Cyclosporine and skin allografts for the treatment of thermal injury. I. Extensive graft survival with low-level long-term administration and prolongation in a rat burn model

The hypothesis tested in the present and accompanying study is that an effective treatment for severe burns involves early excision of necrotic tissue followed by skin allografting and cyclosporine (CsA) immunosuppressive therapy. LEW (RT1) rats served as recipients of thermal injury and/or skin allografts. BN x LEW F1 (LBN, RT1(l+n)) rats served as skin donors. LEW burn recipients received a hot water (90 degrees C for 10 sec) 30% body surface area (BSA) full-thickness burn. As expected, LEW recipients treated with CsA (25 mg/kg/day for 20 days) demonstrated significant graft prolongation compared with controls (P less than 0.005). Skin graft survival was similarly prolonged in LEW recipients undergoing burn injury, primary wound excision, and CsA administration compared with burn-skin allograft controls (P less than 0.001). Mortality was not increased in the thermal injury-CsA-treated recipients compared with burn controls. A final experiment was initiated to investigate how low-level long-term (greater than 100 days) maintenance CsA treatment influenced skin allograft survival for possible future consideration in burn trauma. Recipients receiving skin allografts plus CsA (20 days, 8mg/kg/day, followed by every other day thereafter) did not reject their grafts. However, a possible early sign of rejection (a single small ulcerative lesion) was noted in five of these long-term CsA-treated animals at a mean of 34 +/- 11 (SD) days. The lesion in these animals did not progress any further during CsA administration. Histopathologic study of selected animals removed from the CsA maintenance regimen for greater than 50 days following long-term administration revealed a number of interesting chronic lesions similar to those previously reported in the skin component of composite tissue (limb) allografts following long-term low-level CsA intervention. In conclusion, CsA was very successful in preventing rejection of skin allografts in a rat burn model without apparent adverse effects.     

Site-specific immunosuppression using a new formulation of topical cyclosporine A with polyethylene glycol-8 glyceryl caprylate/caprate.

PURPOSE: Dermal application of immunosuppressants can be an effective means of achieving site-specific immunosuppression (SITE) on skin allografts in burn wound management and in the treatment of various immune skin disorders. We have previously reported success with topical cyclosporine A (tCsA) in the treatment of skin allograft rejection in rats. Using a new tCsA formulation with a penetration enhancer (PE), polyethylene glycol-8 (PEG-8) glyceryl caprylate/caprate (Labrasol, Gattefossé, St. Priest, France), in a trinary drug delivery system, we hypothesized that we would induce SITE and significantly delay rejection of dual skin allografts in rats. METHODS: Dual rat skin allografts from Lewis x Brown-Norway (LBN) donors were grafted to Lewis (Lew) recipients. Experimental animals (EXP, n = 7) received a 10-day course of systemic cyclosporine (sCsA, 8 mg/kg/day) followed by topical application. One of the two allografts on each experimental animal received tCsA/PE application (5 mg/kg/day) until sacrifice (tCsA/PE-treated). The other allograft received vehicle only (vehicle-treated). Allogeneic controls (ALLO-CON, n = 9) received no sCsA or tCsA. First signs of rejection were determined based on the initial observation of erythema, hair loss, flakiness, and/or scabs. RESULTS: The mean time to rejection for ALLO-CON allografts was 6.3 +/- 0.7 days (t test, P = 0.0013); for vehicle-treated allografts, 12.3 +/- 3.8 days (paired t test, P = 0.0146); and for tCsA/PE-treated allografts, 25.6 +/- 5.4 days. The disparity of days to rejection between dual allografts in the ALLO-CON group was 0.0 +/- 0.0 day and that between the tCsA/PE- and vehicle-treated dual allografts was 13.3 +/- 3.9 days (t test, P = 0.0016). CONCLUSIONS: A new formulation of tCsA in a trinary drug delivery system is successful at delaying the onset of rejection in dual skin allografts in rats by SITE, and PEG-8 glyceryl caprylate/caprate may represent a potentially effective transdermal penetration enhancer.     

The relationship between interferon-gamma and keratinocyte alloantigen expression after burn injury.

BACKGROUND: Cultured keratinocyte (CK) and cadaveric skin allografts have prolonged survival in patients with massive thermal injury. It is unclear if this delayed rejection is due to impaired host responsiveness or decreased graft immunogenicity. Although burn injury has been shown to decrease parameters of allograft response, no studies have examined the effect of burn injury on alloantigen expression. This study investigated the effect of burn size on class II antigen expression in CK allografts as well as on tissue levels of interferon-gamma (IFN-gamma), the principle regulator of alloantigen expression. METHODS: Anesthetized CBA mice (n = 64) received a 0%, 20% partial-thickness (PT), 20% full-thickness (FT), or 40% FT contact burn. Forty-eight hours later, wounds were partially excised and covered with CK allografts from C57BL/6 donors. Five days after burn injury, grafts were analyzed for donor-specific class II antigen. Protein expression was determined by Western immunoblotting and quantified with video densitometry. Wound, serum, and unburned skin levels of IFN-gamma were determined by enzyme-linked immunosorbent assay. Groups were compared by Fisher's analysis of variance. RESULTS: As burn size increased, class II antigen expression decreased (p < 0.001). This corresponded with decreased wound and skin levels of IFN-gamma after 40% burn (p < 0.05); however, wound IFN-gamma was significantly elevated after 20% PT and FT burns (p < 0.01). Serum IFN-gamma increased as burn size increased (p < 0.01). CONCLUSIONS: Burn injury decreases the antigenicity of CK allografts, which partly explains delayed allograft rejection after burn injury. Although wound IFN-gamma increases after minor thermal injury, the profound decrease in wound and skin IFN-gamma after a major burn corresponds with diminished class II antigen expression. The decreased availability of IFN-gamma after major thermal injury provides a mechanism for limited allograft tolerance.     

Successful segmental intestinal transplantation in enterectomized pigs.

The aim of this study was to determine whether short-segment jejunal allografts maintained the viability and nutritional status of outbred recipient pigs treated with low-dose cyclosporine. The animals were subjected to total small bowel resection (from the ligament of Treitz to the ileocecal valve, approximately 15 m). Short-gut control animals (n = 8) who had no transplant died of malabsorption on day 62.5 +/- 4.1 (mean +/- SEM). Without cyclosporine immunosuppression, recipients (n = 5) of 3 m to 4 m jejunal allografts died of rejection on day 8.8 +/- 0.7. However enterectomized pigs (n = 11) who had segmental jejunal allograft transplants and were treated with cyclosporine (10 mg/kg/day) demonstrated significantly prolonged survival (to day 80.9 +/- 22.3; p less than 0.05). By 180 days after transplant, surviving animals increased their weight by almost 40%. In conclusion short-segment jejunal allografts significantly improved the mortality and morbidity rates from surgically created short bowel syndrome in pigs.     

Specific unresponsiveness to skin allografts in burns

We have examined the potential to provide long-term or even permanent wound coverage in a mouse model of a 30% total body surface area burn using skin allografts. Treatment of the recipient mouse with rabbit anti-mouse thymocyte serum (ATS) followed by donor bone marrow infusion induces a state of specific unresponsiveness to the skin allograft without the need for chronic immunosuppression. Specifically, a B6AF1 mouse receives a burn on Day -2 relative to grafting, ATS on Day -1, and Day +2, a skin allograft from a C3H/He mouse on Day 0, and infusion of C3H/He donor bone marrow on Day +6. We studied three groups of burned mice: Group I, allograft control (n = 5); Group II, allograft plus ATS (n = 12); and Group III, allograft plus ATS and bone marrow infusion (n = 15). Mean graft survival was compared using a one-way analysis of variance and a Student-Newman-Keuls post hoc test. There was no statistical difference in animal mortality among any of the three groups, and there was no evidence of infectious morbidity. Mean skin allograft survival was as follows: Group I, 9 days; Group II, 29 days; and Group III, 66 days (P less than 0.05 vs Group I and II). Nine animals in Group III had intact hair bearing grafts at 90 days when the study was terminated. This study suggests the potential use of induced specific unresponsiveness to skin allografts for wound coverage in thermal injury without use of chronic immunosuppression. In our animal study this was accomplished without increased mortality or apparent infectious morbidity.     

Initial experience with a composite autologous skin substitute.

Patients with large burns are surviving in increasing numbers, but there remains no durable and reliable permanent skin replacement. After initial favorable small animal experiments, a pilot trial of a composite skin replacement was performed in patients with massive burns. A composite skin replacement (CSR) was developed by culturing autologous keratinocytes on acellular allogenic dermis. This material was engrafted in patients with massive burns and compared to a matched wound covered with split thickness autograft. With human studies committee approval, 12 wounds in 7 patients were grafted with CSR while a matched control wound was covered with split thickness autograft. These 7 children had an average age of 6.4+/-1.4 yr and burn size of 75.9+/-5.0% of the body surface. Nine wounds were acute burns and three were reconstructive releases. Successful vascularization at 14 days averaged 45.7+/-14.2% (range 0-100%) in the study wounds and 98+/-1% (range 90-100%) in the control sites (P<0.05). Reduced CSR take seemed to correlate with wound colonization. All children survived. While CSR did not engraft with the reliability of standard autograft, this pilot experience is encouraging in that successful wound closure with this material is possible, if not yet dependable. It is hoped that a more mature epidermal layer may facilitate engraftment, and trials to explore this possibility are in progress.     

Healing of partial thickness porcine skin wounds in a liquid environment.

This study employs a liquid-tight vinyl chamber for the topical fluid-phase treatment of experimental wounds in pigs. Continuous treatment with normal saline significantly reduced the early progression of tissue destruction in partial thickness burns. Uncovered burns formed a deep layer of necrosis (0.49 +/- 0.004 mm, mean +/- SD) although burn wounds covered with empty chambers demonstrated less necrosis (0.14 +/- 0.01 mm), fluid-treated wounds formed no eschar, and little tissue necrosis could be detected (less than 0.005 mm). Topical treatment with hypertonic dextran increased water flux across burn wounds by 0.24 ml/cm2/24 hr (mean, n = 95) over saline-treated wounds during the first 5 days after wounding. When partial thickness burn and excisional wounds were immersed in isotonic saline until healed, the daily efflux of water, protein, electrolytes, and glucose across the wound surface declined during healing to baseline values found in controls (saline-covered unwounded skin). The declining protein permeability was used as a reproducible, noninvasive, endogenous marker for the return of epithelial barrier function. Saline-treated excisional wounds healed within 8.6 +/- 0.6 days (mean +/- SD, n = 27) and burn wounds within 12.1 +/- 1.4 days (mean +/- SD, n = 15). Healing of fluid-treated wounds occurred without tissue maceration and showed less inflammation and less scar formation than healing of air exposed wounds (no attempt was made to compare rates of healing between air- and fluid-exposed wounds). We consider the fluid-filled chamber a potentially very useful diagnostic, monitoring, and delivery system for wound-healing research and for human wound therapy.     

Trafficking of donor-derived bone marrow correlates with chimerism and extension of composite allograft survival across MHC barrier

We proposed to evaluate differences between recipient's immune response to vascularized skin and combined vascularized skin/bone allografts, under a 7-day alphabeta-TCR plus cyclosporine (CsA) treatment protocol. Thirty-six transplantations were performed in six groups: group I (isograft control-vascularized skin graft; n=6); group II (isograft control-combined vascularized skin/bone graft; n=6); group III (allograft rejection control group-vascularized skin graft; n=6); group IV (allograft rejection control-combined vascularized skin/bone graft; n=6); group V (allograft treatment-vascularized skin graft; n=6); and group VI (allograft treatment-combined vascularized skin/bone graft; n=6). Isograft transplantations were performed between Lewis rats and allografts were transplanted across the MHC barrier from Brown Norway to Lewis rats. In the allograft treatment group, a combined alphabeta-TCR+CsA protocol was applied for 7 days. All groups were compared clinically, immunologically and histologically. Statistical significance was determined with two-tailed Student's t test. Indefinite graft survival was achieved in the isograft control group (>300 days). Allograft rejection controls rejected within 5 to 9 days posttransplant; chimerism levels were undetectable (<.5%). Allografts under the alphabeta-TCR+CsA protocol had significantly extended survival when skin was combined with bone (61-125 days) compared to vascularized skin allografts (43-61 days). Lymphoid macrochimerism was significantly higher in group VI than group V. Histology confirmed skin and bone viability. Combined vascularized skin/bone allografts had higher and sustained levels of donor-specific chimerism and extended allograft survival.     

Thermal injuries in autogenous tissue breast reconstruction.

We report on four patients with partial and full thickness burns following autogenous tissue breast reconstruction. Three burns were confined to the flap and one burn involved the flap and rim of adjacent skin. Heat sources included a heating pad (n = 3) and sunlight through a bathing suit (n = 1). The injuries occurred from 6 days to 4 years following the reconstruction. The burns were the result of impaired thermoregulatory capacity of transplanted tissue. All wounds healed with local wound care or debridement and skin grafting.     

Management of partial thickness facial burns (comparison of topical antibiotics and bio-engineered skin substitutes).

This study compared the effect of standard topical antibiotic management versus a biological skin substitute wound closure for mid-partial thickness burns of the face. Adult patients with mid-dermal facial burns produced by flash flames or flame exposure were studied using a randomized prospective study design. Total daily burn care time, pain (0-10 scale) and healing time were monitored. Immediately after partial thickness debridement, the entire face burn, including ears, was closed with a bioengineered skin substitute coated with fibronectin (TransCyte) or treated by the open technique using bacitracin ointment applied 2-3 times daily. 21 patients were studied, with 10 patients in the skin substitute group. We found a significant decrease in wound care time 0.35 +/- 0.1 versus 1.9 +/- 0.5 h, decrease in pain of 2 +/- 1 versus 4 +/- 2 and re-epithelialization time 7 +/- 2 versus 13 +/- 4 days in the skin substitute group compared to topical antibiotics. We can conclude that a bioengineered skin substitute significantly improves the management and healing rate of partial thickness facial burns, compared to the standard open topical ointment technique.     

A randomised clinical trial comparing a hydrocolloid-derived dressing and glycerol preserved allograft skin in the management of partial thickness burns

Membranous dressings for the treatment of partial and mixed thickness burns are among the most innovative and promising new developments of the last years. In this study, we present data of a randomised prospective comparative study on a carboxymethylcellulose based dressing, Hydrofibre((R)) and glycerolized human allograft skin.In a 2 year period, 80 patients (40 for each material) were enrolled in the trial. Study wounds (<10% TBSA) that had not re-epithelialised after 14+/-3 days were debrided and grafted or, if small enough, managed with a topical antimicrobial agent. Mean total TBSA was 8.3+/-5.2%, study burn 3.7+/-2.0% for the Hydrofibre((R)) group and 7.3+/-4.3% total, 3.4+/-2.1% study burn for the allograft skin group (n.s. Wilcoxon rank sum test). No significant differences between groups were established in number of patients with superficial/deep burns.In both groups about 2/3 of the patients healed completely with the dressings applied (24/40 versus 27/40 for Hydrofibre((R)) versus allograft skin, respectively). However, a higher incidence of post-study excision and grafting was found in the Hydrofibre((R)) group (45% versus 15% in the allograft skin group, P=0.004, Mann-Whitney). At 10 weeks follow-up no significant differences were seen in scar colour, pigmentation, pliability, height or itching (Vancouver Scar Scale). Skin elasticity, measured by the Cutometer((R)), was significantly better for the allograft group (P=0.010, Wilcoxon). These differences were no longer found at 6 months and 1 year follow-up. Incidence of hypertrophy after 6 months was higher, but not significantly, in the Hydrofibre((R)) compared to the allograft skin group (52.5% versus 30%, P=0.09, chi-square).In view of the results from our comparative study on Hydrofibre((R)) versus allograft skin, we prefer the use of allograft skin for the category of larger burns of mixed depth, usually presented to burn centres. However, for partial thickness and small burns Hydrofibre((R)) can be the first choice in treatment.     

Immunosuppression and temporary skin transplantation in the treatment of massive third degree burns.

A method of burn treatment (immunosuppression and temporary skin transplantation) for patients suffering from massive third degree burns is evaluated. The method is based on the prompt excision of all dead tissue (burn eschar) and immediate closure of the wound by skin grafts. Total wound closure is achieved before bacterial infection or organ failure takes place by carrying out all initial excision and grafting procedures within the first ten days post burn and supplementing the limited amount of autograft with allograft. Continuous wound closure is maintained for up to 50 days through immunosuppression. Both azathioprine and ATG have been used but ATG is preferred. During the period of immunosuppression, allograft is stepwise excised and replaced with autograft donor sites regenerate for recropping. Bacterial complications are minimized by housing the patient in the protected environment of the Bacteria Controlled Nursing Unit. Intensive protein and calorie alimentation are provided, and 0.5% aqueous AgNO3 dressings are used. A swinging febrile illness has been associated with large areas of allograft rejection. Eleven children have been treated and seven have been returned to normal, productive schooling.     

The effect of thymectomy on tolerance induction and cardiac allograft vasculopathy in a miniature swine heart/kidney transplantation model.

BACKGROUND: We have previously demonstrated that MHC class I disparate hearts transplanted into miniature swine treated with a short course of cyclosporine developed florid cardiac allograft vasculopathy (CAV) and were rejected within 55 days. However, when a donor-specific kidney is cotransplanted with the heart allograft, recipients become tolerant to donor antigen and accept both allografts long-term without the development of CAV. In the present study, we have investigated the role of the host thymus in the induction of tolerance and prevention of CAV in heart/kidney recipients. METHODS: Total thymectomies were performed in six animals (postoperative day [POD]-21), which on day 0 received either an isolated MHC class I disparate heart allograft (n=3) or combined class I disparate heart and kidney allografts (n=3), followed in both cases by a 12-day course of cyclosporine (POD 0-11). Graft survival and the development of CAV in these thymectomized recipients were compared to the same parameters in non-thymectomized, cyclosporine-treated recipients bearing either class I disparate heart allografts (n=5) or heart and kidney allografts (n=4). RESULTS: In the group of animals bearing isolated class I disparate heart allografts, the thymectomized recipients rejected their allografts earlier (POD 8, 22, 27) than the non-thymectomized recipients (POD 33,35,45,47,55). The donor hearts in both the thymectomized and non-thymectomized animals developed florid CAV. In the group of animals bearing combined class I disparate heart and kidney allografts, the nonthymectomized recipients accepted both donor organs long term with no evidence of CAV. In contrast, none of the thymectomized heart/kidney recipients survived >100 days, and they all developed the intimal proliferation of CAV. CONCLUSION: Thymic-dependent mechanisms are necessary for the induction of acquired tolerance and prevention of CAV in porcine heart/kidney recipients.     

The use of a bioactive skin substitute decreases length of stay for pediatric burn patients

BACKGROUND: To optimize burn care for children, the authors introduced a protocol incorporating the use of a bioactive skin substitute, TransCyte (Advanced Tissue Sciences, La Jolla, CA). This study was designed to determine whether this management plan was safe, efficacious, and decreased hospital inpatient length of stay (LOS) compared with conventional burn management in children. METHODS: All pediatric burns greater than 7% total body surface area (TBSA) that occurred after October 1999 underwent wound closure with TransCyte (n = 20). These cases were compared with the previous 20 consecutive burn cases greater than 7% TBSA that received standard therapy. Standard therapy consisted of application of antimicrobial ointments and hydrodebridement. The following information was obtained: burn mechanism, age, size of burn, requirement of autograft, and LOS. Data were analyzed using the student's t test. RESULTS: Data for age, percent TBSA burn and LOS are reported as means +/- SEM. The children who received standard therapy were 2.99 +/- 0.7 years compared with those receiving TransCyte were 3.1 +/- 0.8 years. There was no difference between the treatment groups with regard to percent TBSA burn: standard therapy, 14.3 +/- 1.4% TBSA versus TransCyte, 12.7 +/- 1.3% TBSA. There was no difference in the type of burns in each group, the majority were liquid scald type, 70% in the standard therapy group versus 90% in the TransCyte group. Only 1 child in the TransCyte group required autografting (5%) compared with 7 children in the standard therapy group (35%). Children treated with TransCyte had a statistically 6 significant decreaed LOS compared with those receiving standard therapy, 5.9 +/- 0.9 days versus 13.8 +/- 2.2 days, respectively (P =.002). CONCLUSIONS: This is the first study using TransCyte in children. The authors found that this protocol of burn care was safe, effective, and significantly reduced the LOS. This new approach to pediatric burn care is effective and improves the quality of care for children with burns.     

Increased rat cardiac allograft survival by the glycosaminoglycan pentosan polysulfate.

BACKGROUND: Modulation of the inflammatory response has proven to be of benefit in salvaging cardiac allografts at risk of irreversible injury. Pentosan polysulfate (PPS), like heparin, is a negatively charged sulfated glycosaminoglycan (GAG) that possesses anti-inflammatory properties including the ability to inhibit activation of the complement system. This study was conducted to determine the potential of PPS to prolong allograft survival in an experimental model of cardiac transplantation. MATERIALS AND METHODS: A heterotopic cardiac transplant was performed by implanting the heart from fetal Brown Norway rats into the ear pinnae of adult Lewis rats. Vehicle (saline) or PPS (30 mg/kg) was administered subcutaneously immediately after transplantation and daily thereafter (n = 6 in each group). Another GAG, heparin, was also analyzed to determine the effect of anticoagulation on transplant survival (n = 6). RESULTS: Treatment with PPS significantly (P < 0. 05) increased allograft survival time as compared to vehicle-treated animals (8.0 +/- 0.3 days vs 5.5 +/- 0.5 days). The results noted with PPS were similar to those observed in cyclosporine (10 mg/kg; n = 6)-treated animals (8.25 +/- 0.25 days). Treatment with heparin (300 U/kg/day) did not significantly prolong cardiac graft survival time, suggesting that anticoagulation is not sufficient to prolong transplant survival. Analysis of tissue histology showed diminished transplant rejection as evidenced by decreased white blood cell infiltration and cellular necrosis. CONCLUSIONS: The results of this study indicate that PPS possesses the ability to prolong cardiac transplant viability in a heterotopic cardiac transplant model, independent of its anticoagulant actions.     

Experience of immediate burn wound excision and grafting for patients with extensive burns

The treatment of the patients with extensive burns has advanced dramatically in the past 10 years, and the mortality rate has also been reduced. The establishment of the skin-bank network as well as the development of emergency and critical care medicine can be cited as reasons Moreover, immediate burn wound excision and grafting for patients with extensive burns may be beneficial. Meticulous management is required perioperatively to perform these procedures safely during burn shock. Patients with extensive burns are susceptible to hypothermia while receiving massive fluid resuscitation. We use a warmer device (Level 1) to keep burn patients warm. From 1991 to 2003, we performed immediate burn wound excision and grafting in 26 extensively burned patients within 24 hours after burn injury. We completed the surgery within 2 hours and excised burn wounds covering 40% of the total body surface area (TBSA). The mean age was 57 +/- 22 (mean +/- SD years), the mean burn surface area (% of TBSA) was 47 +/- 20, the mean burn index was 45 +/- 19, and the mean prognostic burn index was 94 +/- 36. There were 15 survivors and 11 deaths, for an overall mortality rate of 43%.     

Experience with procedural sedation in a pediatric burn center.

BACKGROUND: Burn care requires daily debridement, dressing changes, and assessment regarding the need for skin grafting. These procedures are painful and may require an operating room environment. METHODS: The authors reviewed their experience with 912 consecutive procedural sedations (PS) in 220 pediatric burn patients over a 2-year period to identify what influence PS had on patient care. Median patient age was 32 months, and body surface area burn was 7.2%+/-6%. Pharmacological techniques included oral and intravenous medications and N2O. The authors included all sedations given in the burn treatment area and excluded all treatments given in the intensive care unit or emergency unit. RESULTS: PS allowed for early aggressive wound debridement, virtually eliminated the need for operating room debridement (used in only 22 patients), and eliminated patient discomfort and fear often associated with subsequent debridements. Burn wound-related complications occurred in 54 patients and included wound infection (n = 18), graft loss (n = 9), and pneumonia (n = 4). The incidence of PS complications was 7% with the most common problems including decreased arterial saturation (n = 41), emesis (n = 11), and agitation (n = 8). No patient required intubation or transfer to an intensive care unit bed. The average length of stay (LOS) for all patients was 8.7+/-6.2 days, and 6.2+/-3.8 days in the 200 patients not admitted to the intensive care unit. This compares favorably with the 9.5-day LOS of patients treated in 1990. CONCLUSIONS: PS in burn patients allows for early aggressive debridement, decreases the use of the operating room for debridement, and a decrease in length of stay when compared with our previous burn patients. PS has a modest risk of complications, enhances the family's cooperation and satisfaction with health care provided, and should be an integral part of burn care in children.     

Use of skin allograft and its donation rate in Singapore: an 11-year retrospective review for burns treatment

An 11-year retrospective review (1993 to 2003) of 102 severe burn patients (>40% total body surface area and undergone wound excision surgery) was performed to determine the efficacy of early wound debridement and coverage of large burns with skin allografts, a treatment introduced here in 1998 with the establishment of a skin banking facility. While there was no significant reduction in mortality, length of hospital stay decreased by 15.7 days (P < .05) during the post-skin-banking period. Skin allograft donation rates from multiorgan donors were consistently fewer compared with corneal donation, mainly due to strong cultural beliefs and public misconceptions regarding skin harvesting. The overall tissue donation rate in Singapore may improve if efforts focus on deceased cases sent to the state coroner where retrieval and counseling can be centralized.     

Clinical application and viability of cryopreserved cadaveric skin allografts in severe burn: A retrospective analysis

Introduction

Cadaveric cutaneous allografts are used in burns surgery both as a temporary bio-dressing and occasionally as definitive management of partial thickness burns. Nonetheless, limitations in the understanding of the biology of these grafts have meant that their role in burns surgery continues to be controversial.

Methods

A review of all patients suffering 20% or greater total body surface area (TBSA) burns over an eight year period that received cadaveric allografts were identified. To investigate whether tissue viability plays a role in engraftment success, five samples of cryopreserved cadaveric cutaneous allograft processed at the Donor Tissue Bank of Victoria (DTBV) were submitted to our laboratory for viability analysis using two methods of Trypan Blue Exclusion and tetrazolium salt (MTT) assays.

Results

During the study period, 36 patients received cadaveric allograft at our institution. The average total burn surface area (TBSA) for this group of patients was 40% and all patients received cadaveric skin as a temporizing measure prior to definitive grafting. Cadaveric allograft was used in complicated cases such as wound contamination, where synthetic dressings had failed. Viability tests showed fewer than 30% viability in processed allografts when compared to fresh skin following the thawing process. However, the skin structure in the frozen allografts was histologically well preserved.

Conclusion

Cryopreserved cutaneous cadaveric allograft has a positive and definite role as an adjunct to conventional dressing and grafting where available, particularly in patients with large TBSA burns. The low viability of cryopreserved specimens processed at DTBV suggests that cell viability in cadaveric allograft may not be essential for its clinical function as a wound dressing or even as permanent dermal substitute.     

A historical appraisal of the use of cryopreserved and glycerol-preserved allograft skin in the treatment of partial thickness burns

Two studies into the use of allograft skin in the treatment of partial thickness burn injuries in this burn centre have provided the opportunity to discuss changes and similarities over a 20 year period. The first study described results obtained with cryopreserved allografts in partial thickness burns in the period 1979-1981. The second study concerned patients with partial thickness injuries treated with glycerol-preserved allografts in the period 1998-2000. A reduction was noted concerning the need for secondary autografting in the group treated with glycerolized allografts. The probability that this difference has occurred by chance is small (P=0.089). Various other factors that might account for the differences in outcome, include general improvements in health and social welfare, differences in treatment protocols, and differences in allograft properties. A prospective comparative trial is indicated to study direct differences between the two types of allograft.