Pediatric emergency medicine trisk 1112
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FIGURE 130.46 Direct wound infiltration for local anesthesia.
Continue this process of injection, withdrawal, and reinsertion in a sequential
fashion around the entire perimeter of the wound. Time to full anesthetic effect
depends on the size of the nerve fibers in the affected area. Anesthesia for small,
superficial cutaneous lacerations is nearly immediate. Wait 5 to 10 minutes for
full anesthetic effect if larger nerve fibers are involved (e.g., digital nerve block).
FIELD BLOCK
Indications
Local anesthesia for surgical procedures to be performed in areas of inflammation
or infection (e.g., incision, drainage, and packing of a soft tissue abscess or
anesthetizing a grossly contaminated wound) or for local anesthesia with
preservation of the wound architecture.
Complications
1. Infection
2. Bleeding
Equipment
1. Antiseptic solution
2. 3-, 5-, or 10-mL syringe
3. Local anesthetic
a. Lidocaine 1% or 2% (may alkalinize with NaHCO3 )
b. Lidocaine 1% or 2% with epinephrine (may alkalinize with NaHCO3 )
c. Bupivacaine 0.25% if longer anesthetic/analgesic action is desired
4. 25-, 27-, or 30-gauge needles
Procedure
Check the area for blood supply, sensation, and motor nerve function before
injecting the anesthetic agent. Cleanse the area with antiseptic solution.
Field blocks use the same plane of injection as direct wound infiltration, but the
subdermis is entered through intact skin to prevent carrying debris or bacteria into
uncontaminated tissues.
Insert the needle through the skin into the superficial fascia at the proximal
aspect of the laceration (Fig. 130.47 A ). Aspirate before injecting if in the
vicinity of a large vessel. Inject the lidocaine slowly in small amounts as the
needle is advanced to approximately two-thirds the length of the needle. Continue
to inject slowly as the needle is withdrawn from the insertion site. Reinsert the
needle at the end of the first wheal, where the skin is becoming anesthetized.
Repeat injections (Fig. 130.47 B ) in this fashion. Continue injections until
complete infiltration of the circumference of the wound has been achieved (Fig.
130.47 C ). Allow 5 minutes for anesthesia.
If the field block is used to prevent distortion of the wound margins, then
anesthetic is infiltrated in a diamond-shaped fashion around the wound. The
needle is inserted at the proximal end of the wound, and lidocaine is injected
slowly as the needle is advanced. The needle is then withdrawn and redirected
approximately 90 degrees, and infiltration is continued. The needle is then
reinserted at the other end of the wound and the process repeated until the
diamond-shaped ring of lidocaine is complete (Fig. 130.47 D ). Anesthesia should
be achieved by 5 to 10 minutes.
PERIPHERAL NERVE BLOCKS
Complications
1. Infection
2. Bleeding
3. Intravascular, intraneural injections
Equipment
1. Antiseptic solution
2. 3- to 5-mL syringe
3. 1% or 2% lidocaine (may be alkalinized with 1-mL NaHCO3 to 10-mL
lidocaine) or 0.25% bupivacaine
4. 27- to 30-gauge 1- to 1.5-in needle
Digital and Metacarpal Nerve Block
Indications
Anesthesia of fingers and toes for surgical procedures (i.e., drainage of a felon or
paronychia, removal of a foreign body, or laceration repair) including the
proximal digit
Caution
Do not use a vasoconstrictor such as epinephrine with the anesthetic agent.
Procedure
Identify the area that requires anesthesia. If it includes more than the distal twothirds to three-fourths of the finger or toe, use the metacarpal nerve block. For
more proximal procedures, use the proximal digital nerve block, discussed below.
Check the digit for blood supply, sensation, and motor nerve function before
injecting the anesthetic agent. The site of puncture on the digits for each is shown
in Figure 130.48A , part A.
Consider procedural sedation, assistance from a child life specialist or
employment of distraction techniques, and restraint if required. Have an assistant
grasp the extremity proximal to the digit to prevent movement.
The digital nerves, as shown in Figure 130.48A , part B, run laterally adjacent
to the flexor and extensor tendons on both the dorsal and volar aspects of the
digit, and lidocaine must be injected at both locations medially and laterally to
block the four nerves (see closed circles, Fig. 130.48A , part A).
Cleanse the planned puncture sites on the medial and lateral aspect(s) of the
digit thoroughly with antiseptic solution. Use a 27- or 30-gauge needle attached
to a 5-mL syringe and 1% lidocaine without epinephrine. Inject the site at a 45degree angle from vertical advancing until the needle contacts the periosteum.
Withdraw the needle slowly to just under the skin surface and gently rotate the
syringe to the vertical as shown in Figure 130.48A , part C. Then, advance the
needle to the volar surface while injecting anesthetic until at least three-fourths of
the way through the digit. Remove the needle completely, and then repeat the
procedure on the other side of the digit in a similar manner. Anesthesia should be
achieved within 5 to 10 minutes.
