The burn comb model revisited

IntroductionThe burn comb model is a well-established model for studying secondary burn progression. It creates four rectangular burn surfaces intercalated by three unburned zones prone to secondary burn progression. While burn progression is a tri-dimensional phenomenon, of which the vertical extension from the superficial to deeper tissue layer is clinically most relevant, the models initial focus was mainly on the horizontal surface extension within interspaces. The aim of this study is to evaluate the correlation between horizontal surface and vertical depth burn progression.Methods24 large (400–450 g) Wistar male rats underwent standardized burn injuries using a burn comb. Laser Doppler flowmetry to assess perfusion, planimetric evaluation of burn progression within interspaces and histological analyses assessing burn depth were performed before burn induction (baseline; BL) and after 1 h, as well as after 1, 4, and 7 days. Histological burn depth was graded from superficial (1) to the subcutaneous layer (5). Furthermore, final scarring time and contracture rate were also assessed.ResultsThe burn comb resulted in consistent and uniform superficial burns (mean ± SEM burn depth score: 2 ± 0; hour 1) separated by intact but critically perfused interspaces (63 ± 1% of BL; p < 0.05 vs. BL). Tissue damage significantly progressed to the deep dermis within the first day (burn depth score 4.3 ± 0.2; p < 0.05 vs. hour 1), while significant interspace necrosis at the surface did not develop within this time period (4 ± 3% of interspace necrosis; p n.s vs. hour 1). However, interspace necrosis was observed at day 4 (83 ± 3%; p < 0.05 vs. hour 1) and further progressed until day 7 (94 ± 2%; p < 0.05 vs. hour 1).ConclusionThis study shows the limits of the burn comb model originally described with a discrepancy between horizontal surface and vertical depth progression of the burn injury. We herein propose a necessary refinement of this model to adequately evaluate vertical depth progression using a histological score. This revisited approach focusing on assessment of depth progression of the burn will allow a better evaluation of experimental burn treatments in future.     

Evaluation of a bi-layer wound dressing for burn care I. Cooling and wound healing properties

Severe burns remain a significant cause of morbidity and mortality despite the availability of numerous therapies. We assessed the wound healing and skin-cooling properties of a DRDC hydrogel/polyurethane wound dressing using different pre-clinical models. Our results show that 85% of partial-thickness, non-contaminated porcine wounds treated with our dressing healed within 6 days. In contrast, 85% of the wounds treated with commercial dressings healed within 8 days. Application of a moist DRDC dressing (to simulate a condition of exudate absorption) on a scald burn covering 25% of the dorsal area in rats reduced skin temperature by 1.70 +/- 0.14 degrees C for 5 min, the skin temperature being comparable to that of control burned rats after 20 min. The application of a moist DRDC dressing did not induce significant differences in body temperatures compared with that of burned animals without dressing coverage throughout the 90-min experiment. While no change in body temperatures were observed when standard dressings (i.e., not pre-moistened) were applied, skin temperature increased gradually. These data show that our dressing is effective in promoting faster healing of the treated wound; and providing a transient, but beneficial cooling effect to the skin contact-site, without the adverse effect of inducing whole-body hypothermia.     

A retrospective review of burn dressings on a porcine burn model

This is a study to compare wound healing among three types of dressings on a porcine model with deep-dermal-partial-thickness burns. The burns in this study were from eight animal trials conducted in the past for other purposes and only burns with a uniform pale appearance that had served as controls in original experiments were selected. In total, there were 57 burns in 33 pigs, using one of following three dressings: Acticoat (Silver) (3 trials), Jelonet (Gauze) (3 trials), and Solosite Gel/Jelonet (Gel/Gauze) (2 trials). The wound healing assessments included wound re-epithelialisation during a 6-week period, clinical and histological scar assessments at week 6 after burn. Of all wound healing/scar assessments, only re-epithelialisation showed statistical difference between dressings. Earlier re-epithelialisation was observed in Gel/Gauze dressings compared to Silver and/or Gauze dressings. However, this study revealed huge variation in wound healing outcome between 3 trials within both Silver and/or Gauze dressings, supported by significant differences on re-epithelialisation, clinical and histological scar measurements. In addition, it was found that larger animals healed better than smaller ones, based on weights from 21 pigs. Of all dressings, Silver delivers the best protection for wound colonization/infection. Wound colonization/infection was found to confine wound healing and lead to thinner RND in scars. From this study, we cannot find enough evidence to suggest the beneficial effect of one dressing(s) over others on burn wound healing outcome on a porcine model with small deep-dermal-partial-thickness burns with a relative small sample size.     

Healing effect of carboxymethyl chitosan-plantamajoside hydrogel on burn wound skin

BackgroundIt is known that hydrogels based on carboxymethyl chitosan (CMCS) have properties controling microbial growth, reducing inflammatory cell infiltration, and promoting collagen deposition. Plantamajoside (PMS), a natural Chinese herbal medicine with biological activity, has the properties of reducing inflammation, anti-oxidation, and promoting wound healing. However, the effects of carboxymethyl chitosan/plantamajoside hydrogel on partial thickness burn wounds remain unclear.MethodsThe healing effect of carboxymethyl chitosan/plantamajoside hydrogel was evaluated by in vitro cell viability assay, cell migration assay, and further evaluated in a rat model of partial-thickness burn wounds.ResultsThe hydrogels were highly porous with a pore size of about 250 μm, and these pores were interconnected. After adding plantamajoside, a dense microstructure was further formed. The hydrogels containing 0.25% plantamajoside significantly increased the viability and migration of L929 cells (P < 0.05). Carboxymethyl chitosan/plantamajoside hydrogel significantly improved wound healing, granulation tissue proliferation and re-epithelialization, and promoted collagen deposition (P < 0.05). Carboxymethyl chitosan/plantamajoside hydrogel also significantly decreased IL (interleukin)-1β, IL-6 and TNF-α expression, and increased IL-10 expression (P < 0.05). Furthermore, carboxymethyl chitosan/plantamajoside hydrogel significantly promoted the expression levels of VEGF, CD31, α-SMA (α-smooth muscle actin) and collagen III, and reduced the expression level of collagen Ⅰ (P < 0.05). Our data suggest that carboxymethyl chitosan/plantamajoside hydrogel promotes burn wound healing by accelerating angiogenesis and collagen deposition and reducing the inflammatory response.     

Moist exposed therapy of partial-thickness burn wounds. A multi-center study

Summary In laser-induced partial-thickness burns of pig skin, moist exposed burn ointment (MEBO) produces a moist environment, allows drainage of exudates, reduces eschar formation, and accelerates debridement and wound healing. A prospective multi-center study was conducted to evaluate the effect of MEBO on the healing of partial-thickness burn wounds. We included 52 patients with 100 burn sites ranging from 0.5% to 15% total body surface area in the study. Treatment efficacy was assessed on physical examination of the wound, the course of time of trans-epidermal water loss (TEWL) and moisture values, bacterial wound colonization and the degree of pain experienced by patients during and between dressing changes. Using the Visual Analogue Thermometer device (VAT) a progressive decrease of pain was found throughout the treatment which was statistically significant at 6, 9 and 12 post-burn days. TEWL, as an indicator of re-epithelialization, demonstrated a decreasing trend on day 3, and the reduction became significant from the 6th post-burn day. Moisture was significantly decreased during the first 5 post-burn days. As re-epithelialization progressed there was a net decrease in moisture paralleling TEWL. After 1 week of MEBO treatment, bacterial wound colonization decreased to 10% in the immediate group and to 61% in the late group of application. By the second week, colonization dropped to 5% and 23% respectively. Topical ointment application contributed to the debridement of the wound bed facilitating rapid epithelialization within 2–6 days, depending on the burn depth. MEBO is an ointment that can effectively produce a moist and wet environment for optimal healing of partial-thickness burns.     

A general overview of burn care

The majority of burn victims do not need to be treated in a burn centre. Adequate care can be given by non specialised medical personnel, provided that proper guidelines are followed. The article outlines and reviews these guidelines.     

A recombinant human collagen hydrogel for the treatment of partial-thickness burns: A prospective,self-controlled clinical study

IntroductionAllogeneic and xenogeneic skin are recognized as the best coverings for skin burn wounds, but currently face a supply shortage. To solve this problem, our research group developed a standardized manufactured hydrogel dressing based on a new type of highly bioactive recombinant human collagen.Study designProspective self-controlled trial.ObjectiveTo evaluate the efficacy and safety of recombinant human collagen hydrogel in the treatment of partial burn wounds to the skin compared to those of xenogeneic skin.MethodsThis study included twenty-one patients admitted to Shanghai Changhai Hospital within 48 h after receiving partial-thickness skin burns. The wounds were symmetrically separated along the axis and treated with recombinant human collagen hydrogel (RHCH) or a human-CTLA4-Ig gene-transferred pig skin xenotransplant. The condition of the wound surfaces was recorded on days 0 (of enrollment), 5, 10, 15, and 20, and bacterial drug sensitivity testing, hematuria examination, and electrocardiographic tests were conducted on days 0, 10, 20, or on the day of wound healing.ResultsThere were no statistically significant differences in wound healing time between the two groups. The median number of days to healing was 11.00 ± 0.56 for xenogeneic skin vs. 11.00 ± 1.72 for RHCH.ConclusionDuring the observation period, the therapeutic effect of the RHCH developed by our group on partial-thickness burn wounds was not significantly different from that of gene-transferred xenogeneic skin. Thus, our designed RHCH shows potential for clinical use to treat burn wounds on the skin.     

The concurrent use of probiotic microorganism and collagen hydrogel/scaffold enhances burn wound healing: An in vivo evaluation

Treatment of burn wounds is technically demanding and several attempts have been taken to improve wound healing. Silver sulfadiazine antibiotic has been shown to have some beneficial effects on wound healing via reduction in infection. This study was designed to investigate the impact of collagen hydrogel-scaffold dressing with or without topical use of Saccharomyces cerevisiae on cutaneous burn wound healing in rat. Four circular 1 cm cutaneous wounds were created in the dorsum back of rats, 48 h post-burning. Thirty male rats were divided into the three major groups (1–3, n = 10), then the wounds in each group were equally divided into two subgroup treatments (6 treatments), (1) including (a) silver sulfadiazine (SSD) as positive control (PC) and (b) untreated wounds as negative control (NC) (2) including (c) S. cerevisiae and (S.C.) and (d) collagen scaffold (CS), (3) including (e) collagen hydrogel-scaffold (CH-S) and (f) S. cerevisiae with collagen hydrogel-scaffold (CH-S-S). In each group, the animals were euthanized at 12 and 22 days post-injury (DPI) and the skin samples were used for histopathological and biomechanical investigations. Collagen scaffold and hydrogel modulated the inflammation, especially when combined together. Moreover, they increased wound healing, epithelialization and biomechanical performance of wound area and also reduced the scar size. The best results gained when the combination of collagen scaffold and hydrogel were mixed with probiotic. The CH-S biological dressing along with probiotic microorganism (S.C.) significantly increased collagen content compared to the negative controls. Moreover, the CH-S-S treated lesions demonstrated greater ultimate load and stiffness compared to the untreated wounds. In conclusion, application of S. cerevisiae with a bi-phase biological dressing (CH-S) improved the morphological and biomechanical characteristics of the healing burned wounds in rats and the results were comparable to the positive control.     

Burn healing is dependent on burn site: a quantitative analysis from a porcine burn model

This retrospective review examines healing in different sites on a porcine burn model; 24 pairs of burns on 18 pigs from other animal trials were selected for analysis. Each pair of burns was located on the either the cranial or the caudal part of the thoracic ribs region, on the same side of the animal. The burns were 40-50 cm(2) in size and of uniform deep-dermal partial thickness. Caudal burns healed significantly better than cranial burns, demonstrated by earlier closure of wounds, less scar formation and better cosmesis. To our knowledge, this is the first detailed study reporting that burn healing is affected by location on a porcine burn model. We recommend that similar symmetrical burns should be used for future comparative assessments of burn healing.     

重组人粒细胞/巨噬细胞集落刺激因子联合水凝胶敷料治疗深Ⅱ度烧伤创面临床观察

目的:观察外用重组人粒细胞/巨噬细胞集落刺激因子(rhGM-CSF)联合水凝胶敷料治疗深Ⅱ度烧伤创面的临床效果.方法:选择四肢部位有深Ⅱ度烧伤创面的住院患者24例,48处研究创面,每例患者2个创面,分别位于不同肢体.研究分为4组.随机选取12例患者,每例患者随机选取一个创面作为rhGM-CSF联合外用水凝胶敷料治疗组(联合治疗组,创面清创后外涂外用重组人粒细胞巨噬细胞刺激因子凝胶,覆盖医用水凝胶敷料),另一个创面作为rhGM-CSF联合外用凡士林油纱治疗组(rhGM-CSF对照组,创面清创后外涂外用重组人粒细胞巨噬细胞刺激因子凝胶,覆盖凡士林油纱);余12例患者每例随机选择一处创面作为水凝胶敷料治疗组(水凝胶对照组,创面直接覆盖医用水凝胶敷料);另一处创面作为凡士林油纱对照组(凡上林对照组,创面直接覆盖凡士林油纱).每组12处创面.观察各组创面愈合时间及创面感染情况,创面分泌物行细菌培养,比较创面细菌感染阳性率.结果:联合治疗组创面愈合时间较其他3组明显缩短(P＜0.05);rhGM-CSF对照组和水凝胶对照组创面愈合时间较凡士林对照组缩短(P＜0.05).rhGM-CSF联合外用水凝胶敷料治疗组创面洁净,细菌检出率低(16.7％):rhGM-CSF治疗组感染状况也较轻,细菌检出率较低(25.0％),凡士林对照组感染状况重,细菌检出率最高(83.3％,P＜0.01).结论:深Ⅱ度烧伤创面外用rhGM-CSF联合水凝胶敷料治疗,可以明显减少创面细菌感染概率,缩短创面愈合时间.     

Rescuing the negative effects of aging in burn wounds using tacrolimus applied via microcapillary hydrogel dressing

IntroductionDelays in treatment of burn injuries can lead to significant morbidity, loss of function, and poor aesthetic appearance. Preventing conversion from partial- to full-thickness burns may help mitigate these sequelae. The pathophysiology of burn wound conversion remains unknown, but an overactive immune response is thought to be implicated. The purpose of this study was to determine whether downregulating the immune response via tacrolimus can decrease burn wound conversion.MethodsAssembly of the microfluidic hydrogels was achieved by embedding microfibers within a hydrogel scaffold composed of a gelatin-alginate blend. Tacrolimus stock solution for intraperitoneal injection was made by re-suspending powdered tacrolimus in DMSO at 10 mg/mL. 24 young (2–4 months) and 24 old (>16 months) mice were given partial thickness burns. The treatment cohort received either tacrolimus ointment with a hydrogel dressing (6 young and 6 old) or an intraperitoneal injection of a tacrolimus solution (6 young and 6 old), while the control cohort only received either only the microcapillary hydrogel dressing or an intraperitoneal injection of saline. Mice were euthanized at day 3 after injury and skin samples were taken. Burn depth was evaluated using Vimentin immunostaining.ResultsIn old mice, intraperitoneal injection of tacrolimus was able to significantly reduce burn wound depth compared to intraperitoneal injection of saline (p = 0.011). Similarly in old mice, topical hydrogel with tacrolimus was able to significantly reduce burn wound depth compared to hydrogel alone (p < 0.001). Topical hydrogel with tacrolimus was able to mitigate the detrimental effects of older age on wound conversion, such that burn wounds of older mice treated with tacrolimus hydrogel dressing had similar burn depths as younger mice (p = 0.240).ConclusionsUtilizing a combination treatment of tacrolimus and microcapillary hydrogel is able to rescue the negative effects of aging and prevent partial- to full-thickness burn wound conversion. Hopefully these findings will encourage deeper investigation into the possible therapeutic advantages of utilizing immunosuppressive agents to decrease morbidity after burn injuries. Future research will need to specifically investigate IL-2 as an inhibitory target in the acute inflammatory cascade of burn injury.     

Modeling early thermal injury using an ex vivo human skin model of contact burns

BackgroundEarly mechanisms underlying the progressive tissue death and the regenerative capability of burn wounds are understudied in human skin. A clinically relevant, reproducible model for human burn wound healing is needed to elucidate the early changes in the human burn wound environment. This study reports a reproducible contact burn model on human skin that explores the extent of tissue injury and healing over time, and defines the inter-individual variability in human skin to enable use in mechanistic studies on burn wound progression and healing.MethodsUsing a customized burn device, contact burns of various depths were created on human skin by two operators and were evaluated for histologic depth by three raters to determine reproducibility. Early burn wound progression and wound healing were also evaluated histologically after the thermally injured human skin was cultured ex vivo for up to 14 days.ResultsBurn depths were reproducibly generated on human skin in a temperature- or time-dependent manner. No significant difference in operator-created or rater-determined depth was observed within each patient sample. However, significant inter-individual variation was identified in burn depth in ten patient samples. Burn-injured ex vivo human skin placed into culture demonstrated differential progression of cell death and collagen denaturation for high and low temperature contact burns, while re-epithelialization was observed in superficial burn wounds over a period of 14 days.ConclusionThis model represents an invaluable tool to evaluate the inter-individual variability in early burn wound progression and wound healing to complement current animal models and enhance the translation of preclinical research to improvements in patient care.     

Cytotoxicity testing of silver-containing burn treatments using primary and immortal skin cells

A novel burn wound hydrogel dressing has been previously developed which is composed of 2-acrylamido-2-methylpropane sulfonic acid sodium salt with silver nanoparticles (silver AMPS). This study compared the cytotoxicity of this dressing to the commercially available silver products; Acticoat™, PolyMem Silver^® and Flamazine™ cream. Human keratinocytes (HaCaT and primary HEK) and normal human fibroblasts (NHF) were exposed to dressings incubated on Nunc™ polycarbonate inserts for 24, 48 and 72 h. Four different cytotoxicity assays were performed including; Trypan Blue cell count, MTT, Celltiter-Blue™ and Toluidine Blue surface area assays. The results were expressed as relative cell viability compared to an untreated control. The cytotoxic effects of Acticoat™ and Flamazine™ cream were dependent on exposure time and cell type. After 24 h exposure, Acticoat™ and Flamazine™ cream were toxic to all tested cell lines. Surprisingly, HaCaTs treated with Acticoat™ and Flamazine™ had an improved ability to survive at 48 and 72 h while HEKs and NHFs had no improvement in survival with any treatment. The novel silver hydrogel and PolyMem Silver^® showed low cytotoxicity to all tested cell lines at every time interval and these results support the possibility of using the novel silver hydrogel as a burn wound dressing. Researchers who rely on HaCaT cells as an accurate keratinocyte model should be aware that they can respond differently to primary skin cells.     

Current practice of thromboprophylaxis in the burn population: a survey study of 84 US burn centers

While there is limited prospective data on the incidence of venous thromboembolism (VTE) in the burn population, there are no prospective studies on the efficacy and safety of VTE prophylaxis in these patients. Despite lack of such data, we hypothesized that most burn centers practice some form of prophylaxis. Eighty-four US burn centers were contacted regarding their modality of VTE prophylaxis, if any. Of the 84 US burn centers, 71 were enrolled in this survey. 76.1% centers reported routine VTE prophylaxis. Modalities included sequential compression device (SCD) (33), subcutaneous heparin (31), enoxaparin (13), dalteparin (3), and intravenous heparin infusion (1). Twenty-one reported combined modalities of SCD and subcutaneous heparin (19), SCD and enoxaparin (1), or SCD and dalteparin (1). Survey results underscore the need to definitively establish risk factors for VTE in the burn population and to prospectively define an evidence-based standard of care in prophylaxis for those patients.     

Recombinant human granulocyte-macrophage colony-stimulating factor hydrogel promotes healing of deep partial thickness burn wounds

Objective

To assess the effects of recombinant human granulocyte/macrophage colony-stimulating factor (rhGM-CSF) hydrogel on the healing of deep partial thickness burn wounds.

Methods

Ninety three wounds of 65 burn patients who suffered from a deep partial thickness burn of <5% TBSA and could not heal over 3 weeks were included in this study. The patients were randomly assigned to use rhGM-CSF hydrogel (GC group, n = 32) or hydrogel without rhGM-CSF (control group, n = 33). rhGM-CSF hydrogel or hydrogel without rhGM-CSF was topically applied to the wounds, the dressing was changed once a day. Wound healing time and percentage, wound discharge, periwound inflammation, the positive wound swabs culture count, and adverse drug reactions were observed and compared between two groups.

Results

Healing time was 12.2 ± 5.0 days after the application of rhGM-CSF hydrogel. This was significantly shorter than that of control wounds (15.5 ± 4.7 days). Healing percentage at 14 days in the rhGM-CSF-treated wounds was 97.5 ± 7.7%, which was markedly higher than the control (85.9 ± 6.8%). At 3, 6, 12, 14 day, the GC group was significantly superior to the control group with respect to the score of periwound inflammation, wound purulence and discharge. The positive wound swabs culture count of the GC group on the 7th and 14th day post-treatment was 14 and 4, respectively, which was significantly lower than the control.

Conclusion

rhGM-CSF hydrogel promotes the healing process of deep partial thickness burns effectively. No adverse reaction of the drug was observed during the study.     

Photographic assessment of burn wounds: A simple strategy in a resource-poor setting

Objective

To validate the use of photographic burn wound assessment in evaluation of burn size and wound characteristics.

Methods

Feasibility study of agreement between methods of measurement of burn size and characteristics, in patients admitted to the burn unit at Kamuzu Central Hospital (KCH), Malawi, over two months in 2011. Burn wounds were photographed and assessed clinically, concurrently, by an experienced clinician. Photographs reviewed by two blinded burn clinicians after 4–6 weeks. Correlation between clinical assessment and photographic evaluation was calculated using kappa score and Pearson's correlation coefficient.

Results

Thirty-nine patients were included in evaluation of TBSA, and fifty wounds assessed for their characteristics. Pearson's correlation coefficient for agreement of TBSA between clinical exam and photograph review by expert#1, and #2, was 0.96, 0.93 (p < 0.001), respectively. Pearson's correlation coefficients comparing expert#1 and #2 to the gold standard were: proportion of full-thickness burn (0.88 and 0.81, p < 0.001), and epithelialized superficial burn (0.89 and 0.55, p < 0.001). Kappa scores were significant for wound evolution (expert#1 0.57, expert#2 0.64, p < 0.001), and prognosis (expert#1 0.80, expert#2 0.80, p < 0.001).

Conclusions

Burn assessment with digital photography is a valid and affordable alternative to direct clinical exam, alleviating access issues to burn care in developing countries.     

Obese patients in a burn care unit: A major challenge

ObjectiveObesity is an important predictor of mortality and morbidity during a hospital stay. There is very little data concerning the impact of the BMI on clinical outcomes in obese burn patients.The purpose of this study is to document the general epidemiological aspects of thermal injuries in an obese population and draw attention to topics relating to the management, rehabilitation and prognosis of burns in this emerging subpopulation of patients.MethodsAll patients >16 years of age admitted to the burn unit between January 2008 and December 2012 and fulfilling the burn center referral criteria were enrolled in the study. SPSS version 20 (SPSS GmbH Software, Illinois, USA) was employed for data analysis.ResultsEleven extreme obese patients (men:women, 6:5) had a mean BMI of 38 kg/m². Their incidence in our study was 5.5%. The mean length of stay was 41.5 days, almost twice that of the non-obese. The presence of co-morbidities such as diabetes, hypertension, cardiac disease, or pulmonary disease, the problematic wound healing and the burn wound infection were significantly higher in the obese patients than in the non-obese. The mortality of obese burned patients was 36.4%.ConclusionsThese facts indicate admission of these patients to a burn care unit for the best possible treatment although they might not always fulfill criteria for admission to burn intensive care unit. Burn centers must be also prepared in terms of special nursing equipment for obese patients.     

ArF excimer laser debrides burns without destruction of viable tissue: A pilot study

Introduction

Recent evidence indicates that early removal of eschar by tangential debridement can promote healing. Laser debridement can be used for debridement of areas that prove challenging for debridement using tangential excision. In particular, irradiation with an ArF excimer laser ablates desiccated eschar and is self-terminating, preserving hydrated or viable tissue.

Trends and inpatient outcomes for palliative care services in major burn patients: A 10-year analysis of the nationwide inpatient sample

Introduction

Despite advances in critical care and the surgical management of major burns, highly moribund patients are unlikely to survive. Little is known regarding the utilization and effects of palliative care services in this population.