Heat stroke is a serious medical condition that occurs when the body’s temperature regulation system fails, leading to a dangerously high body temperature, typically above 104°F (40°C). This condition requires immediate medical attention as it can cause significant damage to the brain, heart, kidneys, and muscles and can be fatal if not treated promptly.
What causes heat stroke?
The human body regulates its temperature by balancing heat production and heat loss. Normally, the hypothalamus, a part of the brain, acts as a thermostat. When the body becomes too hot, mechanisms such as sweating and increased blood flow to the skin help dissipate heat. However, these mechanisms can become overwhelmed in extreme heat conditions or during strenuous physical activity.
There are two types of heat stroke:
- Exertional heat stroke: This happens when physical activity in hot conditions generates more heat than the body can dissipate.
- Non-exertional (classic) heat stroke: This typically affects vulnerable populations, such as the elderly or those with chronic illnesses, during prolonged exposure to high environmental temperatures.
What is the difference between heat stroke and a fever?
Heat stroke and fever both involve elevated body temperatures, but they are fundamentally different processes. Fever is a controlled increase in body temperature due to an infection or inflammation regulated by the hypothalamus in response to pyrogens. Heat stroke, on the other hand, is an uncontrolled rise in body temperature due to external heat exposure and the failure of the body’s thermoregulatory mechanisms.
At what temperature is a person at risk for developing heat stroke?
It is generally considered dangerous for a person to be outside when the temperature exceeds 90°F (32°C), especially when combined with high humidity. At this temperature, the body’s ability to cool itself through sweating becomes less effective, increasing the risk of heat-related illnesses. However, the specific danger level can vary depending on individual health, activity level, and acclimatization to heat.
A person is at significant risk for developing heat stroke when the ambient temperature reaches or exceeds 104°F (40°C). Heat stroke can also occur at lower temperatures if humidity is high, physical activity is intense, or prolonged exposure without adequate hydration and cooling measures occurs. The key factor in heat stroke is the body’s inability to regulate its core temperature, leading to a rapid rise in internal temperature, which can be life-threatening if not promptly treated.
Relationship between temperature and humidity
Humidity is the amount of moisture in the air. High humidity levels can make it feel hotter than the actual air temperature. This is because humidity affects the body’s ability to cool itself through evaporation of sweat. When the air is humid, sweat evaporates more slowly, reducing the body’s ability to release heat. The perceived increase in temperature due to humidity is often referred to as the “heat index” or “apparent temperature.”
For example, if the air temperature is 90°F (32°C) with a relative humidity of 60%, the heat index may feel like 100°F (38°C). This increased perception of heat can significantly elevate the risk of heat-related illnesses.
Wet bulb temperature
The wet bulb temperature is the lowest temperature that can be reached by evaporating water into the air. It is a critical measure because it reflects the combined effects of temperature and humidity on the human body. When the wet bulb temperature approaches or exceeds the human body temperature (approximately 95°F or 35°C), the body can no longer effectively cool itself through sweating, leading to a high risk of heat stress and heat stroke.
Examples of wet bulb temperature at different humidity levels:
- Low humidity (20%): At an air temperature of 104°F (40°C) with 20% humidity, the wet bulb temperature would be around 77°F (25°C). The body can still effectively cool itself, although the heat is uncomfortable.
- Moderate humidity (50%): At an air temperature of 95°F (35°C) with 50% humidity, the wet bulb temperature would be approximately 86°F (30°C). The risk of heat-related illness increases as the body’s ability to cool itself diminishes.
- High humidity (90%): At an air temperature of 90°F (32°C) with 90% humidity, the wet bulb temperature would be close to 87°F (31°C). This significantly increases the risk of heat stroke as the body’s cooling mechanism is severely impaired.
- Extreme conditions (100%): At an air temperature of 95°F (35°C) with 100% humidity, the wet bulb temperature would be 95°F (35°C). Under these conditions, the body cannot cool itself at all, leading to a very high risk of heat stroke and other heat-related illnesses.
What are the symptoms of heat stroke?
The symptoms of heat stroke can vary but commonly include:
- High body temperature (above 104°F or 40°C)
- Altered mental state or behavior, such as confusion, agitation, or slurred speech
- Hot, dry skin or profuse sweating (depending on the type of heat stroke)
- Nausea and vomiting
- Rapid breathing and heart rate
- Headache
- Dizziness or fainting
Are the symptoms of heat stroke in adults and children the same?
While the core symptoms of heat stroke are similar in both adults and children, children may exhibit some differences:
- Infants and young children may appear more lethargic or irritable.
- They may have seizures, particularly in severe cases.
- Children may also experience additional symptoms such as thirst or crying without tears due to dehydration.
What are the consequences of prolonged heat stroke?
Prolonged heat stroke can lead to severe complications, including:
- Organ damage: The high temperatures can significantly damage the brain, heart, kidneys, and muscles, potentially resulting in long-term dysfunction.
- Rhabdomyolysis: Breakdown of muscle tissue can lead to kidney damage.
- Disseminated intravascular coagulation (DIC): A condition causing widespread blood clotting and bleeding.
- Heat-induced illness recurrence: Increased susceptibility to future heat-related illnesses.
- Death: Unless treated quickly, severe heat stroke can result in death.
What is the treatment for heat stroke?
Immediate treatment for heat stroke is crucial to prevent complications and improve outcomes. Key steps include:
- Rapid cooling: This can be achieved through methods such as ice water immersion, evaporative cooling (spraying the patient with water while fanning), or applying ice packs to the neck, groin, and armpits.
- Hydration: Administering intravenous fluids to replenish lost fluids and electrolytes.
- Monitoring and support: Continuous monitoring of vital signs, organ function, and supportive care for complications.
It is essential to seek emergency medical care immediately if heat stroke is suspected, as early intervention is critical.
References
- Bouchama, A., & Knochel, J. P. (2002). Heat stroke. New England Journal of Medicine, 346(25), 1978-1988.
- Epstein, Y., & Roberts, W. O. (2011). The pathophysiology of heat stroke: An integrative view of the final common pathway. Scandinavian Journal of Medicine & Science in Sports, 21(6), 742-748.
- Leon, L. R., & Helwig, B. G. (2010). Heat stroke: Role of the systemic inflammatory response. Journal of Applied Physiology, 109(6), 1980-1988.
- Casa, D. J., DeMartini, J. K., Bergeron, M. F., et al. (2015). National Athletic Trainers’ Association position statement: Exertional heat illnesses. Journal of Athletic Training, 50(9), 986-1000.
- Glazer, J. L. (2005). Management of heat stroke and heat exhaustion. American Family Physician, 71(11), 2133-2140.