Understanding Heat Illnesses: What to Watch For and How to React
As global temperatures rise, understanding the risks associated with extreme heat and how to stay safe becomes increasingly critical. This article aims to provide essential information on the topic. Stay safe, stay cool, and stay informed!
Hyperthermia occurs when the body takes in more heat than it can get rid of. This can be due to external factors like high environmental temperatures or internal factors such as intense physical activity. Hyperthermia involves more than just a fever. It includes overheating, hyperthermic reactions, heat stroke, and sunstroke. Unlike a fever, hyperthermia is characterized by the body's inability to regulate its temperature, leading to an uncontrolled rise in body temperature above normal limits.
The most common causes of hyperthermia are:
High environmental temperature with strong sunlight.
This is especially true when performing significant physical activity in conditions of high humidity. The body struggles to cool down effectively under these circumstances.
Conditions that hinder the body's heat dissipation mechanisms.
This includes disruptions in thermoregulation due to age-related changes, as well as wearing air- and moisture-resistant clothing. These factors can prevent the body from effectively releasing heat.
The effect of external factors, especially certain medications, and internal substances.
Some drugs can interfere with the body's ability to regulate temperature. Additionally, certain hormones (like thyroid hormones and pregnancy hormones) and a range of neurotransmitters (such as catecholamines) can influence the body's heat regulation processes.
Skipping over many pathophysiological nuances of developing negative consequences, the general process of developing a hyperthermic state can be described as follows. When the external temperature rises to 30–31°C (86-88°F), the arteries in the skin and subcutaneous tissues expand. This leads to increased blood flow and temperature in the surface tissues. The goal is to get rid of extra body heat through convection, conduction, and radiation. As the temperature rises, these heat dissipation mechanisms become less effective. At an external temperature of 32–33°C (90-91°F) and above, heat loss through convection and radiation almost stops. In this case, the main way the body cools down is by sweating and evaporation of moisture from the body surface and respiratory tract. This can cause serious problems in the body, including the loss of important minerals and vitamins, as well as an increase in blood viscosity.
In this article, we will only consider situations that may arise in connection with a heat wave.
Heat Stroke
Heat stroke is a life-threatening state requiring neurocritical care.
To start, it is important to clarify the difference between heat stroke and sunstroke. Sunstroke has several distinctions from heat stroke in both its cause and the mechanisms of bodily changes. Sunstroke is caused by direct exposure to the sun's energy, whereas heat stroke can develop from being in any environment with high temperatures (often industrial settings). In the context of sunstroke, the infrared part of solar radiation has the greatest impact, that is radiative heat. Unlike convective and conductive heat, radiative heat warms both surface and deep tissues of the body simultaneously, including the brain, where the neurons of the thermoregulation center are located. As a result, sunstroke develops rapidly and can lead to severe consequences. Thus, any suspicion of sunstroke is a clear indication for hospitalization via emergency medical services.
The uniqueness of this condition lies in the rapid failure of thermoregulation compensation mechanisms and the acute development of hyperthermia, with the body temperature quickly reaching life-threatening levels (often measured rectally in scientific literature) of 42–43°C (107.6-109.4°F), which tends to approach the external environment temperature.
The way sunstroke develops is a mix of how the body reacts to heat and the effects of being in the sun. The main thing is that the brain gets too hot, which damages the central nervous system and causes the symptoms we see.
Symptoms of sunstroke / heat stroke include:
High body temperature (103°F or higher)
Hot, red, dry, or damp skin
Rapid heart rate
Headache
Dizziness, fatigue
Nausea and vomiting
Confusion, agitation, stupor, seizures, losing consciousness, and even coma
The first thing you should do is call 911 or your local emergency medical service. Heat stroke is a serious medical emergency, and it needs to be treated by a doctor in a clinical setting. Also, if you think someone might have heat stroke (or another heat-related illness), move them to a cool place right away. Start cooling the person as quickly as you can and keep going until medical help arrives. You can use things like fans, water immersion, cold water bladders, ice packs on the neck, armpits, and groin, or cover the person with cool, damp sheets. Do not give the person anything to drink if they're not conscious to reduce the risk of vomiting and aspiration. If they're conscious, offer them chilled water, a sports drink with electrolytes, or another non-alcoholic, caffeine-free drink.
Heat Exhaustion
Heat exhaustion is the most common heat-related illness and can lead to heat stroke if not recognized and treated promptly. This condition is classified as moderate.
Symptoms of heat exhaustion include:
Thirst
Headache
Fatigue
Rapid heart rate
Weakness
Loss of coordination
Syncope (fainting)
Nausea
Vomiting
Diarrhea
Cold and clammy skin
Core temperature between 101 - 104°F (38.3 - 40°C),
So this is a condition that is very similar to heat stroke, although the mental status is intact.
If you are with someone who is suffering from heat exhaustion, get medical help immediately if they show signs of confusion, distress, or loss of consciousness. If their core temperature reaches 40°C (104°F) or higher, they need immediate cooling and urgent medical attention. In these scenarios, you should deal with heat exhaustion the same way you would deal with heat stroke.
Heat Syncope
Heat syncope is a moderate condition, also known as exercise-associated collapse, that typically occurs after a period of intense physical activity. It involves a sudden drop in blood pressure that leads to fainting or near fainting episodes (presyncope).
Symptoms of heat syncope include:
Lightheadedness
Orthostasis (feeling faint when standing up)
Dizziness
Transient loss of consciousness immediately following cessation of activity
If someone experiences heat syncope, they should be placed lying flat on their back with their legs elevated. They should be encouraged to drink fluids and be cooled if there is any concern for heat exhaustion or heat stroke.
Symptoms typically resolve in 15 to 20 minutes with these interventions.
Heat Cramps
Heat cramps are a mild heat-related condition characterized by painful muscle spasms that occur after prolonged or intense physical activity due to muscular overuse, dehydration, and electrolyte loss. The primary muscles affected by heat cramps are the abdominal muscles, quadriceps (thigh muscles), and gastrocnemius (calf muscles).
If someone is experiencing heat cramps, the following steps should be taken. First, stop any physical activity to prevent further muscle fatigue and move out of the heat to help reduce body temperature. Then, elevate the legs to improve blood circulation. Gently stretch and massage the affected muscles to relieve spasms. Drink fluids, especially those containing electrolytes, to rehydrate and restore electrolyte balance.
With these measures, heat cramps typically resolve quickly, allowing for a return to normal activities.
Heat Edema
Heat edema is a mild heat-related condition characterized by swelling in the extremities due to the pooling of fluid caused by the dilation of blood vessels. When exposed to heat, the blood vessels expand, causing body fluid to move into the hands or legs by gravity.
Symptoms of heat edema include:
Swelling in the extremities (hands, legs)
Occasional facial flushing
Management of heat edema involves simple measures. First, get out of the hot environment to help reduce vasodilation. Then, raising the legs can help reduce swelling by encouraging fluid return to the heart.
Note that diuretics are not indicated for treating heat edema, as this condition typically resolves on its own with these conservative measures.
Heat Rash (Miliaria Rubra)
Heat rash, also known as miliaria rubra, is a mild skin condition that occurs when blocked pores trap sweat in the skin. The sweat ducts are blocked by the outermost layer of the skin, resulting in trapped sweat. This results in the formation of red, inflamed bumps or pustules. There is a possibility of secondary infection if the condition is not properly managed. Areas of skin covered by clothing are most commonly affected.
Symptoms of heat rash include:
Eruption of red papules or pustules
Primarily affects the neck, upper extremities, trunk, and groin
Management of heat rash involves the following steps. Remove excess clothing to allow the skin to breathe and reduce sweat accumulation. Use fans or air conditioning to promote cooling and decrease sweating. Avoid using creams or lotions that may further block the sweat ducts.
Heat rash typically resolves quickly, providing relief from the discomfort and preventing secondary infections.
Want to stay safe in the heat? Download the Body Temperature App today and use our widget and monitor the heat index based on your location to safeguard yourself against heat-related conditions that could pose health risks.
Sources:
Heat-Related Illnesses (Heat Cramps, Heat Exhaustion, Heat Stroke) | Johns Hopkins Medicine
Hifumi, T., Kondo, Y., Shimizu, K., & Miyake, Y. (2018). Heat stroke. Journal of intensive care, 6, 30. https://doi.org/10.1186/s40560-018-0298-4
Gauer, R., & Meyers, B. K. (2019). Heat-Related Illnesses. American family physician, 99(8), 482–489.
Asplund, C. A., O'Connor, F. G., & Noakes, T. D. (2011). Exercise-associated collapse: an evidence-based review and primer for clinicians. British journal of sports medicine, 45(14), 1157–1162. https://doi.org/10.1136/bjsports-2011-090378
