In Australia, as in other parts of the world, common scenarios resulting in death from prolonged exposure to high ambient temperatures include physical illnesses in elderly individuals during heat waves, and leaving children in cars (1). The following cases are reported to demonstrate a range of alternative circumstances that may predispose to environmental hyperpyrexial deaths, with comments on difficulties in autopsy diagnosis.
MATERIALS AND METHODS
Autopsy reports at the Forensic Science Centre, Adelaide, South Australia, were reviewed for the 8 years from January 1991 to December 1998 for cases in which heat-related deaths had been attributed to exposure to high environmental temperatures. Amphetamine-related hyperpyrexial deaths, anesthetic deaths caused by malignant hyperpyrexia, deaths of elderly incapacitated individuals during heat waves, and deaths of children trapped/left in cars were excluded from the study. Files were examined, and details of the age and sex of the victims, the circumstances surrounding the fatal episodes, the maximum ambient temperature, the location of the deaths, the autopsy findings, and any ancillary reports on toxicology were documented.
A 21-year-old man was found dead under a tree at the base of a cliff. It appeared from inspection of the that he had slipped from the top of the cliff and fallen 20 meters into soft sand. He had subsequently removed some of his clothes at the point of impact, and marks in the sand indicated that he had dragged himself to beneath the nearest tree. There were no marks in the sand to indicate the presence or involvement of other individuals. The maximum temperature for the time when he was thought to have fallen was 38°C, with temperatures at the base of the cliff in the sun likely to have been much higher.
At autopsy, the body was markedly putrefactive, with minor abrasions to the legs and buttocks but no fractures, organ disruptions, vascular tears, or intracerebral haemorrhage. It was thought most likely that the deceased had been rendered unconscious by the fall, resulting in prolonged exposure to the sun and high environmental temperatures. On regaining consciousness, the victim was only able to crawl to the nearest shade tree, where death occurred.
A 23-year-old Asian tourist was found collapsed beside his motorcycle in central Australia (the “outback”). He had been dressed in shorts and a T shirt and had been riding in full sun for some time. He was dead on arrival at the local hospital. The ambient temperature at the time was 50°C. At autopsy, he had sunburn of the arms and legs with blistering. A contributing factor to death was prolonged sun exposure.
A 28-year-old European tourist visiting central Australia left her bogged four-wheel-drive vehicle and attempted to obtain assistance. Her decomposed body was subsequently found 30 km from the vehicle. The maximum ambient temperature was 46°C. At autopsy, the body was markedly putrefactive.
A 38-year-old man was found dead lying on a road in central Australia in full sun. The maximum temperature on the day of death was 39.8°C. Autopsy examination revealed micronodular cirrhosis of the liver and a blood alcohol level of 0.2%. Contributing factors to death included alcoholic liver disease and acute alcohol intoxication.
A 39-year-old male tourist wearing heavy leather clothing was found dead beside his motorcycle in central Australia. The ambient temperature at the time was 50°C. At autopsy, the body was markedly putrefactive. A contributing factor to death was the wearing of heavy clothing.
A 45-year-old tourist went for a walk from a camp in central Australia. His body was subsequently found among a series of large sand dunes. His medical history included epilepsy; however, serum carbamazepine levels were within the normal range. The maximum temperature around the time of death was 39°C.
A 46-year-old man was found dead in a ravine. The deceased was wearing multiple layers of female clothing, including a dress, underwear, and seven pairs of stockings/panty hose. The genitals were exposed. The victim’s medication included benztropine and trifluoperazine. The ambient temperature on the day of death reached 39°C and was higher in the sheltered revine where the body was found. At autopsy, the body was putrefactive, with scattered skin blisters. A body mass index (BMI) of 33.6 indicated marked obesity (2). Heat-related death had occurred during autoerotic activity. Exacerbating factors included excessive clothing and medication that predisposes to hyperpyrexia on hot days (i.e., benztropine and trifluoperazine). (Details of this case have been published previously) (3).
A 52-year-old man was found dead at home. His medical history was of manic depressive illness and moderate obesity (BMI 30.7). His prescribed medication included benztropine. The maximum temperature around the time of death was 42.1°C. A contributing factor to death was medication that predisposed to hyperpyrexia on hot days (i.e., benztropine).
A 77-year-old man was found dead sitting in a chair in his backyard. His medical history included alcoholic dementia. The body was wearing five layers of clothing and was mildly obese (BMI 27.8). The maximum temperature on the day of death was 40.8°C. At autopsy, there was moderate cerebral atrophy. Contributing factors to death included dementia and excessive clothing.
In all cases, death was due to exposure to high environmental temperatures, with or without exacerbating factors. No significant injuries or organic illnesses were present, other than those specifically mentioned. Given the time taken to find the bodies, or to arrange for an examination by a pathologist, rectal temperatures were not taken. Details of the cases are summarized in Table 1.
Heat stroke refers to a situation when individuals exposed to high environmental temperatures experience hyperthermia and neurologic dysfunction, manifested by disorientation, lethargy, delirium, and coma (4,5). Common situations that predispose to hyperthermia include leaving infants and children in hot cars, strenuous exercise in hot weather by young individuals, and exposure of elderly ill individuals to heat wave conditions (6). Underlying conditions increasing the risk of heat stroke include cardiovascular, cerebrovascular, and respiratory disease, and alcoholism (6,7). Elderly individuals with reduced mobility who live alone in top-floor apartments without access to air conditioning are at most risk during prolonged periods of hot weather (8,9). Several medications may also predipose to hyperpyrexia by interfering with the body’s heat control mechanisms. They include drugs with anticholinergic effects such as tricyclic antidepressants, antihistamines, and some antiparkinsonian medications, and neuroleptic drugs such as certain of the major tranquilizers (10).
The autopsy diagnosis of heat-related death is often difficult because there are no pathognomonic features of hyperthermia, and it is often too late for meaningful rectal temperature measurement. Petechial or larger hemorrhages may be found in the skin, with slippage, in addition to pleural petechiae and pulmonary and cerebral edema (11). If there has been a period of survival, there may also be evidence of rhabdomyolysis, acute pancreatitis, cerebral neuronal degeneration, centrilobular necrosis of the liver, and acute tubular necrosis of the kidneys (12). Dehydration may be confirmed by vitreous humor electrolyte analysis (13), although prolonged postmortem intervals and putrefaction will complicate this assessment.
Criteria have been proposed for the diagnosis of heat-related death. They include a body temperature of 40.6°C (105°F) or higher, a high environmental temperature at the death scene (>37.8°C [100°F]), body decomposition, and a history of the person being alive at the time of the high environmental temperature (14). Unfortunately, as it is not always possible to fulfil all these criteria (15,16), it has been suggested that the cause of death should be certified as hyperthermia or heat stroke only if the body temperature at the time of collapse was 40.6°C (105°F) or greater (unless there have been attempts to cool the body, a history of mental status change, or raised muscle and liver enzymes) (11). Heat-related death is the term recommended by the National Association of Medical Examiners when exposure to high ambient temperatures has either caused death or significantly contributed to it but the body temperature at the time of collapse or death cannot be determined (11).
Situations predisposing to heat-related deaths may show similarities between countries. For example, the majority of deaths reported from a heat wave in Philadelphia occurred in elderly individuals who lived alone without air conditioning in upstairs rooms. Closed windows and underlying illnesses were exacerbating factors (16). Similar conditions have also resulted in significant numbers of deaths among the elderly and infirm in South Australia, particularly during February. High humidity may result in deaths at lower temperatures than in areas with drier heat.
This study has, however, demonstrated a variety of less common exacerbating factors in a series of heat-related deaths. Lack of familiarity with the harshness of central Australian conditions contributed to the deaths of four tourists (cases 2, 3, 5, and 6), one of whom may have become disoriented near a campsite by the relatively monotonous appearance of desert sand dunes, thus preventing a safe return (case 6). Further disorientation and lethargy produced by hyperthermia in this case would have worsened his situation. Given the therapeutic levels of carbamazepine detected post mortem, it is uncertain whether epilepsy contributed to the terminal episode. A second tourist (case 3) left shelter, food, and water and attempted to walk a considerable distance in the daytime heat of the desert before succumbing to heat exhaustion. Two further tourists (cases 2 and 5) collapsed and died while riding motorcycles through the outback. One of the motorcyclists had been wearing heavy leather clothing.
Excessive clothing also played a role in two other deaths. In one case (case 7), the clothing included seven pairs of stockings/pantyhose used as part of an autoerotic ritual (3). Medication side effects and obesity were also contributing factors to death. In the second case (case 9), an elderly demented man sat out in the sun on a day with temperatures in excess of 40°C, wearing five layers of clothes.
Obesity is another factor that predisposes to hyperthermia, because the increase in mass to surface area ratio reduces body heat loss (16). Three of the cases demonstrated mild to severe obesity (cases 7, 8, and 9).
Incapacitation may result in exposure of the victim to direct sun and high temperatures for prolonged periods. This occurred in case 1, where a 21-year-old man had lost consciousness after a fall from a cliff. Removal of clothes before crawling toward the closest area of shade would be in keeping with hyperthermia. In case 4, an intoxicated man was left by his companions on a road in direct sunlight in central Australia, resulting in his demise. Underlying organic disease, including alcoholic liver disease, epilepsy, and dementia, was present in three cases. The diagnoses of heat-related deaths were made in all these cases, despite the relatively nonspecific autopsy findings, in the light of the histories and ambient temperatures to which the deceased individuals had been exposed.
In conclusion, these cases demonstrate a series of unusual heat-related deaths in which a variety of risk factors were subsequently identified. These included lack of familiarity with Australian environmental conditions, excessive clothing, acute alcohol intoxication, obesity, certain types of medication, and underlying organic disease.
The authors thank the South Australian State Coroner, Mr. Wayne Chivell, for permission to publish details of these cases.
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