Mediastinal Mass

Airway: ETT; aim distal to obstruction
Access: Multiple large IV, consider lower limb if SVC involvement
Pain: Variable
Position: Semi-erect, supine, or prone in extremis
Time: Variable
Blood loss: Risk of major haemorrhage with mediastinoscopy
Special: Complex induction, and management of airway, respiration, and circulation

Mediastinal masses include aneurysms, tumours, and cysts that:

• Occur in the anterior, posterior, middle, or superior mediastinum
  Anterior masses are most likely to cause severe cardiorespiratory problems due to:
  • Proximity to vascular/airway structures
  • Exacerbation of compression in the supine position
• Cause significant physiological upset via compression of:
  • Tracheobronchial tree
  • Main PA
  • SVC

Considerations

• Degree of compression may worsen as the mass shifts, which may occur with:
  • Induction of anaesthesia
  • Loss of spontaneous ventilation
  • Muscle relaxation
  • Supine positioning Life-threatening complications may occur in absence of symptoms in children

Anaesthetic considerations:

• Team
  • Surgeon available
    
    • With rigid bronchoscope
    • To perform emergent sternotomy and relieve compression of mass.
• A
  • Mass effect on airway
    
  • Airway device(s)
    Aim to intubate distal to obstruction, which may be endobronchial.
    • Long ETT
    • Reinforced ETT
    • MLT
    • Jet ventilation
    • LMA
      Permit spontaneous ventilation and bronchoscopy.
• B
  • Mass effect on lungs
    
    • Reduced lung volume
    • Bronchial muscle relaxation
      Occurs under GA, and ↑ airway compressibility.
  • Ventilation strategy
    • Maintenance of spontaneous ventilation
      Desirable to minimise adverse cardiac effects.
    • Positive pressure ventilation
      Ideally commenced gradually, with progressive taking-over of spontaneous ventilation.
• C
  • Mass effect on heart and great vessels
    Evaluate:
    • Size
    • Location
      Relation to vascular tree/airway.
    • Compression
      • SVC obstruction
        
        • ↑ venous pressures and bleeding
        • IV access preferentially in lower limbs
      • PA
        • RV dysfunction
        • Cardiac arrest
  • Invasive pressure monitoring
• D
  • Anaesthetic technique
    See below.
• E
  • Positioning
    • Induction may have to occur in semi-erect or sitting position
    • Post-induction position may need to be changed; consider:
      • Prone
      • Lateral
      • Semi-erect
  • Avoid muscle relaxation
    To maintain spontaneous ventilation.

Preparation

• Presence of symptoms indicates elevated risk
• Especially concerning if worse when supine

Evaluate patient:

• Clinical manifestations:
  • Airway compression
    • Dyspnoea
    • Stridor
    • Wheeze
    • ↓ breath sounds
  • SVC syndrome
    • Dyspnoea
    • Headache
    • Visual disturbance
    • Altered mentation
    • Distended neck veins
  • Pericardial effusion
• Review investigations:
  • CT chest
    Most useful scan to evaluate size, location, and severity of compression.
  • Flow-volume loops
    May demonstrate intrathoracic obstruction, but are unreliable as a diagnostic test.

Prepare:

• Standard ANZCA monitoring
• Multiple IVs
  Consider in lower limb if SVC is involved.
• Arterial line
  Either arterial line or pulse oximeter in right arm for mediastinoscopy, to identify intraoperative compression of the innominate artery.
• NIBP
  On left arm if arterial line is in right side, to monitor systemic perfusion pressures.

Induction

• Asymptomatic patients can develop life-threatening obstruction at induction and during maintenance

Anaesthetic technique:

• Depends on pre-operative risk assessment
  High risk features include:
  • Orthopnoea
  • Cough when supine
  • Syncope
  • SVC syndrome
  • Pericardial effusion
  • Tracheal compression <50% of CSA
• For low-risk patients
  • Standard IV induction +/- muscle relaxation appropriate
• For intermediate-risk patients
  Maintain spontaneous ventilation and avoid muscle relaxation:
  • Semi-erect patient
  • Induction
    May be:
    • IV induction
      Small boluses of propofol/ketamine, or dexmedetomidine.
    • Inhalational
      • May precipitate airway obstruction
      • Difficult to abandon
      • Partial obstruction may lead to very negative intrathoracic pressures
  • Once GA instituted:
    • Stepwise ↑ in support as tolerated and required:
      • Intubation
        
      • Lay supine
      • Transition to IPPV
      • Muscle relaxation
  • If failure at any stage:
    • Revert to previous stage
    • Intubate distal to obstruction over FOB
    • Rigid bronchoscopy
    • Change position
      
      • Semi-erect
      • Prone
    • If the above fail:
      • CBP/ECMO
      • Emergency thoracotomy
• For high-risk patients
  
  • Local anaesthetic is preferable in every instance
  • Sedation should be minimised
    Risk of:
    • Respiratory depression
    • Upper airway obstruction
  • Consider pre-op treatment
  • Consider CPB or ECMO pre-operatively, including awake bypass
    • Unlikely to succeed as a rescue technique; should be established semi-electively
    • Consider when ventilation is unlikely to be successful post-induction, i.e. compression of:
      • Distal 1/3^rd of trachea
      • Mainstem bronchi
      • Carina
  • Consider AFOI with intubation distal to obstruction
    • Safest
    • Allows assessment of site and degree of airway compression
    • Permits intubation distal to site of obstruction

Intraoperative

Surgical Stages

Emergence

Postoperative

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References

1. Chow L. Anesthesia for Patients with Mediastinal Masses. In: Slinger P, editor. Principles and Practice of Anesthesia for Thoracic Surgery [Internet]. Cham: Springer International Publishing; 2019 [cited 2019 Nov 30]. p. 251–63. Available from: http://link.springer.com/10.1007/978-3-030-00859-8_14