Heat Exhaustion

There is no set line that distinguishes heat exhaustion from heat stroke. If a person is suffering from a heat-related illness such as heat exhaustion, and changes in mental status occur, he or she should be considered to be suffering from heat stroke. This includes confusion, lethargy, seizure, or coma.

This is a medical emergency, and if treatment is delayed mortality can be greater than 50%. While victims of heat exhaustion sweat profusely, people suffering from heat stroke stop sweating and have dry skin. This is a warning sign of impending heat stroke.

Individuals with heat exhaustion tend to have symptoms such as

• profuse sweating,
• weakness,
• muscle cramps,
• headache, and
• nausea and vomiting.

As dehydration increases from the loss of body water, lightheadedness may occur and fainting (syncope) may occur, especially if the affected individual stands up quickly (due to orthostatic hypotension).The person also may have a low-grade fever.

Heat exhaustion occurs when a person exercises and works in a hot environment and the body cannot cool itself adequately. Dehydration occurs with water loss from excessive sweating, which causes muscle cramps, weakness, nausea, and vomiting. Nausea and vomiting make it difficult to drink enough fluid to replenish the body's water supply, and the lack of body water impairs further sweating, evaporation, and cooling.

• The relative humidity is an important factor in developing heat exhaustion. If the humidity is too high, sweat on the skin cannot evaporate into the surrounding air and body temperature cooling fails.
• Living in a hot environment may predispose a person to heat exhaustion. During a heat wave, the elderly, the poor, and those who live an isolated life may not have access to air conditioning and are at risk of heat-related illnesses.

Heat exhaustion usually affects people who are working or exercising in a hot environment, and those who do not have access to adequate water. Those at risk for heat exhaustion include:

• Infants and young children are at risk because their temperature regulation mechanisms are not fully developed. They also are dependent upon others for water and appropriate clothing.
• The elderly are similarly at risk because of underlying medical conditions that limit the ability to sweat including poor circulation, skin changes, and chronic medication usage.
• Socioeconomic issues increase the risk of heat exhaustion if access to air conditioning is limited. During heat waves, large cities often open cooling centers to help minimize the risk of large numbers of people succumbing to heat-related illnesses.
• Certain medications such as antidepressants, antipsychotics, and tranquilizers may impair the ability of the body to sweat.
• Alcohol consumption
• The overweight or obese

The body has the ability to acclimate to hot weather but if heat waves come suddenly, or if a person travels from a cooler environment to a hot environment, the risk of heat exhaustion increases. It takes about 7 to 10 days for the body to adapt to hot weather. A non-acclimated person can produce a liter or almost a quart of sweat in an hour to assist in cooling the body. A person who is acclimated to the heat can produce 2 or 3 liters of sweat per hour, doubling or tripling the cooling potential for the body.

This water lost in sweat needs to be replaced for the sweating/cooling mechanism to work. A liter of sweat weighs 1 kilogram or 2.2 pounds.

Heat exhaustion usually can be treated at home as long as the affected individual can replace the lost fluid, keep well hydrated, and find a cool place to rest. Water, electrolyte replacement solutions, or sports drinks are appropriate to consume. If nausea and vomiting prevent rehydration, the individual should seek medical attention and may need IV fluids for rehydration.

• Muscle cramps can be severe and if stretching and rehydration cannot relieve recurrent cramps, medical care may be necessary.

It is important to recognize that if the person stops sweating, becomes confused, or has a seizure, heat stroke, a life-threatening condition, may be developing.

• Emergency medical services should be activated immediately (call 911 if available).
• The affected individual should be moved to a cooler place, have their clothing removed, and attempts should be made to cool the body with cold compresses, spraying or sponging the body with cool water and promoting air circulation with oscillating fans.

Diagnosis of heat exhaustion is made by circumstantial evidence:

1. History (exercising or working in a hot environment, living in a hot apartment with no air-conditioning)
2. Symptoms (excess sweating, headache, weakness, nausea, and vomiting)
3. Physical examination (signs of dehydration)

Laboratory tests are not routinely performed unless the health care professional is concerned about electrolyte imbalance or significant dehydration and kidney failure.

However, it is important for the health care professional to consider other diagnoses, since there are many infectious illnesses that accompany a fever, weakness, nausea, and vomiting.

This is especially the case in the elderly and very young. In these groups, heat exhaustion may be a diagnosis of exclusion, meaning that other more serious illnesses should be considered before settling on heat as the cause of the problem. History and physical examination may be all that are needed.

• Cooling and rehydration are the cornerstones 0f treating heat exhaustion. The affected individual should stop their activity, and then move or be moved from the hot environment to a cooler environment. The person may be placed in the shade or taken to an air-conditioned environment (don't forget that cars have air conditioning). Clothes may be removed to help with air circulation across the body. Misting the skin with cool water also helps by stimulating evaporation and cooling the body.
• Rehydration is the next important step in treating heat exhaustion. This may be a challenge if the person begins to suffer from nausea and vomiting. Small sips of water, a mouthful at a time, might be tolerated even if some vomiting persists. Water, sports drink, and other electrolyte replacement drinks are reasonable options.
• If oral rehydration fails or if symptoms persist, intravenous fluids may be required to replace the water loss because of excessive sweating. Hydration continues until the patient begins to urinate, a signal that the kidneys have sensed that there is enough fluid in the body, and it no longer retains fluid.
• Muscles cramps and pain may be treated with over-the-counter medications like ibuprofen (Advil, Motrin, Nuprin, etc.) and acetaminophen (Tylenol and others).

Heat exhaustion is one part of the spectrum of heat-related illness, and symptoms should be reversible with treatment. However, some affected individuals do not recognize their symptoms and if they are not removed from the hot environment, cooled, and rehydrated, the heat-related illness can progress to heat stroke, a life-threatening condition.

Individuals who have suffered from heat exhaustion are more prone to experience another episode and should be cautious when working or exercising in hot conditions.

Most individuals recover well from heat exhaustion. The key to recovery is recognizing symptoms before they progress to heat stroke. The earlier the activity is stopped, the individual is cooled and hydration begins, the greater the likelihood that complications will not occur.

Understanding one's environment is perhaps the most important step in preventing heat-related illness. If possible, strenuous activities should not be performed in excessively hot or humid environments. However, people often have to work in the heat of the day, or indoors in hot situations and need to make the effort to protect their bodies. These can include frequent breaks taken in cooler areas, adequate fluid intake, and slowing the pace of work to decrease the heat generated by the body.

A person at risk for heat exhaustion should watch their urine output to monitor their hydration status. If the body is dehydrated, the kidneys will hold onto water, and make concentrated, strong-smelling urine. If enough water is present, the urine will turn clear.

Acclimating to conditions allows the body to perform in situations that would otherwise be difficult. The body will make physiologic changes allowing it to cool more efficiently if it has gradual exposure to hot conditions. Moving from a cool to a very hot environment quickly increases the risk of developing heart related-illness symptoms.

It is important to look after the family and loved ones during heat waves. When the temperature rises, the elderly or those less fortunate may not have air conditioning or the ability to cool their homes. Cities often set up cooling centers when the heat index rises, and there is an increased risk of heat-related illness. In 1995, Chicago experienced a record heat wave that killed hundreds of people. Most were elderly and the poor who had no air conditioning or could not afford to use it. Some wouldn't open their windows for fear of crime. In 2015, heat waves were responsible for more than 5,000 deaths in India and Pakistan.