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Evolving practice of the Helsinki Skin Bank

Evolving practice of the Helsinki Skin Bank INTRODUCTION Split‐thickness skin grafting is at present the gold standard for wound coverage in burn surgery. Autografts, however, are not always sufficiently available for coverage of large burns. Despite the wide variety of artificial skin products commercially available nowadays, allograft skin still plays a key role in the treatment of patients with extensive burns and in other cases of severe skin loss, such as toxic epidermal necrolysis or drug eruptions (1–3) . Strict laws control tissue banking. The European Parliament and Council Directive (2004/23/EC) instituted from 31 March 2004 produced a document concerning allogeneic transplants, with the intention of guaranteeing a minimal level of safety in European Union states. This Directive determines that a licenced or fully accredited tissue bank should prepare the grafts. To gain a licence, tissue banks have to fulfil many safety criteria, such as screening of living or deceased donors for health suitability. All processing phases must conform to written procedures, providing traceability of the donor–recipient route, prevention of secondary and cross‐contamination during the processing and storage of the harvested tissues, proof of product microbiology checks and cold chain control with adequate staff training. The Skin Bank of the Helsinki Burn Centre is the only licenced local skin bank in Finland. Glycerolised skin banking began in June 1995, and the first few years are reviewed in an article by Vuola and Pipping (4) . The purpose of this present article is to review the management and running of a departmental/local skin bank in the Helsinki Burn Centre between the years 2001 and 2008. Further aims were to assess the microbiological safety of the allograft skin and analyse the clinical use of donor skin in burn patient operations. MATERIALS AND METHODS The files of the local skin bank, located at the Helsinki Burn Centre, Department of Plastic Surgery, Helsinki University Hospital, Helsinki, Finland were reviewed to identify allograft donors and allograft skin harvested between 1 st Jan 2001 and 31 st Dec 2008. The following data were collected: number of donors per year, donor age, harvested skin area and microbiological findings. The surgical electronic database and the skin bank records were analysed to identify recipient patients, as well as operation indications. Indications were classified into four categories: (i) biological dressing on partial‐thickness burns, (ii) coverage of freshly excised burns, (iii) sandwich technique with widely expanded autografts and (iv) other. The cost of allograft skin per cm 2 was calculated using the skin bank data from the year 2007 including all labour and material costs, as described earlier (4) . Harvesting and processing of the allografts Whenever a multiorgan donor becomes available, the Transplant Team of the Helsinki University are alerted and the donors are subsequently tested for antibodies against hepatitis B and C, human immunodeficiency virus, cytomegalovirus, Epstein‐Barr virus, toxoplasmosis and syphilis. Once the patient is deemed suitable for organ donation and only if located in one of the central Helsinki hospitals, the Plastic Surgical Skin Bank nurses are alerted to the possibility of a skin donor candidate. Following negative serological testing and once the Transplant surgical team have removed the organs, the Skin Bank Team are again informed. At this point the Skin Bank Team consisting of two nurses attend the theatre and the patient is re‐scrubbed and draped. Skin is harvested using a Zimmer dermatome (Zimmer Inc., Warsaw) at a thickness of 10/1000 inch circumferentially from the extremities as well as from the flanks and lateral chest wall. Intravenous and intra‐arterial lines as well as other invasive monitoring devices frequently limit the donor sites. These are required to be left in place, however, for the purposes of forensic pathology. The processing of the allograft skin is as described earlier (4) . After procurement, the donor skin is immersed in 85% glycerol and an antibiotic solution containing G‐Penicillin and Streptomycin. The skin is then transferred to the Plastic Surgery theatre department where the Skin Bank is maintained and incubated at 38°C for 3 hours. At this point, the skin is transferred under sterile conditions and placed in a solution of 85% glycerol and saline. It is then again incubated at the same temperature for a further 3 hours. Once again under sterile conditions, the skin is immersed in 85% glycerol only and refrigerated. After 3 weeks, bacterial cultures are taken. If these are negative, the skin is deemed ready for use. Monitoring of bacterial contamination Immediately before multiorgan harvesting, all donors receive a prophylactic antibiotic; either 1 g meropenem or 1 g imipenem intravenously. The first bacterial culture of the allografts is taken 3 weeks after procurement, once the glycerolisation process has been completed. If after 3 weeks of refrigeration a positive culture is obtained the skin is placed under quarantine and re‐cultured immediately. This donor skin is subsequently made unavailable for recipient use. If the second culture is positive for bacteria, the whole skin batch is discarded. RESULTS During the years 2001–2008, our skin bank collected allograft skin from a total of 115 donors, Table 1 . The number of donors per year varied from 7 to 20 patients. From 2005 to 2008, the number of donors per year has gradually decreased. The mean age of donor patient per year ranged from 42 to 52.5 years. The mean age of donors has steadily increased during the study period. 1 Annual skin bank data Year 2001 2002 2003 2004 2005 2006 2007 2008 Donors, n 18 17 20 15 7 11 14 13 Donors, mean age (years) 42 46.9 49.5 50.1 51.7 50 48.1 52.5 Harvested skin (cm 2 ) 57 084 69 413 62 196 48 733 25 427 29 619 40 684 21 527 Mean harvest per donor (cm 2 ) 3171 4083 3109 3248 3632 2692 2906 1655 Discarded batches – – – – – – – – Recipients, n NA NA 5 5 3 4 14 13 The area of harvested skin per year ranged from 21 527 to 69 413 cm 2 , with a mean of 44 335 cm 2 . The mean harvested skin area per donor varied between 1655 and 4083 cm 2 , with a mean of 3062 cm 2 . During the study period, no skin batches were discarded. Bacterial cultures of the allograft skin batches were negative in 86 (75%) cases. The remaining 29 allograft batches tested positive for microorganisms. None of the repeated microbiological cultures, however, were found to be positive. Table 2 presents the distribution of cultured microorganisms. In total 13 different species of microorganisms were cultured, of which most of the bacteria were Gram positive and could be classified as normal skin flora. Only one Gram‐negative microbe, namely, Enterobacter cloacae , was cultured from the allografts. The majority of the microorganism positive allograft batches, 23/29 (80%), were monomicrobial. The remaining six allograft batches were polymicrobial: three had growth of two types of different microorganisms, and one of each had growth of three, four and five different types of microorganisms. 2 Microbiological culture results of allograft skin Gram positive Coagulase‐negative Staphylococci 14 Staphylococcus epidermidis 5 Bacillus species 4 Bacillus cereus 3 Propionebacter acnes 3 Staphylococcus aureus 2 Anaerobic Gram‐positive rod 2 Diptheroids 2 Streptococcus viridans 2 Enterococcus faecalis 1 Clostridium species 1 Gram negative Enterobacter cloacae 1 Other Candica, not candica albicans 1 From the year 2003 to 2008, we identified 35 donor skin batches that were used for 44 patients in 69 operations. In three cases, allograft skin was applied for two different indications in the same operation. In each of these three cases, the two indications were coverage of freshly excised burns and sandwich technique with widely expanded autografts. The mean number of recipient patients per donor skin batch was 2.5, with a median number of 2, and a range from 1 to 7. During the early years of the study period, there is likely to have been under reporting of the recipient patient operations because of the transition to a new coding procedure electronic database. The various indications and numbers of operations are presented in Table 3 . 3 Recipient operation indication Indication Biological dressing on partial‐thickness burns 37 (52%) Coverage of freshly excised burns 15 (21%) Sandwich technique with widely expanded autografts 13 (18%) Other 6 (9%) one of each: coverage of omphalocele, donor site coverage to reduce exudation, post‐debridement of pressure sore, post‐debridement of meningococcal sepsis skin necrosis, coverage of congenital epidermolysis bullosa skin lesions, coverage of Stevens–Johnson skin lesions The cost of allograft skin calculated from the year 2007 was 0.81 € per cm 2 ; labour costs contributed 75% and material costs 25% to the overall cost. Nurses' wages formed the single largest cost contribution. DISCUSSION This article reviewed the management and running of the Helsinki Skin Bank from 2001 to 2008. The setting up and early years (1995–2001) of our skin bank has been reported earlier (4) . We have managed to implement many of the proposed ideas that were presented in the discussion section of the 2002 article. We now have two trained nurses in the skin harvesting process and the amount of harvested skin per donor has improved. However, during the past few years the number of donors has fallen and consequently the overall amount of harvested skin has diminished as well. The earlier article concluded with an optimistic prophecy that artificial skin would eventually replace allograft skin. However, this has not happened; still today allograft skin plays a pivotal role in the treatment of large and severe burns as well as for other plastic surgical indications, a widespread shared view (1,5,6) . Therefore, there are concerns that there may be a shortage of allograft skin in the future. The total number of donors in each of the two study periods was almost the same. However, the current study period has been 2 years longer so in fact the mean number of donors per year has slightly dropped. During the same time, the number of multiorgan donors nationwide has also decreased (information obtained via communication with Dr Heikki Mäkisalo, Department of Transplantation, Helsinki University Hospital). In addition, another limitation is that we harvest skin only from the Greater Helsinki area hospitals, so potential skin donors from other cities in Finland are not available to us. Patients with major burns are by definition immunosuppressed; consequently, there is a potential risk for acquiring a serious bacterial or viral infection. However, normal human skin is inherently contaminated and colonised with microorganisms. In view of these facts, it is essential that we exercise strict protocols in the harvesting, processing and preserving of the allograft skin. This is in order to avoid contamination and potential cross‐infection of the recipient patient. We believe that our current protocols are effective in minimising this infection risk; 75% of allografts were tested initially negative for bacteria. This compares well with the results reported by Neely et al. (7) . The most commonly cultured bacteria were those of normal human skin flora such as coagulase‐negative Staphylococcus , Proprionibacterium spp. and Dipthteroids, or common environmental organisms such as Bacillus cereus . This variety of microorganisms has been similarly found in other studies (7,8) . The low cost and simplicity of preparing and storing glycerolised allograft skin convinced us to choose this method in the beginning of our skin banking management (4) . Furthermore, glycerol has been showed to possess antimicrobial and antiviral properties. Even Bacillus spp. notoriously known to be resistant to disinfectants and antibiotics do not survive in higher (85%) concentrations of glycerol nor at higher temperatures of incubation (>24°C) (9) . Over the years, accrued clinical experience has resulted in some of our practices becoming more rational and effective. In the early years, the surgeon on‐call and nurse assistant carried out the skin harvesting, sometimes even in the morgue or pathology department. Nowadays, the harvesting takes place solely in an operating theatre under normal strict aseptic conditions. This should contribute greatly to reducing the bacterial load cultured in the allografts. Another improvement in practice has been the evolution from obtaining class I and class II allografts to solely class I allografts. The difference between these two classes of allograft is their size. Class I allografts are individually larger measuring at least 10 × 18 cm. The processing of and working with allografts smaller than 10 × 18 cm was time consuming and in practice more difficult to handle. We are currently pleased with this modification. Our indications for allograft skin use were generally similar to those reported by Mackie (6,10) , although we used allograft skin with a greater frequency (52%) as a biological dressing for partial‐thickness burns. Regarding the use of allograft skin in freshly excised burns our indication is usually rapid temporary coverage of early excised burns in high risk patients in order to reduce operating times, for example, in elderly burn patients. In 9% of cases, allograft skin was applied in non burn patients. These were all paediatric cases with a variety of different indications. In comparison with the year 2000, the cost per cm 2 for 2007 has increased by a third to 0.81 € per cm 2 which we believe is accounted for by annual changing rates of inflation. The Euro Skin Bank in fact charge 0.99 € per cm 2 . In conclusion, the use of allograft skin in the Helsinki Skin Bank is ultimately microbiologically safe and continues to provide a versatile and useful treatment modality in many major burn cases with few observed complications. The use of allograft skin also extends to various indications in paediatric and adult patients with complicated non burn wounds. As compared with synthetically produced temporary dressings currently available, our allograft skin is more economical. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Wound Journal Wiley

Evolving practice of the Helsinki Skin Bank

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Publisher
Wiley
Copyright
© 2010 The Authors. Journal Compilation © 2010 Blackwell Publishing Ltd and Medicalhelplines.com Inc
ISSN
1742-4801
eISSN
1742-481X
DOI
10.1111/j.1742-481X.2010.00684.x
pmid
20492012
Publisher site
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Abstract

INTRODUCTION Split‐thickness skin grafting is at present the gold standard for wound coverage in burn surgery. Autografts, however, are not always sufficiently available for coverage of large burns. Despite the wide variety of artificial skin products commercially available nowadays, allograft skin still plays a key role in the treatment of patients with extensive burns and in other cases of severe skin loss, such as toxic epidermal necrolysis or drug eruptions (1–3) . Strict laws control tissue banking. The European Parliament and Council Directive (2004/23/EC) instituted from 31 March 2004 produced a document concerning allogeneic transplants, with the intention of guaranteeing a minimal level of safety in European Union states. This Directive determines that a licenced or fully accredited tissue bank should prepare the grafts. To gain a licence, tissue banks have to fulfil many safety criteria, such as screening of living or deceased donors for health suitability. All processing phases must conform to written procedures, providing traceability of the donor–recipient route, prevention of secondary and cross‐contamination during the processing and storage of the harvested tissues, proof of product microbiology checks and cold chain control with adequate staff training. The Skin Bank of the Helsinki Burn Centre is the only licenced local skin bank in Finland. Glycerolised skin banking began in June 1995, and the first few years are reviewed in an article by Vuola and Pipping (4) . The purpose of this present article is to review the management and running of a departmental/local skin bank in the Helsinki Burn Centre between the years 2001 and 2008. Further aims were to assess the microbiological safety of the allograft skin and analyse the clinical use of donor skin in burn patient operations. MATERIALS AND METHODS The files of the local skin bank, located at the Helsinki Burn Centre, Department of Plastic Surgery, Helsinki University Hospital, Helsinki, Finland were reviewed to identify allograft donors and allograft skin harvested between 1 st Jan 2001 and 31 st Dec 2008. The following data were collected: number of donors per year, donor age, harvested skin area and microbiological findings. The surgical electronic database and the skin bank records were analysed to identify recipient patients, as well as operation indications. Indications were classified into four categories: (i) biological dressing on partial‐thickness burns, (ii) coverage of freshly excised burns, (iii) sandwich technique with widely expanded autografts and (iv) other. The cost of allograft skin per cm 2 was calculated using the skin bank data from the year 2007 including all labour and material costs, as described earlier (4) . Harvesting and processing of the allografts Whenever a multiorgan donor becomes available, the Transplant Team of the Helsinki University are alerted and the donors are subsequently tested for antibodies against hepatitis B and C, human immunodeficiency virus, cytomegalovirus, Epstein‐Barr virus, toxoplasmosis and syphilis. Once the patient is deemed suitable for organ donation and only if located in one of the central Helsinki hospitals, the Plastic Surgical Skin Bank nurses are alerted to the possibility of a skin donor candidate. Following negative serological testing and once the Transplant surgical team have removed the organs, the Skin Bank Team are again informed. At this point the Skin Bank Team consisting of two nurses attend the theatre and the patient is re‐scrubbed and draped. Skin is harvested using a Zimmer dermatome (Zimmer Inc., Warsaw) at a thickness of 10/1000 inch circumferentially from the extremities as well as from the flanks and lateral chest wall. Intravenous and intra‐arterial lines as well as other invasive monitoring devices frequently limit the donor sites. These are required to be left in place, however, for the purposes of forensic pathology. The processing of the allograft skin is as described earlier (4) . After procurement, the donor skin is immersed in 85% glycerol and an antibiotic solution containing G‐Penicillin and Streptomycin. The skin is then transferred to the Plastic Surgery theatre department where the Skin Bank is maintained and incubated at 38°C for 3 hours. At this point, the skin is transferred under sterile conditions and placed in a solution of 85% glycerol and saline. It is then again incubated at the same temperature for a further 3 hours. Once again under sterile conditions, the skin is immersed in 85% glycerol only and refrigerated. After 3 weeks, bacterial cultures are taken. If these are negative, the skin is deemed ready for use. Monitoring of bacterial contamination Immediately before multiorgan harvesting, all donors receive a prophylactic antibiotic; either 1 g meropenem or 1 g imipenem intravenously. The first bacterial culture of the allografts is taken 3 weeks after procurement, once the glycerolisation process has been completed. If after 3 weeks of refrigeration a positive culture is obtained the skin is placed under quarantine and re‐cultured immediately. This donor skin is subsequently made unavailable for recipient use. If the second culture is positive for bacteria, the whole skin batch is discarded. RESULTS During the years 2001–2008, our skin bank collected allograft skin from a total of 115 donors, Table 1 . The number of donors per year varied from 7 to 20 patients. From 2005 to 2008, the number of donors per year has gradually decreased. The mean age of donor patient per year ranged from 42 to 52.5 years. The mean age of donors has steadily increased during the study period. 1 Annual skin bank data Year 2001 2002 2003 2004 2005 2006 2007 2008 Donors, n 18 17 20 15 7 11 14 13 Donors, mean age (years) 42 46.9 49.5 50.1 51.7 50 48.1 52.5 Harvested skin (cm 2 ) 57 084 69 413 62 196 48 733 25 427 29 619 40 684 21 527 Mean harvest per donor (cm 2 ) 3171 4083 3109 3248 3632 2692 2906 1655 Discarded batches – – – – – – – – Recipients, n NA NA 5 5 3 4 14 13 The area of harvested skin per year ranged from 21 527 to 69 413 cm 2 , with a mean of 44 335 cm 2 . The mean harvested skin area per donor varied between 1655 and 4083 cm 2 , with a mean of 3062 cm 2 . During the study period, no skin batches were discarded. Bacterial cultures of the allograft skin batches were negative in 86 (75%) cases. The remaining 29 allograft batches tested positive for microorganisms. None of the repeated microbiological cultures, however, were found to be positive. Table 2 presents the distribution of cultured microorganisms. In total 13 different species of microorganisms were cultured, of which most of the bacteria were Gram positive and could be classified as normal skin flora. Only one Gram‐negative microbe, namely, Enterobacter cloacae , was cultured from the allografts. The majority of the microorganism positive allograft batches, 23/29 (80%), were monomicrobial. The remaining six allograft batches were polymicrobial: three had growth of two types of different microorganisms, and one of each had growth of three, four and five different types of microorganisms. 2 Microbiological culture results of allograft skin Gram positive Coagulase‐negative Staphylococci 14 Staphylococcus epidermidis 5 Bacillus species 4 Bacillus cereus 3 Propionebacter acnes 3 Staphylococcus aureus 2 Anaerobic Gram‐positive rod 2 Diptheroids 2 Streptococcus viridans 2 Enterococcus faecalis 1 Clostridium species 1 Gram negative Enterobacter cloacae 1 Other Candica, not candica albicans 1 From the year 2003 to 2008, we identified 35 donor skin batches that were used for 44 patients in 69 operations. In three cases, allograft skin was applied for two different indications in the same operation. In each of these three cases, the two indications were coverage of freshly excised burns and sandwich technique with widely expanded autografts. The mean number of recipient patients per donor skin batch was 2.5, with a median number of 2, and a range from 1 to 7. During the early years of the study period, there is likely to have been under reporting of the recipient patient operations because of the transition to a new coding procedure electronic database. The various indications and numbers of operations are presented in Table 3 . 3 Recipient operation indication Indication Biological dressing on partial‐thickness burns 37 (52%) Coverage of freshly excised burns 15 (21%) Sandwich technique with widely expanded autografts 13 (18%) Other 6 (9%) one of each: coverage of omphalocele, donor site coverage to reduce exudation, post‐debridement of pressure sore, post‐debridement of meningococcal sepsis skin necrosis, coverage of congenital epidermolysis bullosa skin lesions, coverage of Stevens–Johnson skin lesions The cost of allograft skin calculated from the year 2007 was 0.81 € per cm 2 ; labour costs contributed 75% and material costs 25% to the overall cost. Nurses' wages formed the single largest cost contribution. DISCUSSION This article reviewed the management and running of the Helsinki Skin Bank from 2001 to 2008. The setting up and early years (1995–2001) of our skin bank has been reported earlier (4) . We have managed to implement many of the proposed ideas that were presented in the discussion section of the 2002 article. We now have two trained nurses in the skin harvesting process and the amount of harvested skin per donor has improved. However, during the past few years the number of donors has fallen and consequently the overall amount of harvested skin has diminished as well. The earlier article concluded with an optimistic prophecy that artificial skin would eventually replace allograft skin. However, this has not happened; still today allograft skin plays a pivotal role in the treatment of large and severe burns as well as for other plastic surgical indications, a widespread shared view (1,5,6) . Therefore, there are concerns that there may be a shortage of allograft skin in the future. The total number of donors in each of the two study periods was almost the same. However, the current study period has been 2 years longer so in fact the mean number of donors per year has slightly dropped. During the same time, the number of multiorgan donors nationwide has also decreased (information obtained via communication with Dr Heikki Mäkisalo, Department of Transplantation, Helsinki University Hospital). In addition, another limitation is that we harvest skin only from the Greater Helsinki area hospitals, so potential skin donors from other cities in Finland are not available to us. Patients with major burns are by definition immunosuppressed; consequently, there is a potential risk for acquiring a serious bacterial or viral infection. However, normal human skin is inherently contaminated and colonised with microorganisms. In view of these facts, it is essential that we exercise strict protocols in the harvesting, processing and preserving of the allograft skin. This is in order to avoid contamination and potential cross‐infection of the recipient patient. We believe that our current protocols are effective in minimising this infection risk; 75% of allografts were tested initially negative for bacteria. This compares well with the results reported by Neely et al. (7) . The most commonly cultured bacteria were those of normal human skin flora such as coagulase‐negative Staphylococcus , Proprionibacterium spp. and Dipthteroids, or common environmental organisms such as Bacillus cereus . This variety of microorganisms has been similarly found in other studies (7,8) . The low cost and simplicity of preparing and storing glycerolised allograft skin convinced us to choose this method in the beginning of our skin banking management (4) . Furthermore, glycerol has been showed to possess antimicrobial and antiviral properties. Even Bacillus spp. notoriously known to be resistant to disinfectants and antibiotics do not survive in higher (85%) concentrations of glycerol nor at higher temperatures of incubation (>24°C) (9) . Over the years, accrued clinical experience has resulted in some of our practices becoming more rational and effective. In the early years, the surgeon on‐call and nurse assistant carried out the skin harvesting, sometimes even in the morgue or pathology department. Nowadays, the harvesting takes place solely in an operating theatre under normal strict aseptic conditions. This should contribute greatly to reducing the bacterial load cultured in the allografts. Another improvement in practice has been the evolution from obtaining class I and class II allografts to solely class I allografts. The difference between these two classes of allograft is their size. Class I allografts are individually larger measuring at least 10 × 18 cm. The processing of and working with allografts smaller than 10 × 18 cm was time consuming and in practice more difficult to handle. We are currently pleased with this modification. Our indications for allograft skin use were generally similar to those reported by Mackie (6,10) , although we used allograft skin with a greater frequency (52%) as a biological dressing for partial‐thickness burns. Regarding the use of allograft skin in freshly excised burns our indication is usually rapid temporary coverage of early excised burns in high risk patients in order to reduce operating times, for example, in elderly burn patients. In 9% of cases, allograft skin was applied in non burn patients. These were all paediatric cases with a variety of different indications. In comparison with the year 2000, the cost per cm 2 for 2007 has increased by a third to 0.81 € per cm 2 which we believe is accounted for by annual changing rates of inflation. The Euro Skin Bank in fact charge 0.99 € per cm 2 . In conclusion, the use of allograft skin in the Helsinki Skin Bank is ultimately microbiologically safe and continues to provide a versatile and useful treatment modality in many major burn cases with few observed complications. The use of allograft skin also extends to various indications in paediatric and adult patients with complicated non burn wounds. As compared with synthetically produced temporary dressings currently available, our allograft skin is more economical.

Journal

International Wound Journal – Wiley

Published: Aug 1, 2010

There are no references for this article.