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Home Books Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e

Chapter 36: Local and Regional Anesthesia

Douglas C. Dillon; Michael A. Gibbs

INTRODUCTION

Before the availability of local anesthetics, local pain control for lacerations, fractures, and minor surgery was achieved by minimizing the pain response centrally, typically with opiates or alcohol. Procaine, which entered clinical use in 1904, was the only local anesthetic available for almost 40 years, but the short duration of action and high rate of allergic reactions limited its effectiveness. Lidocaine was introduced in 1943 and continues to be the local anesthetic most commonly used in the ED.1,2 Additional local anesthetics are available for both topical and injectable use (Tables 36-1 and 36-2). Emergency physicians commonly use local and regional anesthetic techniques for potentially painful procedures performed in the ED.3 Regional anesthesia can also be used to control the pain of acute injuries and reduce the utilization of systemic analgesics.4,5

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 (one 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 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 (one dispenser application) with cotton swab to area to be anesthetized. 5 min
Benzocaine spray (Hurricaine®) Benzocaine 20% Apply 1-s 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 10–15 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† (min) Onset‡ (min) Maximum Dose (milligrams/kg, with epinephrine) Concentration (subdermal use) Concentration (regional anesthesia use)
Amides
Bupivacaine High High 200+ 10–15 3 (5) 0.50%–0.75% 0.25%–0.50%
Lidocaine Medium Medium 30–60 5 4 (7) 0.5%–1.0% 1%–2%
Levobupivacaine High High 200+ 10–15 2 0.25% 0.50%
Mepivacaine Low Low 45–90 3 4 0.5%–1.0% 1%–2%
Prilocaine Medium Medium 30–90 5 5 4% NA
Ropivacaine Medium Medium 200+ 5–15 3 0.5% 0.5%
Esters
Procaine Low Low 40 15–20 7 0.25%–0.5% 0.5%–2.0%
Chloroprocaine Low Low 45 5 8 1%–2% 1%–2%
Tetracaine (amethocaine) High High 200 15 1.5 NA 0.2%–0.3%
Alternatives ...

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