Author : Dr. P. D.GUPTA
Former Director Grade Scientist, Centre for Cellular and Molecular Biology, Hyderabad, India
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THERMAL EFFECT
People who live in the largest hot desert of Rajasthan though know well how to protect from heat wave and are well equipped to face heat wave shocks. However, because of change in climatic conditions in the era of global warming, those that live in more moderate climates also get to suffer from short spells of heat wave. The frequency and intensity of heat waves increases the number of deaths and serious ailment. Therefore, it is necessary to adapt our lifestyles to the changing environment in order to prevent basic health problems in consequence of climatic changes. Because of raising temperatures we may suffer several ailments such as bloody diarrhoea, typhoid, jaundice, dehydration, heat stroke, heat exhaustion, heat cramps, viral fever, influenza or other viral diseases in the summer. As a consequence of insufficient body resistance, children and old people are more prone to heat-related disease, while adults, especially the old, suffer heat stroke, heat exhaustion or heat cramps if they need to stay outdoors for longer periods, as certain working tasks demand. One should consider two common health disorders, heat stroke and dehydration which can be easily prevented.
HEATSTROKE
Sudden exposure to hot weather increases the susceptibility to heat-related illness, after exposure to a sudden increase in temperature, such as during an early-summer heat wave or travelling to hotter climates. One should limit activity for several days, to acclimate to the change. However, one may still have an increased risk of heatstroke, before a delay of several weeks of exposure to higher temperatures. The ability to cope with extreme heat depends on the integrity and resistance of the central nervous system. In the child, the central nervous system is not fully developed, and in adults over 65, the central nervous system begins to deteriorate, leading their bodies to have less ability to cope with fluctuations of body temperature. Both these age groups usually find difficulty in maintaining hydration, which further aggravates the risk. Heatstroke occurs when the body temperature rises to 104 F (40 ºC) or higher. This is the most serious form of heat injury, Untreated heatstroke, can damage the brain, the heart, the kidneys and the muscles. The damage worsens with the delay in treatment. Heatstroke can give rise to a number of complications, depending on how long the body temperature is kept high. Severe complications include: swelling of the brain or other vital organs, with the possible resultant permanent damage and increased risk of serious complications, or death. Heatstroke can occur as a result of exposure to a hot environment and/or strenuous activity under hot environment. Heat stroke symptoms: Heat stroke can be identified by its earliest signs, when there is no need of labo-ratory tests. The symptoms include:
• High body temperature: A body temperature of 104 F (40 ºC) or higher is the main sign of heatstroke. • Altered mental state or behaviour: Confusion, agitation, slurred speech, irritability, delirium, seizures or coma can all result from heatstroke.
• Alteration in sweating: In heatstroke, the skin will feel hot and dry to the touch. However, if it is due to strenuous exercise, the skin may feel moist.
• Nausea and vomiting: Flushed skin; rapid breathing; headache; rising heart rate.
Heatstroke requires emergency treatment. Untreated heatstroke can quickly damage the main vital organs. The damage worsens rapidly if the treatment is longer delayed, with the increasing risk of serious complications or death. Conditions can be brought to control in any type of heatstroke by:
• Getting the person into the shade or indoors
• Removing excessive clothing; (excessively tight clothes prevent the evaporation of sweat and cooling of the body).
• Cooling the person by whatever means available — put in a cool tub of water or a cool shower, spray with a garden hose, sponge with cool water, fan while misting with cool water, or place ice packs or cold, wet towels on the person’s head, neck, armpits and groin.
• Remembering that drinking alcohol, can affect the body’s ability to regulate temperature.
Risk factors of heatstroke: Anyone can develop heatstroke, but several factors increase the risk:
• Age: As previously mentioned infants and elderly have underdeveloped or weakened central nervous system, leading them to lose the ability to cope with extreme temperatures. Both groups also lose the ability to maintain hydration, further increasing their risk.
• Sudden exposure to hot weather: Travellers should limit activities for at least several days, to allow acclimatization to the sudden change.
• Certain medications affect the body’s ability to maintain hydration and to respond to heat. In hot weather, one should avoid, or adapt dosage of vasoconstrictors (medicines that narrow the blood vessels); beta blockers (those that regulate blood pressure by blocking adrenaline), diuretics (those that enhance the body loss of sodium and water), or antidepressants and antipsychotics (to reduce psychiatric symptoms). Stimulants for attention-deficit/hyperactivity disorder and stimulants such as amphetamines and cocaine also enhance the vulnerability to heatstroke.
• Certain health conditions: Certain chronic illnesses, such as heart or lung disease, might increase the risk of heatstroke. The same applies to obesity, extensive surgical intestinal resection, sedentarity, or clinical history of previous heatstroke.
• Complications of Heatstroke: Heatstroke can result in several complications, depending on how long the body temperature is high. Severe complications include:
• Vital organ damage: Without a quick response to lower body temperature, heatstroke can cause the brain or other vital organs to swell, possibly resulting in permanent damage.
• Death: Without prompt and adequate treatment, heatstroke can be fatal. Lifestyle and prevention of heatstroke: Heatstroke is predictable and preventable.
Acclimatization and adaptability are the key issues. Limited time should be spent working or exercising under hot weather, until the body is conditioned to it. Those who are not used to hot weather are especially susceptible to heat-related illness. It can take several weeks for the body to adjust to hot weather. When signs of heat-related illness appear, one should lower the body temperature and prevent the condition from progressing to heatstroke.
Under hot weather, the following precautions should be taken:
• Wear loose fitting, lightweight clothing;
• Protect against sunburn. (Sunburn affects body’s ability to cool);
• Cool off with damp sheets and a fan or by cool shower or bath. Direct air onto the person with a fan;
• Drink plenty of fluids;
• No one should ever be left in a parked car. (This is a common cause of heat-related deaths in children. When parked in the sun, the temperature in your car can rise 20 degrees F (more than 6.7 C) in 10 minutes, especially during the hottest hours of the day.
DEHYDRATION
Dehydration occurs when the usage or loss of fluids is greater than the intake, and the body doesn’t have enough fluids to perform normal functions. Unless there is replacement of the lost fluids, the body dehydrates. Common causes of dehydration include vigorous exercise, especially in hot weather; intense diarrhoea; vomiting; fever or excessive sweating. Insufficient intake of water during exercise, or in hot weather, even without exercise, also may cause dehydration. Anyone may become dehydrated, but young children, older adults and those that suffer from chronic illnesses, are mostly at risk.
One can usually reverse mild to moderate dehydration by drinking more fluids, but severe dehydration needs immediate medical treatment. The safest approach is to prevent dehydration, first. Controlling the quantity of fluid loss during hot weather, illness, exercise, and drinking enough liquids to replace the loss, will be the best preventive measure to take. If untreated, there is gradual evolution between mild to severe dehydration, and further. Whereas the earliest symptoms of mild dehydration can be easily treated, heatstroke is a medical emergency that can be fatal. The best procedure is prevention, which, corresponds to the early detection and treatment of the milder signs of dehydration. Hence, the importance of the following list of signs and symptoms.
Common symptoms of mild to moderate dehydration: Dry, sticky mouth; sleepiness or tiredness (children become less active than usual); thirst; decreased urine output; dry skin; headache; constipation; dizziness or light-headedness.
Symptoms of severe dehydration (a medical emergency):
• Extreme thirst, fussiness or sleepiness in infants and children; irritability and confusion in adults. Very dry mouth, skin and mucous membranes. Little or no urination (any urine that is produced will be darker than normal). Sunken eyes, shrivelled, dry skin that lacks elasticity and doesn’t “bounce back” when pinched into a fold. In infants, sunken fontanels (the soft spots on the top of a baby’s head), low blood pressure, rapid heartbeat, rapid breathing, no tears when crying, fever and in the most serious cases, delirium or unconsciousness.
• Unfortunately, thirst isn’t always a reliable gauge of the body’s need for water, especially in children and older adults. A better indicator is the colour of their urine: Clear or lightcoloured urine means good hydration, whereas dark yellow or amber colour usually signals dehydration.
• Young children and elderly adults should be treated with greater caution. Medical help should be called immediately when the following symptoms are evident: severe diarrhoea (with, or without vomiting or fever) or moderate diarrhoea for 24 hours or more, bloody or black stool, incontinence of fluids, irritability or disorientation and sleepiness or loss of the usual activity.
Causes of dehydration:
• Dehydration occurs when there isn’t enough water to replace the daily loss. The system literally dries out. Sometimes, dehydration occurs for the simpler reason that there is not enough water intake because of sickness or distraction, or as a result of the lack of access to safe drinking water, when travelling, hiking or camping.
• Severe acute diarrhoea (diarrhoea with sudden or violent onset) can cause a tremendous loss of water and electrolytes, in short time. When vomiting is associated with diarrhoea, there is an even greater loss of fluids and minerals. Children and infants, and the mentally handicapped, are especially at risk. Diarrhoea may be caused by bacterial or viral infection, food sensitivity, reaction to medications or other bowel disorders.
• In general, the higher the fever, the more severe the degree of dehydration. Fever in addition to diarrhoea and vomiting, increases the loss of fluids.
• There is water loss with sweating. Vigorous activity without replacement of fluids, leads to dehydration. Hot, humid weather increases the amount you sweat and the amount of fluid loss. But one can also become dehydrated in winter, without the replacement of lost fluids. Preteens and teens who participate in sports may be especially susceptible, both because of their body weight, which is generally lower than that of adults, and because they may not be experienced enough to know the warning signs of dehydration.
• Water also losses due to increased urination. This may be due to undiagnosed or uncontrolled diabetes. Certain medications, such as diuretics and some other blood pressure medications, can also lead to dehydration, generally because they cause patients to urinate or perspire more than normal.
Risk factors of dehydration: Anyone can become dehydrated, if too many fluids are lost. But certain people are at greater risk, including:
• Infants and children are especially vulnerable because of their relatively small body weight and the high turnover of water and electrolytes. They also belong to the group that is most likely to experience diarrhoea.
• Ageing enhances the susceptibility to dehydration for several reasons: The body’s ability to conserve water is reduced, the sense of thirst becomes less acute, and there is reduced ability to respond to changes in temperature. Furthermore, elderly adults, especially those in nursing homes, or living alone, tend to eat less than younger people do and sometimes may forget to eat or drink altogether. Disability or neglect also may prevent them from being well nourished.
These problems are compounded by chronic illnesses such as diabetes, dementia, and the use of specific medications.
• Uncontrolled or untreated diabetes brings a higher risk of dehydration. But other chronic illnesses, such as kidney disease or heart failure, also make them more prone to dehydration. Even a simple cold or sore throat makes them more susceptible to dehydration because they lose appetite or drink less, when they are sick. Fever increases dehydration even more.
• Anyone who exercises can become dehydrated, especially in hot, humid conditions or at high altitudes. Athletes who train for and participate in ultra marathons, triathlons, mountain climbing expeditions or cycling tournaments are particularly at high risk. The longer the exercise, the more difficult it is to stay hydrated. During exercise, the body may lose more water than it can absorb. With every hour of exercise, the fluid debt increases. Dehydration is also cumulative over a period of days, which means that one can become dehydrated even with moderate exercise routine if the water intake is not enough to replace what the loss, on daily basis.
• Living, working or exercising at high altitudes (generally defined as above 8,200 feet, or about 2,500 meters) can suffer a number of health problems. One is dehydration, which commonly occurs when the body tries to adjust to high elevations through increased urination and more rapid breathing. The faster one breathes to maintain adequate oxygen levels in the blood, the more water vapour is exhaled.
• When there is heat and humidity, the risk of dehydration and heat illness increases. When the air is humid, sweat can’t evaporate and cool the body as quickly as it normally does, and this can lead to an increased body temperature and the need for more fluids.
Complications of Dehydration: Dehydration can lead to serious complications, including:
• Heat injury: Insufficient fluid intake, when exercising vigorously and perspiring heavily, may lead to heat injury, ranging in severity from mild heat cramps to heat exhaustion or potentially life-threatening heatstroke.
• Cerebral edema: (swelling of the brain): Sometimes, during the fluid intake to treat dehydration, the body tries to pull too much water back into the cells. This can cause some cells to swell and rupture. This condition is especially severe, when brain cells are affected.
• Seizures: Electrolytes, such as potassium and sodium, help carry electrical signals from cell to cell. If the electrolytes get out of balance, the normal electrical messages get mixed up, leading to involuntary muscle contractions and sometimes, with loss of consciousness.
• Hypovolemic shock (Low blood volume shock): is one of the most serious, and sometimes lifethreatening, complications of dehydration. It occurs when low blood volume causes a drop in blood pressure, hence a drop in the amount of available oxygen in the body.
• Kidney failure: This potentially life-threatening problem, occurs when your kidneys are no longer able to remove the excess of fluids and waste from blood.
• Coma and death: If not promptly and appropriately treated, severe dehydration can be fatal.
Treatments and drugs: The only effective treatment for dehydration consists of the replacement of lost fluids and electrolytes. The best approach to dehydration depends on age, on the severity of dehydration, and on its cause. Treating dehydration in sick children: Medical help can offer specific suggestions for treating dehydration in young children, but some general guidelines include the following:
• Unless otherwise advised, an oral rehydration solution such as Pedialyte should be used for infants and children suffering from diarrhoea, vomiting or fever. These solutions contain water and salts in specific proportions to replenish both fluids and electrolytes. They are also designed for easier digestion. Oral rehydration products are readily available in drugstores, and many pharmacies carry their own brands. We should begin the administration of fluids early in the course of an illness, instead of waiting until the situation becomes urgent.
• Clinical advice may suggest specific amounts, depending on the child’s age and degree of dehydration, but a general rule of thumb is to keep giving liquids slowly, until the child’s urine becomes clear in colour. In case of vomiting, small amounts of solution, at frequent intervals should be tried, as for instance, a spoonful or so, every few minutes. If the child can’t keep this down, one should wait for 30 to 60 minutes and try again. Room temperature fluids are the best.
• Mothers should not stop breast-feeding when the baby is sick, but offer the baby an oral rehydration solution in a bottle, as well. When giving the baby formula, mothers should try switching to lactose-free formulas, until diarrhoea improves — lactose can be difficult to digest during diarrhoea, which in turn, further aggravates diarrhoea. Never dilute formula more than the instructions advice. Doctors may suggest substituting an oral rehydration solution for the formula, for a short time.
• The best liquid for a sick child is an oral rehydration solution — plain water doesn’t provide essential electrolytes, and although sports drinks replenish electrolytes, they replace the loss through sweating, but not the loss through diarrhoea or vomiting.
Milk, caffeinated beverages, fruit juices or gelatines don’t relieve dehydration, and may even further aggravate children’s diarrhoea.
Treating dehydration in sick adults: Most adults with mild to moderate dehydration in consequence of diarrhoea, vomiting or fever, can improve their condition by drinking more water or other liquids. Certain liquids, such as fruit juices, carbonated beverages or coffee, can further aggravate diarrhoea. Treating dehydration in athletes of all ages: For exercise-related dehydration, cool water is the best. Sports drinks containing electrolytes and a carbohydrate solution can also be helpful. There’s no need for salt tablets — too much salt can lead to hypernatremic dehydration, a condition in which the body is not only in shortage of water, but also in excess of sodium. Carbonated beverages, such as soda, should be avoided.
Treating severe dehydration: Severely dehydrated children and adults should be treated by emergency personnel arriving in an ambulance, or in a hospital emergency room, where they can receive salts and fluids intravenously (through a vein), rather than by mouth. Intravenous hydration provides the body with water and essential nutrients, in a much quicker way than oral solutions — which is essential in lifethreatening situations.
Prevention of dehydration: To prevent dehydration, drink plenty of fluids and prefer foods with high water content, such as fruits and vegetables. Letting thirst be your guide is an adequate daily guideline for most healthy people. Fluids can be obtained not just from water, but also from other beverages and foods. But, when exercising, one shouldn’t wait for thirst to keep up the balance of fluids [18]. Under certain circumstances, one may need to enhance fluid intake:
• Start giving extra water or an oral rehydration solution at the first signs of illness. — One shouldn’t wait until dehydration occurs. And although they might sound appealing, traditional “clear fluids” such as ginger ale or other sodas, contain too much sugar and too little sodium to replenish lost electrolytes. • In general, it’s best to start hydrating the day before strenuous exercise. The production of clear, diluted urine is an indicator of good hydration. Before exercising, one should drink 1 to 3 cups (0.24 to 0.70 litres) of water. During the activity, replenish fluids at regular intervals and continue drinking water or other fluids after finishing.
• Drinking too much not only can cause bloating and discomfort and may even lead to the potentially fatal condition of hyponatremia (in which the blood sodium becomes too low). This occurs when there are more intakes of fluids than the loss through sweating.
• Certain work tasks, such as those that imply outdoor work, demand special care for the prevention of heat stress impact on workers. A paradigmatic example of heat stress in work places, that can affect healthy adults, is the particular case of the steel industry.
• Additional water intake is fundamental in hot or humid weather, in order to help lower the body temperature and to replace the loss through sweating. One may also need extra water in cold weather, when sweating inside insulated clothing. Heated, indoor air can cause your skin to lose moisture, increasing your daily fluid requirements. And altitudes greater than 8,200 feet (2,500 meters) also can affect the amount of water in the body. If dehydration occurs when exercising in hot weather, one should get into a shady area, recline, and start drinking water or a sports drink. (The author has his own study and views)
