Topical

Lidocaine-Epinephrine-Tetracaine (LET)

• Use on non-mucosal skin surfaces (including lacerations)
• Apply 1-3mL to the wound with firm pressure for 15-30 minutes

Infiltrated

Drug	Dose (mg/kg)	Max
Lidocaine 1% 10mg/mL	4.5	300mg (30mL)
Lidocaine 1% (w/epi) 10mg/mL	7	500mg (50mL)
Bupivacaine 0.5% 5mg/mL	2	175mg (35mL)

Buffering

Injecting local anesthetics with low pH can be painful (the pH of lidocaine with epinephrine is 4.0). Buffering with sodium bicarbonate creates a solution approaching physiologic pH and may reduce pain.

1. Using a 10mL syringe, draw up 1mL of 8.4% sodium bicarbonate
2. Add 10mL of lidocaine, for a total volume of 11 ml (yes, the syringe can handle the extra mL), to achieve a 10:1 ratio

Local Anesthetic Systemic Toxicity (LAST)

Background

• Life-threatening adverse reaction to local anesthetic toxicity
• Occurs in ~0.2% of nerve blocks
• Generally occurs within minutes of injection

Causes

• Injection of local anesthetic into systemic circulation
  • Most common source of toxicity
  • Intravascular injection can cause toxicity below the maximum recommended dose
• Exceeding the maximum dose of local anesthetic (see table above)
• Absorption of anesthetic into systemic circulation by injection into extremely vascular area

Clinical Features

• CNS
  • Auditory changes/Tinnitus
  • Metallic taste
  • Seizures or drowsiness
  • Coma
  • Respiratory arrest
• Cardiovascular
  • Early signs
    • Tachycardia
    • Ventricular dysrhythmia
    • Hypertension
  • Late signs
    • Bradycardia
    • Conduction block
    • Cardiovascular collapse
    • Asystole

Management

1. Aggressive supportive care: Airway management, ACLS, seizure management
2. NaHCO₃ 1 ampule IV q2 minutes for: VT/VF, severe acidosis
3. Lipid emulsion 20% solution
   1. 1.5 mL/kg bolus over 1 minute
   2. Then, 0.25 mL/kg/min for 20 min or until hemodynamic stability achieved
   3. ↑ to 0.5 mL/kg/min if hemodynamic status declinesc
   4. Maximum total dose 12 mL/kg.

Source

1. WikEM