TECHNIQUE
■ Pain from local anesthesia can be diminished by using a small needle, ie,
<25-gauge, slow infiltration, buffering the local anesthetic with bicarbon-
ate (do not use with bupivacaine because the combination will crystal-
lize), warming the local anesthetic to body temperature, and injecting into
the wound margins (instead of intact epidermis).
■ Anesthetic agents: 0.5–2% lidocaine, 0.5–1% procaine, 0.25% bupivacaine
(Marcaine), 1% diphenhydramine (Benadryl). Higher concentrations do
not provide additional benefit.
■ Lidocaine is most commonly used because of its excellent activity pro-
file, low allergenicity and toxicity, user familiarity, and ready availability.
■ Onset: 2–5 minutes, duration: 1–2 hours
■ Procaine is useful for patients who are allergic to amide anesthetics.
■ Bupivacaine is used because of its prolonged duration and may be pre-
ferred for prolonged procedures, or for short procedures that may be
interrupted in a busy ED.
■ Onset: 2–5 minutes, duration: 4–6 hours
■ Epinephrine: Prolongs anesthesia duration. Epinephrine also provides
excellent wound hemostasis and slows systemic absorption and therefore
may be useful for areas with increased vascular supply (ie, scalp lacerations).
■ Phentolamine, which produces postsynaptic α-adrenergic blockade,
can be used to reverse epinephrine-induced tissue ischemia in a dose of
0.5–5 mg diluted 1:1 with saline infiltration.
■ Sodium bicarbonate: Works by increasing the ratio of nonionized to ion-
ized molecules, which either renders the pain receptors less sensitive or
causes a more rapid diffusion of solution into the nerve and a shorter time
to anesthetic onset.COMPLICATIONS
■ True allergic reactions account for only 1–2% of all adverse reactions.
■ Ester solutions (procaine, tetracaine), which produce the metabolite para-
aminobenzoic acid (PABA), account for the great majority of these reactions.
■ Amide solutions (lidocaine, bupivacaine) are rarely involved and it is
usually the preservative methylparaben (MPB), which is structurally
similar to PABA, that is responsible.
■ As with any allergic or anaphylactic reaction, symptoms include pruri-
tis, urticaria, swelling, laryngospasm, bronchospasm, and even seizures,
coma, and respiratory arrest.
■ Epinephrine can cause headache, hypertension, palpitations, tremors,
tachycardia, diaphoresis, and cardiac arrest.INTERPRETATION OFRESULTS
■ Local anesthesia is achieved when the patient no longer feels the tip of the
needle in area requiring suturing/procedure. Typically, pressure sensation
will remain intact.Regional Nerve BlocksINDICATIONS
■ Regional nerve blocks are effective for closing facial lacerations, especially
those of the lips, the forehead, and the midface, where the swelling caused
by local infiltration is undesirable (see Table 19.1 and Figures 19.10A
and B). They are also useful for providing anesthesia to the hands and feet.
■ Regional blocks are also useful for the control of dental pain.PROCEDURES AND SKILLS