Burns Sustained From Body Heating Devices: An Integrative Review

Heating devices used to provide warmth or relieve discomfort caused by muscle and joint pain are often utilized during colder periods, such as the winter months.¹ Across Australia and New Zealand for the period of July 2016 to June 30, 2017, adult cases accounted for approximately half of the burns (47%) caused by hot water bottles during the winter months.² This reflects the higher levels of exposure to these items in the cooler months that can result in scalds and contact burns.² Specific subpopulations are at greater risk of sustaining burns from body heating devices, including the elderly and those with comorbidities that reduce sensation, such as diabetes mellitus and peripheral vascular disease.³ Burns sustained by those with diabetes may have different characteristics from those without diabetes, and the frequency of burns sustained from hot water bottles is higher in the population with diabetes.³ For these at-risk groups, heating devices present a clear danger, including electrocution, fire, and cutaneous burns. However, these injuries remain largely preventable when appropriate measures are in place. 

Burns from devices (eg, electric heating pads) are often sustained due to improper utilization. Correct usage of heating pads can be compromised by placing a cover over the pad, covering the pad with another surface (eg, pillow), or placing the pad under the body against a seat or mattress.⁴ The improper use confines the heat generated to the area of application on the skin that increases the quality and rate of heat transfer.⁴ Correct use of such a device requires the consumer to place only 1 surface against the skin, therefore allowing the opposing surface to be exposed to the outer atmosphere. This permits the total rate of energy transfer out of the heating pad to be divided so only about half of the energy will be transferred into the body and the rest of the heat is converted or convected away from the exposed side.⁴ Incidence of burns from body heating devices are on the rise, with the US Consumer Product Safety Commission estimating the annual number of burns due to electric heating pads has increased by 33.9%, from 1600 in 1995 to 2142 in 2008.⁴ Similarly, the use of hot water bottles also has attracted attention due to the risk burns pose to consumers. Hot water bottles are primarily made from either rubber or polyvinyl chloride and may be imprinted with a manufactured date.⁵ The bottle has a ferrule, which provides a watertight seal.⁶ 

Some modern hot water bottles are manufactured using silicone-based materials instead of natural rubber. Materials such as silicone rubber can withstand high temperatures better than organic rubbers with less deterioration.⁷ Burns due to hot water bottles can be caused by spillage, rupture of the hot water bottle itself, and misuse by leaning, rolling, lying, or pressing the surface of the hot water bottle. Importantly, the hot water bottle may appear intact, but the rubber can breakdown from the inside, making it vulnerable to cracking or bursting.

Wheat or grain-filled heat packs are another device that have been reported to cause significant burns to individuals.^8,9 These bags are traditionally made of fabric and filled with wheat or some other grain, which are heated in a microwave. Burn injuries from heated wheat or grained-filled heat packs may result from placing the heat pack on or in bedding, being heated in a microwave for longer than the time specified by the manufacturer, being reheated before it is allowed to cool sufficiently, and deteriorating of the bag itself, causing the heated beads to dry out and become combustible.^8,9 

Manufacturers have attempted to minimize the danger of burns related to heating devices with printing the manufacturer’s instructions-for-use and warnings on the product labels that have been publicized by various government bodies. The Australian Competition and Consumer Commission and institutions such as Fair Trading have compiled a hot water bottle safety checklist/tips and alerts in an attempt to reduce the incidence of burns that provides consumers with information on the correct use and storage.^10,11

Even with such preventative measures in place, the incidence of burns from various heating devices continues to rise. Therefore, the aim of this integrative review is to synthesize the incidence, risk factors, outcomes, treatment, and prevention of burns sustained from body heating devices in order to better understand how these burns are sustained.

This integrative review involved identifying the problem and question, searching the literature using a comprehensive systematic strategy, data collection, critical review and analysis of the included studies and case reports, and presentation of the findings.¹²

Studies identification
A systematic search was undertaken using the electronic databases PubMed, CINHAL, EMBASE, and Scopus from inception up until January 13, 2020. No time restrictions were placed on the publication year, but articles were limited to publication in the English language. Boolean connectors AND/OR were used to combine MeSH terms and key search terms: “burn,*” “electric burn,” “thermal, scald,*” “electric blanket,*” “hot water bottle,*” “heat pad,*” “heating pad,*” “hot pack,*” “chemical pack,*” “heating device,” “heating pack,*” and “wheat bag.*” Reference lists of included studies and case reports were reviewed to identify any articles not captured in the initial search (Figure 1). 

Inclusion and exclusion criteria
Study inclusion comprised primary research and case reports focusing on burns sustained from body heating devices. Studies were excluded if they reported animal experimentation. Conference proceedings and reviews also were excluded.

Data extraction and synthesis
A total of 34 studies/case reports were summarized and systematically synthesized, 6 of which were identified through the reference lists of included studies. Primary research studies are summarized in Table 1A and 1B,^13-22 case reports in Table 2A, 2B, and 2C,^19,23-45 and retrospective studies in Table 3.^13-22

Retrospective analyses of medical records
There were 10 retrospective reviews of hospital records yielded by this review. The reviews identified 1343 patients with burns, of whom the majority were women (63.4%), with a mean age of 27.7 years (range, 0–92 years). The size of these studies ranged from 11 to 334 cases. Women comprised the majority of cases in all of the selected studies, with the proportion of women with burns from heating devices ranging from 51.5% to 76.3% of cases. While all studies reported the timeframe for record retrieval, only 3 reported the number of records accessed to allow for proportions of burn injuries resulting from heating devices to be assessed.^14,16,20 A summary of the study characteristics and data is provided in Table 1A and 1B and Table 3.

Six studies investigated hot water bottle burns.^{13,14,18,19,21,22} Collins et al¹⁶ investigated hot wheat bag burns, Mun et al²⁰ reported burns from all physical therapy modalities (ie, hot packs, heating pads), and Choi et al⁴⁶ reported on burns occurring during hospitalization. Saavedra et al²¹ reported on the hospitalization of children due to hot water bottle burns and Foong et al¹⁷ reported on thermal injuries caused by hair straightening devices in children.

Eight studies reported total burn surface area (TBSA). For hot water bottles, the TBSA was low, ranging from 0.1%¹⁴ to 3.2%.²² Collins et al¹⁶ found a mean TBSA for hot wheat bag burns of 1.1%, while Mun et al²⁰ identified 1.5% TBSA for all physical therapy modalities. Choi et al⁴⁶ found 77.4% had deep burns, and burns resulting from direct contact (OR = 4.36, P = .005) and burns to the lower body (OR = 2.85, P = .044) were associated with deep burns occurring during hospitalization. Goltsman et al¹⁸ reported that about a quarter (26%) of hot water bottle burns were full thickness and half (51%) were either partial thickness or deep dermal. Begum et al¹³ reported 37.5% of burns sustained from hot water bottles were full thickness, with 46.0% requiring surgical management. Foong et al¹⁷ found common injuries for burns sustained from hair straighteners were from grabbing (27%) or stepping on the hair straighteners (20%), with most sustaining superficial partial-thickness burns. 

The proportion from all physical therapy modalities can be determined from results reported by Mun et al²⁰ to be 10.9%, although this was not explicitly reported in the article. Hot packs formed the majority (54.3%) of the injuries from therapeutic modalities, with moxibustion (22.3%) and heating pads (17%) the other major causes of burns.²⁰ The proportion of hot water bottle burns among those hospitalized for burns was found by Ben et al¹⁴ to be 5.5%. The proportion of hot wheat bag burns was much lower in the study by Collins et al¹⁶ (0.6%). The proportion of burns due to physical therapy modalities could not be assessed for the remaining studies because they did not report the total number of records accessed. However, Choi et al⁴⁶ identified the major causes of burns during hospitalization as hot packs (23.5%), laser therapy (13.0%), heating pads (13.0%), and grounding pads (13.0%).

Across the studies, burn location was predominantly in the lower limbs and feet, with the abdomen, pelvis, buttocks and perineum, and upper limbs also reported. Hot water bottle burns were due to bursting, spillage, contact, and/or hot steam, with contact burns mostly due to prolonged contact during sleep. There was variation in the proportions of mechanisms of injury due to hot water bottles, and the proportion of burns due to contact ranged from 6.3%¹³ to 79.6%.⁴⁶ Jabir et al¹⁹ also observed the mean TBSA was higher for bursting (3.9%) than spills (2.7%) and contact burns (0.9%). Further, for burn injuries sustained from hot water bottles, Begum et al¹³ found most took place when the patient was asleep.

A number of studies considered risk factors for heating device burns. Mun et al²⁰ found statistically significant differences for patients with burns from therapeutic modalities as compared with nontherapeutic heating devices. These patients were older, had a higher body mass index, and had a higher incidence of diabetes and hypertension. In a multivariate analysis,²⁰ those more than 60 years old were more than twice as likely to have a burn resulting from a therapeutic modality (OR = 2.16, P = .005), while those with diabetes had 4 times the risk (OR = 3.99, P < .001). Goltsman et al¹⁸ found that residing in an area of socioeconomic disadvantage was significantly associated with increased risk of hot water bottle burns; however, the causal factors were not identified. Collins et al¹⁶ identified predisposing factors for hot wheat bag burns to be peripheral neuropathy due to diabetes, paraplegia, spina bifida, and spinal block during caesarean section. 

Presentations were often delayed from the time of initial injury, although the proportion of those with hot water bottle burns presenting on the day of the injury varied from 18.8%¹⁹ to 83%.¹⁴ Injuries occurred most commonly at home. Goltsman et al¹⁸ identified only 26% of presentations from hot water bottle injuries required hospitalization.

Mortality was found to be very low, with a mean length of stay ranging from 1.3 days¹⁹ to 16.5 days.¹⁸ Five studies^{13,14,17,19,22} reported infections, with up to 55.6% having positive swab results.¹⁹ The requirements for surgery varied in the reporting for hot water bottle injuries, ranging from 15%²¹ to 87.4%.¹⁴ For wheat bag burns, 91% resulted in surgery that encompassed a combination of debridement, split-thickness skin grafting, and direct closure, with 1 patient requiring a foot amputation.  

Case reports
The use of case reports and case series allows for the identification of unique cases that are generally uncontrolled and retrospective with a small number of participants. Despite this, these reports influence the scientific literature and continue to advance the body of knowledge.⁴⁷ The use of case reports and case series to inform current practice can be utilized when there is limited higher level evidence available, allowing for narrative or quantitative synthesis.⁴⁷ 

Of the 24 case series and reports included in this review (Table 2A, 2B, and 2C^19,23-45), 10 were case reports with 1 patient^{19,23,32-35,37,41,42,44} and 14 were case series^{24-31,36,38-40,43,45} with 2 to 8 patients, for a total of 52 patients across the studies. Women were predominately represented in the case series/reports with only 10 men identified. As a cohort, apart from 1 pediatric case of 35% TBSA,²³ the patients reported in the case series/reports all had a small TBSA and partial-thickness to full-thickness burns as in the included retrospective reviews. The case series/reports identified hot water bottles and heating pads to be the most common mechanism of injury, and also described the use of sunlamps, hair curlers/straighteners, microwavable wheat bags, hairdryers, electric blankets, and equipment used in operating rooms, such as thermal mattress, hot packs, and warmed intravenous fluid bags. The burns sustained from the heating devices were of a small TBSA. The case series/reports predominately described women (n = 35) who had undergone breast reconstruction and used a heating device for warmth; of which, there were 33 cases reported collectively.

Of the 5 adult men reported, 3 cases involved burns to the lower limbs and buttocks, with a history of diabetes mellitus and peripheral neuropathy. The case series/reports identified that about half of the cases reported the burn healed with dressing changes and conservative treatment (without the need for skin grafting), while others required debridement and skin grafting. Other cases reported the need for further reconstructive surgery and scar revision. 

The mechanism of injury causing burns sustained from heating devices include contact (direct and sustained contact with the skin), scalds (heated liquids/steam), and radiant heat (not touching skin). Scalds have been found to occur in the use of hot water bottles, in particular when filling the bottle or expelling air from it, leaking from improper closure of the plug, and perishing of the rubber that results in leakage or rupture.¹ Contact burns have been linked to the use of hot water bottles, electric heating pads, and electric blankets by means of leaning, rolling, lying, or pressing against the surface of the device. A study found contact burns accounted for 14% of all minor burns experienced by elderly patients admitted to the hospital.⁴⁸ A study of heating pads reported 41% of admissions to the hospital related to heating pad burns were a consequence of the patient falling asleep on or in contact with the device.⁴⁹ Electric blankets, however, could result in not only contact burns but also heat stroke from prolonged exposure that results in a rise in the overall body temperature.⁵⁰ Electric warming mattresses have been linked to faults, such as a break in the conductive strips running internally through the mattress that may result in full-thickness burns.²⁸ Burns from hot wheat packs may be exacerbated by the uneven heating produced by microwave ovens, with the heat largely stored on the outside of the pad where contact is made with the body.⁵¹ This points to a need to educate users of such devices not only on the extent of contact but the temperature of water as well as wear, tear, and maintenance of the device. As temperature is related to both heating time and power of the heating mechanism (eg, microwave wattage), information related to warming these devices needs to consider both power and time.

The majority of burns sustained from heating devices tend to be minor and are largely treated in the outpatient setting.⁴⁸ In this review, the depth of burns sustained from heating devices were relatively smaller; however, the burns sustained were deep, with some requiring debridement and grafting with significant scarring. 

Severity of burns is determined by the length of exposure and temperature in scald burns as described by Feldman et al.⁵² The lowest temperature required to sustain a cutaneous burn is 44°C.^53,54 In an adult, evidence suggests the perception of pain occurs slightly above 43°C and at 44°C; damage occurs at the basal layer of the epidermis.⁵⁴ For a superficial burn injury, tissue damage increases logarithmically with increased temperature and exposure time.^54,55 A study⁵⁶ reported that a full-thickness burn can occur in as little as 30 seconds from exposure to hot water bottles with a surface temperature of 55°C. According to Martin and Falder,⁵⁴ for temperatures between 44°C and 51°C, the damage doubles for each 1°C rise in temperature. The depth of a burn injury is influenced by several factors, including the thickness of the skin, blood flow, and cooling process after the burn.⁵⁴ Blood vessel occlusion in burn injuries is a well-known issue, although its etiology is unclear.⁵⁷ 

As demonstrated in this review, the site of burn injury can vary and depends on the heating device used and reason for use. As reported by Eby et al,⁴⁹ emergency department admissions for burns secondary to heating pad use were mostly localized to the lower trunk (33%), upper trunk (19%), and shoulders (5%). However, those with decreased sensation to the peripheries, including those with peripheral neuropathy, are more likely to sustain burns to these areas due to their inability to perceive temperature and/or pain. Furthermore, those who undergo autologous breast reconstruction (eg, transverse rectus abdominis flap or deep inferior epigastric perforator flap) post mastectomy, or abdominoplasty, also experienced impaired sensation that places them at a greater risk of a burn.^58,59

Conservative management of small burns with appropriate dressings and follow-up was found to be the most frequently reported treatment, both in inpatient and outpatient settings. Some research has reported that only 4% to 5% of patients with such burns require admission,^48,49 and the treatments for these burns include debridement and skin grafting followed by scar management.¹ If the burn is circumferential or is over a joint (eg, wrist, knee, or elbow), the management become more complex with implications for loss of function and range of movement. Individuals with a decreased sensation (eg, those with diabetes mellitus, peripheral vascular disease, or having breast reconstruction) are at a greater risk of sustaining burns from body contact heating devices. Elderly patients and those with diabetes who have comorbidities tend to have a delayed presentation with deeper burns predominantly affecting the lower limbs.⁶⁰ Age is commonly identified as a risk factor for burns from body contact heating devices.¹ Young children and the elderly both tend to have deeper burns due to their thinner skin that allows the burns to occur more quickly and at lower temperatures.¹ 

Prevention strategies
Despite warning labels and instructions-for-use on body contact heating devices, burn injuries still occur through inappropriate use⁴⁸; this highlights the need for better targeted preventative measures. Educating target populations is one of the most prominent strategies, with burn prevention groups publishing factsheets promoting simple measures.¹ These recommendations include replacing devices every 12 months to avoid perishing of product, filling the bottle slowly, not overfilling, and using a cloth between the device and the person’s body.¹ These strategies represent the risks relating to temperature of the device. 

There is also the component of time, for which further strategies have been suggested. Eby et al⁴⁹ recommended the need to educate patients on the use of timers to avoid the user falling asleep while utilizing heating devices. Zhou et al⁵⁰ suggested the use of heating devices, although rare, can lead to fatalities that are highly preventable if a thermostat is incorporated into the design.

There are additional indirect risks of injury from body contact heating devices. Electrical faults in body contact heating devices may result in electrification and ignition, resulting in flame burns. Public education concerning the dangers of electrical faults, contact with hot liquids, and heat stroke in the use of the electric blankets are vital for prevention.²⁸ In addition, assessment of risk should include external factors. For example, the impact of the changing seasons on mechanism of injury can help guide burn prevention strategies and resource utilization.² Further, adopting in-home assessments for high-risk patients could prove an invaluable method to identify and mitigate such risks.⁴⁸

This review was limited in several regards. Studies retrieved as part of the review focused largely on admissions to the hospital setting for burns. It therefore does not incorporate patients who sustain minor burns and receive treatment in general practices or other health centers. Such data may have yielded different results or provided further support to existing data. Second, the search resulted in a relatively small number of studies, perhaps indicating the limited research to date in this particular field. This limited the available studies to review and therefore the generalizability of their findings. By limiting the search to studies only published in the English language, this may have further reduced the pool of possible studies. The approach of this review did not distinguish between hospital and non-hospital settings and covered a range of heating mechanisms, which limits the ability to integrate the evidence. This review did not assess technical aspects associated with the large variety of body contact heating devices available. Many of the studies assessed only 1 type of heating device, limiting the ability to collect evidence across the range of heating devices in terms of incidence, risk, severity, and treatment.  

Body contact heating devices are often used to provide thermal comfort and can provide relief for patients experiencing pain or cold. However, their use, and in particular misuse, can result in burn injuries. Such risks must be mitigated and prevented when possible, acknowledging that heating devices can assist with recovery particularly for conditions with complicated healing pathways. Any preventative strategies need to acknowledge the full extent of patient risk factors, mechanisms of injury, and any factors that may impede capacity to mitigate risk. Developing preventative strategies that involve education of and action by the patient need to assess that person’s capacity and willingness to engage. This can be impacted by many factors, including cognition and time. Otherwise, measures will need to consider how to avoid or limit risk without direct involvement by the patient, such as cut-off switches or even the development of alternative comfort measures that do not pose a risk of burn injury. Industry and regulatory bodies should be aware of the risks associated with body contact heating devices in order to both improve safety features, including technology innovations, and inform health professionals and the public on risk mitigation. Finally, re-evaluation of safety information provided to the end-user must be evidence based. 

Authors: Rachel Kornhaber, PhD, RN^1,2; Denis Visentin, PhD¹; Sancia West, PhD, RN¹; Josef Haik, MD, MPH^1,2,3; and Michelle Cleary, PhD, RN¹

Affiliations: ¹College of Health and Medicine, University of Tasmania, Sydney, NSW, Australia; ²Department of Plastic and Reconstructive Surgery, National Burns Center, Sheba Medical Center, Tel Hashomer, Israel; and ³Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel 

Correspondence: Rachel Kornhaber, PhD, RN, BN, College of Health and Medicine, University of Tasmania, Sydney, NSW, Australia; rachel.kornhaber@utas.edu.au

Disclosure: This work was supported by Improving Mental and Critical Care Health (MaCCH)—UTas funding awarded under the UTAS Research Themes: Better Health Research Development Grant Scheme, supported by the Office of the Deputy Vice-Chancellor and FoH (C0025653).