What are the alternatives to co-phenylcaine (a combination of cocaine and phenylephrine) for flexible nasendoscopy?

Alternatives to Co-phenylcaine for Flexible Nasendoscopy

Tetracaine 2% with oxymetazoline 0.05% is the most effective alternative to co-phenylcaine for flexible nasendoscopy, offering more rapid onset, longer duration, and better patient tolerance. 1

Topical Anesthetic Options

Tetracaine-based Combinations

• Tetracaine 2% with oxymetazoline 0.05%
  • Advantages:
    • More rapid onset than co-phenylcaine (4 min vs 6 min)
    • Longer duration of action
    • More potent anesthetic effect
    • Generally perceived to taste less unpleasant than co-phenylcaine 1
  • Note: May cause dental numbness in some patients (reported in 8/10 participants vs 1/10 with co-phenylcaine)

Lidocaine-based Alternatives

• Lidocaine 2% gel
  • Recommended over lidocaine spray for nasal anesthesia 2
  • Better accepted by patients and yields lower blood levels
  • Maximum safe dose: 8.2 mg/kg in adults (approximately 29 ml of 2% solution for a 70 kg patient)
  • Caution in elderly or those with liver/cardiac impairment

Vasoconstrictor-only Options

• Xylometazoline
  • Effective for reducing overall unpleasantness during nasendoscopy 3
  • Significantly cheaper than combination preparations
  • Provides adequate vasoconstriction without anesthetic properties
  • Available as 0.05% solution for children and 0.1% for adults 4

Administration Techniques

Topicalization Methods

1. Direct application

   • 2-5% lidocaine for nose and larynx
   • 0.5-1% below the larynx
   • Can be instilled directly, sprayed, or nebulized (3-5 ml of 2-4% lidocaine)

2. "Spray-as-you-go" technique

   • Visualized vocal cord can be sprayed under direct vision with 2-4% lidocaine
   • Carina and bronchi anesthetized using 1-2% boluses via the bronchoscope 2

3. Nebulization

   • 4 ml of 4% nebulized lidocaine via mouthpiece can produce satisfactory anesthesia of oropharynx and vocal cords 2

Safety Considerations

Dosing Guidelines

• Lidocaine: Maximum 8.2 mg/kg (not a target but a maximum) 2
• Tetracaine: Use 0.5-2% solutions with caution due to potency 1
• Phenylephrine: 0.5% solution when combined with lidocaine is preferred over cocaine 2

Monitoring

• Test adequacy of topicalization in an atraumatic manner before airway instrumentation
• Monitor for signs of local anesthetic toxicity
• Have lipid emulsion available for emergency treatment of local anesthetic toxicity 2

Clinical Decision Algorithm

1. For routine nasendoscopy in adults:

   • First choice: Tetracaine 2% with oxymetazoline 0.05% (most effective combination)
   • Alternative: Lidocaine 2% gel with xylometazoline (if tetracaine unavailable)

2. For patients with cardiovascular concerns:

   • Consider xylometazoline alone (avoids potential cardiac effects of local anesthetics)
   • Monitor blood pressure closely

3. For pediatric patients:

   • Lidocaine 2-5% applied to nose and larynx
   • Consider conscious sedation with midazolam for anxious children
   • Oxygen supplementation is mandatory in young children 2

Pitfalls and Caveats

• Avoid cocaine due to potential toxic cardiovascular complications and controlled drug status 2
• Beware of total local anesthetic dose when combining with other procedures requiring local anesthesia
• Insufficient topical anesthesia can result in pain, cough, laryngospasm, or bronchospasm due to vagal stimulation 2
• Local anesthetic effect on larynx may falsely result in appearances of laryngomalacia 2
• Dental numbness is more common with tetracaine-based preparations 1

By selecting the appropriate alternative to co-phenylcaine based on patient characteristics and clinical context, flexible nasendoscopy can be performed with minimal discomfort while maintaining patient safety.