What is the effective dose of local anesthesia, such as lidocaine (Lidocaine) or bupivacaine (Bupivacaine), for pain relief?

Effective Dosing for Local Anesthesia

For local infiltration and peripheral nerve blocks, use lidocaine at a maximum of 4.5 mg/kg without epinephrine or 7 mg/kg with epinephrine, and bupivacaine at a maximum of 2.5 mg/kg (or 1 ml/kg of 0.25% solution) for adults. 1, 2

Lidocaine Dosing by Route

Local Infiltration and Peripheral Nerve Blocks

• Without epinephrine: Maximum 4.5 mg/kg 1
• With epinephrine: Maximum 7 mg/kg 1, 2
• Absolute maximum in adults: Do not exceed 500 mg total dose with epinephrine 2
• Calculate doses using ideal body weight for patients with BMI >30 kg/m² 1

Intravenous Lidocaine (Postoperative Pain)

• Loading dose: 1.5 mg/kg over 10 minutes (using ideal body weight) 3
• Maintenance infusion: 1.5 mg/kg/h for maximum 24 hours 3
• Absolute ceiling: No more than 120 mg/h regardless of weight 3
• Minimum weight requirement: Do not use in patients <40 kg 3

Critical Safety Interval

• Do not administer IV lidocaine within 4 hours of any nerve block 3
• Do not perform nerve blocks until 4 hours after stopping IV lidocaine infusion 3
• This prevents cumulative toxicity from overlapping local anesthetic interventions 3

Bupivacaine Dosing by Route

Local Infiltration and Peripheral Nerve Blocks (Adults)

• Maximum dose: 2.5 mg/kg or 1 ml/kg of 0.25% solution 2
• With epinephrine: Up to 225 mg total dose 2
• Without epinephrine: Up to 175 mg total dose 2
• Repeat dosing: May repeat every 3 hours, but do not exceed 400 mg in 24 hours 2

Concentration Selection Based on Motor Block Needs

• 0.25% bupivacaine: Incomplete motor block; use when muscle relaxation not required 2
• 0.5% bupivacaine: Provides motor blockade but may be inadequate for complete relaxation 2
• 0.75% bupivacaine: Complete motor block; contraindicated in obstetrics 2

Epidural Administration

• Incremental dosing: 3-5 ml boluses with sufficient time between doses to detect toxicity 2
• Obstetric epidural: Use only 0.25% or 0.5% concentrations, maximum 50-100 mg per dosing interval 2

Pediatric Dosing (Children >12 years)

Lidocaine

• Without epinephrine: 1.5-2.0 mg/kg 1
• With epinephrine: 3.0-4.5 mg/kg 1

Bupivacaine (from European Society for Paediatric Anaesthesiology)

• Wound infiltration: Maximum 2.5 mg/kg (1 ml/kg of 0.25% solution) 3
• Caudal block: 1.0 ml/kg of 0.25% bupivacaine 3
• Peripheral nerve blocks: 0.2-0.5 ml/kg of 0.25% bupivacaine 3
• Epidural (thoracic): 0.2-0.3 ml/kg of 0.25% bupivacaine (max 10 ml) 3
• Epidural (lumbar): 0.5 ml/kg of 0.25% bupivacaine (max 15 ml) 3

Bupivacaine is not recommended for children <12 years without specific pediatric anesthesia expertise 2

Ropivacaine Dosing (Pediatric)

• Wound infiltration: Maximum 3 mg/kg (1.5 ml/kg of 0.2% solution) 3
• Peripheral nerve blocks: 0.2-0.5 ml/kg of 0.2% ropivacaine 3

Toxicity Thresholds and Warning Signs

Plasma Concentration Thresholds

• Safe range: <5 μg/ml 4, 1
• Early toxicity: 5-10 μg/ml 4, 1
• Severe toxicity: >10 μg/ml 4, 1

Early Warning Signs (CNS Toxicity)

• Circumoral numbness or facial tingling 4, 1
• Metallic taste or tinnitus 4, 1
• Slurred speech or light-headedness 4, 1
• Confusion or agitation 4, 1

Severe Toxicity Manifestations

• Muscle twitching progressing to seizures 4, 1
• Loss of consciousness 4, 1
• Respiratory arrest 4, 1
• Cardiac arrhythmias and cardiovascular collapse 4, 1

Emergency Management of Toxicity

Immediate Actions

• Stop all local anesthetic administration immediately 4
• Administer 20% lipid emulsion: Initial bolus 1.5 ml/kg over 1 minute (approximately 100 ml for 70 kg patient) 4
• Start continuous infusion: 0.25 ml/kg/min for 30-60 minutes 4
• Repeat bolus: May give 1.5 ml/kg once or twice for persistent cardiovascular collapse 4
• Maximum total dose: 10 ml/kg over first hour 4

ACLS Modifications

• Continue standard ACLS protocols alongside lipid therapy 4
• Reduce epinephrine dose: Maximum 1 mcg/kg due to complex interactions with lipid emulsion 4

Preparation Requirements

• 20% lipid emulsion must be immediately available wherever local anesthetics are used 3, 4
• All staff must know exact storage location 3, 4

High-Risk Populations Requiring Dose Reduction

• Age >70 years 1, 2
• Body weight <40 kg 3, 1
• Advanced liver failure (lidocaine contraindicated) 1
• Renal dysfunction 1
• Cardiac disease or electrolyte disorders 1
• Pre-existing neurological conditions 1

Common Pitfalls to Avoid

• Never combine multiple local anesthetics without accounting for cumulative dose 1
• Never use actual body weight for obese patients—use ideal body weight 3, 1
• Never inject rapidly—use incremental dosing with aspiration 2
• Never exceed 12-hour application time for lidocaine patches 1
• Never use preservative-containing vials for epidural or caudal blocks 2
• Never assume absence of early symptoms means safety—maintain vigilance throughout procedure 4, 1