Treating Heat-Related Illness in the Elderly

During periods of cold weather, it seems that a concerted effort is made to ensure the safety of the elderly population in most communities; however, during periods of intense heat and humidity, focus is shifted to those who are younger and live much more active lifestyles. A heat-related death in a young person inevitably leads to a great deal of publicity, especially if the victim is a well-known athlete. Yet, as statistics show, the elderly are much more at risk than any other age group.

According to the CDC, 1,700 people die in the U.S. each year as a result of heat stroke during hot, humid weather.1 Since about 80% of these deaths occur in people over age 50, it is evident that the elderly are more prone to heat-related illnesses than any other segment of the population.

A major problem in any discussion of this topic is the almost universal confusion over the names and symptoms of various heat-related illnesses. These maladies can be classified as either major or minor illnesses.

Heat cramps, probably the foremost minor illness of this category, have a high incidence in athletes. Heat cramps present as involuntary muscle spasms that usually occur after physical activity has stopped. Treatment of cramps consists of cooling the affected region of the body, rest and, most important, fluid replacement. Heat cramps are rarely found in the elderly due to their more sedentary lifestyle.

A much more common manifestation in older people during periods of extreme heat is heat edema. Most EMS personnel have had an older patient with swollen feet and ankles, which is the primary symptom of this illness. Treatment consists of leg elevation, which usually takes care of the problem. However, field medics must be careful in diagnosing heat edema; swollen feet and ankles can also be symptomatic of much more serious problems like cardiac and lymphatic diseases.

Another minor heat-related illness that can affect all ages of the population is a skin condition called prickly heat. This condition can occur when dead skin blocks sweat pores, which, in turn, can lead to development of a secondary staph infection. Prickly heat is easily prevented by wearing loose clothing during humid weather. Treatment consists of applying antibiotic lotions or, in some cases, using systemic antibiotics.

Older patients being treated with beta-blocker therapy must be especially careful of a condition called heat syncope. This condition occurs when the arteries become dilated without compensation for an increased blood flow, resulting in loss of consciousness or feeling faint. This disease can also be present in persons who are not acclimated to hot, humid weather. Treatment for heat syncope consists of leg elevation and/or removal from the extreme weather conditions. Again, however, EMS providers must be cautious, because the symptoms of heat syncope may be symptoms of more severe problems.

Heat exhaustion, which is caused by the inordinate loss of sodium and water, is also classified as a minor condition; however, heat exhaustion is difficult to diagnose because it presents a wide array of symptoms, including weakness, nausea, syncope and dizziness. According to one source, heat exhaustion is a diagnosis of exclusion once heat stroke has been ruled out.2 Treatment consists primarily of gradual cooling and rehydration. Most lay persons understandably confuse heat exhaustion with heat stroke, which means that EMS providers must be careful when compiling patients’ past medical histories.

Heat stroke is classified as a major heat-related illness due to its high mortality rate. Heat stroke is characterized by an elevated body temperature and central nervous system dysfunction.3 Body temperatures can range between 37.8º–41.1ºC (100º–106ºF), accompanied by delirium and/or seizures. In addition, these conditions can lead to a variety of clinical signs, including renal failure, alkalosis and coma. Immediate cooling, especially evaporative cooling involving misting water in front of circulatory fans, is the treatment of choice. Airway management is of utmost concern because of the threat of aspiration and seizure.

Why Are the Elderly More Susceptible?

Why are the elderly especially predisposed to heat-related illnesses? A review of the body’s temperature regulation system is required to answer that question. Body temperature control is a complex process involving interactions between the autonomic nervous system and the endocrine feedback system. Clusters of neurons located in the hypothalamus receive input from temperature receptors located both on the skin and along the great vessels, the abdominal viscera and the spinal cord. In addition, the blood perfusing the hypothalamic region also sends body temperature messages.

Based on the information received from these sources, the regulation system sends signals to nerves that stimulate either vasoconstriction or vasodilation of peripheral blood vessels. The type of signal will depend on whether the body needs to conserve or give up heat. Signals are also sent to the cortex, which motivates the person to seek a change in his or her environment.

As most EMS personnel know, the body produces heat through cellular metabolism—the process of converting foods into adenosine triphosphate. In fact, 35% of the energy released from food is released as heat. The liver,

brain and skeletal muscles produce most of the body’s heat.

The body responds to overheating by employing four mechanisms: vasodilation, sweating, decreased production of heat and behavioral modification.4 In turn, vasodilation has a profound effect on the body because it leads to increased cardiac output, increased heart rate, increased respiratory rate and an increase in oxygen consumption.

All of these systemic increases have a significant impact on the elderly. As the body ages, its thermoregulation system becomes impaired to such an extent that even moderate temperature increases can make bodily adjustments difficult. Also, certain conditions commonly found in the elderly, such as cardiovascular and atherosclerotic diseases and diabetes, affect the ability of the cardiovascular system to dilate. Aging decreases the number of sweat glands, and the sweat glands that remain lose their efficiency.5 Therefore, a higher core temperature is needed before the sweat response is activated.

Additionally, the elderly have a decreased thirst perception, along with a decrease in the mobility needed for rehydration. Thus, oral fluid intake decreases. Finally, certain medications quite common in the older population, such as beta-blockers and tranquilizers, actually increase the risk for heat-related illnesses.

Prevention

The key to decreasing heat-related illnesses among the elderly is dissemination of knowledge by healthcare workers. Family members must understand the risks the elderly endure during hot weather. Physicians must discuss the side effects of certain medications with both patients and their families. All people, not just the elderly, should know what precautions to take during hot, humid weather. These precautions must include knowledge of hydration procedures, use of proper clothing and allowable limits of exertion.

Community programs should be implemented that focus on the elderly during extreme weather conditions, both in the summer and winter. These programs should include access to air conditioning and heating, home nursing visits, meal services and home safety checks.

Finally, EMS providers must be aware of the symptoms of heat-related illnesses on every call to an older patient. We must pay particular attention to what the patient is telling us, to signs and symptoms such as skin color and temperature, and to foot and ankle edema. In addition, we must look beyond the patient to observe the conditions of the home where we find the patient. Noting the temperature of the house, the kind of clothing worn by the patient and the availability of hydrating agents like water will aid immeasurably in making correct patient assessments. Instituting these measures will go a long way toward reducing the number of deaths that occur as a result of heat-related illnesses among the elderly.

References

1. Centers for Disease Control and Prevention. Heat-related illness and deaths: United States 1994–1995. MMWR 44(25):465–468, 1995.
2. Ballester J, Harchelroad F. Hypothermia: How to recognize and treat heat-related illnesses. Geriatrics July 1999.
3. Simon H. Hyperthermia and heat stroke. Hospital Practitioner 29(8): 65–80, 1994.
4. Harchelroad F. Acute thermoregulatory disorders. Clinical Geriatric Medicine 9(3):621–37, 1993.
5. Low P. Sudomotor function and dysfunction. Diseases of the Nervous System, 2nd Ed, pp. 479–89. Philadelphia: W.B. Saunders, 1992.