Fractional Carbon Dioxide Laser Resurfacing - PMC

Overview

The advent of modern ablative fractional CO2 lasers has significantly improved results and reduced downtime while minimizing complications compared to older CO2 laser models. This article will explore the mechanisms of action, treatment protocols, as well as pre- and postoperative care procedures associated with this technology.

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Keywords: fractional, ablative, collagen, CO2

The advanced lasers in use today would have astonished Dr. Leon Goldman, a pioneer in the study of lasers and their interactions with skin in the 1960s. In the 1980s, Anderson and Parrish revolutionized laser application through their innovative concept of photothermolysis using pulsed radiation. The 1990s saw the rise of traditional CO2 lasers which became immensely popular for their ability to effect noticeable changes in skin appearance and function. Physicians regard fully ablative traditional CO2 lasers as the benchmark in their field. However, these lasers also introduce side effects such as extended erythema and delayed hypopigmentation in certain patients. Dr. Jeffrey Dover suggests that there are now limited situations where traditional ablative CO2 laser resurfacing is appropriate today.

The concept of fractional laser treatment was developed in the 2000s by Manstein and colleagues, aiming to create thermal injuries in a fractional pattern to mirror the benefits of full ablative resurfacing while minimizing the side effects. Subsequently, the introduction of ablative fractional CO2 lasers offered the promise of enhanced outcomes.

Mechanisms of Action

The advantages of CO2 laser resurfacing—whether fully ablative or fractional—are clear. However, the precise mechanisms through which these improvements occur have sparked extensive discussion. While both forms entail distinct features, the research surrounding fully ablative CO2 resurfacing informs our understanding of fractional techniques. CO2 lasers emit a wavelength of 10,600 nm, a frequency that is mainly absorbed by water. To effectively achieve ablation with minimal thermal damage, a fluence of 5 J/cm2 should be applied within a pulse duration of less than 1 millisecond, the recognized thermal relaxation time for skin.

The conventional denaturation temperature for collagen is noted to be around 66.8°C, albeit with some variability. Once the collagen fibers are denatured by the heat generated by the laser, they suddenly contract to approximately one-third of their original length. This contraction serves as the primary mechanism for skin tightening, although the processes of vaporizing intracellular water and ablation also play roles. This is quickly followed by a wound-healing phase during which there is a surge of collagenases that work to degrade the fragmented collagen matrix. The reconstitution of the epidermis occurs primarily from adjacent epidermal cells, contrasting traditional resurfacing, where new cells migrate from adnexal structures. A prolonged duration of dermal neocollagenesis can continue for at least six months thereafter.

While ablative tissue removal contributes to effectiveness, the depth of deep wrinkles often surpasses the ablation depth; residual thermal damage, which is the actual extent of injury, remains the key factor that enhances efficacy. The depth of residual thermal damage can be amplified with higher fluence levels, while increased density corresponds to greater ablation depth.

Patient Selection

As with any cosmetic procedure, careful patient selection is essential. Patients must have realistic expectations and a comprehensive grasp of the procedure, particularly regarding postoperative care. While most individuals benefit from a single treatment, they should understand the potential need for multiple sessions to achieve optimal results. Contraindications include active skin infections, conditions that hinder healing (like scleroderma), and any history of illnesses that trigger the Koebner phenomenon, such as vitiligo and psoriasis. Previous isotretinoin use or radiation therapy in the treatment area necessitates cautious approaches with conservative parameters.

Preoperative Care

Every patient undergoes preoperative antiviral prophylaxis utilizing valacyclovir at 500 mg taken twice daily, starting one day before the procedure and continuing for ten days. Additionally, most practitioners prescribe an antibiotic, such as cefadroxil, dicloxacillin, doxycycline, or ciprofloxacin, during the same timeframe. Some experts contend that antibiotics targeting only Gram+ organisms increase the risk of Gram- infections. On the day of surgery, fluconazole 200 mg may be administered. Implementing preoperative facial cleansing with chlorhexidine, executed twice daily for three days, can further mitigate the risk of postoperative infection. In certain cases, surgeons may recommend intranasal mupirocin prior to surgery. The efficacy of skin preconditioning with tretinoin in promoting healing and lessening the chances of postoperative milia and acne remains debatable, and it could lead to increased postoperative erythema.

Treatment Process

The fractional resurfacing procedure starts with adhering to appropriate laser safety protocols and selecting the method of sedation. While general or tumescent anesthesia are viable options, often thorough application of topical anesthesia 1 to 2 hours prior to treatment suffices. Kilmer argues that hydrophilic topical anesthetics like EMLA (eutectic mixture of lidocaine and prilocaine) can alter the body's response to the laser, resulting in fewer side effects. This is logical given that CO2 lasers predominantly target water content. However, Naouri et al assert that the water composition within topical anesthetics is inconsequential. The effect of topical anesthesia on a narrow, focused ablative beam is negligible, though its impact on more superficial treatments is still up for debate. Along with topical anesthetics, utilizing forced cold air through a Zimmer Cooler or similar device can be beneficial.

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At present, a variety of outstanding fractional CO2 devices are available. This section will focus on the Lumenis Ultrapulse Encore fractional CO2 laser, specifically addressing its application for photoaging and scarring of the face and neck. Two distinct delivery methods enable dual-depth ablation—Active FX and Deep FX—utilizing separate handpieces. The Active FX handpiece employs a collimated 1.3-mm spot size in a non-sequential array (Cool Scan mode) to reduce thermal damage. Energy adjustments range from 2 mJ (150 mJ/cm2) to 225 mJ (169 J/cm2), with power settings spanning from 1 W (4.4 Hz) to 60 W (600 Hz). A computer-generated pattern allows for seven configurations in nine different size and density variations. The flexibility to modify density is a distinguishing characteristic of fractional lasers, setting them apart from traditionally fully ablative lasers. For density settings of 1 to 3, with a square pattern, the density ranges between 55% and 82%, while densities 4 to 9 remain fully ablative (100%), albeit at shallower penetration compared to conventional CO2 lasers.

Active FX induces a shallow and broad ablative crater reaching into the superficial papillary dermis and generally requires one or two passes. Typical energy settings for treating facial skin hover between 100 to 125 mJ, with density settings ranging from 2 to 4, potentially increasing for more challenging conditions like acne scarring. Parameters for periorbital skin conventionally lay between 60 to 90 mJ, with density set at 2 or 3. Treatment of the neck, chest, and extremities can occur at lower settings ranging from 70 to 80 mJ, with a density of 1 to 2. There are varying opinions surrounding whether to debride between laser passes during traditional resurfacing; for fractional resurfacing, this step is generally deemed unnecessary.

When addressing deep wrinkles and maximizing collagen regeneration, Deep FX may be utilized from the outset or as a sole method. The Deep FX handpiece produces a narrower, non-collimated beam measuring 0.12 mm, featuring four pattern options and six sizes. A single pulse or stacked dual pulses can be employed, with power up to 600 Hz available for single pulses and 300 Hz for double pulses. Energy offerings span from 2.5 mJ to 50 mJ. At the lowest energy setting of 2.5 mJ, the depth of ablation extends to approximately 76 microns, reaching beyond the epidermis into the superficial papillary dermis depending on the treatment area. Although depths over 1 mm can be achieved, such settings are typically deemed excessive for clinical contexts.

For facial applications, a typical Deep FX energy setting fluctuates between 15 to 22.5 mJ. At 22.5 mJ, ablation may reach around 675 microns, reflecting the deep dermis (contingent upon skin thickness). Density settings of 5 to 25% can be adjusted, corresponding to a 10mm x 10mm area, whereby 196 spots are achievable at a density of 5% and 841 spots at 25%. Aggressive Deep FX settings could penetrate entirely through eyelid skin, thus safe settings for the bony orbit area should remain between 8 to 10 mJ with density at 5 to 15%. These parameters also apply to off-face regions, including the neck, chest, and extremities. The author typically employs a single pulse for all procedures, with dual pulsing occasionally utilized for scarring treatments.

Research conducted by Oni et al indicated that a single pulse at 15 mJ on facial tissue reached an average depth of 416 microns, correlating with the mid-dermis. Interestingly, a double pulsed treatment at 15 mJ achieved histological results comparable to a single pulse at 30 mJ, with extended depths of 881 microns and 854 microns, respectively (affecting the deeper reticular dermis). The clinical significance of such findings remains to be elucidated, and there is a dearth of peer-reviewed literature on the optimal strategies to integrate Active FX with Deep FX.

The precise boundaries of scanned areas may not be immediately visible, leading to possible untreated spaces or instances of pulse stacking during Deep FX resurfacing. Recognizing untreated areas is possible as the skin will generally redden or experience urticaria shortly after treatment, permitting follow-up care on missed sections. If an Active FX treatment is scheduled subsequent to Deep FX, any untreated regions from the latter usually blend in seamlessly.

Postoperative Management

Scrupulous postoperative care is imperative to prevent infection and scarring. Utilizing cold soaks made from one teaspoon of white vinegar in one cup of water, or aluminum acetate (Domeboro), can help diminish erythema, swelling, and provide antiseptic properties. The skin should be maintained in a moist state using white petrolatum or Aquaphor®, with the application of alternative topicals explicitly discouraged. Recently, the idea of using autologous platelet-rich plasma to expedite healing has gained traction.

Occlusive dressings, such as Silon II, have shown potential in accelerating recovery, reducing inflammation, and possibly improving results after traditional resurfacing. However, these dressings are often cumbersome and not requisite for most fractional resurfacing scenarios. The author opts to use Silon II in cases of aggressive treatments focused on substantial acne scarring. The process of re-epithelialization generally takes about 3 to 6 days, after which light moisturizers and sunscreens can be utilized. Mild to moderate erythema commonly prevails for a few weeks post-treatment, and topical vitamin C can aid in fostering neocollagenesis and alleviating erythema.

Final Thoughts

Fractional CO2 resurfacing stands as a significant advancement resulting from over 50 years of exploration into laser-skin interactions. Patients can anticipate remarkable outcomes with minimal complications. Ongoing research will undoubtedly enhance our capability to deliver the highest quality care to our patients.

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