Ablative Laser Resurfacing

Anatomy and Physiology

Understanding the function and anatomy of the skin and its appendages is important to thoroughly appreciate the applications of ablative laser therapy. As the body's largest organ, the skin can be divided into several distinct layers, including the epidermis, dermis, and hypodermis: 

1. The epidermis is an epithelial layer derived from the ectodermal germ layer of the embryo. The layers of the epidermis, from deep to superficial, include:
   1. Stratum basale is a single layer of columnar cells, which are the only layer to undergo mitosis in the epidermis. Cells will migrate upward from the basal layer until they are ultimately shed from the skin surface.
   2. Stratum spinosum consists of eight to ten layers of irregularly shaped cells with prominent intercellular bridges, known as desmosomes, giving this layer a spiny appearance under a microscope.
   3. Stratum granulosum is where the process of keratin formation occurs and where cells are arranged in a sheet of two to four layers filled with granules known as keratohyalin as well as small bodies of glycophospholipids.
   4. Stratum lucidum is a layer of flat keratinocytes closely packed and clear, with typically absent nuclei. This layer is often absent in thin skin (i.e., around the eyelids) and is most prominent on the palms of the hands and the soles of the feet.
   5. Stratum corneum is the most superficial layer of the epidermis and consists of a very thin squamous layer mostly comprising skin cells that are dead and are shedding. This layer is replenished continually by the deeper layers of the epidermis, filled with keratin, and moved to the skin's surface—the stratum corneum functions as a barrier to water, physical trauma, and other environmental threats.
2. The dermis is a relatively dense and vascular connective tissue layer that may average more than 4 mm in thickness. It is divided into a thick reticular layer on the deep aspect and a thinner papillary layer on the superficial surface.
   1. Reticular layer: This deeper layer has a thick network of fibers of mostly collagen and elastin. It serves as a layer of attachment for numerous skeletal and smooth muscle fibers and contains many somatic sensory receptors and hair follicles, and other skin glands.
   2. Papillary layer: The presence of dermal papillae composed of loose connective tissue and thin collagen and elastin fibers is evident in the papillary layer of the dermis. These are responsible for forming frictional ridges in the skin, which are important to the structure of fingerprints.
3. The hypodermis is the subcutaneous layer, which is not strictly part of the skin but lies deep to it. It contains mostly loose fibrous and adipose tissue, and it is responsible for carrying the major blood supply and innervation to the skin.

Laser Basics

Within the ablative laser category, the two major lasing media are CO2 and Er:YAG, with therapeutic options being further subdivided into non-fractionated and fractionated ablation. Non-fractionated, or "full field," lasers provide treatment over the entire targeted area of skin instead of fractionated lasers, which target therapy to specific fractions or columns of skin within the targeted area, thereby minimizing the risk of adverse effects and hastening recovery. Ablative lasers vaporize tissue and are generally considered more aggressive therapies; they produce more dramatic outcomes compared with nonablative lasers, which produce less striking improvements but leave the epidermis otherwise intact. Nonablative lasers are beyond the scope of this review but can be useful to minimize the appearance of less prominent rhytides and dyspigmentation without a significant recovery period.

A laser light emits photons at a particular wavelength, CO2 at 10,600 nm and Er:YAG at 2,940 nm, which will be absorbed by the target tissue's chromophores, namely water and melanin. Laser is an acronym that stands for light amplification by the stimulated emission of radiation; true laser light is collimated (all waves are parallel), coherent (all waves are in phase), and monochromatic (all waves have the same frequency and wavelength). The goal is to ensure adequate but safe depth of penetration of the laser and delivery of sufficient energy to the targeted tissues while minimizing heat transfer to adjacent structures.[6]

Energy delivery to tissues is directly correlated to the power of a laser, measured in watts. Power density or fluence is the energy delivered per unit area (joules/cm2) and must be sufficient to achieve the desired effect while minimizing tissue damage.[7] Excessive thermal energy transfer, particularly to the dermis, can lead to adverse effects, including scarring and dyspigmentation.

The depth of penetration of light energy is generally correlated with increasing light wavelengths. Carbon dioxide lasers generally produce a 20 to 60 μm depth of vaporization on the first pass compared with Er:YAG lasers that produce a 3 to 5 μm depth of vaporization on the first pass, depending on the settings used.[8] The advantage of CO2 and Er:YAG lasers is that the energy they emit is selectively absorbed by water in the epidermis, causing rapid vaporization of the epidermis and ensuring that little light energy reaches the deeper layers of the skin. Nonetheless, there is residual thermal damage caused by the penetration of energy, and this is believed to lead to collagen contraction, remodeling, and skin tightening. Thermal damage with traditional CO2 lasers and Er:YAG lasers may reach depths of 100-150 μm and 10-40 μm, respectively.[9] The choice of laser to employ often depends on a combination of clinician experience, patient factors, and device availability.

CO2 Ablative Lasers

The application of laser ablation to facial rejuvenation began with the use of a continuous wave CO2 laser.[3] The CO2 laser produces an invisible infrared beam, emitting energy at a wavelength of 10,600 nm, which is primarily absorbed by water. This makes this laser excellent for cutting, coagulation, and ablation of the skin. For instance, when pulsed at 5 J/cm^2 for <1 ms, the light from the CO2 laser penetrates to a depth of approximately 20 to 30 μm.[10] The subsequent development of high-energy pulsed CO2 lasers further improved control over the depth of ablation.

Carbon dioxide lasers are thought to produce contraction of the skin immediately by denaturing collagen fibrils and subsequently by stimulating the production of new collagen. Studies have demonstrated improvement in rhytides by up to 90% using CO2 laser ablation.[11] The CO2 laser system is particularly well suited for alleviating fine wrinkles, especially around the eyes and mouth.[12]

The discomfort associated with CO2 laser therapy often requires local anesthetic with additional sedation, anxiolytics, and possible oral analgesia, whereas a topical anesthetic alone is often sufficient for treatment with Er:YAG lasers.[9] After resurfacing with a CO2 laser, erythema will persist for approximately two weeks, for fractional treatments, or a period of several weeks to months for an aggressive non-fractional resurfacing. Re-epithelization of the epidermal layer following CO2 laser therapy occurs after approximately eight days.[13][14] Studies have demonstrated improved clinical outcomes and greater dermal collagen remodeling with CO2 lasers compared with Er:YAG lasers on a per laser pass basis.[15] However, CO2 lasers are associated with a higher rate of dyspigmentation compared with Er:YAG lasers.[16][17] Photodamage is less severe in individuals with dark skin, but laser-induced dyspigmentation is a major concern for these individuals. For this reason, non-fractional CO2 laser use is not recommended for Fitzpatrick skin phototypes IV or higher.[14]

Fractional ablative laser therapy was first available for CO2 lasers in 1998.[18] Fractional laser therapy uses narrow columns of laser light on the skin to create microscopic thermal zones, measuring less than 400 μm in diameter and up to 1300 μm in depth. This modality relies on smaller areas of ablation surrounded by viable tissue that permits rapid re-epithelization, as opposed to traditional laser therapy, which requires migration of epidermal cells. Fractional CO2 laser therapy possesses similar efficacy to traditional CO2 laser therapy, according to a number of studies that demonstrate up to 80% of patients report an acceptable reduction in rhytides.[18] Recovery is also more rapid with fractional therapy than with traditional CO2 laser therapy, with a return to normal activity after 5-10 days, depending on the treatment intensity. In addition, post-procedure topical hydroquinone cream, retinoids, or peeling agents may be prescribed to accelerate the resolution of erythema and edema.[11][13]

Er:YAG Ablative Lasers

The erbium-doped yttrium aluminum garnet laser was developed in the 1990s and produces laser light at a wavelength of 2,940 nm. The chromophore is water, similar to the CO2 laser; however, energy absorption is 12 to 18 times greater. Re-epithelialization of the epidermal layer occurs more rapidly when compared with CO2 lasers, in approximately five days and with erythema persisting only 3 to 4 weeks after treatment.[19]

The Er:YAG laser has a similar mechanism of action to traditional CO2 lasers but typically has less skin tightening effect.[13] The Er-YAG laser also has less of a coagulative effect than the CO2 laser, which may limit the number of passes performed because of the bleeding that results. Fluence levels of 5-15 J/cm^2 are typically used for Er:YAG lasers, although microablative procedures or a single laser pass with lower fluence may also provide some benefit for the treatment of photoaging.

Topical anesthetics are generally sufficient for Er:YAG laser procedures, with local anesthesia available as a contingency plan if needed.[13] Recovery after Er:YAG laser treatment is shorter than after CO2 laser therapy, with less edema and a reduced incidence of adverse effects.[14] Traditional Er:YAG laser therapy requires more laser passes than traditional CO2 laser treatments to achieve a similar depth of ablation, however. Long-pulsed Er:YAG lasers have been used as a less efficient treatment modality for deep rhytides if a pulsed CO2 laser is unavailable.[20] That said, outcomes are similar, and some clinicians insist upon the superiority of the Er:YAG laser over the CO2 laser.[20] The precisely-controlled skin ablation possible with Er:YAG laser systems are useful for areas at high risk for scarring, such as periorbital skin, and some clinicians prefer to use the Er:YAG laser for dyschromia and fine wrinkles, reserving the CO2 laser for deeper rhytides.[13] While the greater precision of the Er:YAG laser is sometimes necessary, it may also reduce the amount of thermal damage occurring in the underlying collagen, thereby resulting in less skin tightening.[14]

Fractional delivery of Er:YAG laser energy was developed and applied in a similar fashion to that of CO2 lasers. Cosmetic outcomes were found to be similar to traditional, non-fractional Er:YAG laser delivery.[21] Although adverse outcomes, such as scarring, are less frequent with Er:YAG lasers than with CO2 lasers, they still occur with Er:YAG laser treatment, and appropriate patient selection is required to minimize the risk of these events. For patients at high risk for dyspigmentation and scarring (Fitzpatrick skin types IV-VI), the use of the Er:YAG laser is preferred over the CO2 laser. Regardless, reactivation and local spread of the herpes simplex virus may occur following any perioral ablative laser therapy.[22]

Indications

Indications for ablative laser resurfacing include:[23]

• Photoaging
• Facial wrinkles
• Acne scars
• Surgical or traumatic scars
• Actinic keratoses
• Seborrheic keratoses
• Warts
• Moles and other nevi
• Xanthelasma
• Skin tags
• Rhinophyma
• Sebaceous hyperplasia
• Pyogenic granuloma
• Neurofibroma
• Angiofibroma
• Actinic cheilitis
• Keloids

Contraindications

Contraindications to ablative laser resurfacing include:[23]

• Fitzpatrick skin types IV-VI (there is an increased risk of dyspigmentation in patients with darker skin)
• History of keloidal scarring
• Recent oral isotretinoin therapy (traditional teaching recommends cessation for 6 to 12 months before resurfacing procedures)
• Ectropion (particularly when considering infraorbital resurfacing)
• Morphea
• Scleroderma
• Prior radiation therapy (which limits the skin's ability to heal in a timely fashion)
• Cutaneous disorders (vitiligo, lichen planus, and psoriasis are relative contraindications)
• Active herpes outbreaks or other ongoing infections in the targeted area (laser treatment should be postponed until the condition has resolved)
• Ongoing ultraviolet exposure
• Recent chemical peel (depending on the depth of the peel, may require six weeks to 6 months before considering ablative laser resurfacing)

Equipment

Anesthetic

• Ablative laser procedures may be performed under local anesthesia, using a combination of topical and local anesthetic. This, of course, depends on the patient's demeanor and pain tolerance and the laser operator's ability to employ effective sensory nerve blocks to the face if a full facial skin resurfacing is planned.
• Regarding topical anesthetic, a eutectic mixture of local anesthesia cream (EMLA) can be used by applying 2 mg/cm2 topically under occlusion for 45 to 60 minutes, with removal just before the procedure is performed.

Laser Selection

• CO2 or Er:YAG lasers
  • Fractional or non-fractional

Laser-safe Eye Protection

• The patient's eyes should be protected using a wet gauze or an eye shield 
• Healthcare personnel should use wavelength-appropriate spectacles

Laser-safe Instruments

• Fire extinguisher
• Wet towels
• Water or saline

Other Considerations

• Laser protocols, pre-procedure laser setting check
• Gloves, masks, and a cap should be used by all healthcare personnel
• Povidone-iodine 5% solution for disinfection (alcohol should be avoided because it is inflammable)

Personnel

All personnel involved with ablative laser treatment should be properly trained regarding the safe use of the laser delivery system. A technician or nurse should assist the primary laser operator with disinfection of the skin, preparation of topical anesthetic, operation of the laser, recording of anesthesia, and patient vitals.

Preparation

A detailed history and physical examination are obtained prior to proceeding with ablative laser therapy.

Patients should be assessed for any contraindications (i.e., history of keloidal scarring, recent oral isotretinoin therapy, sites of scleroderma, radiation, etc.) prior to initiation of therapy. They should also be informed of the risks, and a discussion regarding expectations of therapy should take place at the pre-procedure visit.

Pre-procedure photographs should be obtained in the standard facial views (i.e., frontal, lateral, oblique, both smiling and non-smiling).

Prophylaxis with antivirals including acyclovir, valacyclovir, or famciclovir is recommended to reduce the risk of reactivation of facial herpes infection, starting before treatment and continuing for several days after. An example regimen is valacyclovir 50 mg PO BID x14 days, beginning either the day before or the morning of the procedure.[24]

Pre-procedure topical tretinoin may help prime the skin for quicker healing after ablation.

Prophylactic therapy for bacterial and fungal infections is controversial and not universally recommended.

Technique or Treatment

There is a paucity of well-designed studies comparing the various CO2 and Er:YAG laser settings due to the heterogeneity of described laser protocols and the inconsistency in the definition of a successful treatment outcome. Techniques employed are highly variable and are determined by physician preference, patient goals, and available devices. Therefore, the reader is left to explore which laser (CO2 vs. Er:YAG) and associated protocol best fits their skill level, experience, and patients' expected outcomes. A discussion on the numerous calibrations used for both the CO2 and the Er:YAG is beyond the scope of this article. With that being said, the following discussion will highlight some of the characteristics common to ablative laser skin resurfacing modalities, regardless of the laser or protocol employed.[9][25]

Ablative laser resurfacing should proceed as follows:

1. Obtain informed consent and review indications, intended outcomes, anticipated recovery course, and risks of the procedure with the patient.
2. Administer antiviral +/- antibacterial prophylaxis.
3. Patient position: supine position for the face and chest; the lateral decubitus position may help to target the sides of the face and neck.
4. Laser-appropriate protective material (including eye protection) for both patient and healthcare personnel
5. Cleanse the area to be lasered with a povidone-iodine 5% solution. Avoid alcohol-containing antiseptic solutions because they are inflammable.
6. Anesthesia: general, intravenous sedation, nerve blocks, topical, or a combination thereof; cold air cooling during the procedure may improve patient comfort.
7. Operating the laser:
   1. The foot pedal should be in a comfortable position.
   2. The handpiece should be held perpendicular to the target area. 
   3. A typical ablative skin resurfacing procedure involves the sequential treatment of several cosmetic units (e.g., forehead, temples, eyelids, nose, cheeks, lips, chin). For fractional ablative resurfacing, each treatment pass is performed perpendicular to the prior one to minimize bulk heating. These treatments may result in immediate edema, crusting, oozing, and pinpoint bleeding, which can be wiped gently with sterile gauze soaked in cool water.
   4. The visible clinical endpoint for non-fractional treatment is yellowing the wound bed (to a chamois color), which indicates the exposed papillary dermis. Resurfacing that does not reach this level will not produce as dramatic a result, and treatments that proceed beyond this level will likely result in scarring. The papillary dermis is also characterized by pinpoint bleeding, which may take up to one minute to appear.
8. Post-procedure care:[26] 
   1. Immediate post-procedure period: ice-cold soaks and persistent petrolatum ointment are useful. The face must be kept moist at all times until the crusting has resolved. This should be applied initially in the recovery room.
   2. Sun protection with sunscreen, at least SPF 30, and sun-protective behavior: avoiding direct exposure, wearing wide-brimmed hats, avoiding midday outings in order to reduce risks of post-inflammatory hyperpigmentation (PIH).
   3. Edema, exudate, and skin sloughing: cool compresses, head elevation, saline or water soaks, petrolatum ointment (preferred over topical antibiotics), and occlusive dressings. Systemic steroids may be considered if significant edema is expected or develops (e.g., 30 mg of prednisone PO daily for two days following the procedure)
   4. Erythema: mild steroid (dexamethasone 0.1%), 0.1% tretinoin, and 5% hydroquinone in a cream base; patients should use cosmetics with green tints to reduce the appearance of erythema.
   5. Acne: responds to standard acne treatment. Isotretinoin is avoided for several weeks to months to avoid atypical scarring.
   6. Dermatitis: typically responds to topical steroids +/- oral doxycycline.
   7. Infection: depending on etiology (viral, bacterial, fungal), responds to valacyclovir, cephalexin, or fluconazole.
   8. Pruritus: provide topical steroids and oral antihistamines as necessary.

Complications

Ablative laser resurfacing represents a safe and effective technique associated with a low-risk profile and a high satisfaction rate.

Complications are associated with all types of laser therapy, including full-field and fractional lasers. Fractional laser resurfacing tends to produce a reduced severity and frequency of complications, including:[26]

• Persistent erythema
• Hyperpigmentation/hypopigmentation
• Infections (viral, bacterial, fungal)
• Scarring
• Acneiform eruptions
• Milia
• Ectropion

Clinical Significance

Ablative laser resurfacing is a useful tool to produce cosmetic improvements for photoaging, scarring, and superficial skin lesions. The CO2 and Er:YAG lasers remain the workhorse modalities for ablative treatments; energy delivery should be personalized based on patient goals and expectations, such as degree of change desired and length of recovery tolerated, as well as individual physiological and anatomical factors, such as degree of skin pigmentation and history of scarring. Compared to full field lasers, fractional lasers represent a less aggressive modality that can shorten recovery times while providing a similar therapeutic effect. Overall, ablative laser therapy represents a primary means by which cosmetic physicians can provide safe, effective non-surgical facial rejuvenation.

Enhancing Healthcare Team Outcomes

The key to maximizing outcomes and patient satisfaction is beginning with a thorough history and physical examination of the patient and a discussion of the patient's expectations. Reviewing the anticipated outcome, recovery period, and potential risks are essential before planning ablative laser therapy.

The success of the procedure depends on efficient cooperation among the interprofessional team members, including a physician, a physician assistant, and/or a nurse or technician. A team consisting of personnel who are comfortable and well-trained to provide quality peri-procedural monitoring and care is the cornerstone of effective ablative laser treatment.

Post-procedural care and close follow-up are required to evaluate the patient for possible complications such as infection or dyspigmentation. Patient education regarding proper care for the procedural site during convalescence is essential to minimize adverse outcomes and maximize patient satisfaction. [Level 5]

Nursing, Allied Health, and Interprofessional Team Interventions

The appearance of edema and exudate are expected within the first few days after treatment, and patients should be informed of this during pre-procedure counseling. The use of cooling compresses, saline/water soaks, and head elevation will help minimize edema and keep the skin moist, promoting rapid wound healing. Skin cleansing and application of ointment should be performed routinely until crusting resolves (3 to 4 days for fractional, 7 to 10 days for full-field laser resurfacing).

Pain associated with the post-procedure period can typically be managed with acetaminophen with or without stronger oral analgesic agents. Patients must be counseled to avoid scratching or rubbing the skin and engage in photoprotective activities, including avoidance of the sun and use of sunscreen to minimize the risk of persistent hyperpigmentation. Occasionally, pruritus may occur, and the patient should be monitored and provided with topical corticosteroids to apply twice daily for several days if needed.

The use of topical steroids, hydroquinone cream, retinoids, or peeling agents has been employed to reduce the development of postinflammatory hyperpigmentation and to accelerate its resolution. Scarring can be managed with topical or intralesional steroids as well as nonablative fractional lasers.

Patients can generally return to work 14 to 21 days following a full field face CO2 laser resurfacing and 3 to 8 days following a full field Er:YAG laser skin resurfacing. Fractional CO2 lasers generally require a 4 to 10 day recovery period, while only 1 to 3 days off work are recommended after fractional Er:YAG laser resurfacing.

Patients should be informed of the expected recovery timeframe and regularly monitored by the interprofessional healthcare team to ensure normal healing.

Nursing, Allied Health, and Interprofessional Team Monitoring

Close follow-up during the initial post-procedure period to monitor for signs or symptoms of infection, pruritus, and other issues is imperative to reduce adverse outcomes and maximize the therapeutic benefit of ablative laser therapy. Many patients may require three or more treatments to achieve the desired results, particularly with fractional therapy; therefore, longitudinal follow-up and discussion will maximize the chance of favorable clinical outcomes.