Ann. Medit. Burns Club - vol. VIII - n. 3 - September 1995

A BIOSYNTHETIC SKIN SUBSTITUTE (BIOBRANE) IN THE MANAGEMENT OF BURNS

Terr6n J., Codina J., P6rez del Caz M.D., Safont J., Mirabet V.

Departamento de Cirugia Plàstica y Quernados, Hospital Universitario La Fe, Valencia, Spain

SUMMARY. This study concerns our use of a temporary skin substitute (Biobrane) in the management of excised burn wounds (deep bums). We also use Biobrane to cover meshed autograft. It is demonstrated that this skin substitute diminishes the healing and closing time of the mesh and improves graft take. The use of Biobrane in autograft donor sites is also discussed.

At present the use of a temporary skin substitute (TSS) is an elective therapy in the treatment of full- and partialthickness wounds affecting a large body surface area. When surgeons cannot find sufficient donor sites for skin autografts or when it is difficult to evaluate the depth of excision, a skin substitute has to be found. Other reasons' may be: difficult bleeding control, excision of a massively infected burn, poor general condition of the patient, and test graft.
The ideal properties of a skin substitute are: adherence, control of evaporative water loss, safety (sterile, hypoallergic, non-toxic, non-pyrogenic), flexibility, durability and stability on various wound surfaces, bacterial barrier, ease of application and removal, availability and ease of storage, cost-effectiveness, and haemostatic efficiency.
Cultured skin is the ideal skin substitute, and will be the treatment of the future. Long-term results',' indicate that cultured epithelial autografts regenerate a stable normal epidermis and are capable of inducing regeneration of connective tissue histologically indistinguishable from dermis in the process of wound healing. However, when in vitro cultured keratinocytes have been used, the high costs and the results have been disappointing.
Other TSS used widely at present are: skin allografts, biosynthetic skin substitutes (BSS), and amniotic membranes. Fresh or frozen allografts, when available, are the best choice in a temporary cover. They are rejected by the host within 14 to 21 days of application .
Multiple synthetic materials have also been used : 4 solid silicone, plastic membranes (polyvinyl chlorides and polyurethanes),' cotton gauze bonded to silicone, nylon mesh bonded to silicone (Biobranc), and recently two porous copolymer layers of L-lactide and e-caprolactone with a poly (ether-urethane) membrane dressing.
The aim of this work is to show how Biobrane is able to manage deep burns and to discuss its use in TSS, in covering skin-meshed autografts, and in protecting skin donor sites during healing.

Biobrane, developed in 1979 by Woodroof, consists of a custom-knitted nylon fabric mechanically bonded to an ultrathin silicone membrane. The entire dressing is uniformly coated with collagen peptides covalently and independently bonded to the dressing, rendering the dressing hydrophilic and tissue-compatible.'

Case 1

A 14-year-old Caucasian boy was admitted to the bum centre with deep gunpowder burns affecting the thorax, abdomen and left lower extremity (25% TBSA). He underwent an early bum excision on day 4 post-burn. The whole excised area was covered with Biobrane and a cornpressive dressing with Furacin. This dressing was changed every two or three days. Seven days after debridement we removed Biobrane from the leg (Figs. 1, 2) and grafted the good wound bed with a meshed 3:1 autograft (Fig. 3). We then covered the graft with Biobrane and an occlusive dressing (Fig. 4). We used Biobrane on the donor site (flank of the abdomen and lower back). The thorax and thigh were not ready for grafting and we performed a second debridement on them, even if we had observed an improvement in the bed. Fig. 5 shows how the meshed graft was closing beneath the BSS. Ten days after grafting we removed the Biobrane and found that the graft had completely taken and the mesh was closed (Fig. 6). At the same time the donor site was epithelialized beneath the BSS. We grafted the rest of the areas ten days after the first burn excision and managed them as above with the same good results. Infection was not present anywhere under the BSS.

Fig. 1 - An early excised deep burn in the leg. Biobrane covering the wound. Fig. 2 - Biobrane removed 7 days post-excision. Bed ready for autograft. Fig. 3 - Bed grafted with a 3:1 mesh graft. Fig. 4 - Mesh graft covered with Biobrane. Fig. 5 - Seven days after grafting. Mesh closing beneath Biobrane. Fig. 6 - Ten days after grafting. Biobrane removed and graft take achieved. Whole mesh closed.

Case 2

This was another 14-year-old Caucasian boy, with 45% TBSA deep bums in the face, neck, thorax and upper extremities. He underwent surgical excision on day 4 postburn. A very deep bum on the anterior thorax induced us to perform a fascial excision. The patient's poor general condition obliged us to use a TSS. In this case we used a BSS (Biobrane) because of a temporary shortage in the skin bank. We covered Biobrane with Furacin and a cornpressive dressing in order to achieve haemostasis. The dressing was changed every two or three days. On day 11 post-burn we removed Biobrane and found a good autograft bed. No infection was present.

The use of Biobrane after early burn wound sequential excision (Case 1) was satisfactory, because it enabled us to delay autografting until we were sure of good conditions in the wound bed. We also noticed that some areas of uncertain viability at the end of the first procedure became viable recipients with no further excision. We used one sheet of Biobrane on the leg and two sheets on the thigh and thorax.
Biobrane proved to be a good dressing over the meshed autografts. It reduced the healing time with the mesh and the taking time of the autograft. Ten days after grafting the mesh had closed and the graft had taken and was stable. It improved the quality, stability and amount of graft take. We did not make any change of Biobrane.
The donor site beneath Biobrane healed in ten days and the new epithelium was of good quality. We controlled the evolution of healing every day we made an inspection. We did not need any change of dressing (BSS).
We were able to bath the patients whenever necessary. In Case 2, Biobrane enabled us to delay grafting until the general state of the patient had improved. This did not cause any deterioration of the local status of the wound.

The adherence of Biobrane reduces the incidence of endogenous infection, protects against exogenous bacteria, diminishes pain and allows bathing of the patient. Adherence is slightly less than that of allografts before day five, but after a further 72 hours it is greater.' Woodroof found practically the same bacterial presence beneath Biobrane as beneath allografts (less than 101 bacteria/3.75 CM2).
Biobrane prevents wound dehydration, facilitates drainage of excess fluid and reduces evaporative water loss. Evaporation beneath it is slightly more than that of skin, and still better after day 5. Biobrane favours permeability to antibiotics.
Biobrane improves re-epithelialization :7,8 only one application is necessary, there is no need of changes and there is no tissue aggression due to repeated changes. It is capable of diminishing fibroblast capacity for wound contraction, maintaining the wound at up to 70% of its original size on day 21. After that it loses its efficacy.
The single application reduces pain and costs. It adapts to any body surface. Epithelialization is visible beneath Biobrane. There is less pain when moving the joints. It improves debridement and the patients' comfort.
The drawbacks of Biobrane are: no haemostasis, high cost, less uniformity, potential antigenicity, risk of unusual infection or contaminants, possible hypersensitivity, and overuse due to familiarity or negligence.
Biobrane has been evaluated for use on excised wounds.' It resulted in good beds to accept autografts and its efficacy was comparable to that of allografts. When used to cover a meshed autograft, Biobrane improved the take of the graft, with a substantial difference between covered and uncovered areas. Its use over the mesh also kept the granulation tissue within good limits and assisted epithelialization, which was improved. When used to cover autograft donor sites, Biobrane has also been used effectively, but the healing time and high cost do not recommend this use. We find occlusive hydrocolloids better than TSS for managing donor sites. In conclusion, Biobrane has been shown to be an effective skin substitute for use on excised burn wounds and over meshed autografts, and it exhibits nearly all the ideal properties of a skin substitute. It is a substitute for allografts when these are not available.

RESUME. Les auteurs ont considéré l'emploi d'un succédané cutané provisoire (Biobrane) dans le traitement des brûlures excisées (brûlures profondes). Ils ont aussi utilisé le Biobrane pour couvrir l'autogreffe à mailles. Ils montrent que ce succédané cutané diminue les temps de guérison et de fermeture de la greffe à mailles et améliore la prise de la greffe. Ils considèrent aussi les sites donneurs de l'autogreffe.

1. Koller J., PanAkovd P., Siska 1. et al.: The use of banked skin in excisional treatment of burns. In: "Progress in burn-injury treatment" (Eds. Boecks W., Moserovd J.), Acco, Leuven, pp. 94-7, 1990.

2. Nicholas E., O'Connor M.D., Gallico G., Compton C.: Long-term results in major pediatric burn patients treated with cultured skin. In: "Abstracts book of the IV European Burns Congress", Barcelona, p. 78, 1991.

3. Compton C.: Cultured epithelial autografts from seven days to seven years postgrafting. In: "Abstracts book of the IV European Bums Congress", Barcelona, p. 79, 1991.

4. Hansbrough J.F.: Biologic dressings. In: "The art and science of burn care" (Ed. Boswick J. A.), Aspen Publications, Rockville, p. 60,1987.

5. Herman W.J., Wertheym E., Shafir R.: Synthetic skin substitute for superficial paediatric burns. Arm. Medit. Burns Club, 6: 105-8, 1993.

6. Coenen LM.F.H., Jonkinan M.F., Klasen H.J. et al.: A new concept on artificial skin: the triple-layer. In: "Abstracts book of the IV European Bums Congress", Barcelona, p. 132, 1991.

7. Woodroof E.A.: BiobraneR: a new biosynthetic skin substitute. In: "Care of the bum wound" (Eds. May S.R., Dogo G.), Karger, Basel, pp. 218-30, 1983.

8. Guilbaud L: Inerpan. French multicentric study of the temporary skin substitute. In: "Progress in burn-injury treatment" (Eds. Boecks W., MoscrovA J.), Acco, Leuven, p. 120-7, 1990.

9. Terr6n L, Serna C., Tejerina A. et al.: A comparative study of three new occlusive dressings for healing of graft donor sites versus conventional therapy. Eur. J. Plast. Surg., 16: 98-103, 1993.