17. Ablative Laser Resurfacing

Darreil Wayne Freeman, Molly Burns Austin, Alton Jay Burns

Lasers were originally employed in surgery in the 1960s as a cutting instrument in lieu of a scalpel. They originally used a continuous wave CO₂ laser. As technology advanced, high-energy pulsed CO₂ lasers were developed that could selectively ablate superficial tissue with minimal residual thermal damage (RTD). This resulted in improvement of many signs of photoaging, scars, and lesions on the skin. Throughout the years, newer laser technologies have been developed to include erbium:yttrium aluminum garnet (Er:YAG) lasers and fractional lasers. The goals of all these devices are to eliminate or reduce sun-damaged collagen and encourage new collagen deposition and remodeling through a combination of tissue vaporization and collagen denaturation.

EQUIPMENT

ABLATIVE CARBON DIOXIDE (CO₂) LASER

■ 10,600 nm wavelength

■ Target chromophore: Water

• Absorption coefficient = 800 cm⁻¹

■ Visible helium-neon laser is projected on the skin to show the targeted treatment area.

■ Produces tissue vaporization and thermal coagulation^1–3

• Pulse duration must be <1 millisecond to prevent residual thermal damage (RTD) to surrounding tissue.

• 5 J/cm¹ needed to produce tissue ablation (fluence)

• ∼20-30 |jm of ablative tissue penetration per J/cm¹

► Nonlinear relationship between the number of passes and depth of tissue ablation

► Decreasing depth of tissue ablation with each additional pass

► Limits ablation to ∼200-300 |jm deep⁴

► Ablation limited but thermal damage is much deeper

• 70-120 µm area of RTD

• Surface temperatures reach 120°-200° C

■ CO₂ ablation

• Produces dramatic results but requires a longer healing time because of deeper RTD compared with erbium

• Immediate postprocedure edema and erythema resolve in 1-2 weeks and final results require up to 6 months.

■ Two types^1–3

• High energy pulsed

► Energy delivered in 600 microseconds to 1 millisecond

► Can produce 500 mJ of energy in <900-microseconds pulse

► Uses a spot size of 3 mm or a computer pattern generator (CPG) supplying a pattern of up to 80 pulses with a 2.25 mm spot size

ABLATIVE ERBIUM:YTTRIUM ALUMINUM GARNET (ER:YAG)1

■ 2940 nm wavelength

■ Chromophore: Water

• Absorption coefficient 10 times greater than that of CO₂ laser (12,000 cm⁻¹)

■ Produces more precise tissue vaporization and less thermal coagulation than CO₂ lasers¹

• 1-3 µm of ablative tissue penetration per J/cm²

• 5-30 µm area of RTD

• Produces 1-50 mJ/cm² of energy in 300 microseconds to 10 milliseconds

• 2-7 mm collimated or focused spot size

• Value: Comprehensive and versatile. It can be the most superficial laser with quick healing times, or it can be much more aggressive and ablative than CO₂ with less RTD and an optimal efficacy safety profile (i.e., can be as aggressive or as superficial as needed).

■ Three types

• Single pulse

► Pulse duration of 250-350 microseconds

• Variable pulse

► Pulse duration of 10-50 milliseconds (longer duration causes more RTD with more secondary collagen deposition); however, the RTD never reaches that of CO₂

• Dual ablation/coagulation mode (tunable erbium)

■ Er:YAG ablation⁵

• Most versatile ablative laser

• Can produce superficial wounds from 10 µm that can give quick recovery times and usually require repeat treatments

• Can produce the deepest of all wounds because of the extremely high ablation threshold of 5 J/cm²

• Excellent results possible with even the deepest rhytids

• Less residual thermal damage, so faster healing than with CO₂, even for the same depths (5-20 nm residual thermal damage [RTD], compared with 70-120 µm RTD for CO₂)

ABLATIVE FRACTIONAL LASERS^6–9

■ CO₂, Er:YAG, and yttrium scandium gallium garnet (YSGG) models available

■ Wide variety of models and handpieces provides different fluence and penetration depths.

■ Produces microthermal zones (MTZ) of ablation injury with surrounding layer of denatured collagen heated to 55°-62° C for optimal long-term collagen deposition/remodeling

• MTZ/cm² can be manually set. (Both depth of injury and density of MTZ can be set.)

• Ablation depth up to 1.6 mm (varies based on fluence, wavelength, and spot size)

• Complete healing and reepithelialization by 1 week9

• For more aggressive treatments, erythema may last up to 6-8 weeks.

■ Fractionated lasers

• Multiple treatments are needed, because only a fraction of the skin is treated per session.

• Open wounds last 3-4 days, with erythema lasting 2-8 weeks for aggressive treatment protocols.

• Laser of choice for lower eyelids, acne, and large pore size⁵

TECHNIQUE

SAFETY (LASER INSTITUTE, OCCUPATIONAL SAFETY)

■ American National Standards Institute (ANSI)¹⁰ provides policies for laser safety.

■ Occupational Safety and Health Administration (OSHA)¹¹ provides oversight.

■ Proper documentation of safety training is required for all perioperative personnel.

■ Laser Safety Officer (LSO) provides control over administrative, procedural, and engineering controls.

■ Each treatment area must define the nominal hazard zone (NHZ), have proper signage for eyewear, and have limited access by trained personnel.

■ Windows must be covered with appropriate opaque material.

■ Laser must be test fired before the procedure.

■ Antiflammable precautions, including saline-soaked clothes, irrigation solution, and fire extinguishers

■ Smoke evacuation to remove laser plume

■ Laser kept in standby mode when not actively in use

MARKINGS

■ Each aesthetic unit to be treated is outlined.

■ Light blending between aesthetic units provides a smooth transition.

■ Full-face treatment gives best blend but is not always indicated.

ANESTHESIA

■ Ablative lasers cause more pain than nonablative treatments; therefore, when treating areas not easily blocked by local anesthesia, general anesthesia may be indicated for more aggressive settings. Patient preference for comfort is also a consideration.

■ For very superficial laser resurfacing, topical anesthesia may suffice for limited areas.

• Lidocaine cream (LMX) or lidocaine and prilocaine cream (EMLA) 30-90 minutes before procedure

• 15 g BLT triple anesthetic cream (20% benzocaine, 6% lidocaine, and 4% tetracaine) applied 20 minutes before procedure and again after first laser pass¹²

• Cold-air cooling

Local Anesthesia1,13

■ Central face, including central forehead, cheek, nose, upper and lower lips

• 1%-2% lidocaine with 1:100,000 or 1:200,000 epinephrine

■ Lateral face

• 2% lidocaine with 1:100,000 epinephrine, 0.5% bupivacaine, 1:10 8.4% NaHCO₃, and 75 U hyaluronidase

• Or, equal parts of 1% lidocaine with 1:100,000 epinephrine and 0.5% marcaine with 1 ml hyaluronidase for every 9 ml local anesthesia

■ Nerve blocks: 4% articaine hydrochloride

• Supraoribital nerve

• Supratrochlear nerve

• Infraorbital nerve

• Maxillary nerve

• Mandibular nerve

• Mental nerve

■ Orbital anesthesia

• Three drops of 0.5% proparacaine ophthalmic solution to each eye before application of lubricated eye shields

■ Tumescent local anesthesia

• Kessels et al¹⁴ reported using 0.11% solution of 500 ml lactated Ringer solution, 20 ml 1% ropivacaine, 20 ml 2% xylocaine, and 0.5 ml epinephrine

• Minimum of 6 ml/kg

CAUTION: Tumescent anesthesia introduces water into the tissue which decreases the depth of penetration which may not be desired.

Systemic Analgesia/Anesthesia^1,13 (see Chapters 5 through 7)

■ Oral

• 10 mg diazepam 30 minutes before procedure

■ Intramuscular

• 100 mg meperidine 30 minutes before procedure

• 25 mg hydroxyzine 30 minutes before procedure

■ Inhalation

■ Intravenous⁴

• Propofol 1-2 mg/kg loading dose, 4-8 mg/kg/hr continuous infusion

• Midazolam 0.05-0.1 mg/kg

• Fentanyl 50-100 µg

• Ketamine 10-20 mg (must administer glycopyrrolate 0.2 mg, propofol, and midazolam first)

• Laryngeal mask adaptor (LMA) necessary with heavy sedation

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