Issue link: https://maltatoday.uberflip.com/i/1146457
OPINION 27 maltatoday | SUNDAY • 21 JULY 2019 Which body organs are most at risk during a heat wave? Pieter Vancamp Pieter Vancamp is Post-doctorant, Muséum National d'Histoire Naturelle TheConversation.eu IN June 2019, much of Europe was struck by early heatwave, with temperatures reaching nearly 46 Centigrade (115 Fahrenheit) in France, an all- time record. A heat wave is characterised by extremely high tempera- tures over the course of several days and nights. They have a significant impact on our daily lives – we feel overheated and tired. When a heat wave strikes, many governments activate a "heat action plan", advising those affected to drink water, avoid strenuous exercise, and stay cool. If not, one risks having a heat stroke, which can be potentially life- threatening. But how exactly does the hu- man body deal with such ex- treme temperatures, and why is heat so dangerous? Which organs are affected, and when could things take a turn for the worse? Staying cool The core temperature of the human body usually fluctu- ates between 36 and 38°C (97 to 99°F). Temperatures within this range allow biochemical reactions to proceed normally, which is vital for proper func- tioning of cells and organs. The human body is also well equipped to deal with a variety of environmental conditions that might threaten its core temperature. When the core temperature deviates from the normal range, the body initiates physi- ological responses in order to return its temperature to normal. This thermoregula- tory response is comparable to a thermostat at your home; once the in-house temperature strays from the ideal tem- perature, heating or cooling systems activate to return to the preferred temperature. In the human body, this ther- mostat is located at the base of our brain, in a region called the hypothalamus. Informa- tion provided by temperature sensors located in our skin, muscles, and other organs is analysed, and when neces- sary, physiological response is initiated. The first and most important response to increasing temper- atures is heat dissipation via the skin and extremities of our body, such as our hands and feet. We start producing sweat that will evaporate on our skin, shedding heat in the process. This system is very effective in cooling down the body, but can require up to two litres of water per hour in cases of extreme heat. The body adjusts its water housekeep- ing as much as possible, but to sustain thermoregulation, it's vital for us to refill the body's water reservoir. If not, one risks running out of water, and thus losing the ability to sweat and cool down, resulting in overheating of organs. Via the drinking water, we also need to take up electrolytes and salts, which maintain a normal blood acidity, crucial for cells to function. From brain to kidneys To understand what can go wrong, let's take a look at how the thermoregulatory response affects the function of multiple organs, and how each organ reacts to extreme heat. The first is the cardiovas- cular system. For us to sweat and cool off, blood flow shifts from the central organs to the periphery of the body – you've no doubt noticed that people who are overheated are often blushing. The loss of water through sweat and the redis- tribution of the blood flow causes a fall in blood pres- sure in the central organs. To maintain blood flow to the vital organs, the heart tries to compensate by elevating the heart rate. However, if blood flow redistribution is accompanied by too much water loss, blood pressure will drop dangerously and cause fainting, an im- portant sign of a heat stroke. In a worst-case scenario, it can lead to heart failure if left untreated. Another vital organ that suffers under temperature stress is the brain. Increased temperatures disturb com- munication between nerve cells, as the heat affects DNA and protein structure as well as cellular membrane integ- rity. Dehydration also causes electrolyte imbalances, which can disrupt nerve-muscle cell communication. The longer the overheating lasts, the more serious the consequences can be. Cognitive pathways can be deregulated and provoke emotional alterations such as increased anxiety, headaches and impaired judgement. Remarkably, one of the ways the brain cools is through the respiratory system. The body increases breathing frequency, cooling the blood flowing to and from the brain. The flow- ing air can be seen literally as a sort of natural air-condi- tioning system. However, an adverse effect is that blood pH rises due to decreases in bi- carbonate and CO2 pressure, which could endanger cell functioning in other organs. The intestine is another ma- jor organ system receiving less blood due to its redistribution to the periphery. It impedes proper functioning, and in ex- treme cases can cause nausea and vomiting. Finally, the loss of water and salts also elicits responses in the urinary tract. Under the influence of a special hormone from the brain, antidiuretic hormone, the re-absorption of water and salts is stimulated to counteract the blood pressure loss in the cardiovascular sys- tem. As a result, our kidneys produce less but more concen- trated urine, which is browner in colour, and we go less frequently to the bathroom. Prolonged periods of high temperatures and dehydration can result in tissue damage in the kidneys. Listening to your body One can understand now that drinking water, taking up salts and electrolytes, and staying out of the most intense heat is an absolute necessity for our body's own good. Peo- ple who do not listen to their bodies, do not drink water and neglect the advice given by health authorities during hot weather can push their bodies to the limits of human physiol- ogy. They could suffer exhaus- tion or heat stroke, which can have potentially fatal conse- quences. Those particularly at risk are the elderly and heart patients whose cardiovascular system is already overstressed. Moreo- ver, the elderly might be less aware of the dangers of heat, as their body heat sensors function less well than those of young people. Babies and tod- dlers depend on their parents to take the necessary measures to protect them. The best advice during a heat wave is, in essence, to do what we already know: • Drink plenty of water, while limiting consumption of alcohol and caffeine, which have dehydrating effects on the body. • Stay out of the sun, seek a cool place, and follow the advice given by health authori- ties. • Help those that are particu- larly vulnerable in hot condi- tions, in particular infants and the elderly. But how exactly does the human body deal with such extreme temperatures, and why is heat so dangerous? Which organs are affected, and when could things take a turn for the worse? When a heat wave strikes, many governments activate a "heat action plan", advising those affected to drink water, avoid strenuous exercise, and stay cool. If not, one risks having a heat stroke, which can be potentially life-threatening