17 Sep 2019 Uncategorized


Knowing our body’s reaction to the heat helps us adopt correct and affective attitudes. No therapy variation for cardiopathic and hypertensive patients.

Author Dr. Davide Maged; MSc, PhD in Biomedical Science and Public Health, Department of Public Health, Faculty of Medicine, università cattolica del sacro cuore Roma (Italy).

As summer arrives, we must be prepared to face the consequences that the heat can have on our bodies. The body temperature in resting conditions or moderate physical effort is maintained around the value of 37°, thanks to the thermoregulation system. The thermoregulatory system, in short, is composed of:

– central thermal receptors, located in the hypothalamus (brain), which detect changes in blood temperature;
– peripheral thermal receptors, located in the skin, which measure the changes in the environmental temperature;

– thermoregulatory centre, located in the central nervous system, which receives information from the central and peripheral thermal receptors and, consequently, stimulates the activity of the thermal effector organs that can increase or dissipate heat in the body;

– effector organs, which include small skin arteries, sweat glands, skeletal muscles, and some endocrine glands.

Our body reacts to the heat exposure through two fundamental mechanisms; the vasodilatation of the skin arteries, which allows the heat dispersion, and the sweat production, which cools the body by evaporating on the skin. Moisture is a factor that conditions heat loss; if it is high, it creates a sort of barrier to heat loss through sweating. Conversely, if the air is dry and driven by drafts, the evaporation of sweat is facilitated. Therefore, in a hot-humid environment, the difficulty to dissipate the heat increases and, to counteract the increase in body temperature, our body reacts with an increased heart rate to allow a greater flow of blood to the skin raise the supply of water to the sweat glands.

When sweating is profuse, there is a considerable loss of body fluids, such as to cause a state of dehydration, which, in turn, leads to reduced blood flow to the skin and decreased sweating, compromising the mechanisms of body cooling. In such situations, heat disorders appear. Heatwaves, i.e., meteorological conditions characterized by permanently high temperatures, which can persist for days or weeks, especially in cities, are the main cause of problems.

Who is most at risk?

– Older people are generally in more compromised physical conditions, and their bodies may be less efficient in compensating for heat stress; among these people, those suffering from cardiovascular diseases, hypertension, chronic respiratory diseases, chronic renal failure, and neurological diseases are at greater risk.

– People who are not self-sufficient because they depend on others to regulate the temperature of the environment in which they are located and for the intake of liquids.

– People who regularly take medication may compromise physiological thermoregulation or increase heat production.

– Infants and young children, due to their small body area and lack of complete self-sufficiency, may be exposed to the risk of excessive body temperature and dehydration, possibly with harmful consequences for the cardiovascular, respiratory, and neurological systems.

– People who exercise or work intensively in the open air can dehydrate more easily.

The main health problems related to heat are:

– cramps, caused by electrolytic imbalances due to loss of mineral salts with sweating;

– fainting, caused by the drop in blood pressure due to the stagnation of blood in peripheral areas with a consequent decrease in blood supply to the brain;

– edema, i.e., the stagnation of venous blood in the lower limbs that causes tissue imbibition;

– dehydration, which involves the appearance of thirst, weakness, dizziness, palpitations, anxiety, dry skin and mucous membranes, and arterial hypotension;

– sunstroke, after prolonged exposure to sunlight, which manifests itself in sudden general discomfort, headache, nausea, rapid increase in body temperature (fever) until loss of consciousness;

heatstroke, especially indoors, leading to fever, increased heart and respiratory rates, dilation of the pupils, arterial hypotension to shock, and loss of consciousness. This is the most serious condition and represents a real emergency. Delayed or missed treatment can also lead to death.


The main rules to be respected in case of strong heat, therefore, are:

– avoid going out and exercising during the hottest hours, i.e., from 11 a.m. to 5 p.m;

– refresh the environment in which you stay (with fans, air conditioners);

– cover yourself when changing from a warm environment to an air-conditioned one;

– turn on the air conditioning in the car while maintaining a temperature of 4-5° less than outside;

– wear light-colored, non-adherent clothing made of natural fibers such as cotton;

– immediately get wet with fresh water in case of headaches caused by sunstroke or heat;

– consult your doctor if you are suffering from hypertension and, in any case, do not change the antihypertensive therapy on your own initiative;

– Do not take saline supplements without consulting your doctor;

– drink, frequently, at least 2 liters of water per day.

Finally, it should be remembered that hypertensive people and heart patients, especially if elderly, but also many healthy people, can experience episodes of decreased blood pressure, especially in the transition from lying down to standing up (orthostatic hypotension). In these cases, it is advisable to avoid the abrupt transition from the horizontal to the vertical position, which could also cause loss of consciousness. From the studies conducted so far, it is not yet clear how the trend of blood pressure over the course of 24 hours can be influenced by the interaction between air temperature and the effect of antihypertensive drugs, and it is not yet proven whether the tendency to reduce blood pressure in the warmer months of the year justifies a reduction in the dosage of the therapy. It is, therefore, recommended to keep the antihypertensive and risky therapy unchanged and to independently decide to change the treatment prescribed by the doctor who should be consulted in case of symptoms and pressure change.

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