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Lidocaine Maximum Safe Dosing

Calculate max safe lidocaine doses for local anesthesia. Plain: 4.5 mg/kg (300mg). With epi: 7 mg/kg (500mg). Adjust for hepatic, cardiac, elderly.

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Plain: 4.5 mg/kg, 300mg max With epi: 7 mg/kg, 500mg max Volume = Dose ÷ Concentration (mg/mL)

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Why: Exceeding max doses risks Local Anesthetic Systemic Toxicity (LAST), which can be life-threatening.

How: Weight-based dosing with absolute max. Epinephrine reduces absorption and increases safe dose.

Plain: 4.5 mg/kg, 300mg maxWith epi: 7 mg/kg, 500mg max
Sources:ASRA Guidelines

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🦷 Adult Dental Procedure

45-year-old adult undergoing dental extraction, using 2% lidocaine with epinephrine

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👶 Pediatric Laceration

8-year-old child (25kg) needing local anesthesia for wound repair

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❤️ Elderly with Cardiac History

78-year-old with atrial fibrillation, avoiding epinephrine

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🏥 Hepatic Impairment

55-year-old with chronic liver disease requiring reduced dosing

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✋ Digital Nerve Block

Finger laceration repair - NO epinephrine for digital block

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Patient & Medication Information

Patient Information

Patient body weight
Patient age
Age category

Medication Details

Epinephrine increases max dose and duration
Lidocaine concentration
Site affects absorption and epinephrine use

Risk Factors

Liver metabolizes lidocaine
Cardiac conditions affect safety

For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.

🏥 Health Facts

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LAST: metallic taste, perioral numbness, seizures. Treat with lipid emulsion.

— ASRA

What is Lidocaine?

Lidocaine is an amide-type local anesthetic and the most widely used agent for infiltration, nerve blocks, and dental anesthesia. It works by blocking sodium channels in nerve membranes, preventing depolarization and signal transmission. Understanding maximum dosing is critical to prevent Local Anesthetic Systemic Toxicity (LAST), which can be life-threatening.

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Plain Lidocaine

Maximum: 4.5 mg/kg up to 300 mg total

Duration:

  • Infiltration: 30-60 min
  • Nerve block: 60-90 min
  • Onset: 2-5 minutes
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With Epinephrine

Maximum: 7 mg/kg up to 500 mg total

Epinephrine Benefits:

  • Duration: 90-180 min
  • Reduced bleeding
  • Slower absorption
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Toxicity Signs (LAST)

CNS then cardiac symptoms in progression

Early → Late:

  • Perioral numbness, tinnitus
  • Metallic taste, dizziness
  • Seizures → Cardiac arrest

How This Calculator Works

This calculator computes the maximum safe lidocaine dose based on patient weight, epinephrine use, and patient-specific risk factors. It also calculates the corresponding maximum volume based on the selected concentration.

🔬 Dose Calculation Process

  1. 1Determine base mg/kg limit (4.5 or 7 depending on epinephrine)
  2. 2Apply risk factor adjustments (age, hepatic, cardiac)
  3. 3Calculate weight-based maximum (Weight × mg/kg)
  4. 4Cap at absolute maximum (300 or 500 mg)
  5. 5Convert to volume based on concentration

When to Adjust Lidocaine Dosing

Hepatic Impairment

Reduce dose by 50%. Lidocaine is metabolized by CYP3A4 in liver.

Elderly (≥65)

Reduce dose by 25%. Decreased clearance and increased sensitivity.

Cardiac Disease

Reduce dose by 25% and avoid epinephrine if arrhythmia present.

Lidocaine Dosing Formulas

Maximum Dose (Plain)

Max Dose (mg) = Weight (kg) × 4.5 mg/kg
Absolute Maximum: 300 mg

Maximum Dose (With Epinephrine)

Max Dose (mg) = Weight (kg) × 7 mg/kg
Absolute Maximum: 500 mg

Volume Calculation

Volume (mL) = Max Dose (mg) ÷ Concentration (mg/mL)
1% = 10 mg/mL | 2% = 20 mg/mL

LAST Treatment Protocol

Local Anesthetic Systemic Toxicity (LAST) Management:

  1. 1. Stop injection immediately, call for help
  2. 2. Airway management, 100% oxygen
  3. 3. Seizures: Benzodiazepines (avoid propofol initially)
  4. 4. Cardiac arrest: Standard ACLS with modifications
  5. 5. Lipid Emulsion (Intralipid 20%):
    • • Bolus: 1.5 mL/kg over 1 minute
    • • Infusion: 0.25 mL/kg/min for at least 10 minutes
    • • Repeat bolus if no response in 5 minutes
    • • Max total dose: 12 mL/kg

Common Clinical Applications

Lidocaine is the most versatile local anesthetic with applications across multiple specialties.

Wound Repair

Solution: 1% or 2% with epi

Volume: 3-5 mL typical

Technique: Field or wound edge

Duration: 30-60 min (with epi)

Digital Blocks

Solution: 1% plain (no epi!)

Volume: 2-4 mL per digit

Technique: Web space or volar

Duration: 30-45 min

Dental Anesthesia

Solution: 2% with 1:100,000 epi

Volume: 1.8 mL cartridge

Max: 4.4 mg/kg (7 with epi)

Duration: 60-90 min

IV Antiarrhythmic

Bolus: 1-1.5 mg/kg IV

Infusion: 1-4 mg/min

Indication: VT, VF refractory to defib

Note: Different dosing than local

Topical Anesthesia

Forms: Gel, spray, viscous

Conc: 2-4% typical

Use: Mucous membranes

Caution: Systemic absorption variable

Regional Blocks

Bier Block: 3 mg/kg plain

Peripheral nerves: Variable

Lumbar epidural: 200-300 mg

Duration: 60-90 min typically

Clinical Pearls

Buffering with Bicarb

Add 1 mL 8.4% sodium bicarb to 10 mL lidocaine to reduce injection pain and speed onset.

Warm the Solution

Warming to body temperature reduces injection pain. Body warmers or pocket storage work well.

Small Needle, Slow Injection

Use 27-30G needle and inject slowly to minimize pain. Consider starting in wound if possible.

Duration Extension

Epinephrine extends duration 50-100%. Use 1:100,000 or 1:200,000 concentration.

Digital Block Safety

Traditional teaching avoids epi in digits. Recent evidence suggests dilute epi is safe, but practice varies.

Concentration Math

1% = 10 mg/mL. For 0.5%, dilute 1:1 with saline. Know concentration before calculating volume.

Frequently Asked Questions

Why does lidocaine burn during injection?

Lidocaine solutions are acidic (pH ~4-5) which causes burning. Buffering with bicarbonate raises pH and significantly reduces pain. Warming the solution also helps.

How quickly does lidocaine work?

Onset is typically 2-5 minutes for infiltration. Nerve blocks may take 10-15 minutes. Wait for full effect before starting procedure.

Can I use lidocaine in a patient allergic to "-caine" drugs?

True allergy is rare. Amides (lidocaine) don't cross-react with esters (procaine, benzocaine). Most "allergies" are vasovagal or epinephrine reactions. Consider allergy testing if history is convincing.

Epinephrine Concentration Guide

Understanding epinephrine ratios helps select appropriate formulations.

RatioConcentrationCommon Use
1:50,00020 mcg/mLDental (high hemostasis)
1:100,00010 mcg/mLStandard dental/wound
1:200,0005 mcg/mLRegional blocks
1:400,0002.5 mcg/mLLow epi needs

Plasma Levels and Toxicity

<5 mcg/mL

Therapeutic range

Safe, no symptoms

5-10 mcg/mL

CNS symptoms

Perioral numbness, tinnitus

>10 mcg/mL

Cardiac toxicity

Arrhythmias, seizures

Special Situations

Tumescent Anesthesia

  • • Very dilute lidocaine (<0.1%)
  • • Large volumes for liposuction
  • • Max: 55 mg/kg (much higher than standard)
  • • Slow absorption due to vasoconstriction
  • • Requires specialized training

IV Regional (Bier Block)

  • • Lidocaine ONLY (not bupivacaine)
  • • Dose: 3 mg/kg, max 200-250 mg
  • • 0.5% concentration typical
  • • Keep tourniquet up 20+ minutes
  • • Deflate slowly, watch for toxicity

IV Lidocaine Infusion (Non-Anesthetic Uses)

IV lidocaine has uses beyond local anesthesia including cardiac arrhythmias and chronic pain management.

Antiarrhythmic Use

  • • Ventricular arrhythmias refractory to defibrillation
  • • Bolus: 1-1.5 mg/kg IV push
  • • Infusion: 1-4 mg/min
  • • Different from local anesthetic dosing

Perioperative Pain

  • • Opioid-sparing effect
  • • Loading: 1.5-2 mg/kg over 20-30 min
  • • Infusion: 1-2 mg/kg/hr intraoperatively
  • • Continue postop in some protocols
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