When climate change affects your kidneys

Heat-related kidney complications

In general, our body has various ways of regulating body temperature and releasing excess heat. The best-known method is sweating. If the temperature control centre in our brain, known as the ‘hypothalamus’, detects that our comfort body temperature of 37 degrees is exceeded, the sweat glands in the skin are stimulated to produce more. We consequently give off heat by “evaporating” the sweat on the surface of the body. In addition, the body dilates our skin vessels. The heart pumps more warm blood into the dilated skin vessels, which also dissipates heat.

“The increased sweating naturally leads to a loss of fluid and important body salts, the so-called electrolytes. The lack of fluid and the heat-induced widening of the vessels lead to a drop in blood pressure. The heart no longer pumps enough blood through the body and the kidneys,” explains Professor Dr Christoph Wanner, Head of Nephrology at the German University Hospital in Würzburg and President of the European Renal Association (ERA). “If you don’t compensate for this fluid loss, you become dehydrated. This can result in kidney failure. The risk to develop urinary stones and urinary tract infections is also bigger when the body is dehydrated.”

Older people and people with cardiovascular diseases should pay special attention to the following measures:

Drink enough

Every day, humans excrete just under one litre of water through urine, half a litre through sweat and another half a litre through breathing. On hot days and during intensive exertion, we sweat even more. For our body to continue to function properly, this loss must be compensated for by drinking more – ideally one to two litres in addition to the amount we usually drink, so all in all about two to three litres per day. Experts recommend tap or mineral water, mixed with a little lemon or juice according to taste, as well as unsweetened teas. It is best to drink a large glass of water in the morning immediately after getting up. This replenishes the body’s reserves, boosts circulation, and promotes physical and mental performance.

Younger, healthy people can certainly rely on their sense of thirst. Thirst is a good indicator that the body needs fluids. With age, however, the sense of thirst diminishes. Then, a urine check could help: the brighter the urine, the better!

Signs of a lack of fluids are fatigue, headache, indigestion because the gastrointestinal tract works more slowly, dizziness, muscle cramps, aching limbs, and dry skin.

Fluid intake in case of heart or kidney disease

Patients with heart or kidney disease should discuss their daily amount of fluid intake with their doctor as it may need to be reconsidered. If their body cannot completely eliminate the water, it may accumulate in the legs, lungs or abdomen. Weighing yourself daily helps to prevent fluctuations in your fluid balance. An increase of half a kilo in body weight within one day usually indicates too much drinking.

Replace electrolytes

Many electrolytes, which are valuable minerals such as sodium, potassium, calcium, and magnesium as well as zinc and iodine, are also lost through sweating. In addition to sufficient fluid intake, you should thus also eat a balanced diet. A lack of electrolytes can be successfully counteracted by drinking a vegetable broth or gazpacho, the cold vegetable soup from Andalusia. If you already suffer from a heart condition, you should keep a close eye on your potassium levels, as a potassium deficiency can impair heart function even more. However, do not take potassium tablets on your own without consulting a doctor.

Avoid midday heat and physical exercise

It is recommended to take a siesta at midday on hot days. Physical activities, such as shopping, housework and gardening should be kept to a minimum in the heat and take place in the cooler morning and evening hours instead. This also applies to sporting. Strength and endurance training strengthen the heart and will get you through the heat wave better. On extremely hot days, however, you should not overexert yourself and, at most, go swimming or do moderate sport in cooled rooms.

Keep the heat outside

Ventilate early in the morning and late in the evening or at night and keep windows closed during the day. Lock out the heat by darkening all rooms, preferably with outside shutters, because these protect better against heat than inside blinds or curtains. Also, keep your body as cool as possible by wearing light and airy clothes and staying in the shade if possible.

Closely monitor medication use and blood pressure

Keep a close eye on your blood pressure because, due to the heat, the blood vessels are dilated and the blood pressure could consequently drop. If necessary, medication use must be adjusted. Furthermore, the effects and side effects of certain medications, such as diuretics, can also change with extreme temperatures. To avoid undesirable consequences, you should always discuss the medication dose as well as the adjustment of the amount you drink with your attending doctor during midsummer. Always store your medication in a cool and shady place.