JOURNAL OF SURGICAL RRSRARCH 52,50-58 (19%) Healing of Partial Thickness Porcine Skin Wounds in a Liquid Environment KARL BREUING, M.D., ELOF ERIKSSON, M.D., PAUL LIU, M.D., AND DON R. MILLER, PH.D. The Brigham/Children’s Division of Plastic Surgery of Harvard Medical School, Brigham and Women’s Hospital, Boston, Massachusetts 02115 Submitted for publication November 21, 1990 This study employs a liquid-tight vinyl chamber for the topical fluid-phase treatment of experimental wounds in pigs. Continuous treatment with normal sa- line significantly reduced the early progression of tis- sue destruction in partial thickness burns. Uncovered burns formed a deep layer of necrosis (0.49 f 0.004 mm, mean f SD) although burn wounds covered with empty chambers demonstrated less necrosis (0.14 + 0.01 mm), fluid-treated wounds formed no eschar, and little tissue necrosis could be detected (<0.005 mm). Topical treatment with hypertonic dextran in- creased water flux across burn wounds by 0.24 ml/cm’/ 24 hr (mean, n = 96) over saline-treated wounds during the first 5 days after wounding. When partial thickness burn and excisional wounds were immersed in isotonic saline until healed, the daily efflux of water, protein, electrolytes, and glucose across the wound surface de- clined during healing to baseline values found in con- trols (saline-covered unwounded skin). The declining protein permeability was used as a reproducible, non- invasive, endogenous marker for the return of epithe- lial barrier function. Saline-treated excisional wounds healed within 8.6 f 0.6 days (mean + SD, n = 27) and burn wounds within 12.1 + 1.4 days (mean f SD, n = 15). Healing of fluid-treated wounds occurred with- out tissue maceration and showed less inflammation and less scar formation than healing of air exposed wounds (no attempt was made to compare rates of heal- ing between air- and fluid-exposed wounds). We con- sider the fluid-filled chamber a potentially very useful diagnostic, monitoring, and delivery system for wound-healing research and for human wound ther- apy. 0 1992 Academic Press, Inc. negligible and chance of infection is remote. Healing usually occurs without cosmetic or functional impair- ment. Larger and deeper skin wounds (e.g., deep partial and full thickness burns, burn wound excisions, debride- ments, and donor graft sites) may lead to life-threaten- ing losses of fluid and electrolytes [2] and may provide access for infectious organisms. Although European sur- geons report some success allowing these wounds to desiccate [3, 41 it is widely recognized today that allow- ing poorly perfused, traumatized tissue to dehydrate transforms a “zone of stasis” into a “zone of necrosis” [5], resulting in further tissue damage and undesirable eschar formation. Winter [6] in 1962 first demonstrated that these un- desirable effects could be prevented with an occlusive wound covering. He maintained a moist environment in excisional wounds by trapping wound fluid underneath a polyethylene film. This not only prevented deepening of the wound and eschar development but accelerated re- epithelialization by about 50%. His findings have since been corroborated by other investigators [7-121 and have led to the development of various types of wound dressings [ 131,all designed to prevent wound desiccation by trapping wound fluid [ 141. We have developed a wound chamber that permits the exposure of individual experimental wounds to modifi- able physiologic liquids. The model allows the control of the wound environment as well as monitoring wound physiology in uivo by sampling chamber fluids. In this paper we describe the chamber model and characterize the healing of partial thickness skin wounds in an iso- tonic saline environment in pigs. INTRODUCTION MATERIALS AND METHODS Mammalian cells exist in a physiologic interstitial fluid, isolated by the skin from a hostile external environ- ment [l]. If the skin is damaged, the exposed wound surface begins to dry and may become infected. Small superficial skin wounds are generally allowed to dry dur- ing healing. In such wounds, the loss of fluid is routinely Animals All animal procedures were approved by the Harvard Medical Area Standing Committee on Animals. Female Yorkshire pigs (3-4 months old/4550 kg) used in these experiments were fed a standard porcine diet and were housed at 20-23°C in an atmosphere of about 65% hu- 0022-4804/92 $1.50 Copyright 0 1992 by Academic Press, Inc. All rights of reproduction in any form reserved. 50