Storage media and temperature maintain normal anatomy of cadaveric human skin for transplantation to full-thickness skin wounds.

Cadaveric human skin provides an optimal temporary cover after early excision of full-thickness burns; however, engraftment is reduced greatly by cryopreservation. Refrigerated skin is generally preferred because of its rapid revascularization, presumably caused by its greater viability. In this study, the effects of storage solutions, temperature, and the changing of the storage media on skin graft anatomy were evaluated as an indicator of graft viability. Split-thickness human skin grafts (0.012-0.015 mm) were retrieved from cadaveric donors and grafted to circumferential, full-thickness skin wounds on athymic mice. After clinical determination of engraftment 3 months after grafting, 6-mm punch biopsy samples of the human skin were harvested and separated into two groups. Biopsy samples were stored in either saline or Eagle's minimal essential medium. Media were not changed or were changed every 3 days. All groups were stored at either 4 degrees C or room temperature (RT). After 5, 10, and 21 days of storage, biopsy samples were grafted onto athymic mice for 20 days. The biopsy grafts were then collected and prepared for histologic scoring on a scale of +4 (normal anatomy) to 0 (no epithelial cells). Significant differences in histologic scores were found by the nonparametric Kruskal-Wallis test followed by Wilcoxon pairwise comparison. Skin stored in media maintained better histologic anatomy than skin in saline, suggesting better maintenance of viability. There was also better preservation of anatomy after storage at RT for 21 days with media changes every 3 days when compared to unchanged media and all conditions at 4 degrees C. These results support the hypothesis that increased availability of nutrients and increased storage temperature maintain higher viability of cadaveric human skin for transplantation to full-thickness cutaneous wounds.

Observations on stability and contraction of composite skin grafts: xenodermis or allodermis with an isograft overlay.

Composite skin grafts of xenodermis or allodermis with a thin split-thickness isograft overlay were evaluated for stability and contraction. Male inbred Lewis rats were used as recipients, with Buffalo rats serving as allogeneic dermis donors. Cryopreserved human skin was used for xenodermis grafts. The two components of the composite graft, the xenodermis or allodermis and the isograft overlay, were grafted in one operation to a surgically created wound. Wounds were observed for 1 year. The composite skin grafts took fairly well, although spotty loss of the overlaid isograft was noted. The xenodermis and allodermis remained grossly intact even at 1 year after grafting. However, composite skin grafts in this animal model contracted more than did sheet isografts alone.

Comparison of scar contracture with the use of microskin and Chinese-type intermingled skin grafts on rats.

Wounds that were measured precisely 4 x 5 cm in size were created over the dorsal surfaces of rats. The defects were grafted with the use of either the microskin or Chinese technique of intermingled auto/allograft with an expansion ratio of 10:1. The size of the grafted wound of each rat was recorded on the fifth graft day after grafting and then weekly for 11 weeks. The extent of scar contracture on each rat was calculated weekly as a percentage of the original size. The results showed that the scar contracture associated with the Chinese type of intermingled auto/allograft transplantation was less than that associated with the microskin technique. The healing process in both forms of grafting was uneventful.

Carnitine supplementation vs. medium-chain triglycerides in postburn nutritional support.

The effect of dietary supplementation of carnitine on protein metabolism was studied in a burned guinea-pig model. Animals bearing a 30 per cent total body surface area burn were enterally infused with three isocaloric and isonitrogenous diets via gastrostomy feeding tubes for 14 days. Two diets contained safflower oil (long-chain triglycerides, LCT) and another diet contained medium-chain triglycerides (MCT) as their lipid sources (30 per cent of total calories as lipid). L-Carnitine was added to one of the two diets containing safflower oil. There were no significant differences in nitrogen balance, urinary excretion, serum albumin or transferrin among the three groups. However, the use of MCT in place of LCT appeared to increase liver weight and liver nitrogen. In this model, carnitine supplementation did not enhance the nitrogensparing effect of fat following burn injury.

A new model for studying the development of human hypertrophic burn scar formation.

Hypertrophic scar formation remains the major problem for severely burned patients who survive their injuries. This scarring can result in both cosmetic and functional deformities. One of the major problems in dealing with this complication is the lack of an adequate animal model with which to test various possible therapeutic modalities. We describe an animal model that uses human skin applied to the backs of nude mice to investigate the problem. Immunosuppression is not necessary in this model since the nude mouse lacks a thymus gland and is therefore not able to reject the skin. With this model we have been able to achieve contracture of meshed normal human skin grafts and hypertrophic scar formation in normal human skin that was burned a month after grafting to the mouse. We have also had success in grafting human hypertrophic scars, obtained from burn patients, to the mice. This model offers unique opportunities for investigation of the cause and treatment of burn scars in humans.

Prospective clinical study of Hydron, a synthetic dressing, in delivery of an antimicrobial drug to second-degree burns.

This clinical trial prospectively evaluates the potential beneficial effects of antimicrobial drug delivery from a synthetic dressing (Hydron-AgSD) formed on second-degree burn wounds. A paste composed of polyethylene glycol-400, poly 2-OH ethylmethacrylate, and silver sulfadiazine (AgSD 1%-3%) matured within one hour to form a solid dressing. In 27 patients, comparable areas of second-degree wounds on the same patient were selected at random for test and control (silver sulfadiazine 1% only) sites. The mean total time of the synthetic dressing application per patient was about nine days, and each dressing remained in place for nearly four days. During this interval the control sites required four dressings changes. In 17 tests for infections, the control areas were contaminated but no bacteria were detected under the synthetic dressing; in three tests, the controls had no bacteria, whereas the synthetic dressing did. Healing of burns was similar under both types of dressing. Benefits of Hydron treatment included increased patient comfort because of the reduced number of dressing changes and, in some cases, greater freedom from contaminating bacteria.

An evaluation of Aquaphor Gauze dressing in burned children.

Aquaphor Gauze was evaluated as a dressing for skin graft donor sites, for partial thickness burn injuries and for split thickness skin grafts. Control dressings consisted of: fine mesh gauze for skin graft donor sites. silver sulphadiazine (Silvadene) on coarse mesh gauze for the partial thickness burns, and nitrofurazone cream (Furacin) on fine mesh gauze for the skin grafts. The Aquaphor Gauze was found to be inferior to the fine mesh gauze for donor site dressings. No statistically significant difference was identified between Aquaphor Gauze and controls for the treatment of partial thickness burns. As a dressing for skin grafts the Aquaphor Gauze was significantly superior to the control dressing as measured by graft take and reduced patient pain. We would recommend that Aquaphor Gauze be used as a dressing for skin grafts where the risk of infection is not excessive.

A clinical study of antimicrobial agents delivered to burn wounds from a drug-loaded synthetic dressing.

This report is of an investigation of the release of antimicrobial agents from a solid barrier dressing when applied to second- and third-degree burn wounds. The synthetic dressings were formed by a mixture of polyethylene glycol-400 (PEG), poly-2-hydroxethyl methacrylate (PHEMA) and one of the test drugs: silver sulfadiazine (AgSD), gentamicin, silver nitrate, or nitrofurazone. The dressings were formed directly on the burn wounds of 33 patients from a paste prepared from a mixture of PEG-PHEMA and drug. These dressings remained in place for 3 days, covering 12 to 64 square inches of the wound. In six patients, the entire burn wounds were covered with the dressings in which the treated areas were each about 200 square inches. The use of drug-loaded synthetic dressings extended to cover major portions of the burn wounds reduced the work required for nursing care and lessened patient discomfort.

A silicone-nylon laminated dressing (IP-758) for closure of excised or débrided burn wounds.

A synthetic dressing (IP-758) consisting of a silicone membrane with a laminated layer of nylon fabric was evaluated in patients as a substitute for biological materials to cover excised areas of burn wounds. During a 3-day interval, the tissue developed a tightly adherent bond to the synthetic dressing. The IP-758 conformed to irregularly-shaped regions and stretched with the movements of the wound surface. Seventeen burned children from 3 to 12 years of age and 1 adult are included in this study. In 12 cases, the mean area covered with the synthetic ranged from approximately 39 to 118 cm2. The average dressing remained in place for 3 days and was replaced once. Microbiological sampling (wet swab technique) of the area under the IP-758 after application of second dressing was compared with open control sites treated with topical antibiotics. The results with Staphylococcus aureus, a frequent contaminant, were similar for the two test areas. The IP-758 site in 6 patients contained an average of 10 3 S. aureus per swab test. Immediately following removal of the adherent IP-758 and control of local bleeding, the wounds in most patients provided excellent sites for autografts. The IP-758 dressing is well-tolerated, elastic and adherent to the burn wound permitting maturation of the wound to readily accept autografts.

Control of experimental burn wound infections: comparative delivery of the antimicrobial agent (silver sulfadiazine) either from a cream base or from a solid synthetic dressing.

This report demonstrates prolonged effective release of silver sulfadiazine (AgSD) to experimental burns in rats from a solid dressing by mixtures of polyethylene glycol-400 and poly-2-hydroxyethyl methacrylate. The synthetic dressing, incorporating the antimicrobial drug, may be formed either directly on the burn wound or prepared as a preformed sheet and applied to the wound after it was contaminated with bacteria. The level of silver in the blood following treatment of the burn wound with topical AgSD (Silvadene, Marion Labs) is significantly less when the drug is presented in the dressing than when the drug is applied in a cream base; the concentration of the sulfadiazine moiety in the blood is similar for the two drug preparations. Improved survival of the burned and contaminated rats and reduced nursing care were observed in the burned animals when the synthetic dressing was used to deliver the drug relative to the results when the AgSD was applied in a cream base by standard procedures.

Delivery of the topical antimicrobial agents silver sulfadiazine, gentamicin and nystatin to infected burn wounds in rats from preloaded synthetic dressings.

1. A synthetic burn dressing made from polyethylene glycol - 400 (PEG) and poly-2-hydroxyethyl methacrylate (PHEMA) can be prepared to contain topical antimicrobial agents. 2. Sheets of these antimicrobial loaded dressings may be applied to the wounds or alternatively, the synthetic dressing incorporating the active drugs may be formed directly on the burn wound from the PEG-PHEMA drug mixture. 3. The antimicrobials (silver sulfadiazine, gentamicin and nystatin) are continuously and effectively released from the solid dressing over 2-11 days.