What are the characteristics, advantages, disadvantages, and side effects of local anesthetics, such as Lidocaine, Bupivacaine, and Ropivacaine, in regional and neuraxial anesthesia?

Local Anesthetics in Regional and Neuraxial Anesthesia

Amide local anesthetics (lidocaine, bupivacaine, ropivacaine) are generally preferred over ester types for regional and neuraxial anesthesia due to their more favorable pharmacokinetic profiles, except in specific situations where prolonged regional anesthesia is required. 1

Classification and Characteristics

Amide Local Anesthetics

• Lidocaine

  • Moderate potency and duration (90-200 minutes) 1
  • Maximum dose: 4.4 mg/kg without epinephrine, 7.0 mg/kg with epinephrine 1
  • Faster onset compared to bupivacaine and ropivacaine 2
  • Should be avoided for intrathecal use in lithotomy position due to risk of transient neurologic symptoms 3

• Bupivacaine

  • High potency and long duration (180-600 minutes) 1
  • Maximum dose: 1.3 mg/kg without epinephrine, 3.0 mg/kg with epinephrine 1
  • More cardiotoxic than ropivacaine or lidocaine 4
  • Can cause ventricular tachycardia at high concentrations 4

• Ropivacaine

  • High potency and long duration (180-600 minutes) 1
  • Maximum dose: 2 mg/kg without epinephrine, 3.0 mg/kg with epinephrine 1
  • Less cardiotoxic than bupivacaine 4
  • Less motor blockade compared to equivalent doses of bupivacaine 3

Ester Local Anesthetics

• Procaine

  • Low potency and short duration (60-90 minutes) 1
  • Maximum dose: 6 mg/kg without epinephrine, 10 mg/kg with epinephrine 1
  • Degraded by plasma cholinesterase 1

• Chloroprocaine

  • Low potency and very short duration (30-60 minutes) 1
  • Maximum dose: 12 mg/kg without epinephrine, 20 mg/kg with epinephrine 1
  • Useful for day-case spinal anesthesia due to rapid onset and recovery 3

• Tetracaine

  • High potency and long duration (180-600 minutes) 1
  • Maximum dose: 1 mg/kg without epinephrine, 1.5 mg/kg with epinephrine 1

Advantages of Regional/Neuraxial Anesthesia

• Avoids airway manipulation and potential respiratory complications associated with general anesthesia 1
• Provides excellent postoperative analgesia 5
• Reduces opioid consumption and associated side effects 5
• Peripheral nerve blocks have minimal hemodynamic effects compared to neuraxial techniques 1
• May be advantageous in patients with full stomach 1
• Allows early ambulation and discharge in ambulatory settings when appropriate agents are selected 6

Disadvantages and Limitations

• Time-consuming application, especially in emergency situations 1
• Requires patient cooperation, which may be difficult in agitated or confused patients 1
• Risk of local anesthetic systemic toxicity (LAST) 5
• Neuraxial techniques can cause sympathetic blockade leading to hypotension 1
• Risk of nerve injury, though rare with proper technique 5
• Potential for block failure requiring conversion to general anesthesia 1
• Risk of hematoma formation in patients with coagulopathy (especially with neuraxial techniques) 1

Dosing Considerations

• For neuraxial blocks:

  • Thoracic epidural: Bupivacaine/Levobupivacaine 0.25% at 0.2-0.3 ml/kg (max 10ml) or Ropivacaine 0.2% at 0.2-0.3 ml/kg 1
  • Lumbar epidural: Bupivacaine/Levobupivacaine 0.25% at 0.5 ml/kg (max 15ml) or Ropivacaine 0.2% at 0.5 ml/kg (max 15ml) 1
  • Caudal block: Bupivacaine/Levobupivacaine 0.25% at 1.0 ml/kg or Ropivacaine 0.2% at 1.0 ml/kg 1

• For peripheral nerve blocks:

  • Mass of drug (not volume or concentration) primarily determines block onset, success, and duration 3
  • Bupivacaine/Levobupivacaine 0.25%: maximum dose 1 ml/kg (2.5 mg/kg) 1
  • Ropivacaine 0.2%: maximum dose 1.5 ml/kg (3 mg/kg) 1
  • For ultrasound-guided blocks: 0.2-0.5 ml/kg for most peripheral nerve blocks 1

Side Effects and Complications

• Local Anesthetic Systemic Toxicity (LAST)

  • CNS symptoms: perioral numbness, metallic taste, agitation, seizures 5
  • Cardiovascular symptoms: hypotension, arrhythmias, cardiac arrest 4
  • Treatment: Stop injection, support airway/circulation, administer lipid emulsion (20% lipid emulsion at 1.5 ml/kg over 1 minute) 1

• Neurological complications

  • Transient neurologic symptoms (especially with intrathecal lidocaine) 3
  • Permanent nerve injury (rare) 5

• Hemodynamic effects

  • Hypotension due to sympathetic blockade (more common with neuraxial techniques) 1
  • Bradycardia 4

• Other complications

  • Hematoma formation (risk increased with anticoagulants) 1
  • Infection at injection site 5
  • High or total spinal anesthesia 5
  • Post-dural puncture headache 5

Clinical Pearls

• Ultrasound guidance improves efficacy and minimizes complications for peripheral nerve blocks 5
• Amide local anesthetics are preferred over esters for most blocks due to lower risk of allergic reactions and longer duration 1
• Consider using ester-type local anesthetics when prolonged regional anesthesia is indicated in patients with plasma cholinesterase deficiency 1
• Addition of epinephrine prolongs duration and reduces systemic absorption but should be used cautiously in vascular areas 1
• Calculate maximum allowable dose before administration to prevent LAST 1
• Reduce doses of amides by 30% in infants younger than 6 months 1
• Bupivacaine is more cardiotoxic than ropivacaine or lidocaine at equivalent doses 4

Special Considerations

• In pediatric patients, careful dose calculation based on weight is essential to prevent toxicity 1
• For ambulatory surgery, shorter-acting agents like chloroprocaine or mepivacaine may be preferred for faster recovery 6
• When performing large-volume fascial plane blocks with ropivacaine, be vigilant for signs of LAST 3
• In patients with cardiovascular disease, consider using ropivacaine over bupivacaine due to lower cardiotoxicity 4