Before the discovery of local anesthetics, local pain control
for lacerations, fractures, and minor surgery was only achieved
by minimizing the pain response centrally, typically with opiates
or alcohol. Local and regional anesthesia was founded on the discovery
of both the modern syringe and suitable anesthetic agents. In the
early 1850s, Charles Pravaz and Alexander Wood brought about the
use of small glass and metallic syringes. Cocaine was isolated by
Albert Neimann in 1860 and later refined into the first local anesthetic
and used for ocular surgery by Carl Koller in 1884. Within 1 year,
William Halsted and Richard Hall touted the use of cocaine by performing
the first successful nerve block of the infraorbital plexus. The
major drawbacks to cocaine, toxicity and addiction, fueled the search
for alternative agents.
Procaine (Novocain®) was discovered by
Alfred Einhorn in 1904 and became the local anesthetic of choice
for 40 years. The short duration of action and high rate of allergic
reactions was a limiting factor of procaine; prompting the search
for an alternative. Lidocaine was introduced by Nils Löfgren
in 1943 and continues to be the local anesthetic of choice today.1–3 A
multitude of anesthetic options (Tables 40-1 and 40-2) allow the practitioner to choose the
best agent for the situation at hand. Emergency medicine providers
should be well versed in anesthetic techniques for a number of important
and potentially painful procedures performed in the ED.4
Table 40-1 Topical Anesthetic Agents
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Table 40-1 Topical Anesthetic Agents
|Agent||Active Ingredients||Application||Time to Effectiveness|
|Eutectic mixture of local anesthetic agents (EMLA®)||Lidocaine 2.5%||Apply thick layer 5–10 grams (maximum,
20 grams) to area to be anesthetized, cover with semiocclusive dressing.||60 min|
|Tetracaine 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|
|Lidocaine, epinephrine, tetracaine (LET)||Lidocaine 4%||Apply 5 mL to gauze pad placed into wound,
cover with semiocclusive dressing.||20–30 min|
|Topical anesthetic gel (ZAP®)||Benzocaine 18%||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
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 40-2 Local
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