The Child with a Mediastinal Mass
A 6-year-old, 20 kg girl presents with a 3-week history of cough, night sweats, and a visibly swollen neck. Chest radiograph shows a large anterior mediastinal mass with tracheal deviation. CT shows the mass compressing the trachea to a minimum diameter of 4 mm at the level of the carina, with superior vena cava (SVC) compression. She is comfortable at rest but desaturates to 91% when supine. The oncology team wants a tissue biopsy under general anesthesia.
1. What is the primary anesthetic risk, and how do you assess its severity before induction?
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The primary risk is complete airway obstruction and cardiovascular collapse on induction due to:
- Loss of spontaneous ventilation and muscle tone → the mass compresses the trachea further
- Loss of negative intrathoracic pressure → reduced venous return in the setting of SVC syndrome
- Positioning (supine) worsens compression
Preoperative assessment:
- Symptoms by position: Does she tolerate supine? (She desaturates to 91% - high risk.) Ask about orthopnea, stridor, cough
- CT measurement: Minimum tracheal diameter 4 mm is critically narrow; a mass >50% of tracheal cross-section is high risk
- Echocardiography: Assess for pericardial effusion, cardiac compression, and SVC obstruction
- Flow-volume loops: If cooperative, may show expiratory or inspiratory plateau (variable intrathoracic obstruction)
- Anesthesia consultation with oncology and surgery: Consider whether biopsy can be done under local anesthesia, CT-guided, or after steroids/radiation to shrink the mass first
Key point: The safest anesthetic is often no anesthetic. The exam tests recognition that this is a high-risk airway and that alternative diagnostic strategies should be explored.
2. If general anesthesia is unavoidable, describe your induction and maintenance plan, including rescue strategies.
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Induction:
- Maintain spontaneous ventilation - do not paralyze until the airway is secure and you have a plan
- Position: Semi-upright or lateral decubitus if tolerated; avoid supine
- Inhalational induction with sevoflurane in 100% O2, slowly, keeping the child breathing
- Avoid: propofol bolus (apnea), muscle relaxants, positive pressure until you have a definitive airway plan
- Have ready: rigid bronchoscope, ECMO/cardiopulmonary bypass standby if the mass is severe, multiple ETT sizes, and a surgeon at the bedside
Maintenance:
- Spontaneous ventilation with volatile agent; avoid PEEP if it worsens compression (individualize)
- If positive pressure is needed, use low tidal volumes and inspect for hemodynamic compromise
Rescue:
- Reposition (lateral/prone) - often the fastest rescue
- Rigid bronchoscopy to stent or bypass
- Emergency ECMO if available
- Heliox may buy time
Key point: The exam tests that loss of spontaneous ventilation is the dangerous step, and that positioning is a first-line rescue.
3. What postoperative disposition is appropriate, and why?
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ICU admission with continuous monitoring is appropriate.
Reasons:
- Residual airway edema and mass effect can worsen post-biopsy (bleeding into the mass, edema from instrumentation)
- SVC syndrome may impair venous return and airway drainage
- Risk of re-obstruction during emergence and recovery
- Need for immediate access to rigid bronchoscopy and ECMO if re-obstruction occurs
Post-op plan:
- Keep head elevated
- Continuous SpO2 and capnography if intubated
- Avoid sedatives that depress respiration
- Monitor for bleeding (biopsy site) and airway swelling
- Have a low threshold for reintubation with a smaller ETT or rigid bronchoscopy
Key point: The exam tests that the post-anesthetic period is as dangerous as induction in these patients, and that ICU-level monitoring is standard.