What is the appropriate preparation and dosing of lignocaine (lidocaine) for topical anesthesia during flexible bronchoscopy in adults?

Lignocaine Preparation for Flexible Bronchoscopy

Limit total lignocaine (lidocaine) dose to 8.2 mg/kg in adults—approximately 29 mL of 2% solution for a 70 kg patient—with extra caution in elderly patients or those with hepatic or cardiac impairment. 1, 2

Recommended Lignocaine Dosing and Administration

Maximum Safe Dose

• The British Thoracic Society establishes a maximum dose of 8.2 mg/kg to prevent toxic side effects including seizures and cardiac suppression, which become more likely above plasma levels of 5 mg/L. 1
• For a 70 kg patient, this translates to approximately 29 mL of 2% lignocaine solution or 574 mg total. 1, 2
• Exercise particular caution in elderly patients and those with liver or cardiac impairment, as lignocaine is primarily metabolized hepatically. 1, 2

Optimal Delivery Method

• Use 10 actuations of 10% lignocaine oropharyngeal spray as the primary topical anesthetic, which provides superior patient comfort and procedural satisfaction compared to nebulized lignocaine or combination approaches. 3
• This spray-based approach delivers approximately 100 mg of lignocaine (10 mg per actuation × 10 sprays), well below the maximum safe dose. 3
• Recent high-quality evidence demonstrates that 10 sprays achieve better cough suppression, higher operator satisfaction, and greater patient willingness to undergo repeat procedures than nebulization. 3

Concentration Selection

• Apply 2% lignocaine gel for nasal anesthesia rather than spray to minimize systemic absorption. 2
• For instillation through the bronchoscope using "spray-as-you-go" technique, 1% lignocaine is as effective as 2% concentration while delivering significantly lower cumulative doses (220.89 mg vs 319.55 mg). 4
• The 1% solution provides equivalent operator satisfaction and cough control without increased need for supplemental sedation. 4

Spray-As-You-Go Technique

• Instill the minimum necessary lignocaine through the bronchoscope during the procedure. 1, 2
• Five pharyngeal sprays of 10% lignocaine (50 mg) provide similar procedural satisfaction to 10 sprays but at lower cumulative doses. 5
• However, the 10-spray protocol remains preferred based on the robust 2020 multicenter trial showing superior outcomes. 3

Critical Safety Considerations

High-Risk Populations Requiring Dose Reduction

• Elderly patients: Age-related decline in hepatic metabolism increases risk of lignocaine accumulation. 1, 2
• Hepatic impairment: Patients with liver disease or metastatic malignancy involving the liver have reduced lignocaine clearance and higher toxicity risk. 1
• Cardiac disease: Lignocaine can cause cardiac suppression; use minimum effective doses in patients with severe cardiovascular disease. 1

Monitoring Requirements

• Establish intravenous access before bronchoscopy and maintain throughout recovery. 2, 6
• Implement continuous pulse oximetry monitoring during the procedure. 2, 6
• Provide oxygen supplementation to maintain SaO₂ ≥90% to reduce arrhythmia risk. 2, 6
• Have resuscitation equipment readily available for management of potential lignocaine toxicity. 2

Practical Preparation Protocol

Pre-Procedure Checklist

• Ensure no solid food for 4 hours and permit clear fluids up to 2 hours before bronchoscopy. 1, 2, 6
• Calculate maximum allowable lignocaine dose based on patient weight (8.2 mg/kg). 1, 2
• Identify high-risk patients requiring dose modification (elderly, hepatic/cardiac impairment). 1, 2

Step-by-Step Anesthetic Application

1. Nasal route: Apply 2% lignocaine gel to the nostril. 2
2. Oropharynx: Administer 10 actuations of 10% lignocaine spray (100 mg total). 3
3. Airway topicalization: Use 1% lignocaine solution via spray-as-you-go technique through the bronchoscope, applying only as needed to suppress cough. 4
4. Track cumulative dose: Continuously calculate total lignocaine administered to avoid exceeding 8.2 mg/kg. 1, 2

Common Pitfalls to Avoid

• Do not use nebulized lignocaine as primary anesthetic—it delivers higher cumulative doses with inferior patient tolerance compared to oropharyngeal spray. 3
• Do not exceed 8.2 mg/kg total dose even if cough persists; consider additional sedation rather than more lignocaine. 1, 2
• Do not use 2% lignocaine for spray-as-you-go when 1% provides equivalent efficacy at lower total dose. 4
• Do not forget to account for all sources of lignocaine (nasal gel + oropharyngeal spray + bronchoscopic instillation) when calculating cumulative dose. 1, 2

Post-Procedure Management

• Continue oxygen supplementation for 1-2 hours after bronchoscopy, particularly in patients with impaired lung function or those who received sedation. 1, 2
• Maintain intravenous access through recovery period. 2, 6
• Advise patients who received sedation to avoid driving, signing legal documents, or operating machinery for 24 hours. 1, 2