Approximately six million workers are exposed to occupational heat stress in the United States every summer, with fatalities most commonly occurring in the fields of construction, agriculture, forestry, fishing, and manufacturing. Additionally, athletes and recreationists are frequently the victims of exertional heat-related illness, while children and the elderly are particularly vulnerable to environmental heat stress. (Wexler R. Evaluation and treatment of heat-related illnesses. Am Fam Phys. 2002;65(11):2307-14)
Treatment for most forms of heat-related illness is relatively straightforward: limit exertion, cool the victim, and replace fluids and electrolytes (particularly sodium). Individuals who develop heatstroke, however, are at significant risk of multi-organ system failure, residual neurologic damage, and death.
Since injury caused by heat exposure represents a continuum of physiologic changes, individuals who are suffering from heat-related illness do not always recognize their plight until they are in serious trouble.
Therefore, it is important to prevent heat-related illnesses whenever possible and to recognize the early signs of impairment when exposure to heat is unavoidable.
How to Prevent Heat-Related Illnesses
Common sense and planning are the best preventive measures:
- Children should not be left in vehicles in summertime, even when they are parked in shade. The sun moves, and a vehicle that is in shade when the driver walks away may be in direct sunshine a short time later.
- The elderly and the young should not be left unattended in unventilated homes without air conditioning.
- Athletic activities and other strenuous exertion should not be undertaken in the heat of the day; when such activity is necessary, fluid replacement must be a primary concern. In situations where individuals sweat profusely, or in very hot, dry conditions, electrolyte replacement should also be provided.
- A rounded teaspoon of table salt in five gallons of water, diluted punch, or Kool-Aid provides an adequate hydrating solution.
- Thirst is a poor indicator of hydration status during exertion; therefore, fluids (and electrolytes, if indicated) must be drunk periodically regardless of thirst. However, overhydration must be avoided; although plain water provides adequate hydration for most situations, ingestion of too much water can lead to dilution of plasma electrolytes.
- Cool water is absorbed more readily than warm water.
- Specialized hydrating solutions are rarely required, but flavored drinks may enhance the consumption of fluids. High-glucose solutions should not be used for hydration.
- Appropriate clothing should be worn: protection from the sun is important, but clothing must allow adequate airflow and evaporation.
- Acclimatization over a two-week period provides physiologic benefit for exertion in hot environments: Progressing from 15-20 minutes of exertion in a hot environment to 90 minutes of activity is recommended. Such preparation increases the amount of perspiration (i.e., cooling) for a given level of exertion, while decreasing the concentration of electrolytes in a given volume of sweat.
- Individuals who regularly exert in hot environments should weigh after work or exercise. Persons losing 2 to 3% of body weight should drink enough fluid to regain their starting weight prior to their next exposure. Anyone losing 4% or more of body weight should avoid heat exposure for at least one day until rehydration has occurred.
Heat-related illnesses can be incapacitating or even fatal. The vast majority of cases can be prevented with adequate hydration, electrolyte replacement, acclimatization, and avoidance of excessive exertion in hot environments.
(From The Merck Manual, 18th Edition. Heat Illness. 2006:2607)
Stephen Allen Christensen - Dr. Steve Christensen's writing has appeared in magazines, professional journals, poetry anthologies, and children's books since 1976.
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