FRCA Notes

Traumatic Brain Injury

The curriculum calls for understanding of the 'anaesthesia for emergency surgery for traumatic brain injury' and 'the neurocritical care management of traumatic brain injury'.

The February 2024 CRQ on this topic was 'reassuringly well answered', although the examiners expected more knowledge on indications for CT heads and causes of raised JVO2.

Resources

  • TBI is the leading cause of disability and death in young adults in the developed world

  • Classified according to GCS after resuscitation
    • Mild: GCS 13 - 15
    • Moderate: GCS 9 - 13
    • Severe: GCS ≤8
  • Up to 80% occur in male patients
  • Incidence 1.4million/year
  • Mortality 6 - 10/100,000/yr

  • Minor head injuries (89%):
    • Falls (22 - 43%)
    • Assault (30 - 50%)
    • RTCs (25%)

  • Moderate-severe head injuries (11%) are mostly from RTCs

Primary injury

  • Primary injury occurs as a direct consequence of the physical insult

  • Compression and shearing forces cause:
    • Bony fractures
    • Brain parenchyma contusion, haemorrhage, oedema
    • Diffuse brain injury

  • Microscopically there is:
    • Neuronal cell wall disruption and BBB disruption
    • Increasing membrane permeability and disrupted ionic homeostasis

Secondary injury

  • Neurological injury progresses over the ensuing days
  • Inflammatory and neurotoxic processes cause vasogenic fluid accumulation, leading to:
    • Cerebral oedema & hyperaemia → raised ICP
    • Disruption of the BBB
    • Hypoperfusion & impaired cerebral autoregulation
    • Cerebral ischaemia (focal & general)
    • Release of excitatory neurotransmitters e.g. glutamate, aspartate
    • Release of high levels of oxygen free radicals
    • Cell death and apoptosis

  • Secondary injury is exacerbated by other physiological insults e.g. hypoxia, hypo/hypercapnoea, hypotension and hypo/hyperglycaemia

Pre-hospital care

    • Standard trauma care
    • Aim to treat:
      • Hypoxia; correlates with worse outcome
      • Hypotension; single episodes are associated with increased morbidity and mortality, while the frequency and duration of hypotension correlates with mortality

Initial management

System Targets
Airway I&V (see below)
Respiratory Saturations >97%
PO2 >10-13kPa
PCO2 4.5 - 5.0kPa (ETCO2 4.0 - 4.5kPa)
Cardiovascular MAP >90mmHg
Manage haemorrhage (commonest cause of hypotension)
Reverse anticoagulants
Avoid albumin (SAFE trial: ↑ mortality)
Neurological Maintain CPP >60mmHg
Maintain ICP <20mmHg
Treat seizures
Sedation and analgesia
Metabolic Na+ 145 - 155mmol/L
Glucose 6 - 10mmol/L
Avoid hyperthermia

Imaging


NICE criteria for CT scanning in head injury
GCS <13 on initial assessment
GCS <15 at two hours post-injury on assessment
Suspected open or depressed skull fracture
Any sign of basal skull fracture (hemotympanum, CSF otorrhoea/rhinorrhoea, Battle's sign, panda eyes)
Post-traumatic seizure
Focal neurological deficit
>1 episode of vomiting since head injury
LOC or amnesia + >65yrs, dangerous mechanism, >30mins retrograde amnesia or clotting/bleeding disorder
  • Trauma CT including brain and C-spine
  • MRI is logistically complex, takes longer and are rarely used in the acutely unwell
  • Skull X-rays are only used as part of a skeletal survey in a child with NAI

Transfer

  • Initial resuscitation and stabilisation should be completed before transfer
  • Time-critical transfer to neurosurgical centre

  • I&V is the gold standard for airway management
  • Patients are at higher risk from:
    • Existing hypoxia
    • Intra-cranial hypertension
    • Full stomach
    • Coalescing injuries:
      • C-spine instability
      • Maxillofacial trauma

  • Indications for invasive ventilation:

    • System Indication
    Airway Loss of airway protective reflexes
    Facial trauma inc. bilateral mandible fracture, skull base fracture
    Respiratory Respiratory failure: hypoxaemia or hypercarbia
    Spontaneous hyperventilation causing PCO2 <4kPa
    Neurological Low GCS: ≤8
    Deteriorating GCS: motor score decrease >2 points
    Seizures

Process

  • Full AAGBI monitoring
  • Use of emergency intubation checklist
  • Modified RSI
  • Maintain C-spine control with MILS
  • Opioids to obtund hypertensive response to laryngoscopy
  • Propofol (or ketamine) + rocuronium

  • The ongoing ICU management one can instigate for raised ICP in TBI can be stratified into three tiers

Tier 1

  • Head up 30°
  • Sedation and analgesia
  • Neuromuscular blockade
  • EVD insertion and vent CSF
  • Mild hyperventilation to PCO2 4-4.5kPa

Tier 2

  • Osmotherapies

Tier 3

  • Aggressive hyperventilation
  • Therapeutic hypothermia

  • Barbiturate coma
  • Decompressive craniectomy

Other management

  • VTE prophylaxis
  • Adequate nutrition