Dr Roger Henderson

The dos and don’ts of staying cool

The dos and don'ts of staying cool
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If you were one of those people who ran outside to celebrate Freedom Day only to promptly run back inside because it was too hot, you’re not alone. With an extreme heat weather warning just issued by the Met Office for the first time and with large parts of England and Wales being affected in the coming days, this lays out the potential impact of the heat on people's health. People vulnerable to extreme heat are likely to experience 'adverse health effects', while the rest of the population could suffer heat exhaustion and other heat-related illnesses that are not usually visited on these shores.

These conditions – unsurprisingly - often arise in connection with physical activity in hot weather and loss of fluid as a result of sweating. Problems occur when not enough fluid is drunk to compensate for this, with the body then dehydrating due to water and salt loss. This can trigger the problem of heat exhaustion, where the core body temperature rises to between 37 and 40 degrees C, and those most at risk include toddlers (children under 4), the elderly, the physically active and people with chronic health problems such as heart, lung or kidney disease. Recognising the problem early usually allows for a rapid recovery by going to a cool shaded area, drinking lots of water, taking a cool shower and removing as much clothing as possible. Although water is the main fluid to use here, sports rehydration drinks or a solution of sugars and salt can both rehydrate and help treat any cramping, especially in children.

The warning signs of heat exhaustion include dizziness, passing small amounts of dark urine, nausea and headache and there are often cramps of the legs and feet and a rapid pulse. Personality changes can sometimes occur, with the patient becoming irritable, confused or uncooperative and all these symptoms may be worsened if there are other predisposing factors to the effects of heat already present. These include alcohol and a lack of sleep (the effects of sleeping off a hangover on a sunny and hot beach can be severe), fever due to other illness and any stomach upset causing diarrhoea and vomiting.

Fortunately for most people progress to the next stage is uncommon, especially in this country but if there is continued exposure to unusually high temperatures - and there need not be direct exposure to sunlight - heat hyperpyrexia (better known as heatstroke) can occur, where the body core temperature rises above 40 degrees C. This is a far more dangerous condition, and may not be recognised because sweating has often stopped by now due to severe dehydration. Using oily sunblocks may inadvertently worsen things, and the body becomes intent on saving as much fluid as it can with its temperature sometimes rising to levels of 43 degrees C or higher. This is a medical emergency and should be treated as such with intravenous fluid replacement and rapid cooling. Strict monitoring of the temperature is important and oxygen therapy is often needed. If a young person has been exercising hard in hot weather, apply ice packs to their neck and back and put them in the recovery position if they lose consciousness.

To help reduce the chances of such dramatic events occurring in the coming days, use simple measures such as wearing loose-fitting clothing made of natural fibres such as cotton or linen, drinking four pints of fluid each day as a minimum and avoiding foods which cause sweating such as curries. Try not to drink alcohol and don’t go out into the sun between the hours of 11am and 3pm when the sun strength is at its peak, taking a cool shower or bath when possible. Remember too that south-facing rooms with windows in direct sunlight are hotter than north-facing ones.

The continental habit of taking a siesta began in order to avoid the mid-day sun and its effects - something that mad dogs and Englishmen may forget to their great discomfort this week.