Local Anesthesia Administration

E.J. Mayeaux, Jr, MD, DABFP, FAAFP
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Subject: Local Anesthesia Administration

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Introduction

Most minor or office operations are performed after injection of local anesthesia. Proper administration technique can reduce patient discomfort, improve patient satisfaction with the service, and improve the procedure’s outcome. Unfortunately, the techniques for minimizing discomfort during local anesthetic administration are often overlooked in modern clinical practice. 
Table 1-1 shows available drugs commonly used as local anesthetics. The two main classes of injectable local anesthetics are amides and esters. The amides are more widely used and include lidocaine (Xylocaine) and bupivacaine (Marcaine). The esters, represented by procaine (Novocain), have a slower onset of action than the amides and a higher rate of allergic reactions. Individuals with an allergy to one class of anesthetics generally can receive the other class safely. Administration of the esters is limited to individuals with a prior allergic reaction to amide anesthetics. 
Many patients claim an allergy to “caine” drugs, but they actually have experienced a vagal response or other systemic response to receiving an injection. If the exact nature of the prior reaction cannot be ascertained, administration of diphenhydramine hydrochloride (Benadryl) can provide sufficient anesthesia for small surgical procedures. Between 1 and 2 mL of diphenhydramine (25 mg/mL) solution is diluted with 1 to 4 mL of normal saline for intradermal (not subdermal) injection. 
Epinephrine in the local anesthetic solution prolongs the duration of the anesthetic and reduces bleeding by producing local vasoconstriction. The use of epinephrine also permits use of larger volumes of anesthetic. An average-sized adult (70 kg) can safely receive up to 28 mL (4 mg/kg) of 1% lidocaine and up to 49 mL (7 mg/kg) of 1% lidocaine with epinephrine
Historically, physicians have been taught to avoid administering solutions with epinephrine to body sites served by single arteries, such as fingers, toes, penis, and the end of the nose. The safety of administering epinephrine to the tip of the nose or to the digits has been documented in some reports, but limiting the use of epinephrine in these sites is prudent in the current medicolegal climate. 
 
TABLE 1-1.
Commonly Available Local Anesthetics
Local anesthetics can be injected intradermally or subdermally. Intradermal administration produces a visible wheal in the skin, and the onset of action of the anesthetic is almost immediate. Intradermal injection of a large volume of solution can stretch pain sensors in the skin, aiding in the anesthetic effect. This volume effect is believed to explain the benefit of normal saline injections into trigger points. Other strategies to reduce the discomfort of injection are shown in Table 1-2. Intradermal injection is especially useful for shave excisions, because the anesthetic solution effectively thickens the dermis, elevates the lesion, and prevents inadvertent penetration beneath the dermis. 
Subdermal injections take effect more slowly but generally produce much less discomfort for the patient. Some physicians recommend initial administration of an anesthetic into a subdermal (less painful) location and then withdrawing the needle tip for intradermal injection. The initial subdermal administration often reduces the discomfort of the intradermal injection. 

Equipment

  • Syringes (TB, 5 mL, or 10 mL), anesthetic solutions, and needles (18 or 20 gauge, 1 inch long for drawing up anesthetic; 25 or 27 gauge, 1.25 inch long for delivering anesthetic) can be ordered from surgical supply houses or pharmacies. A suggested anesthesia tray that can be used for this procedure is listed in Appendix F.

Indications

  • Local or regional anesthesia for minor procedures

Contraindications

  • Allergy to local anesthetics

The Procedure

Step 1

Prep the skin with alcohol if it is not already prepped with povidone/iodine or chlorhexidine solution. Stretch the skin with your nondominant hand before inserting the needle into the skin. Patients dread having the needle inserted; the discomfort is reduced if the pain sensors in the skin are stretched. 
  • PITFALL: Replace the needle used for drawing the anesthetic from the stock bottle with a smaller (30-gauge) needle before injection into the patient. A sharp needle decreases pain.

Step 2

The syringe is held in your dominant hand in the position ready to inject. Your thumb should be near (but not on) the plunger. After the needle is inserted into skin, some physicians prefer to withdraw the plunger to ensure that the needle tip is not in an intravascular location. The thumb can be slipped under the back edge of the plunger and pulled back, watching for blood to enter the syringe to ensure that the needle tip is not in a blood vessel. The thumb then slips onto the plunger for gentle injection. However, it is very unlikely that a short, 30-gauge needle tip will enter a significant vessel, and many physicians prefer to inject without withdrawing, because pulling back on the plunger moves the needle tip and causes discomfort for the patient. 
  • PITFALL: Avoid movement of the needle after it enters the skin. Many physicians hold the syringe like a pencil for needle insertion. After insertion, they stop stretching the skin with the nondominant hand and grab the syringe, shift the dominant hand back onto the plunger, and pull back on the plunger to check for vascular entry of the needle tip. They then shift the hands again and move the dominant hand into a position for injection. All of these shifts cause movement of the needle tip in the skin and substantially increase the discomfort for the patient.

Step 3

Insert the needle into skin at a 15- or 30-degree angle. The depth of the needle tip is more difficult to control at a 90-degree angle of entry. 

Step 4

When injecting laceration sites for repair, insert the needle into the wound edge, rather than intact skin. Insertion of a needle into a wound edge produces less discomfort. 

Step 5

Pause after the needle enters the skin. Try to make the patient talk or laugh. Patients fear the needle entry, and after they realize that the discomfort was less than anticipated, they often relax. Maintain skin stretch with the nondominant hand for the injection. 
  • PITFALL: Plunging in anesthetic immediately after needle entry causes continued discomfort and anxiety. Most vagal or syncopal episodes are related to the catecholamine storm produced by the patient’s anxiety. Pausing after needle insertion and slow administration allow patients to relax, reducing their catecholamine production and reducing complications.

Step 6

Intradermal injection creates a wheal in the skin. Administer the local anesthetic for a shave excision below the center of the lesion to be removed. The anesthetic fluid effectively increases the depth of the dermis, reducing chances for subdermal penetration at shave excision. The fluid also floats the lesion upward, facilitating removal by shave technique. 
  • PEARL: When the needle tip is correctly placed, there is resistance to injecting the anesthetic within the skin.

Complications

  • Bleeding and hematoma formation.

  • Allergic reaction is rare. Patients who believe they are allergic to lidocaine are more likely allergic to the preservative methylparaben. Preservative-free lidocaine is available.

  • Infection.

  • Palpitations or feelings of warmth (due to epinephrine component).

Pediatric Considerations

Children older than 6 years are dosed like adults except that the maximal dose is based on weight. The recommended maximal dose for lidocaine in children is 3 to 5 mg/kg, and 7 mg/kg when combined with epinephrine. Remember that 1% lidocaine is 10 mg/mL. Children 6 months to 3 years have the same volume of distribution and elimination half-life as adults. Neonates have an increased volume of distribution, decreased hepatic clearance, and doubled terminal elimination half-life (3.2 hours). 

Postprocedure Instructions

Have the patient report any postprocedure local rashes or blistering that may indicate an adverse reaction or infection. 

Coding Information

Anesthesia codes (00100 to 01999) are usually limited to anesthesiologists providing patient services for surgical procedures. Local anesthesia is not reported in addition to the surgical procedure. Some insurance providers permit billing of regional or general anesthesia by the physician or surgeon performing the procedure. If reporting additional anesthesia services, the -47 modifier is attached to the surgical code. It is unlikely that additional reimbursement will be provided for field blocks; the service is considered part of the reporting of the surgical procedure. 
 
Table 1-2.
Recommendations to Reduce the Discomfort of Local Anesthesia

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