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Chapter 36: Local and Regional Anesthesia

Michael A. Gibbs; Teresa Wu

INTRODUCTION

Local anesthetics (Tables 36-1 and 36-2) are used to reduce pain from acute injury or procedures performed in the ED.1 The most common routes of administration include topical, subdermal, and infiltrative around peripheral nerves (regional anesthesia).2,3

TABLE 36-1Topical Anesthetic Agents
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TABLE 36-1 Topical Anesthetic Agents
Agent Active Ingredients Application Time to Effectiveness
Intact Dermis
Eutectic mixture of local anesthetic agents (EMLA®)

Lidocaine 2.5%

Prilocaine 2.5%

 Apply thick layer, 5–10 grams (maximum 20 grams), to area to be anesthetized; cover with semiocclusive dressing. 60 min
Tetracaine (amethocaine) gel (Ametop®) Tetracaine 4% Apply 1 gram (1 tube) to area to be anesthetized; cover with occlusive dressing. 30 min
Liposome-encapsulated tetracaine Tetracaine 5% Apply 0.5 gram to area to be anesthetized. 60 min
Liposome-encapsulated lidocaine (LMX4® and LMX5®) Lidocaine 4% or 5% Apply 2.5 grams to area to be anesthetized. 30–60 min
Open Dermis
Lidocaine, epinephrine, tetracaine (LET)

Lidocaine 4%

Epinephrine 0.1%

Tetracaine 0.5%

 Apply 3–5 mL to gauze pad placed into wound; cover with semiocclusive dressing. 20–30 min
Mucosa
Topical anesthetic gel (ZAP®)

Benzocaine 18%

Tetracaine 2%

 Apply 0.2 mL (1 dispenser application) with cotton swab to area to be anesthetized. 5 min
Benzocaine spray (Hurricaine®) Benzocaine 20% Apply 1 spray to area to be anesthetized; volume delivered is highly dependent on canister orientation and residual volume. 15–30 s
Viscous lidocaine Lidocaine 2% Apply 10 mL to area (e.g., topical anesthesia before upper airway procedures). 2–5 min
TABLE 36-2Local Anesthetic Agents
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TABLE 36-2 Local Anesthetic Agents
Agent Lipid Solubility* Protein Binding Duration† without epinephrine (min) Onset‡ (min) Maximum Dose milligrams/kg without epinephrine (with epinephrine) Concentration (subdermal use) Concentration (regional anesthesia use)
Amides
Bupivacaine High High 120–240 2–10 3 (5) 0.50%–0.75% 0.25%–0.50%
Lidocaine Medium Medium 30–120 <1 4 (7) 0.5%–1.0% 1%–2%
Levobupivacaine High High >1000 10–20 2 0.25% 0.50%
Mepivacaine Low Medium 30–120 3–20 4 0.5%–1.0% 1%–2%
Prilocaine Medium Medium 30–120 5–6 5 4% NA
Ropivacaine Medium High 120–350 10–45 3 0.5% 0.5%
Esters
Procaine Low Low 15–90 5 7 0.25%–0.5% 0.5%–2.0%
Chloroprocaine Low Low 30–60 5–6 8 1%–2% 1%–2%
Tetracaine (amethocaine) High High 120–240 7 1.5 NA 0.2%–0.3%
Alternatives for patients with reactions to amides and esters
Diphenhydramine§     25     1% NA
Benzyl alcohol with epinephrine     15–25     0.9% NA

Abbreviation: NA = not applicable.

*Lipid solubility determines the potency of the anesthetic, with the more lipophilic anesthetics having enhanced potency compared with less lipophilic agents.

†The more an anesthetic is bound to proteins, generally, the longer the duration of action.

‡The onset of action of an anesthetic is determined by the total dose of anesthetic given and the pH at which 50% of the drug is ionized and 50% of the drug is nonionized.

§Diphenhydramine 1% or ...

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