What is the recommended dosage and preparation regimen for lignocaine (lidocaine) with adrenaline (epinephrine) nebs for awake fibre optic intubation?

Lignocaine with Adrenaline Nebulization for Awake Fibreoptic Intubation

For awake fibreoptic intubation, nebulize 4 mL of 4% lignocaine (without adrenaline) as part of a multimodal topicalization strategy, ensuring total lignocaine dose does not exceed 9 mg/kg lean body weight. 1

Recommended Lignocaine Dosing and Preparation

Nebulization Protocol

• Administer 4 mL of 4% lignocaine solution via nebulizer through a face mask or mouthpiece 1, 2, 3, 4
• This provides satisfactory anaesthesia of the oropharynx and vocal cords 1
• Nebulization alone achieves successful intubation in 79% of patients with acceptable comfort 5

Maximum Safe Dose

• Total lignocaine dose must not exceed 9 mg/kg lean body weight (approximately 630 mg for a 70 kg patient) 1
• This is higher than the 8.2 mg/kg recommended for bronchoscopy, reflecting the Difficult Airway Society's 2020 updated guidance 1
• For a 70 kg patient, this equates to approximately 32 mL of 2% solution total across all routes 1

Adrenaline (Epinephrine) Considerations

Adrenaline is NOT routinely added to nebulized lignocaine for awake fibreoptic intubation. The evidence and guidelines do not support this practice for several reasons:

• Nebulized racemic epinephrine (0.5 mL of 2.25% solution in 2 mL normal saline) is reserved for laryngotracheobronchitis (croup) and acute airway edema, not elective awake intubation 1
• The British Thoracic Society guidelines for bronchoscopy do not recommend adding epinephrine to nebulized lignocaine 1
• The Difficult Airway Society 2020 guidelines make no mention of epinephrine in nebulized preparations for awake tracheal intubation 1

Multimodal Topicalization Strategy

Nebulization should be combined with other topicalization techniques to optimize airway anaesthesia:

Nasal Preparation

• Apply 2% lignocaine gel or 10% lignocaine spray to anterior nares 1
• Gel preparation yields lower blood levels and better patient acceptance 1
• Administer two puffs of 10% lignocaine to nose and postnasal space bilaterally 2

Additional Airway Blocks

• Bilateral superior laryngeal nerve blocks: 1-2 mL of 2% lignocaine each side 1, 2, 3
• Transtracheal (transcricoid) block: 4-5 mL of 2% lignocaine 1, 2, 3
• These regional blocks provide superior haemodynamic stability compared to nebulization alone 5

"Spray-as-you-go" Technique

• Apply 2-4% lignocaine under direct vision through the bronchoscope working channel 1
• Use 1-2% boluses for carina and bronchi 1

Clinical Implementation Algorithm

Step 1: Pre-procedure Preparation

• Premedicate with oral midazolam 7.5 mg and IV atropine 0.5 mg 4
• Position patient in anti-Trendelenburg position 4
• Ensure supplemental oxygen is available throughout 1

Step 2: Topicalization Sequence

1. Nebulize 4 mL of 4% lignocaine (160 mg) via face mask over 10-15 minutes 2, 3, 4
2. Apply nasal preparation: 2% gel or spray (approximately 20-40 mg) 1
3. Perform bilateral superior laryngeal blocks: 2 mL of 2% lignocaine total (40 mg) 2, 3
4. Perform transtracheal block: 4 mL of 2% lignocaine (80 mg) 2, 3
5. Running total: 300 mg lignocaine (well below 630 mg limit for 70 kg patient)

Step 3: Sedation (Optional)

• Administer minimal sedation only after adequate topicalization 1
• Dexmedetomidine offers the best safety profile with fewer desaturation episodes compared to propofol or opioids 6
• Alternative: 2 mg midazolam + 0.05-0.1 µg/kg fentanyl IV immediately before bronchoscopy 4
• Sedation must not substitute for inadequate topicalization 1

Step 4: Intubation Performance

• Limit attempts to three, with one additional attempt by a more experienced operator (3+1 rule) 1
• Continue oxygen delivery through bronchoscope working channel 4
• Apply additional lignocaine via "spray-as-you-go" as needed, monitoring total dose 1

Safety Considerations and Pitfalls

Lignocaine Toxicity Prevention

• Toxic blood levels (>5 mg/L) are uncommon when total dose remains below 9 mg/kg 1
• Exercise extra caution in elderly patients or those with hepatic or cardiac impairment 1
• Partial absorption across mucous membranes means some drug is re-aspirated or swallowed, reducing systemic absorption 1

Common Pitfalls to Avoid

• Do not use sedation to compensate for inadequate topicalization - this increases risk of airway obstruction and desaturation 1
• Do not exceed maximum lignocaine dose - track cumulative dose across all routes of administration 1
• Do not add adrenaline to nebulized lignocaine - this is not evidence-based for awake fibreoptic intubation and may cause unnecessary cardiovascular stimulation 1
• Nebulization alone provides less haemodynamic stability than combined regional blocks 5

Efficacy and Safety Data

• Overall success rate for awake fibreoptic intubation exceeds 99% (2033/2045 successful intubations) 6
• Severe adverse events occur in only 0.34% of cases (7/2045) with no permanent consequences or deaths 6
• Intubation time is significantly faster with regional blocks (69 seconds) versus nebulization alone (92 seconds) 3

When Nebulization Adds Value

• Nebulization improves patient comfort and satisfaction when added to airway blocks 2
• Provides more uniform distribution of local anaesthetic throughout upper airway 2, 4
• Particularly useful for patients who cannot tolerate needle-based regional blocks 4