Injectable Anesthetics

Injectable lidocaine (1% to 2%) reduces pain by blocking neural cell membrane sodium channels and inhibiting impulse propagation. Initially, small delta nerve fibers, which are responsible for pain and temperature sensations, are blocked. Larger beta nerve fibers, which are responsible for pressure and vibration, take longer to anesthetize. For this reason, injectable anesthetics have a rapid reduction of pain but a slower reduction in sensations of pressure and pulling.³

Lidocaine may be buffered with sodium bicarbonate in a 1 : 8 or 1 : 10 ratio to reduce the burning sensation upon injection of anesthetic. See Chapter 3, Anesthesia, for information on side effects and toxicity with lidocaine and alternative options for lidocaine allergic patients.

Regional Nerve Blocks

Lidocaine without epinephrine is used for nerve blocks. Facial nerve blocks are beneficial for cosmetic procedures because anesthetic is placed outside of the treatment area. Profound anesthesia can be achieved with minimal distortion of the treatment area, which is particularly useful with dermal filler treatments.^2,4 Nerve blocks are also useful for painful procedures such as ablative laser resurfacing, particularly in the sensitive perioral area.

Infraorbital and mental nerve blocks are most commonly used with facial cosmetic procedures. The locations of the infraorbital and mental nerves are shown in Figure 20-1 and can be identified by palpating the nerve foramina. The infraorbital and mental nerves lie along a vertical line extending from the supraorbital notch to the mandible. The supraorbital notch lies along the upper border of the orbit and is palpable approximately 2.5 cm lateral to the midline of the face. The infraorbital foramen is palpable approximately 1 cm inferior to the infraorbital bony margin, and the mental nerve is palpable just above the margin of the mandible.

FIGURE 20-1 Major nerves and foramina of the face.

Equipment

• 5.0-mL syringe

• Lidocaine HCl 1% to 2%

• 18-gauge, 1.5-inch needles to draw up anesthetic

• 30-gauge, 0.5-inch needles for injection.

Infraorbital Nerve Block

The infraorbital nerve innervates most of the upper lip, lower eyelid, lateral portion of the nose, and medial cheek. An infraorbital nerve block can anesthetize all of these regions (Figure 20-2).³ The intent of the infraorbital nerve block technique described here, utilizing a short 0.5-inch needle, is to reach the distal portions of the infraorbital nerve, not the nerve foramen, which would require a longer needle (approximately inches long). The philtrum and the corners of the mouth are typically poorly anesthetized with infraorbital blocks, and additional local infiltration is also required when treating these areas.

FIGURE 20-2 Infraorbital nerve and area of anesthesia with nerve block.

Procedure Steps

1. Comfortably position the patient upright at about 65 degrees with the chin tipped upward.

2. Stand on the contralateral side of the patient.

3. Lift the upper lip for good visualization of the gingivobuccal margin.

4. Insert a 30-gauge, 0.5-inch needle at the gingivobuccal margin just lateral to the maxillary canine (third tooth from the midline) and direct the needle superiorly, angling toward the pupil (Figure 20-3).

5. Advance the needle almost the full length and inject 0.5 to 1.0 mL of lidocaine. The anesthetic should flow easily.

6. After removing the needle, compress the deep palpable wheal of lidocaine superiorly toward the infraorbital foramen.

7. Repeat for the contralateral infraorbital nerve.

8. The philtral area requires additional infiltration of local anesthetic to achieve adequate anesthesia. Inject 0.1 mL of lidocaine intraorally in the mucosa just lateral to the upper lip frenulum (Figure 20-4). After the needle is removed, compress the injection site to distribute the lidocaine, and repeat for the other side of the upper lip frenulum.

9. The onset of anesthetic effect is typically 5 to 10 minutes.

FIGURE 20-3 Technique for intraoral infraorbital nerve block.

(Copyright Rebecca Small, MD.)

FIGURE 20-4 Technique for intraoral anesthetic infiltration of the upper lip frenulum.

(Copyright Rebecca Small, MD.)

Mental Nerve Block

The mental nerve innervates most of the lower lip, and a mental nerve block can anesthetize this region (Figure 20-5).³ The corner of the mouth is typically poorly anesthetized, and additional local infiltration is also required when treating this area.

FIGURE 20-5 Mental nerve and area of anesthesia with nerve block.

Procedure Steps

1. Comfortably position the patient upright at about 65 degrees, with the chin tipped downward.

2. Stand on the contralateral side of the patient.

3. Lift the lower lip for good visualization of the gingivobuccal margin.

4. Insert a 30-gauge, 0.5-inch needle at the gingivobuccal margin just lateral to the first mandibular bicuspid (also called the first premolar, which is the fourth tooth from the midline) (Figure 20-6) and direct the needle inferior-laterally toward the mental nerve foramen.

5. Advance the needle halfway to the hub, and inject 0.5 to 1.0 mL of lidocaine. The anesthetic should flow easily.

6. After removing the needle, compress the deep palpable wheal of lidocaine inferiorly toward the mental nerve foramen.

7. Repeat for the contralateral mental nerve.

8. The lateral corners of the mouth require additional infiltration of local anesthetic to achieve adequate anesthesia. Inject 0.1 mL of lidocaine intraorally in the mucosa at the corner of the mouth (Figure 20-7). After the needle is removed, compress the injection site to disburse the lidocaine, and repeat for the contralateral corner of the mouth.

9. The onset of anesthetic effect for nerve blocks is typically within 5 to 10 minutes.

TIP: If adequate anesthesia is not achieved, repeat the procedure, injecting an additional 0.5 mL of lidocaine, and wait an additional 10 minutes.

CAUTION: If the needle is angled too anteriorly, lidocaine may be placed in the dermis, which can be felt as resistance during injection, and adequate anesthesia may not be obtained.

CAUTION: Do not insert the needle to the hub to avoid the rare risk of a buried broken needle.

FIGURE 20-6 Technique for intraoral mental nerve block.

(Copyright Rebecca Small, MD.)

FIGURE 20-7 Technique for intraoral anesthetic infiltration in the corner of the mouth.

(Copyright Rebecca Small, MD.)

Patients will frequently report that their lips feel enlarged or report a sensation of drooling after infraocular and mental nerve blocks, which are good indicators of anesthetic effect. Motor nerves are also affected and patients may have slurred speech due to impaired lip function and limited pucker or smile. Patients may be reassured that these effects are temporary and once the anesthetic effect wears off they will regain sensation and motor function. See Chapter 3, Anesthesia, for additional information about nerve blocks.

Topical Anesthetics

Topical anesthetics are frequently used with cosmetic procedures due to their ease of application (see Table 20-2). They have the same mechanism of action as injectable anesthetics whereby sensory nerves are blocked by neuronal impulse inhibition.

TABLE 20-2 Commonly Used Topical Anesthetic Products for Cosmetic Procedures^a

^a See the Resources section at the end of the chapter for suppliers.

The skin is degreased with alcohol prior to application, and for ointment- and cream-based anesthetics, the product is rubbed gently into the treatment area and then occluded with plastic wrap, taking care not to occlude the nose and mouth. Figure 20-8 shows half the face treated with BLT under occlusion with plastic wrap and the other half face with Pliaglis, a self-occluding topical anesthetic. Pliaglis, temporarily removed from the market for reformulation, is applied as a thick cream and dries on exposure to air, becoming a flexible membrane that is peeled off. The face has a relatively small surface area and there are few complications with topical anesthetics. However, caution must be used with larger areas such as the extremities or the back as systemic absorption is significant, and severe complications have been reported from topical anesthetic toxicity, including death, when applied under occlusion to large skin surface areas.

FIGURE 20-8 Topical anesthetic on the right side of the face with Pliaglis unoccluded, and left side with BLT under occlusion with plastic wrap.

(Copyright Rebecca Small, MD.)

The degree of anesthesia achieved with a topical anesthetic is related to the strength of the product, duration, and method of application. There are many topical anesthetics of different strengths, and it is simplest to select one product for use in the office and vary the time and method of application to suit the degree of anesthesia required for a procedure. For less painful procedures, such as laser hair reduction, topical anesthetics (e.g., BLT) can be applied for shorter duration such as 15 minutes without occlusion, whereas more painful procedures, such as tattoo removal or ablative laser resurfacing, require BLT application for 45 to 60 minutes under occlusion.⁵ Relative to injectable anesthetics, topical anesthetics have the disadvantage of increased visit times required for anesthesia to take effect and greater cost.

Toxicity of topical anesthetics is due to systemic absorption of the product. Several factors affect systemic absorption including the product used, surface area covered, duration of application, and the presence of an intact skin barrier. Anesthetic creams with standard formulas have better safety profiles as it is easier to predict systemic blood levels that will be obtained. For most topical anesthetic creams, systemic blood levels reached with proper use are a small fraction of the blood levels that produce toxicity. For example, 60 g of EMLA cream placed on a 400-cm² area (equivalent to half a back) for 4 hours produces peak blood levels of lidocaine that are 1/20th the systemic toxic level of lidocaine and 1/36th the toxic level of prilocaine. This makes its application very safe, with levels well below the concentration that would cause systemic toxicity.⁶ Cases where topical anesthetic use has resulted in toxicity are mainly a result of patient self-application of large quantities to large surface areas or when procedures are used that disrupt the skin barrier, such as fractional laser resurfacing. Systemic lidocaine toxicity signs and symptoms range from mild dizziness to respiratory depression and correlate with serum levels.⁷ Higher strength topical anesthetics, such as BLT and Pliaglis, should be applied in-office for safety.⁸ See Chapter 3, Anesthesia for more information on topical anesthetics.

Contact Cooling

Ice or contact cooling devices are excellent modalities for achieving anesthesia, and they also improve safety with laser treatments by providing epidermal protection from thermal injury. Contact cooling may be used alone or adjunctively with the other modalities above, for laser hair reduction as well as botulinum toxin and dermal filler injections. Figure 20-9 shows a contact cooling device with adjustable temperature and a contoured tip that can be used for the face. Anesthesia is achieved by applying contact cooling immediately before treatment for approximately 1 to 3 minutes or until the skin is erythematous. The goal temperature for contact cooling is 5°C.⁹ Overcooling, with prolonged blanching of the skin, can result in epidermal injury.

FIGURE 20-9 Contact cooling device (ArTek Spot by ThermoTek).

(Courtesy of ThermoTek, Flower Mound, Texas.)

Analgesic Devices

Analgesic devices can be used with laser treatments to reduce patient discomfort and to reduce the risk of complications from thermal injury. Many lasers have built-in cooling mechanisms. Those that do not have built-in cooling mechanisms can use external analgesic devices such as cool air blowers or pneumatic skin flattening. Cool air blowers force air through a hose that is directed over the treatment area to achieve a goal skin temperature of 20°C.¹⁰ (Figure 20-10 shows an example of a forced air cooling device, the ArTek Air by ThermoTek.) This noncontact method of cooling is particularly useful with ablative laser treatments.

FIGURE 20-10 Air cooling device (ArTek Air by ThermoTek).

(Courtesy of ThermoTek, Flower Mound, Texas.)

Pneumatic skin flattening utilizes negative pressure to elevate and flatten skin against the device window (Figure 20-11A). The mechanism of action of these devices is based on the gate theory of pain, whereby the pressure generated by the pneumatic device inhibits pain sensation through overwhelming and blocking the pain pathways (Figure 20-11B). Some laser devices have pneumatic skin flattening incorporated into the laser and others have a separate pneumatic device that is attached to the treatment tip (Figure 20-12).¹¹ The disadvantages of assistive external cooling devices are the additional use of space, cost of the device, and for air blowers, an occasional requirement for an assistant and risk of overcooling if the device remains stationary in one spot on the skin.

FIGURE 20-11 (A) Pneumatic skin flattening window utilizes the gate theory of pain inhibition. (B) Pressure-sensing nerves block the synaptic gate in the dorsal horn that transmits pain impulses to the brain (Serenity by Candela).

(Courtesy of Candela Corp, Wayland, MA.)

FIGURE 20-12 Pneumatic skin flattening device attached to an intense pulsed light treatment head (Serenity by Candela).

(Courtesy of Candela Corp, Wayland, MA.)

Conclusion

Certain minimally invasive aesthetic procedures, such as dermal filler injections, laser hair reduction, tattoo removal and laser skin resurfacing require anesthesia. Adequate anesthesia reduces anxiety, offers the patient a more pleasant experience, and allows for greater treatment precision and optimal technique to achieve the best possible results. Providing anesthesia is an essential part of performing cosmetic procedures and successfully incorporating them into office practice.

Resources