How to Administer the Local Anesthetic

Direct Infiltration Around the Wound
In many cases, injecting the anesthetic agent around the wound is
an easy and reliable way to anesthetize the area. It is best to use as
small a needle as possible. The bigger the number, the smaller the
needle: use a 25- or 27-gauge needle, and inject slowly. Injection of
the anesthetic agent can be painful, and a slower injection rate
causes less pain.
You can inject directly into the wound to get the anesthetic into the surrounding
skin if the wound is reasonably clean. Alternatively, inject in
the noninjured skin along the outside of the wound. Inject until you
see the skin start to swell.
One technique is to push the needle into the tissues completely to the
hub, and then slowly infiltrate the anesthetic as you bring the needle
out of the tissues. Be sure to allow enough time for the agent to take
effect before starting your procedure (at least 5 minutes).

Nerve Blocks
In some areas of the body, discrete nerves that are responsible for sensation
to the injured area are easy to locate. In these instances, local
anesthesia can be infiltrated around (not into) the sensory nerve for
pain control to the area around the wound. This approach is advantageous
because the patient needs to undergo fewer injections than if
you anesthetize the entire wound margins directly.
Nerve blocks are also a good choice when the wound is deep, because
they often give a more complete block of the entire area, not
just the skin. This approach is especially appropriate for larger
wounds, because it usually requires less anesthetic agent than direct
infiltration.
Whenever possible, use a relatively small needle (23- or 25-gauge) for
the injection. Always draw back on the syringe before injecting the anesthetic.
The nerves that you are blocking often are located near blood
vessels.
Caution: You are probably injecting the anesthetic directly into the
nerve if the patient complains of strong electric shocks or severe pain
radiating along the distribution of the nerve. Stop the injection immediately
and reposition the needle.
It usually takes a few minutes longer for the anesthetic to take effect
than with direct wound injection. Often you must wait 10–15 minutes
after giving a nerve block before proceeding with the procedure.