Local anesthetic systemic toxicity

Background

• Complication of lidocaine injection (accidental into systemic circulation)
  • 0.2% of nerve blocks
• Occurs within minutes of injection
  • 75% occuring within 5 minutes

Maximum Doses of Anesthetic Agents

Agent	Without Epinephrine	With Epinephrine	Duration	Notes
Lidocaine	5 mg/kg (max 300mg)	7 mg/kg (max 500mg)	30-90 min	1% soln contains 10 mg/ml 2% soln contains 20 mg/ml
Mepivicaine	7 mg/kg	8 mg/kg
Bupivicaine	2.5 mg/kg (max 175mg)	3 mg/kg (max 225mg)	6-8 hr	0.5% soln contains 5 mg/ml May cause cardiac arrest if injected intravascularly Do not buffer with bicarbonate
Ropivacaine	3 mg/kg
Prilocaine	6 mg/kg
Tetracaine	1 mg/kg	1.5 mg/kg	3hrs (10hrs with epi)
Procaine	7 mg/kg	10 mg/kg	30min (90min with epi)

Clinical Features

• CNS symptoms
  • Agitation
  • Auditory changes
  • Metallic taste
  • Seizures or drowsiness
  • Coma
  • Respiratory arrest
• Cardiovascular
  • First excitation
    • Tachycardia
    • Ventricular dysrhythmia
    • Hypertension
  • Followed by depression
    • Bradycardia
    • Conduction block
    • Asystole

Differential Diagnosis

• Anaphylaxis
• Anxiety

Diagnosis

• Clinical diagnosis

Workup

• Directed by clinical picture
• Blood levels of anesthetic are available, but not clinically useful.

Management

• Lipid emulsion, 20% solution
  • 1.5 mL/kg bolus over 1 minute
  • Then, 15 mL/kg per hour x 20-minute infusion (0.25 mL/kg/min for 20 min or until hemodynamic stability)
• Manage seizures with benzodiazepines; propofol is an option but may worsen CV toxicity
• ACLS modifications per ASRA (Am Soc of Regional Anesthesia):
  • Small initial doses of 100 μg boluses in adults
  • No vasopressin
  • Avoid CCBs and BBs
  • Amiodarone preferred in ventricular dysrhythmias

See Also

• Nerve Blocks (Main)
• Lidocaine

External Links

Medscape:Local Anesthetic Toxicity