Carbon Dioxide Laser Resurfacing

I congratulate Ward and Baker¹ for their review of carbon dioxide laser resurfacing. This is a procedure that has fallen into disrepute in recent years despite its potential to provide outstanding results unachievable with other modalities. I have treated hundreds of patients since 1995, and patient satisfaction has been very high. This has been documented by others as well.² Adverse effects, such as acne, erythema, and hyperpigmentation, are temporary and treatable. Scarring should never occur in experienced hands. The one truly significant adverse effect that has caused carbon dioxide resurfacing to lose favor is hypopigmentation, which can be unpredictable and resistant to treatment.

Regarding hypopigmentation, I am confused by the authors' statement that “nearly all patients experience some degree of hypopigmentation.”^{1 (p238)} This seems to contradict the findings of their own series of 47 patients in which 6 (13%) developed hypopigmentation. Perhaps the discrepancy is attributable to including cases of pseudohypopigmentation with cases of true hypopigmentation. Pseudohypopigmentation is caused by the removal of pigmentation, such as that found in lentigines, ephelides, and actinic bronzing (not simply “areas of treated skin that are lighter than untreated skin^{1 (p242)}”). It reflects no damage to normal melanocytes and is usually cosmetically beneficial. True hypopigmentation is caused by damage to melanocytes. Although absolute melanocyte numbers are not diminished by carbon dioxide resurfacing, the melanin synthesis pathway is functionally impaired in areas demonstrating hypopigmentation.³ Possibly the discrepancy between the statement that nearly all patients experience hypopigmentation and the 13% incidence rate in this study reflects a difference in actual physical examination findings vs findings in a subsequent review of photographs only.

The 13% incidence rate of hypopigmentation reported by Ward and Baker¹ is similar to that reported by other laser surgeons, although the range has varied from 8% to 57%.⁴ This wide discrepancy can be explained by differences in the definition of hypopigmentation (true hypopigmentation vs pseudohypopigmentation) and by a wide range of treatment parameters used by various laser surgeons. In general, the incidence of hypopigmentation increases with increasing depth of cutaneous injury. This can be caused by an excessive number of passes with the laser, excessive energy per pass, and even use of subablative fluences. To achieve pulsed laser ablation, a fluence of 5 J/cm² is necessary. Less energy has the potential to produce diffuse tissue heating without vaporization.⁵

Although it has traditionally been thought that char debridement between laser passes is necessary to avoid excessive thermal damage,⁶ a recent article⁷ disputes this theory. Furthermore, aggressive debridement may actually contribute to persistent erythema, prolonged healing, and dyspigmentation.⁸ Ward and Baker¹ state that the risk of hypopigmentation can be minimized by the use of sunscreens before and after the procedure. I know of no data to support this assertion.

Melanocyte toxicity from preoperative hydroquinone-containing topical bleaching agents has also been suspected of causing hypopigmentation.⁹ However, the melanocytes that repopulate the skin surface following laser vaporization arise from deep adnexal structures, which likely are beyond the reach of topical agents.

Prevention of hypopigmentation is possible by reducing the number of passes with the laser. The maximal tissue contraction occurs with the second laser pass, and further passes should be reserved for only the most severely damaged skin. I routinely perform only 1 pass over the mandible with feathering onto the neck because this area is particularly prone to hypopigmentation and lines of demarcation. Hydration of the skin preoperatively, as with topical anesthetic agents, can also reduce the incidence of hypopigmentation (Suzanne Kilmer, MD; e-mail communication; October 4, 2008). Appropriate postoperative wound care is critical to prevent hypopigmentation as well as other adverse effects. Prolonged erythema is to be avoided and can be treated with topical steroids or oral fluconazole if subclinical candidiasis is suspected.

Treatment of hypopigmentation has been frustratingly difficult. Successful modalities have included topical photochemotherapy,¹⁰ the excimer laser,¹¹ and autologous cell transplantation.¹² Lines of demarcation can be minimized by using bleaching agents, intense pulsed light and other light-based devices on the normally pigmented skin adjacent to areas of demarcation.

In skilled hands, the carbon dioxide laser remains a remarkable tool for facial rejuvenation. It is beginning to come back into favor owing to the inability of other light-based devices to achieve equivalent results. The article by Ward and Baker¹ is timely and appreciated.

Correspondence: Dr Ramsdell, 102 Westlake Dr, Ste 100, Austin, TX 78746 (wmr@centexderm.com).

Financial Disclosure: None reported.