Validating the relationship between burn temperature, duration of exposure and tissue injury severity for scald burns

Abstract

Listen

Translate article

Introduction: Scald injury events are a common occurrence in early childhood. To reduce the risk to children of sustaining severe burn injuries, understanding the relationship between water temperatures, duration of exposure and tissue injury severity is essential. Current data used to predict the severity of burn injury and guide global scald burn prevention strategies is from the 1940s and has never been validated histologically for differentiating between superficial and deep dermal damage. While all burn injuries are painful and distressing for a child, severe deep dermal burns will require hospitalisation for extensive medical treatment, surgical intervention and may lead to scarring in the long term. Therefore it is essential to appreciate not only the burn conditions predicted to result in a cutaneous injury, but also to estimate the severity of injury, with particular reference to the more serious and clinically relevant deep dermal and full thickness burns. Thesis aim: The primary aim of this research was to review the current field of burn injury prediction and obtain evidence for the burn conditions required to cause severe deep dermal scald injuries. An appropriate animal model was used, with both histological and clinically relevant assessments of tissue injury severity. Methodology and Results: Systematic review: Forty-two studies were included in a review of porcine burn models where depth of burn was evaluated histologically. The mechanism of burn injury e.g. scald or contact with hot metal, was shown to affect injury severity results. Additionally, a gap in knowledge was identified regarding predicting the severity of injury to the dermis from exposure to moderate temperature water (50–70oC), as seen with hot tap water immersion scalds. Experimental animal studies: A porcine scald model was successfully developed and optimised to examine the range of burn conditions representative of spill/splash and immersion scald injury events similar to those encountered by children. In total, 20 burn combinations were tested including 50 to 60oC water for 1 to 10 minutes (immersion) and 60 to 100oC water for 5 seconds (spill/splash). Wound examination, histological assessments and blood perfusion to the wound were analysed in the acute post-burn period (7 days). The burn conditions to result in mid-to-deep dermal injury were identified and included: 50oC for 10 minutes, 55oC for 2 minutes, 60oC for 30 seconds, and ≥ 75oC for 5 seconds. To evaluate the relationship between histologically determined tissue injury severity and the clinically relevant outcome of time to complete wound re-epithelialisation for these moderate to severe burns, a subset of 10 burn combinations were followed for 21 days. Damage to ≥ 75% of the depth of dermis was associated with burns taking longer than 3 weeks to fully re-epithelialise. Burns which were not fully re-epithelialised by day 21 included: 50oC for > 10 minutes, 55oC for 5 minutes, 60oC for 60 seconds, 70oC for > 15 seconds, and 85oC and 90oC for 5 seconds. Mathematical modelling: Temperature changes within the skin during experimental scalding were recorded and used to develop a mathematical model to examine the thermal properties of skin. Overall, the thermal diffusivity (α) was estimated to be 0.03 ± 0.02mm2/s, and was independent of the burn duration, burn temperature, and skin thickness. Clinical translation: A retrospective database review of Queensland’s major paediatric burns referral centre was conducted to identify and characterise the occurrence of severe scald burns in children. Forty-three cases of severe scald injuries which required surgical treatment ((split-thickness skin grafting (SSG)) were identified. The majority of SSG cases arose from a spill/splash event, with hot beverages (n = 17) and water from a saucepan/kettle (n = 14) the most common mechanisms. Freshly boiled water or recently made black tea/coffee were most likely to result in severe scalds. Discussion: The body of work presented in this thesis delivers compelling evidence for the first time to show that previous prediction data from the 1940s overestimates burn injury severity. Updated evidence-based estimates for the burn conditions (temperature and duration of exposure) to result in clinically relevant severe scald injuries are established and can be used to guide future global scald burn prevention strategies/legislation. This study also provided valuable, quantitative information about heat conduction in living skin with broad application to heat transfer modelling investigations of thermal injury prevention and thermal therapy studies. Outcomes from this research project have already been used by burns clinicians in Queensland to inform police investigations where inflicted immersion scalds were suspected. This work also provided scientific evidence for regulators setting safety standards in Australia for oven door temperatures. There are three approaches to burn prevention: education of risk, safer physical design of products, and regulation and legislation. This research project provides valuable evidence-based scald injury prediction data to better inform these approaches and help keep children safe from burns.