perfusion pressure) that aims to keep a dynamic equilibrium among the essential non-compressible components inside the rigid compartment of the skull

SEE SLIDES

Question 5

What patients with head injury would get sent to the hospital?

Answer 5

• Extremes of age (< 5 years or >65 years)
• Amnesia for events before or after injury
• Any loss of consciousness
• High energy injury
• Vomiting
• Seizure (previous neurosurgery)
• Bleeding /clotting disorder

Question 6

Describe the Glasgow coma scale.

Answer 6

Eye Opening:
Score 1- Eyes open spontaneously
Score 3- Eyes open to speech
Score 2- Eyes open in response to pain
Score 1- Eyes do not open

Verbal response:
Score 5- Orientated
Score 4- Confused
Score 3- Inappropriate words
Score 2- Incomprehensible sounds
Score 1- No response despite verbal & physical stimuli

Motor response:
Score 6- Obeys commands
Score 5- Localises to central pain
Score 4- Normal flexion towards source of pain
Score 3- Abnormal flexion
Score 2- Extension to pain
Score 1- No response to painful stimuli

Degree of Head injury:
Minimal: 15 (no history of unconsciousness)
Mild: 13-15
Moderate: 9-12
Severe: 8 or less

Question 7

How do you calculate Cerebral perfusion pressure?

Answer 7

(Mean arterial pressure (MAP)) - (Intracranial pressure (ICP))

** Mean arterial pressure is diastolic pressure + (1/3 pulse pressure)

Question 8

Describe cerebral auto regulation.

Answer 8

• Normally autoregulation maintains a constant blood flow between MAP 50 mmHg and 150 mmHg.
• Traumatised or ischaemic brain, CBF may become blood pressure dependent.

Question 9

What should you to when managing severe head injury?

Answer 9

• Maintain CPP above 60 - 70mmHg
• Maintain systolic blood pressure higher than
  90mmHg (preferably higher than 120mmHg)
• ICP less than 20mmHg (invasive pressure monitor)

Question 10

What can peri-orbital signify?

Answer 10

Anterior cranial fossa fracture

Question 11

What can battle’s sign (bruising over mastoid process signify?

Answer 11

Petrous temporal bone fracture.

Question 12

Describe an extradural hematoma.

Answer 12

• Relatively uncommon
• Strongly associated with
  skull fracture
• Middle meningeal artery
• 1/3 due to venous bleeding
• Classically a lucid interval
• Good outcome if treated!

** SEE CT

Question 13

Describe a subdural hematoma.

Answer 13

• Common
• Complicates 20-30% of
  head injuries
• Rupture of the veins travelling from the brain surface to the saggital sinus
• Prognosis worse

** SEE CT

Question 14

Describe a subarachnoid haemorrhage.

Answer 14

• Associated with ruptured aneurysm
• More commonly caused by head injury

** SEE CT

Question 15

Describe an intracerebral haemorrhage.

Answer 15

• Stretching & shearing injury
• Impact on inside of skull
• Often contre coup injury

** SEE CT

Question 16

What are the clinical signs or herniation?

Answer 16

• Dilated or unreactive pupil(s) (compression of oculomotor nerve)
• Extensor posturing
• Decrease in GCS of 2 or more points