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 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 Infection Bleeding Equipment Antiseptic solution 3-, 5-, or 10-mL syringe 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 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the needle is advanced to approximately two-thirds the length of the needle Continue to inject slowly as the needle is withdrawn from the insertion site Reinsert the needle at the end of the first wheal, where the skin is becoming anesthetized Repeat injections (Fig 130.47 B ) in this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 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at the proximal end of the wound, and lidocaine is injected slowly as the needle is advanced The needle is then withdrawn and redirected approximately 90 degrees, and infiltration is continued The needle is then reinserted at the other end of the wound and the process repeated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 to 10 minutes PERIPHERAL NERVE BLOCKS Complications Infection Bleeding Intravascular, intraneural injections Equipment Antiseptic solution 3- to 5-mL syringe 1% or 2% lidocaine (may be alkalinized with 1-mL NaHCO3 to 10-mL lidocaine) or 0.25% bupivacaine 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 to 10 minutes