Methods of preparing porcine skin for bioassay of thermal injury.

Clipping, shaving, and depilation methods of hair removal were evaluated on porcine .skin in preparation for its use as a bioassay substrate for thermal injury. Each method provides distinct advantages and disadvantages. Criteria for selecting the proper methodology are identified for a bioassay substrate for thermal injury studies. APPROVED: ~~~ Commanding A COMPARISON OF METHODS OF PREPARING PORCINE SKIN FOR BIOASSAY OF THERMAL INJURY INTRODUCTION Skin preparation (hair removal) is an important factor in preoperative management 1 and is required for porcine skin to be anatomically similar to human skin. 2 Preoperative shaving has been the traditional method of hair removal in preparing the body surfaces of human beings for surgery. 3 Depilatory hair removal is considered a good or superior alternative method. l '3ll . Clipping hair with a #40 clipper head has been considered the standard for animals, although published data to support thi~ m~thod are not available. Clinical and field experience from inforrpal experiments and from trial and error forms the major source of informai~ion for using clipping in animals rather than other methods. Objections have been raised over the hair stubble which inevitably is present following careful clipping. In addition to the fact that hair in the operative field is to be abhorred, using the skin of pigs as a substrate for the bioassay of thermal injury requires that this stubble not interfere with thermal transfer by shadihg the skin from radiant or convective heat nor act as a scaffold to elevate a test fabric sample enough to provide a thermal insulating air gap. These factors must be evaluated against the inevitable irritation and microscopic injuries of shaving 3 and the time consuming and costly process with depilatory agents. 5 It is in light of these questions that the following studies were undertaken prior to further studies using porcine skin for bioassay of thermal injury. METHODS AND MATERIALS Three white female domestic (35. 9-37.2 kg) swine (Sus scrofa domesticus) were used for this study. They were locally procured, quarantined, and verified to be healthy and free of internal parasites prior to their use in this experiment. Their entire skin was clear and free of any lesions (insect bites, scratches, nicks, excoriation, irritation, dermatitis, etc.). Following an overnight fast, each animal was premedicated with atropine (0. 02 mg/lb) and Innovar-Vet* (l mg/20 lb), intubated, and anesthetized with Halothane, USP. 12 Both sides of the animal were clipped with a #40 clipper head. Three 3x10 inch test areas (long axis vertical) separated by one inch buffer areas were selected on each side and marked off (Figure 1). The sequence of test procedures for each of the six flanks used was randomly selected. TEST AREA CONFIGURATION FIGURE 1 *McNeil Laboratories, Ft. Washington, PA 19304