Surface Cooling Effect on Epidermal Damage by 585-nm Pulsed Dye Laser

ABSTRACT

Extensive clinical research has demonstrated that the 585-nm pulsed dye laser(PDL) is effective in eradicating port-wine stains(PWS) and telangiectasia with an extremely low incidence of scarring. The successful treatment of laser therapy is based on selective photothermolysis of blood vessels without damaging the normal overlying epidermis. Unfortunately, the native epidermal melanin acts as an optical shield that absorbs the laser light and reduces the heat generated in blood vessels. When melanin absorbs laser light, the resultant temperature increase can induce epidermal blistering. In these patients, the laser treatment dosages must be kept low, often subtherapeutic, to avoid damage to the epidermis and to prevent the possibility of scarring. Cryogen spray cooling of skin may be an effective method for minimizing epidermal thermal injury. The objective of this study is to determine histologically the effectiveness of the cryogen cooling by spraying the skin with a brief spurt of cryogen prior to the laser pulse, so as to reduce epidermal damage (hypo/hyperpigmentation) caused by this laser. We present a histologic study of the thermal response of the skin of the Sprague-Dawley rats to spray cooling in conjunction with 585-nm pulsed dye laser irradiation with 6J/cm. Both treatment sites with and without the use of the cryogen spray were compared. Under light microscope, the epidermal and dermal histologic changes were compared. A significant reduction in epidermal damage was found in study groups using the cryogen cooling without changing the efficacy of the laser treatment statistically. And a significant reduction in healing periods was observed in study groups using the cryogen cooling prior to the laser pulse. This study suggests that cryogen cooling can reduce epidermal damage during PWS treatment with the 585-nm PDL without reducing treatment efficacy. The absence of epidermal damage suggests that precooling with the cryogen may allow the use of higher laser input to expedite clearance without inducing epidermal change.