2023-07-11 08:15:48
With the rise in temperatures there are different effects on the body to try to adapt, but when we exceed certain figures we can end up suffering a heat stroke.
Although this summer the heat has been slow to arrive, it has been strong and without having finished the first half of July we are already going through the second heat wave. Do the months ahead of us expect the same as last year? The situation does not look good at all: The Spanish Meteorological Agency (Aemet) has been warning of this second wave for days, with rises in temperatures that will be especially noticeable starting tomorrow, reaching 45 degrees in many areas. Although some thermal models forecast 48.2 degrees in Seville, which would exceed the current national record (47.6 degrees in La Rambla, Córdoba).
Obviously these extreme temperatures are harmful to health, leading to death from heat stroke, among other things. Thus, according to data from the Daily Mortality Monitoring System (MoMo) of the Carlos III Health Institute (ISCIII), which estimates excess mortality, in the month of June and the first week of July there were more than 300 deaths attributable to heat (319 as of Friday).
According to INE data, from May to August 2022, 157,580 deaths were registered, 20.5% more than in the same months of 2019, before the covid pandemic. The increase occurred mainly among people over 75 years of age and the cause was heat (highlighting heat stroke and dehydration), in addition to covid, among others.
Alteration of cardiac function due to heat
To precisely measure the body’s ability to adapt to heat, a team of researchers from the University of Roehampton (United Kingdom) led by Lewis Halsey is conducting a study in which they have discovered that the resting metabolic rate -the amount of energy consumed by the human body to continue functioning – is greater in certain circumstances of humidity and temperature (between 40 and 50 degrees).
They have also seen that heart function is affected and these effects are different between people depending on age, physical condition and sex. Their goal is to determine whether these important physiological responses can lead to heat adaptation or stress to the body.
Before reaching death, a series of effects take place in our organism. Above 38º we begin to function poorly, so when temperatures rise the body activates to eliminate part of that heat and keep us at acceptable figures: the heart rate increases to pump more blood to the skin and extremities, the arteries they vasodilate (that’s why we get red) and sweat is activated to cool us down.
Those are our defense mechanisms, but the body has a limit of exposure to the sun and when the heat begins to accumulate in the body, vasodilation causes our blood pressure to drop, we feel tired and, if we do not ingest enough fluids (especially water ), we can become dehydrated. If there are circulation problems and varicose veins, there may be heaviness and tingling in the legs, as well as swollen ankles.
Effects on skin, behavior and other organs
The heat also affects those who have dermatitis and can also cause a rash on the skin (miliaria or sudamina). “In children, the skin in the diaper area suffers from friction and humidity. In miliaria, sweat ends up clogging the pores of the sweat glands and a rash forms, sometimes with small red dots, especially in areas where there are folds: groin, elbows, armpits, neck, chest and shoulders”, emphasizes José David Torres Peña, associate internist at the Reina Sofía Hospital in Córdoba and member of the Spanish Society of Internal Medicine (SEMI).
Due to the so-called tropical nights, it is difficult to fall asleep, which prevents rest and affects behavior (we are more irascible). “If you also have basic mental pathologies, they can be aggravated and decompensated,” explains Torres. “If we exceed 38 degrees, there is a malregulation of neuronal functioning, with slight and transitory changes in memory and reasoning, and if someone with a mental health problem is subjected to neurological stress and neurotransmitters do not work well, they may exacerbate your problem, for example, someone who has anxiety.
Through sweat, the body will continue trying to cool itself, so the blood that goes to the skin will stop being available for other organs: the kidneys will stop filtering well, the heart will be affected because it has to work at a faster rate and the brain will slow down. You will be without blood and therefore without oxygen. This is what happens in heat strokes, which are basically a collapse of the circulatory system, and can lead to multi-organ failure.
What can happen to us from the slightest to the most serious
Although it depends on age and comorbidities, mortality after suffering a heat stroke can be higher than 70%, Torres points out. But until you get there, you gradually go through other manifestations. When the heat accumulates, we suffer from heat exhaustion due to the drop in blood pressure and the decrease in water and electrolytes in our body. “There is weakness, poor general condition, there may even be some dizziness, headache, tiredness and notice tachycardia and symptoms as if one had, for example, an episode of anxiety,” Torres details.
“Thermal stress is basically suffered by workers, like those who died last summer. When continuous work is done with a certain degree of physical activity and you add the accumulation of heat continuously (the one that sweeps in the street, the one that unloads a truck or the one that is in a furnace or foundry), what happens is that there is a physiological overload of our organism, the temperature increases and already the mechanisms that we have commented previously of sweating and vasodilation are failing. When they fail, the temperature increases until it exceeds 38º and damage begins to be produced. If the body temperature exceeds even 40 degrees, you can suffer a heat stroke”, emphasizes Torres.
.Do not forget dehydration. “There are many degrees, from as mild as it can be when, for example, you work in an office all morning and don’t drink fluids. Thirst and a little tiredness are experienced, but it is solved by drinking water. And be careful on the beach that many times, in addition to being exposed to the sun, we drink alcohol and it dehydrates ”, warns the internist. “The most extreme situation occurs with those older patients who have a little bit of dementia, they start with an infection and stop eating and drinking, they become dehydrated and lose electrolytes. They arrive at the hospital with impaired consciousness and may end up in a coma, which depending on the degree is reversible after hydration and hospital support”, emphasizes Torres.
And finally, the dreaded heat stroke, the worst that can happen as a result of these high temperatures, with cramps, convulsions and general failure of different organs.
Most vulnerable populations
Although the entire population in general is affected, with the particularities of the chronically ill and workers exposed to heat sources, there are groups that are much more vulnerable to high temperatures. The symptoms are not different from the rest of the population, but they can suffer them with less exposure to heat.
Children and infants
Their thermoregulatory system is not fully developed and they are also more vulnerable because they sweat more and are exposed to the outside, in the words of Valero Sebastián Barberán, a Primary Care pediatrician in Valencia and a member of the Health Promotion Committee of the Spanish Association of Pediatrics ( AEP). “Children tend to lose a lot of fluid because their number of sweat glands is much higher compared to adults having a very small body surface area. They have a lot of evaporative loss and break down quickly.”
Hydration is essential to prevent those situations of dehydration and heat stroke. “You have to force them to drink water.” In the case of infants, sweating is the same as in children and adults, so it is necessary to avoid dehydration, they do it faster, explains the pediatrician. “If apathy and decay appear, you have to rehydrate and go immediately to the emergency room because an infant is in much more danger than a child.”
Greater
In this case, “the greater vulnerability to high temperatures is determined by the alterations that occur in the thermoregulatory center, generating a lower sensation of heat, which increases the risk of experiencing heat stroke,” says Francisco Tarazona, a geriatrician and Member of the Board of Directors of the Spanish Society of Geriatrics and Gerontology (SEGG).
The specialist adds that the perception of thirst decreases, which entails a high risk of dehydration, which is even higher “in those with neurodegenerative and chronic diseases that condition the prescription of drugs that promote dehydration, such as diuretics. They should not abandon the medication, but they should take extreme care and ensure a correct intake of fluids. According to Tarazona, the elderly -especially those with cognitive disorders and comorbidities- have higher mortality rates and are at greater risk of presenting the most serious manifestations of heat stroke, such as multiple organ failure and hypovolemic shock.
pregnant
The pregnant woman has certain peculiarities due to the fact of being pregnant, such as physiological adaptation mechanisms since pregnancy is an overload for the woman’s body: the volume of blood increases, which practically has to double to attend all the irrigation of the uterus, placenta, umbilical cord and fetus. That already means more work for the heart and this hemodynamic overload means that the mother has fewer resources to defend herself against heat stroke, since the pregnant woman’s heart cannot reach a certain rhythm to cool her body.
It must be added that the pregnant woman already sees her basal temperature increased and sweats more (so she has a greater risk of dehydration), especially in the third trimester. In addition, she has hypotension – which can lead her to faint or faint – and due to physiological adaptation, the ventilatory respiratory capacity decreases. Rocío R.García-Abadillo
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