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The use of xenografts in the treatment of burns
44
Burns, 2, 44-46
The use of ×enografts in the t r e a t m e n t of burns Dan Mahler and Bernard Hirshowitz, Department of Plastic Surgery, Elaine and Neville Blond Burns Unit, Rambam University Hospital, Haifa, Israel Summary The modern surgical approach of early excision of burns entails the need for immediate adequate coverage of the denuded areas. In severe and extensive burns, and in case of mass burns, there is a shortage of autografts or viable allografts, and the conventional dressings, using topical agents, are prone to allow contamination of the burn surface. A solution for these conditions is provided by the use of porcine xenografts, viable or frozen, or in form of lyophilized porcine skin as a biological dressing. Fifty-nine patients have been treated by early excision and early skin grafting, using lyophilized porcine skin as the primary skin cover prior to final autografting. The results, as shown in this series, demonstrate absence of mortality, low infection rate and short morbidity time. THE m e t h o d of aggressive surgery in burns, which entails early excision and early grafting of necrotic burned tissue, is being widely used at present, and with it is the need to provide i m m e d i a t e skia coverage over extensive exposed areas. In cases of large, severe burns, there is a s h o r t a g e of autografts for such purpose. This can be overcome by the use of other sources o f skin, such as a t e m p o r a r y biological dressing. In this paper we wish to deal with the place of xenografts (foreign skinL particularly in the form of lyophilized porcine skin,* in this form of treatment. The use of xenografts started in the second half of the nineteenth century, and was called by Reverdin ' zoografting ' ( R o g e r s , 1959). The aim, as it is today, was to find a substitute for autografts, especially in cases of burns. At that time *Armour Porcine Skinmtemporary biological dressing. Armour Pharmaceutical Co. Ltd., Eastbourne, Sussex.
a false concept was held, and that was that zoografts could take permanently. Silvetti (Silvetti et al., 1957) provided the u n d e r s t a n d i n g of the biological nature of the foreign skin, and he demonstrated that it could only be used in the form o f a ' b i o l o g i c a l d r e s s i n g ' . This was followed by B r o m b e r g et al. (1965) and R a p p a port et al. (1970) who confirmed the basic concepts o f the modern use of xenografts.
T H E C L I N I C A L USE OF X E N O G R A F T S The xenograft which is used at the present time is a split-thickness, porcine skin graft. It can be used in form o f ' v i a b l e ' or ' l y o p h f l i z e d ' skin. The viable form js either a freshly taken skin graft, which can be transplanted immediately, or one which has been kept for a long period in liquid nitrogen (Mahler and Hackett, 1972) after having been processed in a controlled freezing chamber. The lyophilized form can be' h o m e - m a d e type ' - - C h e m l a b Freeze-drier (Mahler and H a c k e t t ) - - o r in its commercial f o r m - - A r m o u r Porcine Skin. In this series we used m a i n l y the latter, which is readily available and which has the advantage of ease of storage for an unlimited time. It comes in sterile packages in which the sheets o f skin are of u n i f o r m width and thickness. Its disadvantage is its cost, and serious efforts are now taken for local production o f lyophilized skin. Xenografts play an i m p o r t a n t role in the technique o f early excision and early skin grafting of burn~. After performing the tangential or fullthickness excision o f the burn, and after meticulous haemostasis has been secured, the exposed viable tissues, either deep dermis or subcutaneous fat,.are covered with xenografts. Preparing the frozen or the commercial skin entails soaking it
Mahler and Hirshowitz : Use of Xenografts
in sterile saline for 10-20 minutes prior to use. It is important that the xenografts will overly one another, so that no exlSosed area of the deep dermis will be left uncovered. The reason for this is to avoid loss of viability of this tissue, which occurs on exposure. The whole area is then covered b2r a burn dressing, except for the chest and abdomen which are left uncovered. After 48 hours the dressings are changed, and the xenograft, viable or lyophilized, is peeled off. At this point one should not misjudge the situation: the greasy secretions under the xenograft, especially when using lyophilized porcine skin, is not pus. This is mainly a sterile secretion formed by the tissue response to the xenograft. It is easily swabbed off by means of a gauze swab or towel and the underlying clean, reddish, bleeding tissue is discovered. This is now an excellent base for autografting procedure, which should be performed as soon as possible. There is place, however, to re-use xenografts in cases of shortage of donor sites or where the recipient area is not fully prepared for autografting. One may, of course, leave the xenografts for longer periods, but the main aim is to attain rapid coverage by autogenous skin. R ES U L T S
In this series we dealt with a group of 59 burned patients, treated during a period of 6 weeks as a result of the October War. These patients underwent 427 procedures under general anaesthesia: 149 were surgical interventions, 276, changes of burn dressings. Twelve patients, suffered from deep burns of over 40-60 per cent of body surface (Group A); 16 patients suffered from deep burns of over 20-40 per cent of body surface (Group B); and 31 patients suffered from burns of up to 20 per cent (Group C). Except for a few cases, the commercial porcioe skin was used in all instances as a primary coverage following the early excision. The porcine skin was replaced after 48 hours, either by autografts or by a new application of lyophilized skin. The results were as follows: Group A. Healing of the burns was achieved between day 20 and 42 post burn, where the mean healing time was 28 days. Group B. Healing was between day 10 and 26 post burn, the mean healing time being 19 days. Group C. The mean healing time was 16 days. There was no death in any of the 3 groups (59 patients)---4 fatal cases of 95-100 per cent deep burns, who died during the first 24 hours post burn, were not included in this series.
45
The rate of comphcations was low: infection rate was generally not of a serious nature, and there were only 4 cases of septicemia~2 due to Candida albicans, and 2 due to coagulase-positive staphylococcus.
DISCUSSION It would appear that the use ofxenografts, mainly in the form of Armour Porcine Skin, has an important bearing concerning the good results described above. One of the most effective means for overcoming the danger of infection in the treatment of burns is early excision and early grafting of the burned surface (MacMillan, 1970). In order to avoid contamination of the newly exposed excised areas, one has to use skin as a biological covet'. In view of the fact that in severe, extensive burns there is always a shortage of autogenous skin, the solution is provided by the use of xenografts as a temporary biological dressing, until the final stage of autografting. The use of the xenograft has the following ad van t ages: 1. It acts as a temporary biological cover in case of shortage of autografts. 2. it prevents and also reduces infection, it is assumed (Burleson and Eisrnan, 1973) that this is in part a result of a foreign body reaction, leading to the enhancement of local resistance response. 3. It prevents loss of fluids, proteins, electrolytes and energy, fl'om the burn surface. 4. It promotes the growth of granulation tissue. 5. It provides an alternative to the use of autografts in the presence of bleeding, and the patient's own skin is thereby conserved. 6. It provides a test for future successful take of autografts. 7. It aids in desioughing necrotic tissue. 8. It is easy to store and easy to use. The simplicity of its preparation and use and its advantages, as described above, makes the xenograft--in its viable or lyophilized f o r m ~ a n important aid in the primary treatment of burns. REFERENCES BROMBERG B. E., SONG 1. C. and MOHN M. P. (1965) The use of pig skin as a temporary biological dressing. Plash Reconstr. Surg. 36, 80. BURLF~ON R. and E~SMANN. (1973) Mechanism of antibacterial effect of biological dressing. Am. J. Surg. I77, 181. MACMILLAN B. G. (1970) Indications for early excision. Surg. Clin. North Am. 50, 1337.
Burns VoI. 2/No. 1
46
MAI{LER D. and H,XCK~'rT M. ~1972) Resurfacing of burns with pre.,,erved skin. Isr. J. Med. Sci. 8, I..ll. RAPPAPORT 1., PEPlNO A. T. and DJL'rrlcH W. (1970) Early use o1" xenografts a.,~ a biological dressing in burn trauma..qm. J. Sttrg, 120, 144.
Ro~.;vl~s B. O. (1959) Historical development of free skin grafting. Surg. CIhl. North Am. 39, 289. SILVE'FTI A. N., COTTEN D., BYRNE R. J., BI-RMAN J. R. and MENENDEZ A. F. (1957) Preliminary experimental studies of' bovine embryo skin grafts. Transpl. Bull. 4, 25.
Requests for rept hits should be, athlre~'~ed to: D r D. Mahler, 19 Sinai A~enue, i-laflil. Israel.
ERRATUM We regret that the name of H..J. Birkhahn, Department of Anaesthesia, Rambam University Hospital, Haifa, was omitted from the hst of authors for the article ' Early management of severe burns ", Burns, 1,309.
Burns, 2, 44-46
The use of ×enografts in the t r e a t m e n t of burns Dan Mahler and Bernard Hirshowitz, Department of Plastic Surgery, Elaine and Neville Blond Burns Unit, Rambam University Hospital, Haifa, Israel Summary The modern surgical approach of early excision of burns entails the need for immediate adequate coverage of the denuded areas. In severe and extensive burns, and in case of mass burns, there is a shortage of autografts or viable allografts, and the conventional dressings, using topical agents, are prone to allow contamination of the burn surface. A solution for these conditions is provided by the use of porcine xenografts, viable or frozen, or in form of lyophilized porcine skin as a biological dressing. Fifty-nine patients have been treated by early excision and early skin grafting, using lyophilized porcine skin as the primary skin cover prior to final autografting. The results, as shown in this series, demonstrate absence of mortality, low infection rate and short morbidity time. THE m e t h o d of aggressive surgery in burns, which entails early excision and early grafting of necrotic burned tissue, is being widely used at present, and with it is the need to provide i m m e d i a t e skia coverage over extensive exposed areas. In cases of large, severe burns, there is a s h o r t a g e of autografts for such purpose. This can be overcome by the use of other sources o f skin, such as a t e m p o r a r y biological dressing. In this paper we wish to deal with the place of xenografts (foreign skinL particularly in the form of lyophilized porcine skin,* in this form of treatment. The use of xenografts started in the second half of the nineteenth century, and was called by Reverdin ' zoografting ' ( R o g e r s , 1959). The aim, as it is today, was to find a substitute for autografts, especially in cases of burns. At that time *Armour Porcine Skinmtemporary biological dressing. Armour Pharmaceutical Co. Ltd., Eastbourne, Sussex.
a false concept was held, and that was that zoografts could take permanently. Silvetti (Silvetti et al., 1957) provided the u n d e r s t a n d i n g of the biological nature of the foreign skin, and he demonstrated that it could only be used in the form o f a ' b i o l o g i c a l d r e s s i n g ' . This was followed by B r o m b e r g et al. (1965) and R a p p a port et al. (1970) who confirmed the basic concepts o f the modern use of xenografts.
T H E C L I N I C A L USE OF X E N O G R A F T S The xenograft which is used at the present time is a split-thickness, porcine skin graft. It can be used in form o f ' v i a b l e ' or ' l y o p h f l i z e d ' skin. The viable form js either a freshly taken skin graft, which can be transplanted immediately, or one which has been kept for a long period in liquid nitrogen (Mahler and Hackett, 1972) after having been processed in a controlled freezing chamber. The lyophilized form can be' h o m e - m a d e type ' - - C h e m l a b Freeze-drier (Mahler and H a c k e t t ) - - o r in its commercial f o r m - - A r m o u r Porcine Skin. In this series we used m a i n l y the latter, which is readily available and which has the advantage of ease of storage for an unlimited time. It comes in sterile packages in which the sheets o f skin are of u n i f o r m width and thickness. Its disadvantage is its cost, and serious efforts are now taken for local production o f lyophilized skin. Xenografts play an i m p o r t a n t role in the technique o f early excision and early skin grafting of burn~. After performing the tangential or fullthickness excision o f the burn, and after meticulous haemostasis has been secured, the exposed viable tissues, either deep dermis or subcutaneous fat,.are covered with xenografts. Preparing the frozen or the commercial skin entails soaking it
Mahler and Hirshowitz : Use of Xenografts
in sterile saline for 10-20 minutes prior to use. It is important that the xenografts will overly one another, so that no exlSosed area of the deep dermis will be left uncovered. The reason for this is to avoid loss of viability of this tissue, which occurs on exposure. The whole area is then covered b2r a burn dressing, except for the chest and abdomen which are left uncovered. After 48 hours the dressings are changed, and the xenograft, viable or lyophilized, is peeled off. At this point one should not misjudge the situation: the greasy secretions under the xenograft, especially when using lyophilized porcine skin, is not pus. This is mainly a sterile secretion formed by the tissue response to the xenograft. It is easily swabbed off by means of a gauze swab or towel and the underlying clean, reddish, bleeding tissue is discovered. This is now an excellent base for autografting procedure, which should be performed as soon as possible. There is place, however, to re-use xenografts in cases of shortage of donor sites or where the recipient area is not fully prepared for autografting. One may, of course, leave the xenografts for longer periods, but the main aim is to attain rapid coverage by autogenous skin. R ES U L T S
In this series we dealt with a group of 59 burned patients, treated during a period of 6 weeks as a result of the October War. These patients underwent 427 procedures under general anaesthesia: 149 were surgical interventions, 276, changes of burn dressings. Twelve patients, suffered from deep burns of over 40-60 per cent of body surface (Group A); 16 patients suffered from deep burns of over 20-40 per cent of body surface (Group B); and 31 patients suffered from burns of up to 20 per cent (Group C). Except for a few cases, the commercial porcioe skin was used in all instances as a primary coverage following the early excision. The porcine skin was replaced after 48 hours, either by autografts or by a new application of lyophilized skin. The results were as follows: Group A. Healing of the burns was achieved between day 20 and 42 post burn, where the mean healing time was 28 days. Group B. Healing was between day 10 and 26 post burn, the mean healing time being 19 days. Group C. The mean healing time was 16 days. There was no death in any of the 3 groups (59 patients)---4 fatal cases of 95-100 per cent deep burns, who died during the first 24 hours post burn, were not included in this series.
45
The rate of comphcations was low: infection rate was generally not of a serious nature, and there were only 4 cases of septicemia~2 due to Candida albicans, and 2 due to coagulase-positive staphylococcus.
DISCUSSION It would appear that the use ofxenografts, mainly in the form of Armour Porcine Skin, has an important bearing concerning the good results described above. One of the most effective means for overcoming the danger of infection in the treatment of burns is early excision and early grafting of the burned surface (MacMillan, 1970). In order to avoid contamination of the newly exposed excised areas, one has to use skin as a biological covet'. In view of the fact that in severe, extensive burns there is always a shortage of autogenous skin, the solution is provided by the use of xenografts as a temporary biological dressing, until the final stage of autografting. The use of the xenograft has the following ad van t ages: 1. It acts as a temporary biological cover in case of shortage of autografts. 2. it prevents and also reduces infection, it is assumed (Burleson and Eisrnan, 1973) that this is in part a result of a foreign body reaction, leading to the enhancement of local resistance response. 3. It prevents loss of fluids, proteins, electrolytes and energy, fl'om the burn surface. 4. It promotes the growth of granulation tissue. 5. It provides an alternative to the use of autografts in the presence of bleeding, and the patient's own skin is thereby conserved. 6. It provides a test for future successful take of autografts. 7. It aids in desioughing necrotic tissue. 8. It is easy to store and easy to use. The simplicity of its preparation and use and its advantages, as described above, makes the xenograft--in its viable or lyophilized f o r m ~ a n important aid in the primary treatment of burns. REFERENCES BROMBERG B. E., SONG 1. C. and MOHN M. P. (1965) The use of pig skin as a temporary biological dressing. Plash Reconstr. Surg. 36, 80. BURLF~ON R. and E~SMANN. (1973) Mechanism of antibacterial effect of biological dressing. Am. J. Surg. I77, 181. MACMILLAN B. G. (1970) Indications for early excision. Surg. Clin. North Am. 50, 1337.
Burns VoI. 2/No. 1
46
MAI{LER D. and H,XCK~'rT M. ~1972) Resurfacing of burns with pre.,,erved skin. Isr. J. Med. Sci. 8, I..ll. RAPPAPORT 1., PEPlNO A. T. and DJL'rrlcH W. (1970) Early use o1" xenografts a.,~ a biological dressing in burn trauma..qm. J. Sttrg, 120, 144.
Ro~.;vl~s B. O. (1959) Historical development of free skin grafting. Surg. CIhl. North Am. 39, 289. SILVE'FTI A. N., COTTEN D., BYRNE R. J., BI-RMAN J. R. and MENENDEZ A. F. (1957) Preliminary experimental studies of' bovine embryo skin grafts. Transpl. Bull. 4, 25.
Requests for rept hits should be, athlre~'~ed to: D r D. Mahler, 19 Sinai A~enue, i-laflil. Israel.
ERRATUM We regret that the name of H..J. Birkhahn, Department of Anaesthesia, Rambam University Hospital, Haifa, was omitted from the hst of authors for the article ' Early management of severe burns ", Burns, 1,309.