Laser Carbon Dioxide Resurfacing

Anatomy and Physiology

Laser resurfacing is a process wherein energy generated at a specified wavelength is used to ablate the most superficial layers of the skin. This process may be total, in which all portions of the treatment area are ablated, or fractional, in which smaller regions are ablated, and adjacent areas are left untreated, typically in a pattern of closely spaced ablated and non-ablated areas.

Carbon dioxide lasers emit energy with a peak wavelength of 10,600 nm, which is preferentially absorbed by intracellular water.[5] Absorption of this wavelength by the epidermis ablates the most superficial layers, promoting subsequent re-epithelialization from residual skin appendages and adnexal structures in the dermis: the sweat glands and hair follicles.[6] The thermal injury that occurs below the zone of ablation induces heat-mediated contraction of collagen and subsequent collagen remodeling in the dermis.[7] Contraction of collagen fibrils, in turn, causes tightening of the skin. Compared with other lasers, such as the erbium-doped yttrium-aluminum-garnet laser, CO2 lasers generate more heat and cause greater coagulation of small blood vessels in the dermis, leading to substantially less bleeding when a large surface area is ablated. The heat resulting from photocoagulation produces the additional effect of stimulating the deep dermal layers to promote re-epithelialization more rapidly and produce a near-sterile ablated surface.

Indications

Carbon dioxide lasers are employed for a variety of cutaneous conditions and indications. These include treatment and prevention of photoaging and reduction in the appearance of scarring, among others. Carbon dioxide lasers may also be used for prophylaxis and treatment of premalignant lesions and keratinocyte skin cancers (squamous cell carcinoma and basal cell carcinoma), as well as cutaneous vascular lesions such as hamartomas. Carbon dioxide laser resurfacing produces its optimal results in patients with Fitzpatrick type I-II skin - fair-skinned Caucasians - because they have fewer melanocytes, which are prone to causing dyspigmentation as a result of post-procedure inflammation.

Cosmetic indications for CO2 laser resurfacing include the treatment of photoaging and rhytids. Photoaged skin is characterized by increased laxity, irregular color and texture, and the presence of static rhytids. In comparison to other methods of addressing photoaging, such as dermabrasion and chemical peels, the use of CO2 lasers allows for more precise control over the area, depth, and extent of thermal damage. A number of blinded studies have demonstrated significant improvement in photoaging of the forehead and glabella and the periorbital and perioral regions, resulting from the collagen remodeling after CO2 laser treatment.[6]

Treatment of scarring from acne, trauma, or surgical procedures can be achieved effectively with CO2 laser resurfacing as well.[8] Carbon dioxide lasers can reduce the appearance of acne scarring by inducing thermal damage below the area of scarring and subsequently stimulating collagen production. They also reduce the prominence of the shoulder of the scar, effectively "blending" the scar with surrounding normal skin. For the treatment of surgical scars, CO2 lasers are reputed to produce less bleeding and crusting than dermabrasion does. 

For the treatment of premalignant lesions and actinic damage, CO2 lasers may not be as effective as other methods, such as chemical peels or dermabrasion. When compared with topical 5-fluorouracil and trichloroacetic acid chemical peels, CO2 laser treatments have been shown to be equally effective in reducing the number of premalignant actinic keratoses and keratinocyte skin cancers that ultimately develop.[9] However, trichloroacetic acid has the lowest cancer incidence and the highest patient satisfaction rates compared with other modalities.[9]

Carbon dioxide lasers can also be employed for the treatment of keratinocytic skin cancers.[10] They may have an advantage when treating patients who are on anticoagulation medication, as CO2 lasers induce coagulation and reduce bleeding, and also for patients who have multiple malignant lesions that are not readily amenable to surgical excision. A disadvantage to carbon dioxide laser use is the inability to confirm the histologically complete excision of malignant lesions due to ablation and coagulation artifact. The technique nevertheless seems effective; in 2002, Nouri et al. treated a large number of basal cell carcinomas with CO2 lasers and, at follow-up visits, assessed for residual malignant tissue by Mohs micrographic surgery. Histology confirmed a lack of malignant tissue in these treated areas.[11]

Contraindications

There are a number of contraindications to CO2 laser resurfacing. The presence of active acne lesions may result in infection or abnormal colonization following the procedure. Open wounds or active infection, particularly from herpes simplex virus, should also postpone the procedure until after resolution. Adnexal damage from autoimmune disease, burns, or irradiation can interfere with re-epithelialization, and patients with histories of these conditions may not be candidates for treatment with CO2 lasers. Furthermore, the recent use of oral isotretinoin within the previous 6 to 12 months may lead to delayed wound healing or undesirable scarring. Lastly, a history of diseases associated with kobnerization phenomenon, including vitiligo and psoriasis, are also contraindications for this therapy.

Equipment

Carbon dioxide refers to the lasing medium within the device, the part of the laser that produces the beam of collimated, coherent, and monochromatic light. The lasing medium of medical carbon dioxide lasers contains CO2, nitrogen, hydrogen, and helium gasses and produces infrared light with a peak wavelength of 10,600 nm. The chromophore - the molecule that predominantly absorbs the laser's energy - for this wavelength is water. 

Laser-safe protective eye equipment is required for use by both the laser operator and the patient. The patient's eyes can be protected with wet/moist gauze as well as photoprotective opaque eye shields. The operator and all other personnel should also use goggles that are laser-protective for 10,600 nm. Protective goggles for CO2 lasers are typically clear.

Personnel

Personnel required for CO2 laser resurfacing include the operator, who can be a licensed physician, including dermatologists, otolaryngologists, plastic surgeons, and oral surgeons, or who may be a clinician with a lower level of training supervised by a physician. Assistance for the procedure can be provided by physician assistants or nurses who are trained in the use of lasers for cutaneous ablation. All members of the healthcare team must have training in laser safety. This same team should also provide pre-procedure evaluation and counseling as well as post-procedure follow-up.

Preparation

A thorough patient history and physical examination should be performed. Assessment of the patient’s Fitzpatrick skin type is particularly important in order to assess the risk of complications and to determine the potential efficacy of laser treatment as well as the optimal manner in which to deliver the laser energy. Patients with higher Fitzpatrick class skin types may benefit from a regimen combining hydroquinone and glycolic acid in order to reduce the likelihood of dyspigmentation. Clinicians should counsel patients at the pre-procedure visit regarding expected results as well as pre-procedure and post-procedure care. Patients should also be provided with details of all complications that may potentially result from treatment.

When skin resurfacing is planned in the perioral region, prophylactic antiviral medications should be prescribed to begin the day before or the morning of the procedure in order to reduce or eliminate the risk of post-procedure herpetic outbreaks, which may be severe and result in significant scarring. An example regimen is valacyclovir 500 mg PO BID for 14 days.[12]

Technique or Treatment

An appropriate means of controlling pain should be selected. Typically, general anesthesia or dissociative anesthesia is used for full facial CO2 laser resurfacing. For smaller areas or fractional resurfacing, a series of topical anesthetic applications followed by a local anesthetic block or infiltration may be sufficient to provide patient comfort. Occlusive inserts, eyewear, or laser goggles may be chosen for patient ocular safety depending upon the area being treated, and caution should be exercised regarding the potential of light to be reflected onto the cornea.[13][14]

The general standard of practice is to initiate antiviral therapy for all patients. Most patients have been exposed to the herpes simplex virus, and antiviral prophylaxis significantly reduces the risk of infectious complications. Antibiotics such as cefadroxil, dicloxacillin, doxycycline, or ciprofloxacin are often prescribed after the procedure.[15] Patients treated with antifungals, such as fluconazole, have shorter healing times, and an antifungal is often administered on the day of the laser treatment.

To achieve successful ablation of the skin without causing excessive thermal damage, a fluence of 5 J/cm^2 is applied with a pulse duration of less than 1 millisecond.[16] A short pulse duration allows the skin to have sufficient thermal relaxation time.[16] Individual pulse duration and depth should be determined based on the patient's concerns and skin type, according to the guidelines provided by individual machine manufacturers.

Re-epithelialization typically occurs 6 to 7 days after treatment. Following the procedure, crusting and serous exudate may develop over denuded skin in the treated area. Post-procedure care includes using bio-occlusive films, petroleum-based ointments, or hydrogels for the first 48 hours to decrease the formation of crusting over the treated area, which can facilitate appropriate healing.[17] Swelling, pain, and erythema can persist for 1 to 2 weeks following treatment, with inflammation typically resolving over the course of the following six weeks. In some cases, this inflammation can last up to 6 months post-treatment.

Complications

The typical post-procedure course involves the development of erythema, peeling, and skin fragility, which can last for up to 3 months after the treatment.

Short-term complications of treatment include the formation of milia and acneiform eruptions in the treated area. Herpes simplex virus reactivation may also occur, for which prophylactic valacyclovir should be given in patients with a known history of herpes simplex virus infection.[12]

Any procedure carries the risk of infection. Bacterial and fungal infections are less commonly seen after CO2 laser resurfacing due to "thermal sterilization" but are often seen in the setting of prolonged use of occlusive dressings, which should generally be removed 48 hours after the procedure.

Changes in pigmentation, both hyperpigmentation, and hypopigmentation, are also common. The risk of these changes is increased in Fitzpatrick skin types III-VI compared with types I-II. Hyperpigmentation is more likely to be self-limited than hypopigmentation; hyperpigmentation is also, fortunately, the more common sequela. Bleaching preparations and chemical peels may be used to reduce the appearance of hyperpigmentation, either prophylactically or therapeutically. Hypopigmentation is more common with the use of CO2 lasers than with other laser types due to the degree of thermal injury and subsequent inflammation that occurs; this complication can be very difficult to treat. Common methods of addressing hypopigmentation include topical steroids, fractionated CO2 laser treatment, blue lasers or intense pulsed light, and ultraviolet light exposure.[18]

Clinical Significance

Carbon dioxide laser skin resurfacing is a technique effective for both cosmetic and medical applications. It is an excellent modality for treating and preventing wrinkles and skin laxity that occur with photoaging. It is also effective in the treatment and prevention of keratinocyte skin cancers.

Appropriate patient selection and education are essential for successful outcomes with CO2 laser treatments. Patients with Fitzpatrick skin types I-II are most amenable to treatment with CO2 lasers; however, CO2 lasers may also be used for patients with skin types III-VI with careful adjustment of treatment parameters, particularly when a fractionated delivery system is employed.

Infectious complications, including herpes simplex virus reactivation, and bacterial and fungal infections, can impair healing, and appropriate prophylaxis should be administered. Patients should be followed carefully after treatment to provide clinicians the opportunity to identify and promptly manage any complications that may arise.

Enhancing Healthcare Team Outcomes

The provision of care by an interprofessional team can increase the likelihood of achieving optimal outcomes for patients. Patient education regarding pre- and post-procedure care, as well as expectations for outcomes, can improve overall satisfaction with treatment as well as aesthetic outcomes.[19][Level 4] When CO2 laser resurfacing is employed in conjunction with other surgical modalities, such as face-lifts and blepharoplasty, laser operators and cosmetic surgeons should follow a team-based approach to improve communication, reduce patient confusion, and maximize long-term outcomes.