The optimal duration and delay of first aid treatment for deep partial thickness burn injuries
Introduction
The current recommendation for the first aid treatment of burns from the Australian and New Zealand Burn Association [1], is to cool the burn wound with cold running tap water for 20 min, up to 3 h after the injury has occurred. However, the published first aid experiments that these guidelines are based on are conflicting and it is surprising that these recommendations could be made from the evidence to date. The conflicting results are probably due to the studies being conducted in different animal models, using different depth and mechanism of injuries and examining different outcome measures (such as edema, Evans blue dye perfusion, mortality and histological damage).
If pain is used as an outcome, most people advocate application of cold treatment until no pain is felt on removal of the cold [2], and this has been described as 30 min—several hours [3], [4]. However, when examining edema as an outcome, one study found that the longest duration of treatment tested (2 h at 0 °C) was found to be most beneficial [5]. Another study using Evans blue dye perfusion found that although there was benefit for up to 4 h duration of cooling, the effect was not much better than cooling for 30 min [6]. They recommended that first aid should be applied for at least 30 min duration, but for up to 3 h was acceptable. Most recently, Bartlett et al. [7] found that a duration of 20 min in a porcine burn model lead to less injury measured histologically 9 days after injury.
Delays after which positive effects can still be seen are reported as <2 min [8], <5 min [9], [10], <30 min [6], 30 min [11], [12], 45 min [13], <60 min [14], 60 min [15], 2 h [16] or 3 h [17]. Many studies report that immediate treatment is the most beneficial, however positive effects are still seen after periods of delay.
In this study, we used our clinically relevant [18], [19] porcine burn model [20], [21] which has previously been used to test other first aid treatments such as temperature [22] and alternative therapies [23]. This time we tested various durations and delays of first aid (15 °C running water) on deep partial thickness burns. Our aim was to determine the optimum duration of first aid and the delay after the burn for which first aid is still effective. The outcomes we measured were: wound re-epithelialisation, subdermal temperatures, change in wound and scar area over time, histology of the scar and cosmetic appearance of the scar. The endpoint was 6 weeks after the burn, allowing us to examine the full re-epithelialisation process and scar appearance.
Section snippets
Animal surgery
All animal work was approved by the institutional animal ethics committee and all animals were treated in a humane manner. Forty Large White juvenile pigs of 15–20 kg (approximately 8 weeks of age) were used for the study. Anaesthesia was inducted with an intramuscular dose of 13 mg/kg ketamine hydrochloride (Ketamine 100 mg/mL, Parnell Laboratories, Alexandria, Australia) and 1 mg/kg xylazine (Xylazil 20 mg/mL, Ilium, Troy Laboratories, Sydney, Australia) and was maintained with isoflurane via a
Animal operations
One animal was euthanized during the surgery and four wounds were excluded as they had superficial areas (>5% total area was red). The average pig weight at scald creation was 21.7 ± 1.0 kg (mean ± SE). The average scald area was 45.4 ± 3.0 cm2.
Duration
With longer durations of cold water, the skin subdermal temperature continued to decrease (Fig. 1A). At the end of the treatment period, the average subdermal temperatures were 29.1 ± 1.01 °C, 28.2 ± 0.83 °C, 26.1 ± 0.22 °C and 23.7 ± 0.26 °C for 10, 20, 30 min and 1 h
Discussion
This study shows beneficial effects on re-epithelialisation and amount of scar tissue when first aid treatment is applied to burns and specifically, when cold water is applied immediately, for 20 min duration. Although many clinicians promote the immediate treatment of burns (probably predominantly for analgesia), this report actually demonstrates a significantly positive effect of immediate treatment. The optimal duration of first aid treatment of 20 min has also been confirmed by others using a
Conflict of interest
There are no conflicts of interest for any of the authors.
Acknowledgements
This work is supported by a grant from the Royal Children's Hospital Foundation, an NHMRC Biomedical Postgraduate Scholarship and an NHMRC Project Grant.
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