18 Nov

Traumatic brain injury

Traumatic brain injury

Important anatomy and physiology

Skull: Houses the brain and brainstem. Consist of the frontal, temporal, parietal and occipitalBase of the skull comprises of anterior, middle and posterior cranial fossa.

Meninges: a soft covering between the skull and brain. Consist of three layers; dura mater, arachnoid membrane and pia mater. CSF circulates between these layers.

Brain

Cerebrum: major portion of the brain. Controls the cognitive, motor and sensory

Cerebellum: located at the lower part of brain. Controls motor coordination

Brainstem: lowest portion of the brain and connected to the spinal cord. Controls alertness and cardiorespiratory centres.

The Monroe-Kellie doctrine

The skull is a rigid box hence the total volume of the intracranial contents must remain constant. An increase in one component should cause a decrease in one or both remaining component (Brain, CSF and blood volume).

However, due to the rigid skull, an increase in pressure would eventually lead to devastating effects such as herniation.

Cerebral perfusion pressure (CPP)

Cerebral perfusion pressure (CPP) = Mean arterial pressure (MAP) – ICP

CPP should always remain constant due to the autoregulation of brain. Any changes could lead to hypoxia and death. Any traumatic brain injury may disrupt this autoregulatory mechanism and cause problems.

 

TBI can be categorised into:

Mild: GCS of 13 to 15

  • Most common injury with brief history of loss of consciousness.
  • Good prognosis

Moderate: GCS of 9 to 12

  • Appear confused with or without neurological deficit.
  • May progress to severe TBI

Severe: GCS ≤ 8

  • May need early intubation due to inability to maintain the airway.
  • Accepted definition of coma
  • Even with treatment, patients may have disabilities

Evaluation of patient with TBI

History and examination

  • Mechanism on injury: road traffic accident, penetrating, etc
  • Loss of consciousness
  • Persistent vomiting
  • Severe headache
  • Low GCS
  • Unequal pupils
  • Otorrhea
  • Rhinorrhea
  • Battle’s signs
  • Raccoon’s eye

Early detection and treatment are needed to prevent secondary brain injury.

ABCDE

Airway (A) and cervical spine protection

Airway patency is usually compromised in GCS less than 8. However, the physician should be prepared for early intubation if any evidence of respiratory difficulty.

An unconscious patient should always be suspected to have any spine injury until proven otherwise.

Breathing (B)

Always identify any life-threatening condition which might compromise ventilation and cause hypoxia. Normal ventilation is also needed in cerebral resuscitation.

Circulation (C)

Intravascular volume and blood pressure should be maintained to ensure adequate cerebral perfusion.

Disability (D)

Monitoring of the GCS and identify any changes. Always document the observe GCS during examination including a tubed patient. (e.g. E1 VT M2)

Medication

Depending on the injury and severity of the condition, common medication used in a TBI patient include:

  • Analgesia
  • Sedation
  • Muscle relaxant

Investigations

Routine blood investigation such as full blood counts, renal and liver function. Other important tests are serum sodium and osmolality to rule out SIADH which is common in TBI patients.

Imaging

CT brain and cervical is indicated in any TBI patient to confirm the injury. A CTA of the neck is also needed in cases of equivocal symptoms and signs in unconscious patients.

Treatment

The choice of therapy depends on the trauma sustained and severity of the patient.

  • Subdural bleeding: Craniectomy
  • Extradural bleeding: Craniotomy or Burr hole
  • Subarachnoid haemorrhage: cerebral resuscitation

Cerebral resuscitation technique and management

Initial therapy
  • Head elevated
  • Loosen collar
  • Optimize ventilation
  • Optimize electrolyte imbalance, treat hyperglycaemia
  • sedation
  • Seizure control (if indicated)
Progression of condition
  • Mannitol/furosemide/hyperventilation as temporary measures
  • Sedation
  • Paralytic agent
  • CSF drainage and monitoring via EVD
  • Maintain normothermia
Deterioration of condition
  • Use of barbiturate coma
  • Decompressive craniectomy or craniotomy

Key parameters to maintain in traumatic brain injury

  • PCO2= 28-30 mmHg
  • PO2 > 60 mmHg
  • MAP = 80-90 mmHg
  • ICP <20 mmHg
  • CPP >60 -70 mmHg
  • Na+ > 140mmol/l
  • K+ > 4mmol/L

Read here for first aid tips

Leave a Reply