NIH - Heat emergencies (Medical Encyclopedia) - Illustration

NIH - Heat emergencies (Medical Encyclopedia) “Heat emergencies fall into three categories of increasing severity: heat cramps, heat exhaustion, and heatstroke. ... If the problem isn't addressed, heat cramps (caused by loss of salt from heavy sweating) can lead to heat exhaustion (caused by dehydration), which can progress to heatstroke. Heatstroke, the most serious of the three, can cause shock, brain damage, organ failure, and even death. ... Symptoms: The early symptoms of heat illness include: • Profuse sweating • Fatigue • Thirst • Muscle cramps Later symptoms of heat exhaustion include: • Headache • Dizziness and light-headedness • Weakness • Nausea and vomiting • Cool, moist skin • Dark urine The symptoms of heatstroke include: • Fever (temperature above 104°F) • Irrational behavior • Extreme confusion • Dry, hot, and red skin • Rapid, shallow breathing • Rapid, weak pulse • Seizures • Unconsciousness First Aid: 1. Have the person lie down in a cool place. Elevate the person's feet about 12 inches. 2. Apply cool, wet cloths (or cool water directly) to the person's skin and use a fan to lower body temperature. Place cold compresses on the person's neck, groin, and armpits. 3. If alert, give the person beverages to sip (such as Gatorade), or make a salted drink by adding a teaspoon of salt per quart of water. Give a half cup every 15 minutes. Cool water will do if salt beverages are not available. 4. For muscle cramps, give beverages as above and massage affected muscles gently, but firmly, until they relax. 5. If the person shows signs of shock (bluish lips and fingernails and decreased alertness ), starts having seizures, or loses consciousness, call 911 and administer first aid accordingly. DO NOT: • DO NOT underestimate the seriousness of heat illness, especially if the person is a child, elderly, or injured. • DO NOT give the person medications that are used to treat fever (such as aspirin or acetaminophen). They will not help, and they may be harmful. • DO NOT give the person salt tablets. • DO NOT give the person liquids that contain alcohol or caffeine. They will interfere with the body's ability to control its internal temperature. • DO NOT use alcohol rubs on the person's skin. • DO NOT give the person anything by mouth (not even salted drinks) if the person is vomiting or unconscious. “

NIH – Dehydration (Medical Encyclopedia) “Dehydration means your body does not have as much water and fluids as it should. Dehydration can be caused by losing too much fluid, not drinking enough water or fluids, or both. Vomiting and diarrhea are common causes. Infants and children are more susceptible to dehydration than adults because of their smaller body weights and higher turnover of water and electrolytes. The elderly and those with illnesses are also at higher risk. ... Causes: Your body may lose too much fluids from: • Vomiting or diarrhea • Excessive urine output, such as with uncontrolled diabetes or diuretic use • Excessive sweating (for example, from exercise) • Fever ... Symptoms: • Dry or sticky mouth • Low or no urine output; concentrated urine appears dark yellow • Not producing tears • Sunken eyes • Markedly sunken fontanelles (the soft spot on the top of the head) in an infant • Lethargic or comatose (with severe dehydration) ... Treatment: • Drinking fluids is usually sufficient for mild dehydration. It is better to have frequent, small amounts of fluid (using a teaspoon or syringe for an infant or child) rather than trying to force large amounts of fluid at one time. Drinking too much fluid at once can bring on more vomiting. • Electrolyte solutions or freezer pops are especially effective. These are available at pharmacies. Sport drinks contain a lot of sugar and can cause or worsen diarrhea. In infants and children, avoid using water as the primary replacement fluid. • Intravenous fluids and hospitalization may be necessary for moderate to severe dehydration. The doctor will try to identify and then treat the cause of the dehydration.”

NIH – Skin Turgor (Medical Encyclopedia) “Skin turgor is an abnormality in the skin's ability to change shape and return to normal (elasticity). Considerations: Skin turgor is a sign commonly used by health care workers to assess the degree of fluid loss or dehydration. Fluid loss can occur from common conditions, such as diarrhea or vomiting. Infants and young children with vomiting, diarrhea, and decreased or no fluid intake can rapidly lose a significant amount of fluid. Fever speeds up this process. To determine skin turgor, the health care provider grasps the skin on the back of the hand, lower arm, or abdomen between two fingers so that it is tented up. The skin is held for a few seconds then released. Skin with normal turgor snaps rapidly back to its normal position. Skin with decreased turgor remains elevated and returns slowly to its normal position. Decreased skin turgor is a late sign in dehydration. It occurs with moderate to severe dehydration. Fluid loss of 5% of the body weight is considered mild dehydration, 10% is moderate, and 15% or more is severe dehydration.”

NHS – Heat exhaustion and heatstroke “Causes of heat exhaustion and heatstroke: Heatstroke occurs when the temperature of the body rises sharply. This may happen because of excessively high outside temperatures, physical exertion, extensive burns, and severe sunburn or because of an undiagnosed medical condition such as an overactive thyroid gland. The heat can affect anyone, but some people are at greater risk of serious harm. These include: • older people, • babies and young children, • people with a serious chronic condition, particularly breathing or heart problems, • people with mobility problems, • people who are physically active, like manual workers and sportsmen and women. Certain medications can also make you more susceptible to heat exhaustion. These include: • diuretics - these drugs increase the production of urine, so they can add to dehydration, • lithium, anti-epileptics, statins - these may not work properly if you get dehydrated, • beta-blockers - these drugs help reduce blood pressure but they also interfere with the body's processes of thermoregulation (how it copes with getting too hot), such as sweating. Diagnosing heat exhaustion and heatstroke: A body temperature of 39.5C or higher in conjunction with the described symptoms is heatstroke. If the patient's temperature is above 41C, they are in a critical condition and require emergency medical attention. On arrival at hospital, the doctor should be told about: • the exposure to high temperatures, • whether the person has taken part in physical exercise, • if there is a pre-existing medical condition, and • previous attempts to cool the person down. Temperature and pulse will be closely monitored, and the doctor will also look for signs of neurological illness such as confusion, irrational behaviour, seeing things that aren't really there (hallucinations) and fits (seizures).”

Highlighted Articles

Dehydration and youth sports: Curb the risk (2008) “If you're sweltering in the stands at a youth sporting event, imagine what it's like for the athletes. Learn who's at risk of dehydration — and how to prevent it. Children don't adapt as well as adults do to exercise in hot, humid weather. They produce more heat, sweat less and may be less likely to drink enough fluids during exercise — all of which increase the risk of dehydration. Dehydration can lead to mild to severe heat-related illnesses, such as heat cramps, heat exhaustion and heatstroke. … If your child plays sports in hot weather, encourage him or her to drink plenty of fluids before, during and after practices and games. Teach your child the signs and symptoms of dehydration, as well as the importance of speaking up if they occur. Involve your child's coach, too. Talk to the coach about adjusting the intensity of practice depending on the temperature and humidity on the field — and support the coach's decision to cancel games and practices when it's dangerously hot outside. “

Water (2008)“Remember, fluid comes in a variety of forms, including the water in solid foods. Many fruits, vegetables and soups are at least 80 percent water, so they can count toward your daily intake. Milk, diet sodas, unsweetened carbonated waters, most herbal teas, decaffeinated teas and decaf coffee can substitute, cup-for-cup, for pure water. The same is no true of fruit juices and sugar-sweetened drinks. Although theses other beverages still count as fluid sources, there sugar content can slow down your body's water absorption. Finally, don't count coffee or alcohol as a water substitute: Caffeine is a mild diuretic (a substance that helps remove water from the body via urine). This makes coffee and other caffeinated beverages poor sources of water.”

NIH - Extreme Heat a Deadly Risk for Older Adults: Their bodies don't cool quickly, so caution should rise with temperatures “Most of the 200 Americans who die of health problems caused by high heat and humidity are age 50 or older. To help seniors stay safe this summer, Murphy suggested: • Stay in the air conditioning, whether home or out and about. • Fans do not adequately cool down the body during intense heat waves. • Avoid extended periods of sun exposure, walking long distances, lifting heavy objects or other strenuous activities. • Drink plenty of water and other nonalcoholic, non-caffeinated clear beverages. If one's urine is a light yellow color, enough water is being taken into the body, but if it's darker, the body needs more water. • Take cool showers, baths, or sponge baths. • Wear lightweight, light-colored, loose-fitting clothing and hats. “

Hot Weather Exercise "The most general dangers from heat are dehydration and overheating. Water lost through perspiring comes directly out of your bloodstream. If the water isn't replaced, you can develop heat exhaustion, — a condition marked by fatigue, dizziness, pale skin and shortness of breath. Heat exhaustion can occur in as little as 30 minutes if you're sweating heavily. … Heat stroke is a less common but even more serious danger. Heat stroke occurs when you generate so much heat that your body can no longer release it. Your body's overloaded cooling mechanism shuts down, causing body temperature to skyrocket. Heat stroke can develop in just a few minutes if you're exercising intensely, even when you're well hydrated. The usual treatment for heat stroke is putting the person in a tub of cool water. If not treated immediately, heat stroke can be fatal. Anyone who becomes disoriented or faints while exercising should be taken to a hospital. The solution: Be extremely careful when doing any intense exercise in weather over 80° Fahrenheit or 90-percent humidity. In a hot, humid climate, even a three-mile running race can boost body temperatures to dangerous levels. Keep your efforts comfortable and steady. … Helpful Tips [see article] "

The Wonders of Water "A 2002 study published in the American Journal of Physiology questioned the old recommendation of 8 ounces of water, eight times a day. After a thorough review, researcher Heinz Valtin concluded there was inadequate evidence that healthy adults -- living in temperate climates and not engaged in rigorous activities -- need large amounts of water. For normal, healthy adults, Valtin recommended simply drinking when thirsty. And he reported that even caffeinated drinks can count toward satisfying our fluid requirements. In February 2004, the Institute of Medicine (IOM) issued new recommendations that agree with Valtin's findings. The new guidelines remove the eight-glasses-a-day recommendation, and say healthy adults may use thirst to determine their fluid needs. Exceptions to this rule include anyone with a medical condition requiring fluid control; athletes; and people taking part in prolonged physical activities or whose living conditions are extreme. The IOM report did not specify requirements for water but made general fluid intake recommendations of 91 ounces (that's 11-plus cups a day) for women and 125 ounces (15-plus cups a day) for men. Remember, these guidelines are for total fluid intake, including fluid from all food and beverages. Approximately 80% of our water intake comes from drinking water and other beverages, and the other 20% comes from food. Assuming these percentages are accurate for most of us, the recommended amount of beverages, including water, would be approximately 9 cups for women and 12.5 cups for men. "

Water: How much should you drink every day?

Cold Water Immersion: The Gold Standard for Exertional Heatstroke Treatment (Exerc Sport Sci Rev. 2007) "The key to maximize the chances of surviving exertional heatstroke is rapidly decreasing the elevated core body temperature. Many methods exist to cool the body, but current evidence strongly supports the use of cold water."

Heat-Related Illness in Athletes. (Am J Sports Med. 2007) "The continuum of heat illness includes mild disease (heat edema, heat rash, heat cramps, heat syncope), heat exhaustion, and the most severe form, potentially life-threatening heat stroke. Heat exhaustion typically presents with dizziness, malaise, nausea, and vomiting, or excessive fatigue with accompanying mild temperature elevations. The condition can progress to heat stroke without treatment. Heat stroke is the most severe form of heat illness and is characterized by core temperature >104 degrees F with mental status changes. Recognition of an athlete with heat illness in its early stages and initiation of treatment will prevent morbidity and mortality from heat stroke. Risk factors for heat illness include dehydration, obesity, concurrent febrile illness, alcohol consumption, extremes of age, sickle cell trait, and supplement use."

Rapid IV versus oral rehydration: responses to subsequent exercise heat stress. (Med Sci Sports Exerc. 2006)

Voluntary fluid intake and core temperature responses in adolescent tennis players: sports beverage versus water. (Br J Sports Med. 2006) "CONCLUSION: Ad libitum consumption of a CHO-E drink may be more effective than water in minimising fluid deficits and mean core temperature responses during tennis and other similar training in adolescent athletes."

Oral Versus Intravenous Rehydration of Moderately Dehydrated Children: A Randomized, Controlled Trial (PEDIATRICS 2005)

Highlighted Internet Sites

NIH - Heat Illness

NIH - Fluid and Electrolyte Balance

NHS – Dehydration