Abstract
This study was designed to analyse the characteristics and aetiology of low‐temperature burns and explore the prevention and treatment strategies. In total, 206 patients hospitalised with low‐temperature burns in a major burn center in Beijing from 2017 to 2021 were included. There were 35–49 cases per year, with an average of 41 ± 4.5 cases. The prevalence of low‐temperature burns was higher in female than in male and are mainly resulted from two kinds of incidents: unintended burns from heat treatment (50.97%, 105/206) and improper use of heating devices to keep warm (43.69%, 90/206). Most cases occurred in autumn (33.01%, 68/206) and the least in spring (17.96%, 37/206); cases in summer (24.27%, 50/206) and winter (24.76%, 51/206) accounted for nearly a quadrant respectively. Low‐temperature burns in summer were mainly unintended burns from heat treatment (80%, 40/50), whereas in autumn were mainly resulted from improper use of heating devices to keep warm (55.88%, 38/68), the difference was statistically significant (χ 2 = 42.801, P < .001). Of all the cases, the burn size ranged from 0.2% to 5% TBSA, mostly less than 1% (85.92%, 177/206); third‐degree burns accounted for 98.54% (203/206). Patients admitted after 3 weeks post‐injury accounted for 42.23% (87/206). All patients were cured, and most of them were by surgeries (70.87%, 146/206). The results of the study show that low‐temperature burn injury features a predictable morbidity among different seasons, a higher prevalence in adult women and a frequent occurrence at home. The wounds of low‐temperature burns are often small in size but deep in depth, and can be easily misdiagnosed as superficial burns. However, most low‐temperature burn wounds require surgical treatment. The study also suggests that based on the characteristics and aetiology of low‐temperature burns, targeted prevention and treatment measures should be mapped out.
Keywords: aetiology, diagnosis, low‐temperature burns, prevention, treatment
1. INTRODUCTION
A burn is an injury to the skin or other organic tissue caused primarily by excessive heat, and sometimes by radiation, radioactivity, electricity, friction or chemicals. 1 Thermal burns are usually caused by flame, steam, hot liquids and hot surfaces, and burn degree depends on the temperature of the heat source and the time length of the skin's contact with the source. High temperature heat sources such as flames or boiling water can cause deep burns within seconds. When the heat source has a milder temperature (44–51°C), it would take hours to cause thermal burns. Burns resulted by prolonged contact with such kinds of heat sources are known as low‐temperature burns in clinical settings and their degree has been found to be positively correlated with the length of contact time. 2 , 3 , 4
In the early stage of low‐temperature burns, the depth of the wound would be superficial, and blisters would form between the epidermis and dermis. However, if the heat sources were not removed in time, the deeper tissue would get burned under the continuous heating and the formed blisters would continue to exist. Therefore, the depth of deep low‐temperature burns can be easily misdiagnosed and the injury ignored due to the small wound size and mild pain, resulting in improper post‐injury treatment, delayed wound healing, and compromised life quality subsequently. This study analysed the aetiology and wound characteristics of low‐temperature burns in 206 patients admitted to our burn center during the past 4 years to support the formulation of more targeted and effective prevention and treatment strategies.
2. METHODS
2.1. Ethics approval
This retrospective study was approved by the Ethics Committee of Chinese PLA General Hospital. Informed consent was not required in this study.
2.2. Data extraction
The clinical data of 206 hospitalised patients with low‐temperature burns from January 1, 2017 to October 31, 2021 were collected. The data including age, gender, cause, burn site, burn size and depth, date of burn injury, time from injury to admission, other wound characteristics, treatment measures, wound healing time, and length of hospital stay were analysed.
2.3. Statistical analysis
The data were recorded using Microsoft Excel 365 (USA, Microsoft), and data analyses were conducted using SPSS 26.0 (USA, IBM analytics) and GraphPad Prism 6 (USA, GraphPad Software Inc.). Categorical variables were presented as frequencies and percentages (%), and continuous variables were presented as mean ± SD. Chi‐square test, Fisher's exact test, and Bonferroni correction were used to analyse categorical variables. P < .05 was considered statistically significant.
3. RESULTS
3.1. General characteristics
The number of hospitalised patients with low‐temperature burns accounted for 0.43% (206/47920) of the total patients admitted to the hospital in the same period. The number of low‐temperature burn cases was 35–49 (41 ± 4.5) per year, without obvious fluctuations.
Among all the low‐temperature burn cases, female patients accounted for 60.19% (124/206) and most of the cases occurred at home, accounting for 83.98% (173/206). All patients aged 3 months to 88 years (mean age: 50.39 ± 19.20 years). The results were shown in Table 1.
TABLE 1.
General characteristics of patients
| Characteristics | Total (N = 206) | |
|---|---|---|
| N | % | |
| Gender | ||
| Male | 82 | 39.81 |
| Female | 124 | 60.19 |
| Age (years) | ||
| 0–17 | 11 | 5.34 |
| 18–59 | 120 | 58.25 |
| ≥60 | 75 | 36.41 |
| Year | ||
| 2017 | 40 | 19.42 |
| 2018 | 41 | 19.90 |
| 2019 | 41 | 19.90 |
| 2020 | 35 | 16.99 |
| 2021 | 49 | 23.79 |
| Place of occurrence | ||
| Home | 173 | 83.98 |
| Workplace | 8 | 3.88 |
| Physiotherapy institution | 19 | 9.22 |
3.2. Aetiology
Low‐temperature burns can be categorised as two types: unintended burns from heat treatment (hereinafter referred to as treatment accidents) and burns from improper use of heating devices to keep warm (hereinafter referred to as heating accidents), accounting for 50.97% (105/206) and 43.69% (90/206) respectively. Burn injuries caused by moxibustion were the most common treatment accidents, accounting for 62.26% (66/105), and those caused by hot‐water bag and heating pad were the most common heating accidents, accounting for 77.78% (70/90). The results were shown in Figure 1 and Table 2.
FIGURE 1.
Aetiology of low‐temperature burns
TABLE 2.
Causes of low‐temperature burns
| Number | % | |
|---|---|---|
| Treatment (N = 105) | ||
| Moxibustion | 66 | 62.26 |
| Physiotherapy instrument | 26 | 24.53 |
| Application of herbal products | 12 | 11.32 |
| Cupping | 1 | 0.94 |
| Heating (N = 90) | ||
| Hot‐water bottle | 43 | 47.78 |
| Hot pack | 27 | 30.00 |
| Others | 20 | 22.22 |
The number of female patients suffering from low‐temperature burns caused by the aforementioned two types of accidents was larger than that of male patients, but the percentage of each cause in the female and male did not show a statistical difference (Table 3).
TABLE 3.
Causes of low‐temperature burns in male and female
| Male (N = 82) | Female (N = 124) | |||
|---|---|---|---|---|
| N | % | N | % | |
| Treatment | 41 | 50.00 | 64 | 51.61 |
| Heating | 36 | 43.90 | 54 | 43.55 |
| Others | 5 | 6.10 | 6 | 4.84 |
Respectively, treatment accidents and heating accidents accounted for 9.09% (1/11) and 81.82% (9/11) in juvenile patients, 47.50% (57/120) and 47.50% (57/120) in young and middle‐aged patients, 62.67% (47/75) and 32.00% (24/75) in elderly patients, and there were significant differences between the groups (χ 2 = 12.802, P = .012). The results were shown in Figure 2 and Table 4.
FIGURE 2.
Causes of low‐temperature burns in different age groups
TABLE 4.
Causes of low‐temperature burns in different age groups
| 0–17 (N = 11) | 18–59 (N = 120) | ≥60 (N = 75) | χ 2 | P | ||||
|---|---|---|---|---|---|---|---|---|
| N | % | N | % | N | % | |||
| Treatment | 1 | 9.09 | 57 | 47.50 | 47 | 62.67 | 12.802 | .012 |
| Heating | 9 | 81.82 | 57 | 47.50 | 24 | 32.00 | ||
| Others | 1 | 9.09 | 6 | 5.00 | 4 | 5.33 | ||
3.3. Seasonal distribution
The seasonal distribution of low‐temperature burns was identifiable. The most cases occurred in autumn (33.01%, 68/206) and the least in spring (17.96%, 37/206). The number of cases in summer (24.27%, 50/206) and winter (24.76%, 51/206) were close. Low‐temperature burns occurred in summer were mainly treatment accidents (80%, 40/50), and those that happened in autumn were mainly heating accidents (55.88%, 38/68); the difference was statistically significant (χ 2 = 42.801, P < .001). The results were shown in Table 5.
TABLE 5.
Causes of low‐temperature burns in different seasons
| Spring (N = 34) | Summer (N = 50) | Autumn (N = 68) | Winter (N = 51) | χ 2 | P | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| N | % | N | % | N | % | N | % | |||
| Treatment | 22 | 59.46 | 40 | 80 | 29 | 42.65 | 14 | 27.45 | 42.801 | <.001 |
| Heating | 11 | 29.73 | 6 | 12 | 38 | 55.88 | 35 | 68.63 | ||
| Others | 4 | 10.81 | 4 | 8 | 1 | 1.47 | 2 | 3.92 | ||
3.4. Clinical characteristics
For all burn cases studied, the size of low‐temperature burn wounds was often small (0.2%–5% TBSA), mostly less than 1% TBSA (85.92%, 177/206). Third‐degree wounds accounted for 98.54% (203/206); most cases occurred in extremities (86.41%, 178/206). Patients admitted after 3 weeks post‐injury accounted for 42.23% (87/206). The wounds complicated by infection accounted for 10.09% (21/206). All cases were cured and discharged: the majority of the patients had been cured by surgeries (70.87%, 146/206); 26.21% of them had been hospitalised for more than 3 weeks (54/206). The results were shown in Table 6.
TABLE 6.
Clinical characteristics of low‐temperature burns
| Variable | |
|---|---|
| Full thickness burns | 203 (98.54%) |
| Burn site | |
| Limbs | 178 (86.41%) |
| Trunk | 26 (12.62%) |
| Perineum, buttocks | 11 (5.34%) |
| Head, neck | 1 (0.49%) |
| Time from burn onset to admission | 23.06 ± 26.12 |
| <1 week | 35 (16.99%) |
| 1–2 weeks | 49 (23.79%) |
| 2–3 weeks | 35 (16.99%) |
| ≥3 weeks | 87 (42.23%) |
| Length of stay | 19.12 ± 21.05 |
| <1 week | 37 (17.96%) |
| 1–2 weeks | 53 (25.73%) |
| 2–3 weeks | 62 (30.10%) |
| ≥3 weeks | 54 (26.21%) |
| Wound infection | 21 (10.19%) |
| Patients who received surgery | 146 (70.87%) |
| Skin graft | 57 (39.04%) |
| Flap coverage | 15 (10.27%) |
| Primary closure | 70 (47.95%) |
| Debridement | 4 (2.74%) |
3.5. Typical case
A 23‐year‐old female sustained a low‐temperature burn injury on the right calf from using a heating pad to keep warm while sleeping under quilt. The patient placed the heating pad on the right calf and went to sleep. Seven hours later, she felt itchy and observed blisters on the right calf. She went to the community physician who drained the blister fluid, disinfected the affected skin with iodophor, and covered it with a dressing. Subsequently, she underwent more than 3 weeks of dressing changes and was observed with bloody discharges on the wound surface, obvious hyperemia and edema of the marginal cutaneous tissue. Finally, she was admitted to our burn center.
The wound was sutured directly after the non‐viable tissue was removed under local anaesthesia, and the incision healed well after the operation (Figure 3). The pathology was shown in Figure 4. There was chronic purulent inflammation with interstitial haemorrhage in the wound (Figure 4A, B), hyperplasia of collagen fibres in the subcutaneous tissue in the wound margin, acute and chronic inflammatory cell infiltration and interstitial haemorrhage around small blood vessels (Figure 4A, C).
FIGURE 3.
Burn wound of the 23‐year‐old female patient. (A) The wound on the first day after injury. 
The blister. (B) The wound after 14 days dressing change in a community hospital. 
The pale wound bas. (C) The wound after 28 days dressing change in a community hospital. (D) Excising necrotic tissue surgically. (E) Suturing the wound. (F) Healing of the surgical incision at 3 weeks after the operation
FIGURE 4.
Pathology of low‐temperature burns. (A) Pathology of the junction of the wound edge and the wound surface. (B) Pathology of the wound surface. (C) Pathology of the marginal cutaneous tissue
4. DISCUSSION
According to the statistics by WHO, more than 10 million burn patients are in need of specialist treatment of burn care each year globally, and 180 000 of them eventually died. 1 In severe cases, subcutaneous tissue such as muscles, bones, joints, and even internal organs, can also be injured. The depth of burn injury was determined by the temperature and the time length of the contact with the heat source. 2 Low‐temperature burns are caused by prolonged contact with a hot resource of a milder temperature. This study suggested that the incidence of low‐temperature burns was stable, and the number of patients admitted to the hospital each year was close. In view of this, it is necessary to study the aetiology, clinical characteristics of low‐temperature burns to provide evidence facilitating the formulation of prevention and treatment strategies.
This study found that females were more prone to low‐temperature burns than males, a result consistent with previous studies. For example, in a previous epidemiological study of low‐temperature burns caused by floor heating system, the proportion of female patients was 65.1%. 3 Another epidemiological study of low‐temperature burns caused by moxibustion showed that the proportion of female patients reached 72.8%. 4
A retrospective study indicated that the improper use of the hot pack and moxibustion were the main causes of low‐temperature burns and most of the cases occurred at home. 5 In this study, most of the incidences also occurred at home and are mainly heat treatment adverse events and heating accidents. Heating accidents would occur when heating sources, such as hot‐water bags, heating pads, and electric blankets, and so forth, are used improperly and some area of the body surface is kept in a prolonged contact with the heating source and becomes compressed, leading to a slowed blood circulation for a long period.
Heat treatment accidents can happen during the application of moxibustion, physiotherapy instrument, and herbal products. Among these events, nearly two‐thirds are caused by moxibustion, which is an important treatment procedure of traditional Chinese medicine like the widely practiced acupuncture. By directly hanging or applying a moxibustion device to the skin above the meridians of the body, the heat and medicinal effects of the wormwood moxa stick fire would stimulate and improve the body's immunity function to resist diseases. Moxibustion can be used in the treatment of hundreds of diseases related to the immune system, nervous system, digestive system, endocrine system and tumour and has been widely used in China, Korea, Malaysia, and other eastern Asian countries. 6 , 7 It has been reported that infections, allergic reactions were the most common adverse events of moxibustion 8 and the treatment should be carried out in a clinic or hospital by a TCM therapist. To ensure a both safe and effective procedure, the recommended distance between the burning moxa sticks and the skin is about 3–4 cm and the recommended treatment time is 30–60 min. Should the distance be too short or the time too long, low‐temperature burns may occur. 9 This study found that low‐temperature burns caused by moxibustion all occurred at home due to the improper operations by the patients themselves. Given this, the public awareness of the potential burns from moxibustion during self‐care should be strengthened, and people should be encouraged to go to medical institutions for such treatment for the reduced risk of sustaining low‐temperature burns.
This study found significant differences in the causes for different age groups of low‐temperature burns. The proportion of heating accidents gradually decreased with age, while heat treatment accidents gradually increased. This study holds that young people in good health generally are less likely to take moxibustion or other heat treatment but are prone to low‐temperature burns when using heating devices without sufficient safety awareness. That's where the preventive measures focusing on raising awareness and enhancing education should step in. As for the older people, their accumulated life experience and enhanced safety awareness make them less prone to heating accidents. However, due to their increasing demand for moxibustion and other medical heating products in treating some illnesses, heat treatment accidents increased. Therefore, preventive measures should advocate the standard operations and safe use concerning moxa sticks, cupping, some herbal products and physiotherapy instrument.
This study also found that the incidence of low‐temperature burns reached the highest in autumn, decreased respectively in summer and winter, and reached the lowest in spring. The aetiology showed that low‐temperature burns in autumn are mainly heating accidents, possibly due to the temperate semi‐humid continental monsoon climate featuring short autumns and cold and dry winters in Beijing (39°54′ N 116°24′ E). In Beijing's autumn, the temperature can be as low as 7°C, far more lower than the human cold pain threshold (17.8 and 18.8°C for the calf and foot, respectively). 10 When the weather gets cold, people would use simple heating products such as heating pads, hot‐water bags, and electric blankets to keep warm, hence the increase in low‐temperature burn incidence. The typical case in this study involving the improper use of a heating pad while sleeping due to the cold weather happened just 2 days before Beijing's central heating works. The seasonal distribution of cases may vary according to varied regional climatic conditions. This study also found that there was also a large number of low‐temperature burn cases in summer, close to the number of low‐temperature burn patients in winter. 80% of low‐temperature burns in summer were unintended injuries from moxibustion, physiotherapy, and some other treatments.
General speaking, skin burns are graded as first‐degree, second‐degree, and third‐degree burns according to the depth. First‐degree burns, involving only the epidermis, are dry and do not blister. Second‐degree burns, involving all epidermises and extending into the dermis, are moist and hyperemic and may blister. Third‐degree burns, destructing the entire dermis and all deep epidermal elements, are avascular and appear pale to carbonaceous black. 11 , 12 However, low‐temperature burns have unique clinical features. Due to the skin's prolonged contact with the heating sources, thermal energy accumulates and heat is continuously conducted to deeper tissue, resulting in progressive damage extending from the superficial skin to the deeper tissue. In the early stage of low‐temperature burns, the injury is superficial, and blisters would form between the epidermis and dermis. If the heating sources were not removed in time, the deeper tissue would become injured under the continuous accumulation of heat (Figure 5). The clinical manifestations of low‐temperature burn skins have the following characteristics: the early post‐injury wounds often have blisters which are small and often dark in appearance and caused by bloody blisters or wound congestion; necrotic foci may appear after the blisters are treated, and some wounds may be pale and painless. Low‐temperature burns can be easily misdiagnosed as superficial burns, which might not be taken seriously, thus leading to inadequate post‐injury treatment, delayed wound healing, and undermined life quality. In this study, the average time length between getting burned and being admitted into the hospital was more than 3 weeks, much longer than that in ordinary burns.
FIGURE 5.
Schematic diagram of low‐temperature burns
Public awareness and prevention measures of low‐temperature burns should be promoted via all kinds of media such as newspapers, television, radio, social platforms, portal websites, and community education programs. Healthcare professionals in communities and primary hospitals should acquire more knowledge of the clinical characteristics and more training on the treatment of low‐temperature burns to avoid misdiagnosis and improve patient care.
This research has several limitations. Being a retrospective study, some clinical data were incomplete, such as the distance between the moxa stick and the skin and the treating time. Prospective clinical studies are needed to further analyse the characteristics of low‐temperature burns. In addition, experimental studies are also needed to explore the differences between low‐temperature burn wounds and acute burn wounds and explore the mechanism of low‐temperature burns.
5. CONCLUSION
Low‐temperature burns feature a predictable morbidity among seasons, a higher prevalence in adult women and a frequent occurrence at home. They are mainly unintended burns from heat treatment (heat treatment accidents) and burns resulted by the improper use of heating devices (heating accidents). The wounds of low‐temperature burns are often small in size but deep in depth, and can be easily misdiagnosed as superficial burns. Most low‐temperature burns need surgeries to get cured. The study also suggests that based on the characteristics and aetiology of low‐temperature burns, targeted prevention and treatment measures should be mapped out.
CONFLICT OF INTEREST
No relevant conflicts of interest.
ACKNOWLEDGEMENTS
Financial support: This work is supported by the Major Program of Military Logistics Research Plan (ALB18J001), the Program of National Natural Science Foundation of China (82072169, 82272279), the Major Program of Healthcare Special Project (22BJZ35).
Xie X, Liu X, Cai J, et al. Characteristics and aetiology of low‐temperature burns in Beijing of China. Int Wound J. 2023;20(6):2105‐2112. doi: 10.1111/iwj.14085
Xiaoye Xie and Xinzhu Liu are co‐first authors and contributed equally to this work.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available on request from the corresponding author.
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Associated Data
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Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author.