Is it safe to use more than 3mg/kg of lignocaine (lidocaine) as a local anesthetic?

Maximum Safe Dosage of Lignocaine (Lidocaine)

The maximum safe dose of lignocaine with epinephrine is 7 mg/kg for adults and 3.0-4.5 mg/kg for children, which exceeds the 3 mg/kg threshold mentioned in the question. 1

Dosage Guidelines by Patient Population

Adults

• With epinephrine: 7 mg/kg (maximum safe dose) 1
• Without epinephrine: 4.5 mg/kg (maximum safe dose) 1
• For tumescent anesthesia: Up to 55 mg/kg has been found safe for office-based liposuction 1

Children

• With epinephrine: 3.0-4.5 mg/kg (maximum safe dose) 1
• Without epinephrine: 1.5-2.0 mg/kg (maximum safe dose) 1

Special Considerations for Dosing

Route of Administration

The maximum safe dose varies depending on the administration route:

• Local infiltration: Higher doses (up to 7 mg/kg with epinephrine) are generally safe 1
• Topical airway application: Should not exceed 9 mg/kg lean body weight 1

Duration and Timing

• Incremental dosing: A prospective cohort study found 500 mg of 1% lidocaine delivered incrementally over approximately 8 hours to be safe in Mohs micrographic surgery, with no signs of toxicity or toxic serum levels 1
• Single bolus: Lower maximum doses apply compared to incremental administration

Patient Factors Requiring Dose Reduction

• Elderly patients
• Patients with liver or cardiac impairment 2
• Acutely ill patients
• Low body weight patients

Monitoring for Toxicity

Signs and Symptoms of Local Anesthetic Systemic Toxicity (LAST)

• Early signs: Circumoral numbness, facial tingling, pressured/slurred speech, metallic taste, auditory changes, hallucinations
• Progression: Hypertension, tachycardia, seizures, CNS depression
• Severe cases: Cardiac failure or arrest 1

Prevention Strategies

1. Calculate maximum allowable dose before administration
2. Use epinephrine (when not contraindicated) to reduce systemic absorption
3. Aspirate before injection to avoid intravascular administration
4. Use the lowest effective concentration and volume
5. Consider incremental dosing for lengthy procedures 1

Common Pitfalls and Caveats

1. Calculation errors: Always calculate the maximum dose based on patient weight and formulation concentration

   • Example: For a 70 kg adult using 2% lidocaine with epinephrine, maximum dose would be 490 mg (7 mg/kg × 70 kg), equivalent to 24.5 mL of 2% solution

2. Additive effects: Consider the total dose when using multiple formulations or routes

   • The total dose of all local anesthetics administered, regardless of route, must be considered 1

3. Manufacturer recommendations vs. clinical evidence:

   • Manufacturer recommendations (3 mg/kg) are often conservative
   • Clinical evidence supports higher maximum doses, especially with epinephrine 1
   • The 2016 guidelines from the American Academy of Dermatology support the higher doses (7 mg/kg with epinephrine) 1

4. Misunderstanding maximum doses:

   • Maximum doses are not targets but upper limits 1
   • The lowest effective dose should always be used 2

5. Failure to have emergency protocols in place:

   • Have lipid emulsion 20% available for treatment of severe toxicity 3
   • Be prepared to manage airway and provide respiratory support if needed

Conclusion

While the traditional 3 mg/kg limit for lignocaine is often cited, current evidence-based guidelines support higher maximum safe doses, particularly when using epinephrine. The American Academy of Dermatology guidelines specifically state that 7 mg/kg of lidocaine with epinephrine appears safe for local infiltration in adults, and 3.0-4.5 mg/kg with epinephrine appears safe in children 1.