Too Hot to Handle: A Primer on Heat-Related Illness


Extreme heat is the natural enemy of any desert dweller. In Utah, as we make the transition into spring and summer, rising temperatures can quickly cause heat-related illnesses. As Utah sees greater temperature extremes due to climate change, high temperatures earlier in the year are not unusual. Adding physical exertion to the mix can be the perfect recipe for heat-related illnesses including dehydration, heat exhaustion, heat injury and heatstroke.

Elevated temperature is a measure of the increased energy of molecules. When the outside temperature increases, there is a transfer of this excess energy from air and objects to the body, which has lower energy molecules that can absorb energy. Environmental conditions like humidity can also increase heat transfer because water more effectively transfers heat than air. Interestingly, sweat — which is mostly water — similarly helps dissipate heat and uses up additional energy through evaporation. Sweat, therefore, serves a significant purpose in aiding bodily cooling. The body also dilates blood vessels in the skin to bring warm blood to where the skin can lose heat.

Many additional factors play into the personal risk of having a heat-related illness including age, medications taken, medical conditions, clothing, hydration, acclimatization to heat and exercise tolerance. While having minimal risks with these factors is protective, no one is immune to heat-related illness. If the human body does not maintain a stable body temperature within 96 and 104 degrees, its components begin to fail and breakdown. At temperatures higher than 104 degrees, system-wide inflammation and toxin release that trigger diffuse organ injuries can occur.

The first signs of heat illness are body temperature elevation, fatigue, headache, nausea and/or vomiting, increased heart rate and decreased blood pressure. This is called heat exhaustion. The human body can lose up to three liters of water an hour via sweating to help lower an elevated temperature, and without adequate replacement of this volume, the body shows signs of dehydration by speeding up the heartbeat and dilating systemic blood vessels to adequately circulate blood and oxygen. Dehydration is also a loss of the electrolytes that travel with water, like potassium and sodium, which stresses body cells and may cause discomfort and gastrointestinal distress.

When heat exhaustion starts to cause more serious organ dysfunction, heat injury occurs. The causes of such dysfunctions are often multifactorial and hard to pinpoint. The combination of a lack of blood circulation to deeper organs as blood is diverted to the skin, toxin circulation from distressed cells and inflammatory responses from cells caused by the heat can be attributed to heat injury. Heat injury is not initially differentiable from heat exhaustion in the early stages of illness, but it can become apparent over time and with further testing.

If heat exhaustion or heat injury begins to cause changes in mental status such as confusion, disorientation, seizure or coma — all of which indicate toxicity to the brain — the diagnosis becomes grave: heatstroke. In heatstroke, body temperature can rise above 104 degrees. At this point, most people have exhausted their body’s abilities to cool itself through sweating and blood vessel dilation, and they can stop sweating altogether. Additionally, more toxins and inflammation cause permanent organ damage. At its most severe, heatstroke can also cause coagulation of blood, and when all the blood clotting factors are used up, profuse bleeding may occur. All of these conditions — if not immediately acted upon — can quickly lead to death.

Intervention for heat-related illness depends on its severity. If someone is suffering from heat exhaustion, rapidly cooling them down by whatever means possible is the first step. Encouraging rest, removing clothing, cooling skin and relocating the patient to shade are all helpful measures. Administering fluids with electrolytes is also important to correct dehydration. These measures will help prevent the progression to heatstroke. If someone is experiencing heatstroke, immediate cooling becomes necessary, and the person should be taken to medical support as quickly as possible. When someone is in heatstroke, they are unable to cool themselves down without significant support, and they may lose their ability to keep breathing and to keep their heart beating without support. They will also require fluids directly into their bloodstream via intravenous injection, as well as interventions necessary to aid in recovery from organ damage. All of this is best done in a hospital.

Heat-related illnesses can become severe and life-threatening, but with proper preparation and an awareness of warning signs, they can mostly be avoided. Staying hydrated, dressing appropriately and avoiding overexertion on hot days are all extremely important preventative tools. Longer-term preventative measures include slow acclimatization to heat to build tolerance. Reducing risk factors can help increase overall heat tolerance. Watch fellow recreators for fatigue, headache and nausea and/or vomiting on hot days. Prevention is key to keeping everyone safe.