Duration of Numbing Effect After Local Lidocaine Infiltration
Local lidocaine infiltration provides 60-90 minutes of anesthesia when used alone, and 90-200 minutes when combined with epinephrine. 1
Duration Based on Formulation
Plain Lidocaine (Without Epinephrine)
- Duration: 60-90 minutes of effective anesthesia after subcutaneous infiltration 1
- Onset is rapid, with anesthetic effect beginning within minutes of injection 2
Lidocaine with Epinephrine
- Duration: 90-200 minutes of effective anesthesia 1
- Epinephrine prolongs duration in a dose-dependent manner, with all concentrations (even as dilute as 1:3,200,000) extending anesthetic effect 3
- Addition of epinephrine in standard concentrations (1:50,000 to 1:200,000) increases duration by approximately 200% compared to plain lidocaine 3
- The mechanism involves vasoconstriction that reduces systemic absorption, with the magnitude of vasoconstriction correlating with prolonged analgesia 3
Dosing Considerations That Affect Duration
Maximum Safe Doses
- With epinephrine: 7 mg/kg (up to 500 mg) in adults 1
- Without epinephrine: 4.5 mg/kg (up to 300 mg) in adults 1
- For a 70 kg adult, this allows up to 49 mL of 1% lidocaine solution when using epinephrine 1
Practical Volume Calculations
- 1% lidocaine = 10 mg/mL
- 2% lidocaine = 20 mg/mL
- Calculate total dose carefully when infiltrating multiple sites to avoid cumulative toxicity 1
Critical Safety Timing
Wait at least 4 hours between lidocaine infiltration and any other local anesthetic intervention to prevent cumulative toxicity 4, 2. This includes:
- Nerve blocks or fascial plane blocks 4
- Epidural or wound catheter boluses 4
- Additional infiltration at other surgical sites 4
Common Pitfalls to Avoid
- Underestimating cumulative doses: When infiltrating multiple sites, sum the total lidocaine dose across all injection points 1
- Using actual body weight in obese patients: Always calculate dose using ideal body weight to prevent inadvertent overdosing 1
- Failing to add epinephrine when longer duration is needed: Epinephrine doubles the duration with minimal additional risk in most anatomic locations 3
- Injecting too rapidly: Slow injection with frequent aspiration reduces risk of intravascular administration and systemic toxicity 1
Factors That May Shorten Duration
Dose reductions (which may affect duration) are necessary in patients with 1:
- Hepatic dysfunction
- Cardiac failure
- Hypoalbuminemia
- Low body weight or reduced muscle mass
- Concurrent use of beta-blockers or amiodarone
Monitoring for Toxicity
Early signs of lidocaine toxicity include 2:
- Circumoral numbness or facial tingling
- Slurred speech
- Tinnitus
- Light-headedness
Toxic plasma levels begin at approximately 6 μg/mL, with serious toxicity (CNS depression, convulsions, hypotension) occurring at 9-10 μg/mL 1. Have 20% lipid emulsion immediately available when using high doses 1.