Subglottic Stenosis (SGS) – Anesthesia Considerations

Subglottic stenosis (SGS) is a narrowing of the airway below the vocal cords and above the trachea. It can be congenital or acquired and presents significant challenges for airway management in anesthesia.

1. Etiology of Subglottic Stenosis

A. Congenital Subglottic Stenosis

• Definition: Subglottic diameter <4 mm in a full-term neonate or <3 mm in a preterm neonate.

• Causes:

• Incomplete canalization of the laryngotracheal tube.

• Associated with congenital syndromes (Down syndrome, Pierre Robin sequence, CHARGE syndrome).

B. Acquired Subglottic Stenosis

• Most common cause: Prolonged endotracheal intubation (post-intubation injury).

• Other causes:

• Laryngotracheal trauma

• Iatrogenic (post-surgery, post-tracheostomy)

• Infections (croup, bacterial tracheitis, tuberculosis)

• Autoimmune disorders (Wegener’s granulomatosis, sarcoidosis)

• GERD (chronic acid exposure causing inflammation)

• Radiation therapy

3. Clinical Features of Subglottic Stenosis

• Progressive stridor (inspiratory and expiratory)

• Respiratory distress

• Barking cough

• Hoarseness or weak voice

• Cyanosis (in severe cases)

• History of prolonged intubation, trauma, or previous airway surgery

Note: In neonates and infants, symptoms may appear only when the airway narrows to <50% of normal diameter due to their high airway resistance.

4. Diagnosis of Subglottic Stenosis

A. Clinical Evaluation

• History of intubation, trauma, or recurrent airway infections.

• Presence of biphasic stridor (suggestive of fixed airway obstruction).

B. Imaging Studies

• Flexible Laryngoscopy: First-line investigation for airway assessment.

• CT/MRI of the airway: Defines the length, severity, and location of the stenosis.

• Fluoroscopy: Assesses dynamic airway collapse.

C. Gold Standard: Rigid Bronchoscopy

• Provides direct visualization of stenosis.

• Determines feasibility of endoscopic dilation.

5. Anesthetic Considerations for Subglottic Stenosis

A. Preoperative Preparation

• Detailed airway assessment (CT, MRI, bronchoscopy).

• Avoid sedatives that cause airway collapse (use ketamine if necessary).

• Prepare for a difficult airway:

• Small-diameter endotracheal tubes

• Rigid bronchoscope

• Tracheostomy setup ready

• High-frequency jet ventilation (HFJV) as an alternative

B. Intraoperative Management

1. Induction of Anesthesia

• Spontaneous ventilation preferred to maintain airway patency.

• Avoid muscle relaxants unless absolutely necessary.

• Induction agents:Sevoflurane (preferred in pediatrics), Ketamine (preserves spontaneous breathing)

2. Airway Management Options

• Small-diameter endotracheal tube (ETT)

• Choose 0.5-1.0 mm smaller than predicted size.

• Risk of increased airway resistance and need for higher ventilatory pressures.

• Supraglottic airway (LMA)-Suitable for mild stenosis or short procedures.

• High-Frequency Jet Ventilation (HFJV)-Used for airway surgery, minimizes movement of ETT.

• Tracheostomy- Considered in severe cases (Grade 3-4 stenosis).

3. Maintenance of Anesthesia

• TIVA (Propofol + Remifentanil) preferred for airway surgery.

• Avoid N2O (causes gas trapping).

• Monitor airway pressures continuously.

4. Extubation Considerations

• Fully awake extubation preferred to prevent airway collapse.

• Have emergency equipment ready (rigid bronchoscope, tracheostomy set).

• Steroids (Dexamethasone 0.1 mg/kg) to reduce airway edema.

7. Postoperative Considerations

• Airway edema and stridor monitoring.

• Steroid therapy to reduce inflammation.

• Nebulized epinephrine (for airway swelling).

• Delayed extubation in severe cases.

MCQs on Subglottic Stenosis

1. What is the most common cause of acquired subglottic stenosis?

A) Laryngomalacia

B) Prolonged endotracheal intubation

C) GERD

D) Laryngeal trauma

✅ Answer: B (Post-intubation injury is the leading cause).

2. What is the most accurate diagnostic test for subglottic stenosis?

A) CT scan

B) Flexible bronchoscopy

C) Rigid bronchoscopy

D) Fluoroscopy

✅ Answer: C (Rigid bronchoscopy is the gold standard).

3. What is the best induction technique for a child with severe subglottic stenosis?

A) Rapid Sequence Intubation (RSI) with Suxamethonium

B) Sevoflurane induction with spontaneous breathing

C) Propofol induction with Rocuronium

D) Awake fiberoptic intubation

✅ Answer: B (Preserves spontaneous ventilation, avoids airway collapse).

4. What is the preferred ventilation technique during laser surgery for SGS?

A) High-frequency jet ventilation

B) Conventional volume-controlled ventilation

C) Non-invasive ventilation

D) Pressure-controlled ventilation

✅ Answer: A (HFJV provides adequate ventilation without interfering with the surgical field).