killing heat

Summer blues

YOUR HEALTH DR GITA MATHAI

The killing heat” is not just a figure of speech. Every summer, newspapers report deaths from sunstroke, heat and dehydration. This may only be the tip of the iceberg as medical documentation and statistics on illness in India are still unsatisfactory. We really do not know exactly how many people are affected. Human beings are sensitive to outside temperature. To survive, the body has to maintain its internal body temperature at 98.4°F. If it is cold outside, we have to insulate the body by covering ourselves. If it is hot, the temperature has to be brought down. The skin is provided with four million sweat glands distributed all over its surface. As the temperature rises, the brain sends chemical signals to these glands and they start functioning. The body becomes drenched in a film of sweat. As this evaporates, the temperature drops. The volume of water lost in sweat daily is highly variable, ranging from 100 to 8,000 millilitres a day, depending on the outside temperature and the extent of physical activity. Sweat is not pure water. It contains small amounts (0.2 - 1 per cent) of chemicals like sodium (0.9 gram/ litre), potassium (0.2 gram/litre), calcium (0.015 gram/litre), magnesium (0.0013 gram/litre) and other trace elements. When a person moves from a cold climate to a hot climate, adaptive changes, called acclimatisation, occur in their sweating mechanisms, regulating not only the fluid lost but also the chemical content. Summer months are vacation months when people travel to the hills from the plains and vice versa. If you are travelling to a warmer environment, it takes your body a couple of days to adjust to the new temperatures. The maximum rate and quantity of sweat has to increase and it has to become more dilute. This acclimatisation period is the time when people are most vulnerable to the effects of heat. The sweating mechanism is inefficient and immature in children till the age of about four. It does not function well in the elderly, the obese and those with diabetes. The system also breaks down with some of the medications taken for high blood pressure and depression. This subset of the population is, therefore, more vulnerable to the effects of heat. The body’s natural cooling mechanism can fail: • If sweat cannot evaporate because the outside environment is humid. The internal temperature continues to rise even though the body remains bathed in sweat. • When inadequate fluid intake with dehydration prevents adequate sweating. • Due to continuous physically taxing work or exercise in a hot environment without sufficient intake of fluids. Heat exhaustion occurs first. You may get a headache, giddiness, a feeling of weakness, palpitations and painful cramps in the leg muscles. The body temperature rises and may eventually be as high as 104°F. If heat exhaustion is not recognised and treated, this can progress to a heat stroke. The temperature rises even to 105°F. There may be confusion, disorientation, seizures and even death. Unfortunately, children often cannot express the early symptoms of heat exhaustion. The only sign noted by the parents may be the temperature. Fearful of fever, they may cover up the child with inappropriate warm clothing and bed sheets. Thirst may be ignored. This accelerates the progress to a heat stroke. To deal with the summer • Try to stay indoors as much as possible, going out only before sunrise and after sunset. • Confine exercising outdoors to the same time. Even swimming in the hot sun can lead to heat exhaustion and stroke. • Avoid synthetic garments. Wear clothes made of cotton, linen, jute and other natural fibres. • Drink plenty of fluids. Do not wait to feel thirsty. The best liquids are tender coconut water or lightly salted lime juice and buttermilk. • Avoid aerated drinks. They add unnecessary calories. Many of them are hypertonic and will not quench your thirst. • Dehydration and the ill effects of heat are aggravated by caffeinated beverages, whether they are colas, tea or coffee. • nAlcohol has a similar effect. If you suspect heat exhaustion • Immediately move the person to the shade, under the fan or to an air-conditioned or air-cooled place. • Give plenty of fluids, preferably with salt. There are many commercially available oral rehydrating solutions that conform to World Health Organization standards. These sachets can be reconstituted and administered. Most of us live in heat radiating concrete jungles where we have to go out to work in the summer. Frequent power cuts and inadequate voltage make amenities like fans, coolers and air conditioners dysfunctional. In this scenario we have to be careful about the effects of the summer heat, particularly on the vulnerable young and old members of our families. Dr Gita Mathai is a paediatrician with a family practice at Vellore. Questions on health issues may be emailed to her at yourhealthgm@yahoo.co.in