Rising summertime temperatures lead to an increasing number of heat-related medical emergencies. Over 600 deaths per year occur in the United States due to extreme heat. These deaths are preventable and understanding the populations at greatest risk, in addition to the preventative strategies are key to decreasing the number of annual deaths. The very young and very old are among the most vulnerable populations, as are those with chronic diseases such as heart failure.
The body normally cools itself by radiating heat into the environment, by conduction (heat transfer by the skin directly coming into contact with another object), convection (heat transfer via air or liquid moving across the skin), and evaporation (sweating). When the environmental temperatures rise to >95°F (>35°C), the body begins to rely on evaporation for thermoregulation as the external temperatures are too high to allow for heat to be radiated to the environment. However, if the humidity is also very high, the mechanism of evaporation may also be ineffective, leaving the body without the ability to thermoregulate. Thermal autoregulatory functions begin to fail at core temperatures of >104°F (>40°C).
Heat related illnesses can range from mild, such as dependent edema, or a rash known as miliaria rubra (prickly heat) to life-threatening complications such as heat stroke. Patients with heat stroke typically demonstrate a core temperature of >104°F (>40°C) and altered mental status (confusion, irritability). About half of patient will demonstrate anhidrosis, or lack of sweat. Some may even progress to seizures due to neurologic injury. The diagnosis is determined based upon the history and clinical presentation.
Mortality directly correlates with the number of affected organ systems, the degree of temperature elevation, and the time to initiate cooling. It is imperative to seek medical management immediately if a patient demonstrates symptoms of heat stroke as the mortality is very high. Proper preventative measures in addition to proving early management for heat-related emergencies will help to reduce the number of annual mortalities.
Read More About Heat-Related Emergencies:
Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e: Chapter 210: Heat Emergencies
Harrison's Principles of Internal Medicine, 19e: 479e: Heat-Related Illnesses