What is the preferred concentration of lidocaine (local anesthetic) for a penile block in circumcision, 1% or 2%?

Lidocaine Concentration for Penile Block in Circumcision

Both 1% and 2% lidocaine are effective and safe for penile blocks in circumcision, with no significant clinical difference in outcomes. 1

Evidence Analysis

The Journal of the American Academy of Dermatology guidelines (2016) specifically address the use of lidocaine for penile blocks during circumcision. While the guidelines don't explicitly state a preference between 1% and 2% concentrations, they confirm the safety of using lidocaine with epinephrine for penile blocks 1. This contradicts the historical concern about using vasoconstrictors in terminal vessel areas.

Early research from 1978 demonstrated successful use of 1% lidocaine (0.5 ml) for penile dorsal nerve blocks in neonates 2, establishing its efficacy for this procedure.

Concentration Considerations

When choosing between 1% and 2% lidocaine:

• Volume vs. Concentration: The total dose (mg) of lidocaine is more important than the concentration
• Maximum Safe Dosage: Should not exceed 7 mg/kg when used with epinephrine 3
• Typical Volume Used:
  • For neonates: 0.5-1 ml of lidocaine 2
  • For adults: Average of 0.9 ml of 2% lidocaine reported in some studies 4

Safety Considerations

Safety should be the primary concern when administering penile blocks:

• Risk of Systemic Toxicity: Cases of lidocaine toxicity have been reported, particularly in infants 5, highlighting the importance of proper dosing
• Signs of Toxicity: Early signs include circumoral numbness, facial tingling, and light-headedness 3
• Anatomical Safety: The penile anatomy makes perfusion complications highly unlikely, even with epinephrine 6

Technique Recommendations

For optimal results:

• Ring Block Technique: A circumferential subcutaneous injection around the proximal third of the penis is effective 4, 6
• Consider Adding Epinephrine: Adding epinephrine to the lidocaine solution is safe for penile blocks and provides:
  • Longer duration of anesthesia
  • Reduced bleeding
  • Better visualization of the surgical field 1, 6
• Consider Buffering: Addition of sodium bicarbonate to reduce pain of infiltration 1

Multimodal Approach

For optimal pain management, especially in neonates and children:

• Consider combining penile block with other modalities such as:
  • Pacifier dipped in sucrose (for infants)
  • Comfortable restraining chairs
  • Post-procedure acetaminophen 7

Common Pitfalls to Avoid

1. Overdosage: Calculate the maximum safe dose based on patient weight
2. Accidental Intravascular Injection: Always aspirate before injecting
3. Inadequate Block: Ensure complete circumferential distribution of anesthetic
4. Relying Solely on Topical Anesthetics: These are less effective than injectable lidocaine 7

Both 1% and 2% lidocaine concentrations are appropriate for penile blocks in circumcision, with the choice depending more on the total volume needed and the patient's size rather than the concentration itself.