What is the recommended protocol for a lidocaine (local anesthetic) block of the lip?

Lidocaine Block Protocol for Lip Anesthesia

For lip anesthesia, use 1-2% lidocaine with epinephrine (1:100,000) at a maximum dose of 7 mg/kg, administered via infiltration or nerve block technique, with onset of action within 1-5 minutes and duration of 1-2 hours. 1, 2

Dosing Guidelines

• Adult maximum safe dose:

  • 7.0 mg/kg lidocaine with epinephrine
  • 4.5 mg/kg lidocaine without epinephrine 1

• Pediatric maximum safe dose:

  • 3.0-4.5 mg/kg lidocaine with epinephrine
  • 1.5-2.0 mg/kg lidocaine without epinephrine 1

• Concentration considerations:

  • 1% lidocaine (10 mg/mL) produces less injection pain than 2% lidocaine 3
  • Total dose (mg) is more important than concentration 2

Administration Technique for Lip Block

1. Calculate appropriate dose based on patient weight

2. Prepare injection:

   • Use 1-2% lidocaine with 1:100,000 epinephrine
   • Consider buffering with sodium bicarbonate (1:9 or 1:10 ratio) to reduce injection pain 1
   • Draw up in appropriate syringe (27-30 gauge needle recommended)

3. For upper lip:

   • Infraorbital nerve block: Insert needle at the infraorbital foramen
   • Infiltration: Direct infiltration along the vermilion border

4. For lower lip:

   • Mental nerve block: Insert needle at the mental foramen
   • Infiltration: Direct infiltration along the vermilion border

5. Technique:

   • Aspirate before injection to avoid intravascular administration
   • Inject slowly to minimize pain
   • Use incremental injections to monitor for toxicity 1, 2

Timing Considerations

• Onset of action: 1-5 minutes 4, 5
• Peak effect: 4-5 minutes after application 5
• Duration: 1-2 hours with epinephrine; shorter without epinephrine
• Optimal procedure window: 3-8 minutes after application for topical; 5-10 minutes after injection 5

Safety Precautions

Contraindications

• Active infections at injection site
• True lidocaine allergy (rare, <1% of adverse reactions) 1
• Uncontrolled diabetes
• Severe hypertension
• Heart failure 2

Alternatives for Lidocaine Allergy

• Ester-type local anesthetics (minimal cross-reactivity)
• 1% diphenhydramine injection (onset: 5 min vs. 1 min for lidocaine)
• Bacteriostatic normal saline (0.9% benzyl alcohol in normal saline) 1

Toxicity Prevention

• Use lowest effective dose
• Aspirate before injection
• Use incremental injections
• Monitor for early signs of toxicity:
  • Circumoral numbness
  • Facial tingling
  • Light-headedness
  • Tinnitus 2

Special Considerations

• Adding epinephrine: Provides longer duration of anesthesia, reduces bleeding, improves visualization 2
• Buffering: Adding sodium bicarbonate reduces injection pain 1, 2
• Monitoring: Continuous assessment during and after procedure, especially in pediatric patients 2
• Documentation: Record amount used and time of application 2

Common Pitfalls to Avoid

• Exceeding maximum recommended dose
• Failure to aspirate before injection
• Injecting too rapidly (increases pain)
• Not allowing sufficient time for onset of action
• Not recognizing early signs of toxicity
• Using lidocaine within 4 hours of other local anesthetic interventions 2

Remember that true lidocaine allergy is rare, occurring in only about 1% of adverse reactions to these medications. Most reactions are vasovagal responses or anxiety-related 1.