What are the considerations for performing a glossopharyngeal nerve block in a patient with a predicted difficult airway and a history of neck surgery, radiation, or respiratory disease?

Glossopharyngeal Nerve Block in Difficult Airway with Neck Surgery, Radiation, or Respiratory Disease

In patients with predicted difficult airway and history of neck surgery, radiation, or respiratory disease, glossopharyngeal nerve block can be performed as part of a comprehensive topical anesthesia strategy for awake tracheal intubation, but requires extreme caution due to the risk of bilateral vocal cord paralysis if contralateral recurrent laryngeal nerve injury exists from prior surgery. 1, 2, 3

Critical Pre-Procedure Assessment

Mandatory Airway Evaluation

• Perform preoperative vocal cord examination in all patients with history of neck surgery or radiation to identify pre-existing asymptomatic recurrent laryngeal nerve (RLN) paralysis, which occurs in 0.5-3% of patients after thyroid or neck surgery 3
• Conduct thorough airway assessment including history, examination, and appropriate investigations for all patients with head and neck pathology, previous surgery, or radiotherapy 1
• Identify and mark the cricothyroid membrane before starting the procedure as part of a "double set-up" approach, with emergency front-of-neck airway equipment immediately available 4

High-Risk Features Requiring Awake Intubation

Awake tracheal intubation must be considered when you have: 1, 2

• Head and neck pathology (malignancy, previous surgery, or radiotherapy)
• Reduced mouth opening
• Limited neck extension
• Progressive airway compromise
• Respiratory disease with inability to tolerate brief apneic episodes

Glossopharyngeal Nerve Block Technique and Considerations

Role in Topical Anesthesia Strategy

• Use glossopharyngeal nerve block as a supplemental technique to direct topical application, not as the sole method of airway anesthesia 2, 5
• The block provides anesthesia to the posterior third of tongue and lateral/posterior oropharyngeal and hypopharyngeal walls 5
• Combine with superior laryngeal nerve block and transtracheal injection for complete airway anesthesia from nares to vocal cords 2

Technical Approach Selection

• In patients with neck surgery history, consider ultrasound-guided or CT-guided paramaxillary approaches rather than traditional peristyloid approaches to reduce risk of neurovascular injury 6, 7
• The paramaxillary approach eliminates trans-parotid trajectory and reduces complications related to parotid gland and intraparotid facial nerve injury 7
• Topical anesthesia may be difficult in patients with limited mouth opening or inflammation, making nerve blocks more valuable 6

Critical Safety Precautions

The most dangerous complication is bilateral vocal cord paralysis from combining ipsilateral nerve block with pre-existing contralateral RLN injury. 3

• If vocal cord examination reveals pre-existing unilateral RLN paralysis, do not perform glossopharyngeal nerve block as this creates risk of complete airway obstruction 3
• In patients with respiratory disease, the combination of nerve block and sedation increases risk of hypoventilation and airway obstruction 1
• Monitor total local anesthetic dose to avoid systemic toxicity, keeping patients nil by mouth for at least 2 hours following airway topicalization 2

Procedural Setup and Environment

Location and Team Requirements

• Perform awake tracheal intubation in the operating theatre environment with ready access to skilled assistance, drugs, equipment, and space 1
• For high-risk patients with significant airway obstruction, hypoxia, or respiratory failure, the operating theatre provides greater space and immediate surgical assistance compared to anaesthetic rooms 1
• Ensure planning and communication with anaesthetic assistants, operating theatre nursing staff, surgeons, and skilled anaesthetic colleagues 1

Monitoring Requirements

• Maintain continuous pulse oximetry and capnography monitoring throughout the procedure 2
• Monitor for signs of inadequate ventilation: absent/inadequate exhaled CO2, absent/inadequate chest movement, decreasing oxygen saturation, or changed mental status 8

Oxygenation and Sedation Strategy

Pre-Oxygenation Approach

• Use high-flow nasal oxygen (HFNO) at 50-60 L/min as the primary oxygenation technique, reducing desaturation incidence to 0-1.5% compared to 12-16% with low-flow oxygen 4
• Continue HFNO throughout the entire procedure to maintain oxygenation during airway manipulation 4
• In patients with respiratory disease, this is particularly critical as they have reduced apnea tolerance 2

Sedation Protocol

• Administer minimal sedation only—the patient must remain responsive to verbal commands throughout 4
• Start with 1 mg midazolam IV given over at least 2 minutes for patients under 55 years without significant comorbidities, maximum total dose 5 mg 4
• In patients with respiratory disease, err on the side of less sedation to avoid hypoventilation and airway obstruction 1

Intubation Technique Selection

Device Choice for Difficult Anatomy

• In patients with neck surgery or radiation causing distorted anatomy, videolaryngoscopy may be preferable to flexible bronchoscopy for most cases without airway lesions or pathology 1
• Use a channeled videolaryngoscope for patients with submandibular masses or distorted anatomy, as it provides a guided pathway with 92% success rates 4
• Flexible bronchoscopy remains indicated when airway lesions, pathology, or severe anatomical distortion exists 1, 2

Attempt Limitations

• Limit to maximum 3 attempts plus 1 additional attempt by the most experienced operator 4, 2
• If unsuccessful, immediately call for help, apply 100% oxygen, stop and reverse any sedatives, and prepare for emergency front-of-neck airway 4, 2

Post-Intubation Considerations

Extubation Planning

• Patients requiring awake intubation for predicted difficult airway are at high risk of complications at extubation and require an appropriate extubation strategy 4, 2
• Consider performing laryngoscopy before extubation to assess the airway 4
• In patients with neck surgery or radiation, airway edema may worsen post-operatively, increasing extubation risk 1

Common Pitfalls to Avoid

• Never proceed with glossopharyngeal nerve block without preoperative vocal cord examination in patients with neck surgery history 3
• Do not rely solely on nerve blocks for airway anesthesia; always combine with direct topical application 2, 5
• Avoid excessive sedation in patients with respiratory disease, as this compounds the respiratory depressant effects of nerve blocks 1, 3
• Do not perform the procedure outside the operating theatre environment in high-risk patients with respiratory disease or previous neck surgery 1
• Never exceed safe local anesthetic doses when combining multiple nerve blocks with topical anesthesia 2