Craniotomy

Time: Highly variable
Pain: Moderate
Position: Variable, may be supine, head up, or lateral
Blood loss: Variable. G+H, consider cross-match.

Techniques

Under GA:

  • Volatile
    • Avoid N2O
    • Use < 1 MAC
  • TIVA
    May be preferred in cases with high ICP. One approach:
    • TCI propofol at 3-6ug/mL
    • Remifentanil 0.1-0.3ug/kg/min
      Reduces need for top-up muscle relaxation.

Considerations

  • A
    • Airway is not accessible intraoperatively, intubate and secure well
    • Use a reinforced tube
  • B
    • Coughing is not allowed
      Ensure adequate muscle relaxation (test regularly, consider use of muscle relaxant infusion) or use deep opioid anaesthesia (e.g. remifentanil infusion not less than 0.2ug/kg/min).
    • Ventilate to normal PaCO2 in most instances
      Avoid cerebral ischaemia.
  • C
    • Aim normotension during most procedures
  • E
    • Aim normothermia
      36°C-37°C.

Preparation

  • Standard monitoring
  • Arterial line
  • Core temperature monitoring
  • CVC
    • Administration of vasoactives
    • Aspiration of air in case of venous air embolism

Induction

Haemodynamic stability is important:

  • Remifentanil infusion usually adequate
    • Begin at 0.2-0.3ug/kg/min, and titrate to effect
      Can be bolused, but this ↑ risk of bradycardia and CVS instability.
    • Once adequately loaded (~1ug/kg), can then commence induction with propofol
  • Otherwise fentanyl (5ug/kg) or alfentanil (25-50ug/kg/hr)

Intraoperative

  • Anaesthesia can be maintained with either sub-MAC dose of volatile or propofol TIVA
  • Remifentanil allows for substantial reduction in anaesthetic requirement

Surgical Stages

Beware stimulating parts of this procedure and aim to maintain haemodynamic stability throughout:

  • Intubation
  • Application of clamps:
    • Associated with significant hypertension
    • Cover with bolus of 0.5-1ug/kg remifentanil or 0.5-1mg/kg propofol
  • Local anaesthetic with adrenaline
    Intravascular adrenaline will also cause CVS compromise.
  • Skin and skull incision
  • Once dura is opened, surgical stimulation drops markedly

Closure of dura:

  • Typically indicates ~30-45 minutes of operating time remaining
  • Administer a long-acting opioid when remifentanil infusion is ceased

Postoperative

  • May require additional IV opioid recovery
    Monitor carefully for ↓ GCS as this may be either anaesthetic or surgically related.

References