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Abstract
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Epidemiology: Heat-related illnesses such as heat cramps, heat exhaustion and heat stroke occur when the environmental temperature and humidity exceed the body's natural ability to disperse heat. Heat-related deaths are usually preventable, but occur annually. The Centers for Disease Control and Prevention (CDC) estimated heat-related deaths for the years 1999-2003 using death certificates and including deaths where exposure to excessive natural heat was listed as the underlying cause and/or hyperthermia was listed as a contributing factor. The estimated annual mean number of deaths nationwide was 688. In Mississippi, excessive heat was listed as an underlying or contributing factor in 11 deaths in 2007 and 12 in both 2006 and 2005. Heat as a contributing or underlying cause of death is expected to be underreported, as overheating can exacerbate many existing medical conditions and may be difficult to identify without witnessing the onset of symptoms and/or the death, therefore these numbers are likely an underestimate. In Mississippi, as is true nationally, males outnumbered females, accounting for about 70% of deaths each year. Fifty-four percent were aged 65 years or older, and 15% were aged 3 years or younger.
BACKGROUND: The human body dissipates heat through two main mechanisms: 1) convection of heat from the body's core to the skin's surface through circulation, and 2) the cooling effect of evaporation of sweat into the ambient air. Sweating and resulting evaporation is the most effective means of getting rid of excess body heat. When ambient Fahrenheit temperatures reach 90° or higher, and relative humidity exceeds 90%, sweat can no longer evaporate efficiently to cool the body, so the most effective means of controlling body temperature becomes severely compromised. Persons who are less able to dissipate heat are at especially high risk for heat-related illness. The very old and the very young are at increased risk, as are the obese, those with limited or no access to air-conditioning (and therefore the poor and the homeless) and those with heart disease and other chronic illnesses. Such people may be at particular risk if they rely on fans for cooling in closed, cramped rooms during hot weather, especially if they are unable to maintain replenishment of water lost in sweat. Fans lose cooling efficiency as ambient Fahrenheit temperatures rise into the high 90's and above. Certain medications including antihistamines, anticholinergics, α-adrenergics, pseudephedrine, β-blockers, calcium channel blockers, amphetamines, benzodiazepines, neuroleptics, tricyclic antidepressants, anticonvulsants, thyroid hormones and diuretics increase patients' risk of heat-related illness. Of particular concern this summer are the dramatic increases in fuel and energy costs which may translate to less access to cooler shelter for some people such as elderly citizens on a fixed income. Even among young, healthy, well-conditioned athletes, excessive heat can be a killer if proper precautions are ignored in scorching conditions. Individuals are less likely to have difficulties with strenuous activity under high heat and humidity conditions if given days to weeks to acclimatize. Prevention: In advising patients and their communities on prevention of heatstroke and death among various groups, health care professionals may wish to stress the following:
• Stay indoors, in an air-conditioned place if possible. If the home is not air-conditioned, spend time in the public library, shopping mall, or community designated heat shelter,
• Monitor those at high risk: Persons in the community should check on elderly and physically or mentally-impaired relatives, friends, and neighbors to ensure adequate water replenishment and access to cooler shelter during hot weather. Elderly persons, physically and mentally impaired people, and others without home air-conditioning should seek or be taken to air-conditioned shelters during periods of extreme heat and humidity,
• Young children, elderly or impaired persons, or pets should never be left unattended in closed automobiles. Even with windows cracked 1.5 inches, the temperature inside a car will increase, on average, 3.1°F per 5 minutes, with 80% of the total temperature rise occurring in the first 30 minutes.... KW: Hyperthermia in automobiles
Language: en |