Local anesthesia

Last updated: November 24, 2022

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Local anesthesia refers to the reversible numbing of pain conduction by blocking nerve endings at and around the site of administration. It is commonly used for minor procedures and wound repair and is further subdivided into topical anesthesia and infiltration anesthesia, which is the loss of sensation in a localized superficial area via injection of a local anesthetic agent into subcutaneous or submucosal tissue. Contraindications include allergy to the class of anesthetic agent. The preparation consists of performing a baseline neurovascular examination and selecting the appropriate local anesthetic. Complications are rare.

See also “Regional anesthesia” and “Local anesthetic agents.”

Local anesthesia is used to decrease the pain associated with minor procedures. [1]

Topical anesthetics may help reduce pain and anxiety in children before minor invasive procedures (e.g., IV placement, wound repair). [2]

We list the most important contraindications. The selection is not exhaustive.

Physical examination

Medication selection

There are various combinations of local anesthetics; selection is based on the type of agent and potential benefit of additives.

Dose-to-volume conversion guide for common local anesthetics [1]
Concentration Maximum dose in adults Maximum volume for adults
Lidocaine without epinephrine 0.5% 300 mg 60 mL
1% 30 mL
Lidocaine with epinephrine 0.5% 500 mg 100 mL
1% 50 mL
Bupivacaine without epinephrine 0.25% 175 mg
70 mL
Bupivacaine with epinephrine 0.25% 225 mg 90 mL

Calculate the maximum dose of local anesthetic, especially in pediatric patients, to avoid local anesthetic systemic toxicity.

This section describes common procedures for infiltration anesthesia.

Single-point local anesthesia infiltration [1]

  1. Don PPE and prep skin.
  2. Attach a 25–27 gauge needle of appropriate length to the syringe.
  3. Insert the needle into the site and advance to the desired depth.
  4. Aspirate to ensure the needle is not located intravascularly.
  5. Inject the anesthetic slowly while withdrawing the needle.

If multiple injections are needed, minimize skin punctures by withdrawing the needle almost completely, then redirecting the needle along another path.

Local anesthesia for wound repair [1]

  1. Don PPE and prep skin.
  2. Attach a 25–27 gauge needle of a length comparable to that of the wound to the syringe.
  3. Insert the needle into the subcutaneous tissue through the wound margin.
  4. Advance the needle to the hub while following wound margins.
  5. Aspirate to ensure the needle is not located intravascularly.
  6. Inject the anesthetic slowly while withdrawing the needle.
  7. Repeat as needed until wound margins are fully anesthetized.

In patients with a grossly contaminated wound, consider injecting the anesthetic agent through intact, clean skin. [1]

Complications are rare; see “Adverse effects of local anesthetic agents.”

We list the most important complications. The selection is not exhaustive.

  1. Roberts JR. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. Elsevier ; 2018
  2. Achar S, Kundu S. Principles of office anesthesia: part I. Infiltrative anesthesia.. Am Fam Physician. 2002; 66 (1): p.91-4.
  3. Mace SE, Whiteman P, Avarello JT, et al. Local and Topical Anesthetics for Pediatric Patients in the Emergency Department. Pediatr Emerg Care. 2020; 36 (12): p.593-601. doi: 10.1097/pec.0000000000002285 . | Open in Read by QxMD

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