How To Do Local Wound Infiltration

• Laceration or other surgically treated skin lesion

• Foreign body removal

• Incision and drainage

Absolute contraindications

• History of allergy to the anesthetic agent or delivery vehicle (choose a different anesthetic)

Relative contraindications

• Large wounds (local infiltration of which may require toxic amounts of anesthetic)*

• Wounds requiring precise anatomic alignment (eg, vermilion border lip lacerations), for which wound edge distortion caused by infiltration is problematic*

* Nerve blocks and procedural sedation and analgesia should be used as needed.

• Adverse reaction to the anesthetic (eg, allergic reaction to the anesthetic [rare] or to methylparaben [a preservative])

• Hematoma

• Spread of infection, by passing the needle through an infected area

• Nonsterile gloves

• Barrier precautions as indicated (eg, face mask, safety glasses or face shield, cap and gown)

• Syringe (eg, 1 to 10 mL) and needle (eg, 25 or 27 gauge) for anesthetic injection

• Topical anesthetic§ (eg, LET solution: 4% lidocaine, 0.1% epinephrine, 0.5% tetracaine) plus cotton ball or dental pledget; optional and often used for children

• Tissue forceps (eg, Adson forceps), tissue hook as needed to expose the sides of the wound

• #11 scalpel blade for tissue undermining and debridement (if needed)

* Local anesthetics are discussed in Lacerations.

• Document any preexisting nerve deficit distal to the wound before doing anesthetic infiltration.

• Stop the anesthetic infiltration procedure and consider sedation for patients who are unable to cooperate.

• Intradermal anesthetic injection is painful. Inject subdermally (subcutaneously) to cause less pain during local wound infiltration.

• Position the patient comfortably, with the wound exposed and well-illuminated.

• Do a neurovascular examination of structures distal to the wound.

• Wear gloves and use appropriate barrier precautions.

• Cleanse the skin from the wound edges outward, making several outwardly expanding circles with antiseptic solution. Do not introduce a cleansing agent directly into the wound because many are toxic to tissues and may interfere with wound healing.

Topical anesthesia (optional, for children and anxious adults)

• Soak a cotton dental pledget (or cotton ball) the length of the wound in several mL of the topical solution and place it within the wound for 30 minutes.

• If anesthesia is incomplete, give supplementary local infiltration anesthesia through the partially anesthetized wound edges (usually resulting in only minimal pain).

Local infiltration anesthesia

• Hold the local anesthetic syringe at a shallow angle to the skin.

• Insert the needle directly into the exposed subdermal layer of the wound edge (ie, do not insert the needle percutaneously) and advance the needle to the hub.

• Aspirate to exclude intravascular placement and then slowly inject the anesthetic while withdrawing the needle.

• Redirect the already injected needle into unanesthetized skin to maximize the area anesthetized with a single needlestick. Continue to anesthetize, covering the entire wound circumference.

  For grossly contaminated or infected wounds, consider injecting instead percutaneously through the intact, uninfected (or otherwise disinfected) skin around the wound (field block).

• Allow several minutes for the anesthetic to take effect. You may gently massage the overlying skin with your fingertip to facilitate spread of the anesthetic in the tissues.

How To Anesthetize Wounds Usin...

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• Inject directly into clean wound edges, rather than through adjacent intact skin. It is less painful and does not increase the risk of wound infection.

• Position the needle along the long axis of the wound making only a single injection (or minimum number of injections) necessary to anesthetize each side of the wound.

• Consider anesthetizing wounds before cleansing and irrigating, because these procedures can be quite painful.

• Consider using topical anesthetics particularly for wounds of the face and scalp and those closed by topical skin adhesives.

• Minimize the pain of injection by injecting slowly (eg, 30 to 60 seconds), warming the anesthetic solution to body temperature, and buffering the anesthetic.