Annals of Burns and Fire Disasters - vol. XVI - n. 4 - December 2003

ORGANIZATION AND PURPOSES OF A BURNS CENTRE SKIN BANK

Melandri D.

Burns Centre, Ospedale Bufalini, Cesena, Italy

SUMMARY. This paper considers the organization and purposes of a skin bank in a burns centre. The advantages and disadvantages of homologous skin for grafting are considered, and the history of skin transplants for burn repair is reviewed. The organizational aspects are also considered. Methods of finding, removing, and storing skin are described, together with the use of cryoconservation. The risk of the transmission of disease by infection is a constant presence, but can be overcome by careful screening. The Cuono technique has proved to be a very useful grafting technique. Skin banks play an important role, especially when autografts are not available.

Introduction

Current trends in the treatment of deep burns recommend early removal of the eschar and rapid coverage of raw areas with autologous dermoepidermal grafts. Early treatment offers clear advantages: reduction of infection risks, hydroelectrolytic losses, and caloric requirements and a better recovery in a shorter time.1-3

When however it is not possible, owing to the extent and the depth of the burn, to find sufficient healthy donor areas for autologous grafts, it is necessary to use alternative solutions involving the coverage of areas subjected to early escharectomy with skin substitutes or the more expensive “living skin equivalents”.

Despite the great number of methods available commercially, homologous skin is still today the best skin substitute existing (Table I).3-6 Homologous skin acts as a physiological and mechanical barrier and can be used as a temporary cover (Fig. 1); the coverage can be permanent if the Cuono technique is used (Fig. 2).7,8

Historical background

The use of homologous skin for transplants dates back many years. After the first use of variable-thickness autologous grafts by Reverdin in 1869,9 numerous publications reported on homologous skin grafts.4,10-13 In the early 1950s the grafting of homologous skin was a routine technique in the treatment of severely burned patients at the Brooke Army Medical Center in San Antonio, Texas. This was the period of the creation of the US Navy Skin Bank at Bethesda in Maryland, which marked the beginning of the modern era of skin banks.14 In the USA there are some 300 tissue banks, of which at least 50 provide skin. Tissue and skin banks now operate all over Europe, including Italy, and in many countries outside Europe.

Clearly one of the most important aspects of the use of homografts is related to the possibility of their preservation for use at some subsequent date, maintaining their integrity and viability. An important breakthrough in this field was made in 1949, when Polge15 chanced upon the cryoprotective properties of glycerol in cells that were deep-frozen and then defrozen.

Numerous experimental studies were carried out,16-19 and Cochrane20 described a technique of controlled freezing and preservation in liquid nitrogen at -100 °C in 15% glycerol.

Skin bank - organizational aspects

Skin banks are facilities that stockpile skin and its derivatives and provide them on request. The staff of a skin bank consists of physicians, who are involved in the organization of the bank and in research, and biologists, whose role is more specifically technical.

A skin bank has been operative for over two years at the Burns Centre in Cesena, Italy. This skin bank is essential for the treatment of seriously burned patients because it provides the Burns Centre with homologous skin as and when required, thus extending the range of possible therapies in our patients. The bank is now able to cool-treat both autologous and homologous skin; cool-treated skin has to be used within a period of not more than three weeks.

Cryofrozen homologous skin is also provided. Other banks are able to provide glycerolized homologous skin, de-epidermidized skin, and lyophilized skin as well as autologous and homologous cultivated keratinocytes.21

Skin bank: tasks and aims

A skin bank is responsible for obtaining, preparing (or processing), and preserving donor skin. During all phases of the production process, the skin bank has to make use of standardized procedures that can be documented (e.g. microbiological tests and viability tests in vivo and in vitro) that guarantee the integrity and viability of the processed skin. In other words, it provides quality control for the finished product.22

Sources of skin

Skin is obtained by a skin bank surgeon (in our case, a physician from our centre), following the notification of a donor by a regional centre for transplant referral or directly by a hospital. The skin is removed after the donor’s heart has ceased to beat, as part of a multi-organic transplant in an operating theatre; this procedure can however be performed in the morgue up to 12 h after death.

If the body is refrigerated, the possible time for removal of the skin extends up to 24 h.

The donor, when found, is subjected to a series of tests regarding his or her general condition. It is necessary to be able to exclude the presence of any pathologies that might be dangerous for the recipient. Tests are therefore made for HIV 1-2, HTLV 1-2, HBV, HCV, syphilis, cytomegalovirus, and toxoplasma.

A search is made for the presence of neoplasias and neurological and autoimmune diseases; microbiological tests are conducted for aerobes, anaerobes, fungi, and yeasts. Finally, if the donor is deemed suitable, a clinical file is compiled that records the consent for the transplant and the operating procedure for skin removal.23

The skin is removed in conditions of absolute asepsis and is then placed in special sterile containers containing physiological solution. The containers are kept in ice and sent to the skin bank for further processing.

During this procedure skin samples are taken for culture tests for aerobic and anaerobic bacteria, fungi, and yeasts.

Depending on the burns centre’s needs, the skin is cooled for short-term use or else deep-frozen for preservation in liquid nitrogen at -196 °C. When the skin is cooled in a refrigerator at +4 °C, the maintenance solution is changed every three days, along with the antibiotics and the sterile containers; samples are also taken for control culture tests. Skin treated in this manner can be used for up 21 days. If the skin is not needed for short-term use, it is deep-frozen within 72 h of removal. This procedure

is performed using a programmable cryofreezer, or “planner”, after each single strip of skin has been placed, unrolled, in special heat-sealed envelopes containing cryoprotective liquid.

During this procedure it is extremely important to follow rigorous parameters in order to be sure of obtaining the freezing curve most appropriate for the preservation of the skin’s integrity and viability. Cryopreserved skin can be used for up to five years, and is always ready for use. To guarantee its integrity and viability, it has to be defrozen before use by rapid heating in a thermal bath at 37 °C, passing from -196 °C to 0 °C in 3-4 min.2,3

Conclusion

Early escharectomy, followed by immediate coverage of raw areas, is now standard care in seriously burned patients.

The fresh autologous skin graft is still the best possible coverage.

However, in deep and extensive burns, there is often a lack of suitable autologous donor areas. In such cases, the best possible coverage continues to be homologous skin, despite its limitations (immunogenicity and the risk of the transmission of infectious disease).

The risk of infection can be reduced by careful screening and new laboratory techniques such as PCR. The donor’s skin can be removed, in appropriate conditions, up to 24 h after death, and the number of potential donors is vast. After removal of the skin, it can be either used immediately or cryopreserved.

Apart from their use as temporary coverage, homografts can be used for permanent coverage, using the Cuono technique. In this method, autologous epidermis is placed over allodermis after removal of the alloepidermis.7

In the not too distant future, it is hoped that research on new bioengineered tissues and the availability of simple, effective, and safe immunosuppressive treatments will enable skin banks to provide burns centres with an extremely valid alterative to the autograft, thus extending the available range of therapeutic options.

RESUME. L’Auteur considère l’organisation et les buts d’une banque de la peau dans un centre des brûlures. Il considère en outre les avantages et les désavantages de la peau homologue dans les greffes, et fournit des renseignements sur l’histoire des greffes cutanées dans le traitement des brûlures. L’Auteur ensuite décrit quelques aspects de l’organisation d’une banque de la peau, et les méthodes pour trouver, enlever et conserver le matériau cutané. Le risque de la transmission d’une maladie à travers l’infection est toujours présent mais les techniques modernes de dépistage peuvent le surmonter. La technique de Cuono s’est démontrée une technique de greffage très utile. Les banques de la peau jouent un rôle très important, particulièrement en l’absence de la disponibilité d’autogreffes.

Bibliography

1. Martyn J.A.J.: “Acute Management of the Burned Patient”. W.B. Saunders, Philadelphia, 1990.
2. Settle J.A.D.: “Principles and Practice of Burn Management”. Churchill Livingstone, New York, 1996.
3. Herndon D.N.: “Total Burn Care”. W.B. Saunders, London, 1996.
4. O’Donaghue M.N., Zarem H.A.: Stimulation of neurovascularization. Comparative efficacy of fresh and preserved skin grafts in burn patients. Plast. Reconstr. Surg., 22: 42-55, 1958.
5. Morris P.J., Bondac C., Burke J.F.: The use of frequently changed skin allografts to promote healing in the non-healing infected ulcer. Surgery, 60: 13-19, 1966.
6. Shuck J.M., Pruitt B.A., Moncrief J.A.: Homograft skin for wound coverage. Arch. Surg., 98: 472-8, 1969.
7. Cuono C., Langdon R., McGuire J.: Use of cultured epidermal autografts and dermal allografts as skin replacement after burn injury. Lancet, 1: 1123-4, 1986.
8. Hickerson W.L., Compton C. et al.: Cultured epidermal autograft and allodermis combination for permanent burn wound coverage. Burns, 20 (suppl. l): 52-6, 1994.
9. Reverdin J.L.: Greffe épidermique. Bull. de la Soc. Impériale de Chir. de Paris, 493-511: 1869.
10. Girdner J.H.: Skin grafting with grafts from a dead subject. Med. Record NY, 20: 119-20, 1888.
11. Bettman A.G.: Homogenous Thiersch grafting as a life-saving measure. Am. J. Surg., 39: 156-62, 1938.
12. Webster J.P.: Refrigerated skin grafts. Ann. Surg., 120: 431-49, 1944.
13. Zaroff L.I. et al.: Surgery, 59: 68-372, 1966.
14. Tier W.C., Sell K.W.: United States Navy skin bank. Plast. Reconstr. Surg., 41: 543-8, 1968.
15. Polge C., Smith V.A., Parkes A.S.: Revival of spermatozoa after UV factors and dehydration at low temperatures. Nature, 164: 66, 1949.
16. Mathews D.: Storage skin for autogenous grafts. Lancet, 1: 775, 1945.
17. Strumia M.M., Hodge C.C.: Frozen human skin grafts. Ann. Surg., 121: 860-5, 1945.
18. Baxter H., Entin M.E.: Experimental and clinical studies of reduced temperatures in injury and repair in man. III. Direct effect of cooling and freezing on various elements of the human skin. Plast. Reconstr. Surg., 3: 303-34, 1948.
19. Lehr H.B., Berggren R.B., Lotke P.A., Coriell L.L.: Permanent survival of preserved skin autografts. Surgery, 56: 742-96, 1964.
20. Cochrane E.T.: The low-temperature storage of skin. A preliminary report. Br. J. Plast. Surg., 118-25, 1966.
21. Braye F., Pascal P. et al.: Advantages of using a bank of allogenic keratinocytes for the rapid coverage of extensive and deep second-degree burns. Med. Biol. Eng. Comput., 38: 248-52, 2000.
22. May S.R., De Clement F.A.: Skin banking methodology. An evaluation of packaging format, cooling and warming rates and storage efficiency. Cryobiology, 17: 33-45, 1980.
23. American Association of Tissue Banks. Technical Manual for Tissue Banking, Arlington, VA, AATB 1987.
24. Donati L.: “La Malattia da Ustione”. Tamburini, Milan, 1975.
25. Barisoni D.: “Le Ustioni e il loro Trattamento”. Piccin, Padua, 1984.
26. Deitch E.A.: The management of burns. N. Eng. J. Med., 323: 1249-53, 1990.