Ben D.F., Chen Xu L., Xia Z.F., Huan J.N., Chen X.L., Huang J.R, Ge S.D.

Department of Burns, First Affiliated Hospital of Second Military Medical University, Changhai Hospital, Shanghai, People’s Republic of China

SUMMARY. The aim of this study was to evaluate the epidemiology of burns due to the use of hot-water bottles. We performed a 10-yr survey of all hot-water bottle burns treated in our burns centre. Two hundred and ninety-four patients were identified with hot-water bottle burns between 1 January 1991 and 31 December 2001. Records were kept of age, sex, size, depth and site of burn, time period before first reporting of burn, incidence by month, type and rate of operations, time before hospitalization, length of hospital stay, morbidity, mortality, types of bacteria in wounds, and aetiology. The majority of the patients were female, and the mean age was 21.4 yr. The mean time period before reporting the burn injury was 8 h, with a range of 0.5-78 h. Patients presented late to our unit in 41% of cases, with an average delay of 6 days. Patients were hospitalized on average within the first 13.5 days, with a range of 2-113 days. Usually the burn surface area was less than 0.1% off the total body surface area and consisted mainly of full-thickness burns. The body area most commonly burned was the leg. One hundred and eighty-six patients (63.2%) were injured in the months of November, December, and January. Two hundred and eighty-two patients (95.9%) required surgery. Eschar excision and skin-grafting (75.8% of cases) and the creation of local flaps (24.2%) were performed within the first 6 days in full-thickness burns. The mean period of hospital stay in hospital was 13.4 days, with a range of 1-47 days. Two patients died in this series, giving a mortality rate of 0.68%. Fifty-six patients presented 63 registered burn wound infections. The micro-organisms most commonly observed in the burn wounds were Staphylococcus aureus and Pseudomonas aeruginosa.

Introduction

In the River Yangtze drainage basin in China, it is a very popular habit to use a hot-water bottle to keep oneself warm when sleeping or sitting on cold days because there is no central heating, which is usually provided only in northern areas. Nearly every family has two to four hot-water bottles owing to their cheapness and convenience. Before going to bed, people prepare several thermos bottles of hot water. After being filled with the hot water and placed between the bedclothes, the hot-water bottle will keep warm for four to six hours. Families thus do not need to use heaters, which are expensive and noisy and make the air dry. On falling asleep, people may be burned as a result of prolonged contact with the hot-water bottle. Recently there has been an increasing frequency of burns caused by the use of hot-water bottles to relieve pain caused by certain diseases such as angina pectoris and cholecystitis.

There are no previous reports on hot-water bottle burns in the literature, apart from one case in which buttock and perineum burns were caused by use of a hot-water bottle to relieve pain due to an anal fissure.

The aim of this study is to review the background to hot-water-bottle-related burns, describe their characteristics, and provide data for the improvement of prevention and management of this type of burn.

Patients and methods

With the aid of our burns unit databank, a retrospective study was made of the epidemiology of patients suffering from burns caused by hot-water bottles who were hospitalized in the Changhai Hospital burns centre between 1 January 1991 and 31 December 2001. Annually, between 17 and 34 burns were hot-water-bottle-related, with a total number of 294 hot-water bottle burns in the time period considered. The clinical notes of 294 patients were available for review, and only these patients were included in the study. The medical notes were retrieved and a retrospective review was undertaken. Data were collected regarding age, sex, size, depth, and site of burn, time period before first reporting of burn, incidence by month, type and rate of operations, time before hospitalization, length of hospital stay, morbidity, mortality, types of bacteria in wounds, and causes of burns. All data were entered into a computer database and analysed.

Results

Age and sex. The age distribution of the 294 patients is shown in Table I. The median age was 21.4 yr (range, 1-89 yr). Of the 294 patients, 106 (36%) were aged between 16 and 25 yr, and 243 (82.6%) were female. Female predominance occurred in all age groups between 6 and 75 yr. Overall, 213 patients (72.4%) were females aged between 6 and 55 yr (Table I).

Percentage of total burn surface area and full-thickness burn. The size of the burns in the majority of patients was very small - most commonly they were contact burns covering only a few square centimetres. The total body surface area (TBSA) burned varied between 6 sq cm and a maximum of 15%. Of the 294 patients, 245 (83.3%) had burns in less than 0.1% TBSA. The mean and median TBSA burned among patients burned by contact with the hot-water bottle were 0.1 and 0.2%, compared with 6.9 and 8.4% among patients scalded by hot-water leakage from the bottle, respectively. All but four patients burned by contact with the bottle had full-thickness burns, and all but six patients scalded by hot water had partial-thickness burns.

Incidence by month. The months with the highest frequencies of incidence were, in decreasing order of frequency, January, December, and February (228 patients, i.e. 77.6%). Next came November and March (42 patients, i.e. 14.3%). No cases of hot-water-bottle burning were recorded in May, June, or August (Fig. 1).

Sites of burn injury. The anatomical regions most commonly affected were the leg (178 patients), followed by the foot (53 patients), the lower limb except the leg (42 patients), and the buttocks and perineum (32 patients).

Time period before being reported. Unlike other burns, most hot-water-bottle burns were not reported at once. Of the 234 patients with contact burns, 187 (79.9%) discovered the accident only a few hours later or the following morning. A family member of one old woman noticed her burns only after nine days.

Causes of burns. The causes of the burns were contact (79.6%), scalding (18.4%), and hot steam (2.0%). Contact burns mostly occurred owing to prolonged contact with a hot-water bottle or electric hot pads during sleep. Hot-water scalds were mostly due to the bottle breaking or leaking. Hot-steam burns were mostly due to steam escaping accidentally from the bottle aperture when water was poured in too quickly.

Time before hospitalization. Only seventeen patients presented to the unit on the day of injury - the majority were first treated in out-patient clinics for several days. Two hundred and eleven patients were not admitted to our ward during the first week after injury, the average delay being 14.9 days (range, 1-57 days).

Number and type of operation. Two hundred and fifty-seven patients (87.4%) needed surgical treatment and, of these, 215 were operated on once, 24 twice, and 18 more than twice. The operations consisted of debridement and skin-grafting, or local flap-transfer.

Length of hospital stay. The mean time period spent in hospital was 18.4 days (range, 1-56 days). More than two-thirds of the patients stayed between two and four weeks.

Morbidity and mortality. The 294 patients burned by use of a hot-water bottle, among the 5342 patients admitted to our burn ward in the period of study, constituted 5.5% of all cases referred to the unit during the period. Two patients died as a result of their hot-water-bottle-related injuries (mortality rate, 0.68%).

Micro-organisms found in the wounds. Fifty-six patients presented 63 registered burn wound infections. Fifty patients had one infection, five had two infections, and one patient had three. The micro-organism that most commonly caused wound infection was Staphylococcus aureus, followed by Pseudomonas aeruginosa, Escherichia coli, Bacillus proteus, Lactobacillus, Klebsiella, Enterococcus, and Streptococcus.

Discussion and conclusion

In 1966, the first report of “A case of negligence. Burns caused by a hot-water bottle” was presented in Tidskr Sver Sjukskot. It is a pity no authors are listed and no abstract is available regarding this first report. Thirteen years later, Herman reported on the hot-water bottle in disease of the prostate.1 In 1999, Lapid et al.2 described a case of burns in the buttock and perineum caused by use of a hot-water bottle to relieve pain caused by an anal fissure - this was the first complete report. Burn injuries caused by hot-water bottles have rarely been reported in the more developed countries because nowadays they are little used. But in China hot-water bottles are to be found in almost every department store and supermarket and even in street displays. Hot-water bottles sell for only half to one dollar in price, and even an electric hot pad costs only two to four dollars. It is estimated that at least 60,000 hot-water bottles, some of poor quality, are sold every year in the Shanghai area alone, where the population is over seventeen million. Hot-water bottle burns occur most frequently in winter when the weather is very cold. In our study, the 294 cases of burns caused by hot-water bottles over a period of ten years represented the considerable percentage of 5.5% of all the 5342 patients hospitalized in our ward.

The distribution of the age of these burn patients shows that young people in the 16 to 25 yr age group were at greatest risk. The highest incidence of hospitalization was observed respectively in female and male patients in the age ranges of 16 to 25 yr and 6 to 15 yr. This can be explained by the fact most people of this age are students or single persons, their sleeping quarters are cold and without heating, and they usually sleep alone. If the incidence of hospitalization is related to gender and age range, it is clear that women were affected by such burns more frequently than men in the 6-75 yr age period (Table I). The difference in the incidence of hospitalization in male and female burn patients was greatest in the age ranges of 16-25 yr, 26-35 yr, and 36-45 yr. This may be because females are more afraid of cold than males, especially in the age range of 16-25 yr, so that this kind of burn occurs most frequently in this particular age range.

Most of the burns were small in size, with an average BSA of 0.1%, owing to the fact that the patients’ bodies usually had reduced contact with the hot-water bottle. However, 241 patients (98.4%) of the patients’ contact burns were full-thickness burns, and all but a few required surgical treatment. This indicates that the burn injuries caused by the hot-water bottle were mainly deep burns, clearly the result of prolonged low-temperature contact. Such burns are caused by the protracted duration of contact with the hot bottle, usually several hours - even more than ten hours or all night, although the bottle temperature was not in fact very high. It was clearly impossible to achieve immediate cooling of the burn by means of water, which is important in order to preventing superficial burns from developing into deep burns.

The higher incidence of burns in the winter months (January, December, and February) can be attributed to the lower temperatures in that season. Climatic factors also explain why such burns did not occur in May, June, or August. In this study, the leg and foot were the areas most commonly injured by the hot-water bottle. This may also be related to the fact that the leg and foot are poor areas for circulation of the blood. The distal areas of the lower extremity usually become cool first - there is a Chinese expression, “cold in the feet”, and many people customarily place the hot bottle between their feet.

Among the 234 patients with contact burns, 187 (79.9%) discovered the accident a few hours later or the following morning. This may be explained as follows: people’s sensation of pain declines during sleep, especially in distal areas; they do not notice the direct contact immediately as the water temperature is not elevated; and it is not easy to locate such small burns. Most hot-water-bottle contact burns, especially low-temperature ones, appear to be nearly normal skin or just a blister, and they are often considered to be more superficial than they really are.

Except for a few patients, the total burn area was relatively large in patients scalded by hot water. Most of the scalds were virtually all superficial or deep-partial burns, and this may be explained by the fact that the patients realized the injury immediately and skin cooling was provided in time.

If we consider the causes of hot-water bottle burns, we find that most of the contact accidents were caused by the excessively high temperature of the water placed in the bottle, the lack of any protective wrapping material, the excessive amount of hot water in the bottle, and the close contact of the legs and feet with the bottle during sleep, with little interspace. Scald accidents were caused by breakage of the hot-water bottle or leakage. Breakage was due to the poor quality of bottles produced by private factories, while leakage usually occurred when the bottle was stoppered without due care. Carelessness was also the cause of scalding in six patients burned by the overflow when they filled the bottle too quickly.

After analysing the causes of the hot-water bottle burns considered in our study, we believe that certain measures could significantly reduce the incidence of such burn injuries. First, the temperature of the water should not exceed 95 °C and the volume of water should not be excessive. The hot water should be poured slowly into the bottle a few minutes after boiling. The rubber washer of the bottle should be carefully examined in order to ensure that it is intact and correctly positioned before the stopper is screwed in. A protective covering, which may consist of a towel, should be wrapped around the bottle before it is placed in the bedding. Special attention should be paid when dealing with the elderly, children, diabetics, paralytics, and stroke patients, since their nervous senses may be inadequate. It should be emphasized that it is advisable to buy hot-water bottles in large department stores or supermarkets rather than in small shops and street displays and to discard bottles with ageing rubber and in any case after two years of use. It is very important to pay close attention to the quality of the bottle, especially from private or family businesses, and to ban poor-quality bottles from the market.

Despite their reduced size, the cost of surgical treatment in our unit of a case of hot-water bottle burns has been estimated to be 430 dollars, and most patients preferred conservative treatment in our out-patient clinic, which was cheaper. This is the main reason why the average delay in treatment was 14.9 days. Many patients thought that their wound was small and could heal in a few weeks without surgery. Also, many patients were

students busy at school who could not stay weeks in hospital.

Annually, some 40 to 60 patients burned by a hot-water bottle were referred to our unit. Almost 50% of all the patients were admitted to our ward, with 44% requiring surgery. In other words, 87.4% of the patients in the ward needed surgery. The high rate of surgery can be attributed to the fact that over 79% of the patients sustained burns caused by prolonged contact and that most of the wounds were full-thickness burns - nearly all the patients had been treated for some weeks without healing, even though the size of the burns was limited. In the majority of cases, escharotomy and skin grafting were required, which may reflect the high incidence of small, deep burns. The leg is worse off than other body regions as regards tissue blood, especially in the lower one-third of the leg where these burns usually occur, so that few patients needed local flap grafting. Most of the patients were subjected to surgery, and the average period of hospitalization was 18.4 days.

Two patients, both elderly men, died as a result of their injuries, giving a mortality rate of 0.68%. The cause of death was the original diseases, which were pneumonia, coronary heart disease, and diabetes mellitus. Both the patients were treated conservatively rather than surgically because of their advanced age and their concurrent diseases. They died after five weeks in hospital.

RESUME. Dans cette étude les Auteurs se sont proposés d’évaluer l’épidémiologie des brûlures causées par l’emploi de le bouillotte. Ils ont considéré tous les cas de ce type de lésion qui se sont vérifiés pendant une période de 10 ans et qui ont été traités dans leur centre des brûlures. Globalement, 294 patients brûlés par la bouillotte ont été identifiés dans la période 1 janvier 1991-31 décembre 2001. Les données enregistrées concernaient l’âge des patients, le sexe, les dimensions de la brûlure, la profondité et le site, le délai avant les premiers secours, l’incidence par mois, type et numéro d’interventions chirurgicales, le délai avant l’hospitalisation, la durée de l’hospitalisation, la morbidité, la mortalité, les types de bactéries observées dans les lésions, et l’étiologie. La majorité des patients était de sexe féminin, avec un âge moyen de 21,4 ans. La période moyenne avant les premiers secours était 8 h (variation, 0,5-78 h). Les patients se sont présentés avec un certain délai à notre unité des brûlures dans 41% des cas (délai moyen, 6 jours). Les patients ont été hospitalisés moyennement entre les premiers 13,5 jours (variation, 2-113 jours). Normalement la surface brûlée recouvrait moins de 0,1% de la surface corporelle totale et consistait principalement en brûlures à toute épaisseur. L’aire corporelle la plus atteinte était le membre inférieur. Cent quatre-vingt-six patients (63,2%) ont subi leurs brûlures dans les mois de novembre, décembre et janvier. Deux cents quatre-vingt-deux patients (95,9%) ont nécessité une intervention chirurgicale. L’excision de l’escarre et la greffe de la peau (75,8% des cas) et la création de lambeaux locaux (24,2%) ont été effectuées entre les premiers 6 jours dans les brûlures à toute épaisseur. La période moyenne de l’hospitalisation était 13,4 jours (variation, 1-47 jours). Deux décès de sont vérifiés dans cette série (taux de mortalité, 0,68%). Cinquante-six patients ont présenté 63 infections enregistrées des brûlures, et les micro-organismes les plus communs observés dans les brûlures étaient Staphylococcus aureus et Pseudomonas aeruginosa.

Bibliography

1. Hennan J.R: Hot-water bottle for diseased prostate. Urology, 14: 545, 1979.
2. Lapid O., Walfisch S.: Perianal and gluteal burns as a complication of hot-water-bottle treatment for anal fissure. Burns, 25: 559-60, 1999.