What Is Heat Stroke and How to Prevent It?

Heatstroke is becoming more and more common, as rising global temperatures and climate change are hot on our heels. Learn to prevent this very serious picture.

Written and verified by el biólogo Samuel Antonio Sánchez Amador.

Last update: 15 July, 2023

We all like the warmer times of the year, as they tend to be the holidays, trips away from home and the most attractive recreational activities (such as going to the beach, the pool, or the countryside). Despite this, the heat and climate change bring with them a very important concern to take into account in these moments of enjoyment: heat stroke.

Establishing the global epidemiology a heat stroke is a very complex task, as it does not always become an emergency. Even so, as we will see later on, various media agree that rising global temperatures have increased their incidence. If you want to know everything about this pathological event, read on.

Mechanisms of thermoregulation in humans

Before exploring what heatstroke is, it is necessary to briefly understand the mechanism that prevents its occurrence. We are talking about thermoregulation processes in mammals. This mechanism refers to the ability of a biological organism to maintain its internal temperature within certain limits.

The perfect physiological state is reached when the rate of heat formation (thermogenesis) is balanced by the amount of energy dissipated (thermolysis). However, when the ambient temperature is too high or the human being burns too much energy (when running, for example), several thermoregulatory mechanisms must be activated. These are the following:

• Sweating: Sweating is the release of fluid from the sweat glands, especially those located under the arms, on the feet, and on the palms of the hands. As the sweat released to the body surface evaporates, the body cools down a bit. This mechanism is activated when the external temperature is high.
• Vasodilation: this mechanism is also activated when it is very hot. Superficial blood vessels dilate, allowing increased blood flow and temperature exchange with the environment. Since the core of the body is always warmer than the surroundings, heat is lost in the process.
• Vasoconstriction: the opposite effect to the previous one. When it is cold and the body wants to retain heat, the superficial blood capillaries constrict.
• Thermogenesis: Thermogenesis is defined as the ‘production of organic heat within the human body’. This process can be exemplified by tremors or stimulation of the thyroid gland.

As you can see, there are many mechanisms that keep the temperature of the human body within reasonable limits (from 36.1°C to 37.2°C – 97 to 99 Fahrenheit). However, sometimes balance isn’t possible and the dreaded heat stroke occurs. We’ll tell you what it is and how to prevent it in the following lines.

What is heat stroke?

As the Mayo Clinic indicates, the term “heat stroke” refers to a disorder caused by excess heat in the body, especially as a result of exposure to excessively high ambient temperatures. Medically, it is defined as a ‘body hyperthermia above 40.6 ° C, accompanied by disorientation and other symptoms’.

As the ambient heat increases, the aforementioned thermoregulatory mechanisms become apparent. However, sometimes these aren’t enough. Some of the clearest environmental predisposers when it comes to suffering from heat stroke are the following:

• Ambient humidity above 75%: When the ambient humidity is very high, the perspiration mechanism by producing sweat becomes ineffective.
• Extreme temperatures: a heat wave is such when the ambient temperature is higher than 32.2 ° C for 3 days in a row.
• Rapid onset of heat: thermoregulatory mechanisms are better tuned when the body has time to get used to the heat. If the temperature rises drastically and quickly, it’s more likely that heatstroke will appear.

All of these are environmental predisposers, but there are also many more that lie with the person themselves. Age, previous medical conditions, too many clothes, the use of certain medications, and other endogenous factors lead to heat stroke.

Pathological mechanism

The Statpearls portal shows us the pathological mechanism of heat stroke. In the first place, it should be noted that when the ambient temperature exceeds the internal temperature, the aforementioned thermoregulatory mechanisms lose much effectiveness. The processes of conduction, radiation, and convection cease to make sense when it’s hotter outside than inside, simply put.

As the temperature rises, the body sweats to try and reduce the heat. This results in electrolyte abnormalities, specifically dehydration and hypernatremia (high level of sodium in the blood). If it’s very severe, hypernatremia and lack of water can cause neurological damage.

Hyperkalemia (high blood potassium level) has also been associated with heat stroke. This mineral is a vasodilator associated with the heart muscles, so a mismatch on this front leads to heart problems. For this reason, in this event, coagulation problems, heart rhythm problems are observed, and sometimes lethal arrhythmias appear.

In addition to all of the above, excess body temperature leads to different clotting and inflammation responses. By reducing the number of circulating platelets in the body or disrupting their functioning, lethal hemorrhages appear, or, failing that, disseminated intravascular coagulation. In short, various systemic failures occur during this process.

Epidemiological figures

In the United States, between 2006 and 2010 there were more than 3,300 deaths directly attributable to heat stroke. In any case, these figures are considered to be very low and don’t reflect reality, since not all people who suffer from one of these conditions die and many other cases are not reported.

What has been observed, as studies indicate, is that the incidence of heat stroke has increased significantly in recent years. For example, during the year 2021 in the Canadian heat wave 70% of spontaneous deaths were attributed to adverse weather conditions. Almost all the patients were older than 65 years.

Symptoms of heat stroke

Once the pathological mechanism has been explored, it’s necessary to highlight the symptoms produced by heat stroke. Some of the most common clinical signs in this scenario are the following:

• High body temperature: this must exceed 40 ° C.
• Altered mental states: confusion, dizziness, incoordination, irritability, speech problems, delusions and coma, in the most severe cases.
• Alteration in sweating patterns: curiously, people with heatstroke have very hot skin, but dry to the touch. The absence of sweat is one of the first indications of a serious condition as far as thermoregulation is concerned.
• Nausea and vomiting: Although not all patients experience it, it is also common to vomit during heat stroke.
• Reddened skin: this clinical sign is due to the vasodilation previously described.
• Tachypnea: rapid breathing, with a frequency greater than 20 respiratory cycles per minute.
• Tachycardia: the heart is one of the organs that suffers the most from heat stroke. Because it urgently needs to dissipate temperature, it beats faster than normal.
• Headaches and other systemic clinical signs.

In addition to this, it should be noted that 1/4 of the patients will present hypotension (low blood pressure). As you can see, almost all the signs are systemic and indicate a general failure in the body of the person who suffers the blow. Anhidrosis (lack of sweating) is a differential clinical sign, as people who have not yet reached this condition continue to sweat in an attempt to dissipate heat.

What to do when detecting a person with these symptoms?

Everyone should know the protocol of action in the face of this clinical picture, especially now that summers are characterized by a greater presence of heat waves. The Centers for Disease Control and Prevention (CDC) tell us the steps to take if we find someone in this extreme situation:

1. Move the heat stroke victim carefully to a shady area. Although it seems simple, this step is important, since there can be several degrees more in the environment when the sun is exposed to direct. Call 911 as soon as the person is protected from sunlight.
2. Reduce the patient’s body temperature however possible: If possible, put the person with heatstroke in a bathtub or shower with cool (not ice-cold) water. If you’re on the street, try to access a source of cold water and spread it on the patient’s body. Fan their entire body with a piece of paper, cardboard, or whatever you have on hand to increase evaporation from the skin.
3. Continue helping the patient until their body temperature drops to 38 ° C (if you can measure it) or until help arrives.
4. If ER is late, call again and ask for instructions to keep the patient stable before the healthcare professional arrives.
5. Do not give the patient any type of alcoholic beverage to hydrate. This will further increase their body temperature.

How to prevent heat strokes?

After reviewing all the pathophysiological, epidemiological and symptomatic characteristics of heat stroke, it only remains to discover how to prevent it. The NHS medical portal shows us the most effective measures, and we summarize them in the following sections.

Drink lots of liquids

An adult human being should consume 35 milliliters of water a day for every kilogram of weight. A 50-kilogram person needs 1.7 liters, while a 70-kilogram person requires 2.4 liters. Following these indications is necessary in the warmer times of the year, as sweat can dissipate much more water than we think.

Take refreshing showers or baths

The normal thing is to shower once a day, but during a heat wave you can expose yourself to warm water 3 or 4 times in 24 hours without any problem. The water does not have to be ice cold: it is enough that it refreshes your body surface, as this facilitates perspiration and dissipation of heat.

Wear comfortable and loose clothing

The more layers of clothing you wear, the more difficult it will be for your body to dissipate the excess heat produced within you. The ideal is to wear sweat shorts and loose-fitting tank tops during heat waves and during the hottest times of summer. Avoid tight garments no matter how aesthetic they are.

Use a water spray on your skin

If you feel very hot and you’re worried about suffering from heat stroke, then keep a water spray in the fridge at all times during the summer. When the excess ambient temperature is unbearable, use the spray on your skin. The evaporation of cool water on your epidermis will reduce your surface temperature a bit.

Don’t leave the house between 12 in the morning and 5 in the afternoon

Without a doubt, this is the most important tip when it comes to preventing heat stroke. The more perpendicular the sun’s rays fall on the surfaces of the environment, the more they heat up and the more the general temperatures rise. This occurs with its greatest force when the sun is at its zenith (at 12: oo hours), but it is at 15: 00-16: 00 in the afternoon when the hottest points are reached.

If you want to exercise outside the home during the summer, it’s best to go out first thing in the morning and late in the afternoon. In case you want to exercise during a heat wave, you just have to go to an air-conditioned gym or wait for the general heat to subside.

Keep an eye on the young children and the elderly in the family

During a heat wave, you shouldn’t only watch over yourself. Pay attention to the elderly and vulnerable people in your family, as they’re the ones who are most likely to suffer heat stroke and die in the course of the illness. Call your most vulnerable acquaintances and visit them if possible to make sure everything is okay.

Heat stroke and its severity

The probability of dying after an exercise-induced heat stroke is less than 5%, while if it occurs “naturally” (due to the weakness of the patient), it increases to 65%. In other words, a healthy and young person almost never dies from this condition, but an elderly person or an already ill patient is at serious risk.

This must be taken into account when treating these health problems. Although you always have to take care of yourself and avoid subjecting the body to adverse environments, be especially careful if you are older or have any previous conditions. If you want to prevent heat stroke, avoid exercising and leaving the house during the hottest hours of the day.