What are the typical dosages of local anaesthetics (e.g. lidocaine, bupivacaine) for blocks?

Local Anesthetic Dosing for Regional Blocks

Maximum Safe Doses

The maximum safe dose of bupivacaine 0.25% is 2.5 mg/kg (1 ml/kg) and lidocaine without epinephrine is 4.5 mg/kg, with these limits being critical to prevent systemic toxicity. 1, 2, 3

Bupivacaine Dosing by Block Type

Peripheral Nerve Blocks & Wound Infiltration:

• Bupivacaine 0.25%: 1 ml/kg (2.5 mg/kg maximum) for wound infiltration and peripheral nerve blocks 1, 4
• Levobupivacaine 0.25%: 1 ml/kg (2.5 mg/kg maximum) - offers similar efficacy with potentially improved cardiac safety profile 1, 4
• Ropivacaine 0.2%: 1.5 ml/kg (3 mg/kg maximum) - allows higher volumes when needed 1, 4

Neuraxial Blocks:

• Caudal block: 1.0 ml/kg of bupivacaine 0.25% - widely used in pediatrics for postoperative analgesia 1, 5
• Lumbar epidural: 0.5 ml/kg (maximum 15 ml) of bupivacaine 0.25% initially 1, 5
• Thoracic epidural: 0.2-0.3 ml/kg (maximum 10 ml) of bupivacaine 0.25% initially 1, 5

Fascial Plane & Truncal Blocks:

• Paravertebral block: 0.2-0.5 ml/kg of bupivacaine 0.25% 1, 4
• Fascia iliaca/femoral nerve block: 0.2-0.5 ml/kg of bupivacaine 0.25% 1, 4
• Rectus sheath/TAP block: 0.2-0.5 ml/kg per side of bupivacaine 0.25% 1, 4
• Intercostal block: 0.1 ml/kg of bupivacaine 0.25% 1

Facial Blocks:

• Maxillary/nasal nerve blocks: 0.15 ml/kg of bupivacaine 0.25% 1, 4

Lidocaine Dosing

Maximum doses vary significantly with epinephrine:

• Without epinephrine: 4.5 mg/kg (maximum 300 mg total) in healthy adults 1, 3
• With epinephrine: 7 mg/kg - epinephrine reduces systemic absorption 1
• Paracervical block: 200 mg total maximum (100 mg per side, inject slowly with 5 minutes between sides) 3

For dental blocks: 1.8 ml (9 mg) per injection site of 0.5% lidocaine with epinephrine, maximum 90 mg total per session 2

Ropivacaine as Alternative

Ropivacaine 0.2% provides higher allowable volumes:

• Maximum dose: 3 mg/kg (1.5 ml/kg) - 20% higher than bupivacaine 1, 4
• Duration: up to 21.5 hours for digital blocks, significantly longer than lidocaine's 1.8 hours 6, 7
• Onset time: 4.5 minutes (slower than lidocaine's 1.3 minutes but acceptable) 6

Critical Safety Considerations

Dose calculations must account for patient factors:

• Use ideal body weight for obese patients (BMI >30 kg/m²): ideal body weight = (height in cm - 100) for men; (height in cm - 105) for women 1
• Reduce doses by 30% in infants <6 months for amide local anesthetics 1
• Elderly and debilitated patients require dose reduction 2, 3
• Do not use in patients <40 kg for IV lidocaine (though this applies to IV infusions, not blocks) 1

Avoid concurrent local anesthetic administration:

• Wait 4 hours after nerve/fascial plane blocks before starting IV lidocaine 1
• Wait 4 hours after IV lidocaine before performing new blocks 1
• Single-shot spinal blocks are safe to combine due to small doses 1

Epinephrine considerations:

• Adding epinephrine 1:200,000 prolongs duration and reduces systemic absorption 1, 4, 2
• Maximum doses increase by approximately 50% with epinephrine (e.g., lidocaine from 4.5 to 7 mg/kg) 1

Continuous Infusions

For continuous regional anesthesia:

• Bupivacaine 0.25% or ropivacaine 0.2%: 0.1-0.3 ml/kg/h 1, 4
• Preservative-free clonidine: 0.2-0.4 mcg/kg/h can be added 1

Adjuvants to Prolong Duration

Preservative-free clonidine extends block duration:

• 1-2 mcg/kg added to local anesthetic for most blocks 1, 4
• Provides 4-8+ hours of analgesia without using long-acting formulations 4

Onset and Duration Comparison

Lidocaine provides fastest onset but shortest duration:

• Onset: 1.3 minutes, duration: 1.8 hours 6, 7
• With epinephrine: duration extends to 3-4 hours 7

Bupivacaine offers intermediate onset with long duration:

• Onset: 7.6 minutes, duration: 8-12 hours 7
• No advantage to mixing lidocaine with bupivacaine - onset times remain similar to bupivacaine alone 8, 9

Ropivacaine provides longest duration:

• Onset: 4.5 minutes, duration: up to 21.5 hours 6, 7

Common Pitfalls

Always calculate maximum dose before administration - write down the mg/kg calculation to avoid exceeding toxic thresholds 1, 2

Use incremental dosing for epidurals - give 3-5 ml boluses with time between doses to detect intravascular or intrathecal injection 2

Do not use preservative-containing vials for neuraxial blocks - only single-dose ampules for epidural/caudal 2

Mixing local anesthetics provides no clinical benefit - the combination does not speed onset or improve duration compared to using bupivacaine alone 8, 9