Different demand on temporary skin substitutes for different indications.

In the past, the authors centred their attention on the effect of various skin substitutes on dermal burns. In the present study, the effect of various synthetic and biological skin substitutes on full thickness skin defects was studied. Experiments were carried out on laboratory pigs; the effect of various materials was evaluated in excised full thickness burns and in tangentially excised dermal burns. A parallel study was carried out in burned patients. It was concluded that for different indications, different qualities (or properties) of temporary skin substitutes are desirable or preferable. None of the materials available to date has all desirable qualities for all types of skin defects.

The histology of early necrectomy.

The healing of deep dermal burns after tangential excision and full-thickness burns after total excision was examined. The study was carried out in laboratory pigs. The results were compared with results obtained in unexcised burns. It appears that early excision of thermally damaged skin, even if the ensuing defect is left without further treatment, shortens considerably the process of healing both in tangentially excised deep dermal burns and excised full-thickness burns. (In full-thickness burns, the percentage of scar contraction during the process of healing is demonstrated and compared with scar contraction in unexcised full-thickness burns and in mechanical wounds.)

[Experimental comparison of different skin substitutes (author's transl)]. / Vergleichsstudie verschiedener Hautersatzmittel.

The authors discuss indications for using different temporary skin substitutes in local burn therapy. The clinical philosophy is based on an experience of 15 years. The advantages of those biological materials containing epidermis are stressed. Experimental results obtained in laboratory pigs show the importance of local therapy applied during the first 24 hours following injury, especially in cases of dermal skin loss. The healing of experimental dermal burns, mechanical defects, defects after necrectomy of dermal and full thickness burns were studied. In a further series of experiments in vitro, various biological and synthetic materials were tested as to their efficacy in evaporative waterloss prevention. Best clinical and experimental results were obtained with allografts (fresh and deep frozen) and with xenografts.

Temporary skin substitutes and evaporative water loss.

The authors worked out a simple method, which enables an orientative evaluation of different skin substitutes as to their effectiveness in preventing gross evaporative water loss from decorticated dermis. The method is based on the loss of weight of decorticated dermis samples (covered by different materials) incubated in a thermostat for 1, 2, 3 and 4 hours at 37 degrees C. Following skin substitutes were tested: Lyofoam; Epigard; collagen foil; freeze dried amniotic membrane; freeze dried porcine xenografts; deep frozen porcine xenografts; and fresh porcine xenografts. Controls lost during 4 hours incubation at 37 degrees C 61.34% of the original weight (similarly as samples covered by synthetic skin substitutes or amniotic membrane). Samples covered by freeze dried xenografts lost only 33.07%, samples covered by deep frozen xenografts 13.20% and by fresh xenografts, 6.06%.

Evaporative water loss in partial skin loss in the first 24 hours.

In experiments on laboratory pigs the healing of decorticated dermis and in deep dermal burns was studied. In both groups, the controls were left uncovered, while the experimental wounds were covered with an indifferent ointment for the first 24 hours only. After the first 24 hours all wounds were left exposed without further treatment. It was found, that wounds, covered by an indifferent ointment for the first twenty-four hours only penetrate to a lesser depth as compared to the uncovered controls; histological studies of the course of healing confirm this fact, as the wounds treated for the first 24 hours only heal one week earlier then the controls. The differences were more pronounced in burns than in mechanical decorticated wounds. The authors presume, that these facts underline the importance of evaporative water loss during the first 24 hours in deep dermal burns as well as the importance of local treatment at this initial stage.

Histology of healing of deep dermal burns in pigs.

A standard deep second degree burn was worked out in pigs. The burn was inflicted with a hot iron, standardized by immediate retraction measurements. Biopsies were taken from the wounds on days 0, 1, 4, 7, 14, 21. Standard staining methods were used. Spontaneous healing was followed and results compared with mechanical partial skin loss healing.