Improved Healing of Sulfur Mustard-Induced Cutaneous Lesions in the Weanling Pig by Pulsed Co₂ Laser Debridement

Abstract

The healing of cutaneous wounds induced by the chemical war-fare agent sulfur mustard [bis(2-chloroethyl)sulfide; HD] following pulsed CO₂ laser debridement was examined in weanling pigs. Six animals (7-9 kg) were used to examine the efficacy of a Tru-Pulse CO₂ laser in promoting improved healing. Each animal had 24 exposure sites on the dorsum. Eight sites were sham exposed, eight sites were exposed to saturated HD vapor for 5 min, and eight sites were exposed to saturated HD vapor for 15 min. Twelve sites on each pig were debrided using a pulsed CO₂ laser. Two pigs were debrided each at 6, 24, and 48 h postexposure. The pigs were monitored during a 14-day healing period for erythema (by reflectance colorimetry), edema (Draize scoring), systemic toxicity (by hematological and clinical chemistry examinations), and lesion size (by video dermatoscopic examination and image analysis). At the end of the 14-day period, animals were euthanized and biopsies taken of all exposure sites for histopathological analysis.

Laser-and HD-induced edema resolved within 3 days; erythema within 10 days. The HD exposures did not appear to cause systemic toxicities. For those sites exposed to HD vapor for 15 min, 46% of all nondebrided sites showed significant gross lesions at 14 days compared with small lesions in 17% of the debrided sites. Viability, thickness, and organization of the epidermis were all significantly improved by pulsed CO₂ laser debridement. By 14 days postexposure, nondebrided HD-exposed sites had reepithelialized; however, the epidermis was characterized by cytological atypia, disordered maturation, scattered apoptotic/necrotic keratinocytes, and marked squamoid changes. A scale crust with intraepidermal inflammatory infiltrate was apparent on sites exposed to HD vapor for 15 min. The dermis was characterized by focal areas of mild necrobiotic changes with a sparse to moderately dense mononuclear infiltrate with scattered neutrophils (15 min exposures). In contrast, the epidermis of all sites debrided at 6,24, or 48 h postexposure was thick, well organized with rete ridge formation, contained a well-formed basal cell layer showing a cuboidal morphology, and showed an ordered maturation with no cytological atypia and no intraepidermal inflammatory infiltrate. The papillary dermis showed increased stromal cell proliferation, no necrobiotic changes, and minimal inflammatory infiltrate. Laser debridement played a useful role in the management of mild to moderately severe cutaneous HD burns in weanling pigs.