- Email: [email protected]
Important improvements to porcine skin burn models, in search of the perfect burn
burns 35 (2009) 454–455
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/burns
Letter to the Editor
Important improvements to porcine skin burn models, in search of the perfect burn Sir, We previously developed a reproducible porcine model for deep dermal partial thickness (DDPT) burn injury in juvenile Large White pigs [1]. This contact burn is created under general anesthetic using water at 928 for 15 s with a bottle with the bottom removed and replaced with plastic wrap. Upon creation, the circular wound area developed a white eschar and a hyperemic zone around the wound border. The depth of injury was determined by a histopathologist who examined tissue sections 2 and 6 days after injury in a blinded manner. During creation and implementation of this model we have seen variability in both the depth of injury within the wound and the rate of healing, although the entire process involved in applying the burn has remained constant. We noted that pink or red colored areas appearing within the burn wound at creation (day 0) were associated with faster healing of the
wound (Fig. 1) and formation of thinner dermal scar tissue at 6 weeks post-injury ( p = 0.045). These findings suggested that a whiter, non-blanching burn indicates deeper damage. This was confirmed by an experienced histopathologist who subsequently examined skin burn wound sections (removed at day 0) and each wound was classified into either a red or white color category, in a blinded manner. We observed a difference in the depth of damage between these two burn categories. The red areas on our burn model exhibited superficial damage (extending to the superficial to middermis) compared to the white areas (which had cellular damage extending into the deep dermis). Other groups have also encountered this phenomenon which we refer to as inconsistent and variable burns [2,3]. To achieve reproducible non-blanching, white, uniform, burns with the consistent depth of injury, we examined different factors. Our model porcine animal weight is
Fig. 1 – A difference in healing can be seen as early as day 14. At day 0, a white, non-blanching burn (A) compared to a burn containing pink or red colored areas (B), will heal more slowly (C), compared to the red areas which were healed by day 14 (D).
455
burns 35 (2009) 454–455
restricted to between 17 and 25 kg at initial injury. Our burn device is a 500-ml laboratory Schott Duran bottle, the bottom replaced with an extremely tight and firmly stretched plastic wrap taped to the smoothened bottle edges with heat resistant tape. The shaving of the animal is performed with clippers [4,5], with shaving performed in the opposite direction of hair growth so no hairs project into the area to be burned. In addition, any kind of scratches, abrasion or rubbing must also be avoided. For consistency the same person always applies the burn implement to the wound. Another person assists with lifting the animal slightly to arch the animal’s body before placing the burn device onto the flank to achieve optimum contact. A few seconds before the burn is created, a fine mist of water is sprayed onto the pre-marked wound site. When the water temperature in the bottle has reached exactly 92.08C (within W0.1 8C) it is horizontally, rather than vertically placed onto the pre-marked site to provide optimum contact with the skin surface. If a burn does fail to have good contact due to air pockets or the presence of excessive water on the skin surface due to mist trapped under the bottom of the bottle (i.e. red spots, which could be seen through the bottle’s plastic) the device is rapidly lifted and immediately reapplied for the full duration of the injury. This results in a uniform-white DDPT burn. In summary, optimum, close contact is the most important factor in this burn creation model. Furthermore, our bottomless bottle sealed with malleable plastic wrap is a safe burn device which allows monitoring of the burn appearance during creation. Compared to other groups using a metal bar [6] the main advantage of our model is that the wound area can be larger and our method has the added advantage of accounting for the curved body contour on the flank of our animal model. We consider the use of open bottles (with uncontained hot liquid, as reported in other papers [7]) for creating scalds as unsafe for both the animal and the scientist. In conclusion, when using a porcine model for DDPT burns, the phenomenon of redness should not be ignored as a sign of uneven thermal injury. If redness does appear during burn creation it is likely to have a crucial influence on the final outcome of the wound.
Conflict of interest There are no conflicts of interest for any of the authors.
Acknowledgements This work was kindly supported by The Royal Children’s Hospital Foundation, Brisbane, Australia. We thank Dr. James
R. McMillan for his comments and kind proofreading of this manuscript.
references
[1] Cuttle L, Kempf M, Phillips GE, Mill J, Hayes MT, Fraser JF, et al. Porcine deep dermal partial thickness burn model with hypertrophic scarring. Burns 2006;32: 806–20. [2] Papp A, Kiraly K, Harma M, Lahtinen T, Uusaro A, Alhava E. The progression of burn depth in experimental burns: a histological and methodological study. Burns 2004;30: 684–90. [3] Singer AJ, Mc Clain SA. A porcine burn model. Methods Mol Med 2003;78:107–19. [4] Alexander JW, Fischer JE, Boyajian M, Palmquist J, Morris MJ. The influence of hair-removal methods on wound infections. Arch Surg 1983;118(March (3)):347–52. [5] Seropian R, Reynolds BM. Wound infections after preoperative depilation versus razor preparation. Am J Surg 1971;121(3):251–4. [6] Middelkoop E, van den Bogaerdt AJ, Lamme EN, Hoekstra MJ, Brandsma K, Ulrich MM, et al. Porcine wound models for skin substitution and burn treatment. Biomaterials 2004;25(9):1559–67. [7] Jandera V, Hudson D, de Wet PM, Innes PM, Rode H. Cooling the burn wound: evaluation of different modalities. Burns 2000;26(3):265–70.
Margit Kempf* Leila Cuttle Pei-Yun Liu Xue-Qing Wang Roy M. Kimble Royal Children’s Hospital Burns Research Group, University of Queensland, Brisbane, QLD, Australia *Corresponding author at: University of Queensland, Department of Paediatrics and Child Health, Royal Children’s Hospital, Brisbane 4029, Australia. Tel.: +61 7 363 69068; fax: +61 7 336 55455 E-mail address: [email protected] (M. Kempf) 0305-4179/$36.00 # 2008 Elsevier Ltd and ISBI. All rights reserved. doi:10.1016/j.burns.2008.06.013
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/burns
Letter to the Editor
Important improvements to porcine skin burn models, in search of the perfect burn Sir, We previously developed a reproducible porcine model for deep dermal partial thickness (DDPT) burn injury in juvenile Large White pigs [1]. This contact burn is created under general anesthetic using water at 928 for 15 s with a bottle with the bottom removed and replaced with plastic wrap. Upon creation, the circular wound area developed a white eschar and a hyperemic zone around the wound border. The depth of injury was determined by a histopathologist who examined tissue sections 2 and 6 days after injury in a blinded manner. During creation and implementation of this model we have seen variability in both the depth of injury within the wound and the rate of healing, although the entire process involved in applying the burn has remained constant. We noted that pink or red colored areas appearing within the burn wound at creation (day 0) were associated with faster healing of the
wound (Fig. 1) and formation of thinner dermal scar tissue at 6 weeks post-injury ( p = 0.045). These findings suggested that a whiter, non-blanching burn indicates deeper damage. This was confirmed by an experienced histopathologist who subsequently examined skin burn wound sections (removed at day 0) and each wound was classified into either a red or white color category, in a blinded manner. We observed a difference in the depth of damage between these two burn categories. The red areas on our burn model exhibited superficial damage (extending to the superficial to middermis) compared to the white areas (which had cellular damage extending into the deep dermis). Other groups have also encountered this phenomenon which we refer to as inconsistent and variable burns [2,3]. To achieve reproducible non-blanching, white, uniform, burns with the consistent depth of injury, we examined different factors. Our model porcine animal weight is
Fig. 1 – A difference in healing can be seen as early as day 14. At day 0, a white, non-blanching burn (A) compared to a burn containing pink or red colored areas (B), will heal more slowly (C), compared to the red areas which were healed by day 14 (D).
455
burns 35 (2009) 454–455
restricted to between 17 and 25 kg at initial injury. Our burn device is a 500-ml laboratory Schott Duran bottle, the bottom replaced with an extremely tight and firmly stretched plastic wrap taped to the smoothened bottle edges with heat resistant tape. The shaving of the animal is performed with clippers [4,5], with shaving performed in the opposite direction of hair growth so no hairs project into the area to be burned. In addition, any kind of scratches, abrasion or rubbing must also be avoided. For consistency the same person always applies the burn implement to the wound. Another person assists with lifting the animal slightly to arch the animal’s body before placing the burn device onto the flank to achieve optimum contact. A few seconds before the burn is created, a fine mist of water is sprayed onto the pre-marked wound site. When the water temperature in the bottle has reached exactly 92.08C (within W0.1 8C) it is horizontally, rather than vertically placed onto the pre-marked site to provide optimum contact with the skin surface. If a burn does fail to have good contact due to air pockets or the presence of excessive water on the skin surface due to mist trapped under the bottom of the bottle (i.e. red spots, which could be seen through the bottle’s plastic) the device is rapidly lifted and immediately reapplied for the full duration of the injury. This results in a uniform-white DDPT burn. In summary, optimum, close contact is the most important factor in this burn creation model. Furthermore, our bottomless bottle sealed with malleable plastic wrap is a safe burn device which allows monitoring of the burn appearance during creation. Compared to other groups using a metal bar [6] the main advantage of our model is that the wound area can be larger and our method has the added advantage of accounting for the curved body contour on the flank of our animal model. We consider the use of open bottles (with uncontained hot liquid, as reported in other papers [7]) for creating scalds as unsafe for both the animal and the scientist. In conclusion, when using a porcine model for DDPT burns, the phenomenon of redness should not be ignored as a sign of uneven thermal injury. If redness does appear during burn creation it is likely to have a crucial influence on the final outcome of the wound.
Conflict of interest There are no conflicts of interest for any of the authors.
Acknowledgements This work was kindly supported by The Royal Children’s Hospital Foundation, Brisbane, Australia. We thank Dr. James
R. McMillan for his comments and kind proofreading of this manuscript.
references
[1] Cuttle L, Kempf M, Phillips GE, Mill J, Hayes MT, Fraser JF, et al. Porcine deep dermal partial thickness burn model with hypertrophic scarring. Burns 2006;32: 806–20. [2] Papp A, Kiraly K, Harma M, Lahtinen T, Uusaro A, Alhava E. The progression of burn depth in experimental burns: a histological and methodological study. Burns 2004;30: 684–90. [3] Singer AJ, Mc Clain SA. A porcine burn model. Methods Mol Med 2003;78:107–19. [4] Alexander JW, Fischer JE, Boyajian M, Palmquist J, Morris MJ. The influence of hair-removal methods on wound infections. Arch Surg 1983;118(March (3)):347–52. [5] Seropian R, Reynolds BM. Wound infections after preoperative depilation versus razor preparation. Am J Surg 1971;121(3):251–4. [6] Middelkoop E, van den Bogaerdt AJ, Lamme EN, Hoekstra MJ, Brandsma K, Ulrich MM, et al. Porcine wound models for skin substitution and burn treatment. Biomaterials 2004;25(9):1559–67. [7] Jandera V, Hudson D, de Wet PM, Innes PM, Rode H. Cooling the burn wound: evaluation of different modalities. Burns 2000;26(3):265–70.
Margit Kempf* Leila Cuttle Pei-Yun Liu Xue-Qing Wang Roy M. Kimble Royal Children’s Hospital Burns Research Group, University of Queensland, Brisbane, QLD, Australia *Corresponding author at: University of Queensland, Department of Paediatrics and Child Health, Royal Children’s Hospital, Brisbane 4029, Australia. Tel.: +61 7 363 69068; fax: +61 7 336 55455 E-mail address: [email protected] (M. Kempf) 0305-4179/$36.00 # 2008 Elsevier Ltd and ISBI. All rights reserved. doi:10.1016/j.burns.2008.06.013