Local anesthetics

Background

• Amides have two "i's" (prilocaine, lidocaine, etc)
• Esters have one "i" (tetracaine, procaine, benzocaine, etc)
• Ester local anesthetics more likely to cause allergic reaction due to metabolite PABA
• If patient allergic to amides and esters, consider local Diphenhydramine (Na blocker)
  • Sodium channel blocker mechanism
  • 1-2 mL of 1% diphenhydramine at a time, to not exceed excessive sedation dose
  • Typical vial is 50 mg/mL, so to make 10 mg/mL:
    • 10 mL NS removed from 50 mL vial
    • Add 10 mL of 50 mg/mL diphenhydramine to 40 mL of NS
    • Sedation is dose related and is similar to what would be expected for IM doses
    • Relative contraindications are the same for IM diphenhydramine administration

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)

Side Effects

• CNS
  • Perioral numbness
  • Seizure
• Cardiovascular
  • AV blocks
  • VT and VF
  • Asystole
• Allergic reaction
• Methemoglobinemia

See Also

• Local Anesthetic Systemic Toxicity (LAST)