Heat exhaustion is experienced as fatigue following exposure to high temperatures for a long period of time as the body’s loss of fluid and salts leads to decreased blood pressure and volume. Treatment is generally through the provision of fluids, removal of excess clothing and relocation to a cooler environment. Untreated, heat exhaustion can progress to heatstroke, a more serious condition. This occurs when the body temperature reaches dangerously high levels as a result of being unable to cool itself sufficiently or being overcome by external conditions (exertional heatstroke). Heatstroke can also result from the use of a range of illicit and prescribed drugs such as ecstasy and anticholinergics or in the chronically ill (classic nonexertional heatstroke). Both types of heatstroke are associated with a high morbidity and mortality, especially when therapy is delayed.
Heatstroke is defined as hyperthermia with a body temperature greater than 40.6 °C due to heat exposure with a lack of thermoregulation. Signs of heat stroke include dry skin, vertigo, confusion, headache, thirst, nausea, hyperventilation and muscle cramps. Heatstroke should be considered a medical emergency and treated immediately.
To help recognise the symptoms of heat related illness, download our educational poster.
The risk of heatstroke increases proportionately with rising ambient temperature and humidity.
- There is a widely held, erroneous view that heat stroke only rarely leads to permanent or debilitating effects. A review by the University of Chicago Medical Centre followed 58 subjects of near fatal heat stroke following the 1995 Chicago heat wave. It was found that nearly half (49%) of the patients died within a year and many others suffered loss of independent function.
- Widespread incidence of heatstroke is generally confined to the hotter regions of the globe, however from 1999 to 2010, a total of 7,415 deaths in the United States were associated with exposure to excessive natural heat.
- In the United States, heat waves claim more lives each year than all other weather-related exposures combined (hurricanes, tornadoes, floods, and earthquakes).
- In 1998, one of the worst heat waves to strike India in 50 years resulted in more than 2,600 deaths in 10 weeks. Unofficial reports described the number of deaths as almost double that figure.
- With the influence of global warming, it is predicted that the incidence of heat stroke cases and fatalities will also become more prevalent.
Treatment of heat stroke is simple: the underlying cause of the overheating must be removed and the body’s temperature reduced to normothermia as rapidly as possible. Generally, cool water immersion has been identified as the best treatment for heat stroke and, accordingly, advice is to follow this treatment approach wherever possible. However, where immersion is not possible, CAERvest® may be used effectively to cool the core body temperature to safe levels in almost any environment. Intervention by any means to keep temperatures lower than 41ºC is a generally well accepted recommendation.
The American College of Sports Medicine recommends that cooling should be initiated at the scene prior to transporting the patient to an emergency department for further evaluation and treatment.
The United States Department of Labour also has an educational resource on heatstroke which can be viewed here.