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[1]
  • If pt allergic to amides and esters, consider local Diphenhydramine (Na blocker)[2]
    • 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

References

  1. GlobalRPH. Local Anesthetics (ester and amide-type). http://www.globalrph.com/local-anesthetics.htm.
  2. Pavlidakey PG et al. Diphenhydramine as an Alternative Local Anesthetic Agent. J Clin Aesthet Dermatol. 2009 Oct; 2(10): 37–40.