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Heat exhaustion facts
Heat exhaustion is one part of the spectrum of heat-related illnesses that include, heat cramps, heat exhaustion, and heat stroke.
The body cools itself by sweating and allowing that sweat to evaporate. This requires enough fluid in the body to make sweat, air circulating across the skin, and low air humidity to allow that sweat to evaporate.
Activity in a hot environment can overwhelm the body’s ability to cool itself, causing heat-related symptoms.
Symptoms of heat exhaustion include profuse sweating, weakness, nausea, vomiting, headache, light-headedness, and muscle cramps.
Heat exhaustion can progress to heat stroke when the body’s temperature regulation fails. The affected individual becomes confused, lethargic and may have a seizure; the skin stops sweating and the body temperature may exceed 106 F (41 C). This is a life-threatening condition and emergency medical attention is needed immediately.
Treatment for heat exhaustion includes recognizing the symptoms, stopping the activity, and moving to a cooler environment. Rehydration with water or a sports drink is the cornerstone of treatment for heat exhaustion. If nausea or vomiting prevents the affected individual from drinking enough water, intravenous fluids may be required.
What is heat exhaustion?
The body cools itself most efficiently by sweating and then the sweat evaporating. Should sweating be unable to meet the cooling demands of the body, heat-related illness can occur. This is a spectrum of conditions with minor symptoms such as prickly heat or heat rash, progressing to heat cramps, then heat exhaustion, and finally to heat stroke, a life-threatening medical condition.
The line between each diagnosis is not sharply drawn. Heat cramps tend to involve involuntary spasm of the large muscles of the body while heat exhaustion has more systemic complaints. These can include profuse sweating, weakness, nausea, vomiting, headaches, and muscle spasms. The affected individual may be a low grade fever. Heat stroke is a life-threatening situation where the body’s cooling system fails. The body temperature spirals out of control usually greater than 106F (41C), sweating stops and there are mental status changes like confusion, seizure, or coma.
Heat exhaustion occurs when a person exercises or works in a hot environment and sweating cannot dissipate the heat generated within the body. Often dehydration occurs because the person hasn’t replaced the water lost by sweating.
What causes heat exhaustion?
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, which causes muscle cramps, weakness, and nausea and vomiting. This makes 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.
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.
Who is at risk for heat exhaustion?
Heat exhaustion usually affects people who are working or exercising in a hot environment.
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 centres to help minimize the risk of large numbers of people succumbing to heat-related illness.
- 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.
What are the symptoms of heat exhaustion?
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, light-headedness may occur and fainting (syncope) may occur especially, if the affected individual stands up quickly (orthostatic hypotension). A low grade fever also may be present.
When should an individual seek medical care for heat exhaustion?
Heat exhaustion usually can be treated at home as long as the affected individual can maintain proper hydration. Water, electrolyte replacement solutions or sport drinks are appropriate to consume. If nausea and vomiting prevent rehydration, the individual should seek medical attention.
Muscles 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) and move the affected individual to a cooler place, remove their clothing, and try to cool the body with cold compresses, ice, and oscillating fans.
How is heat exhaustion diagnosed?
Diagnosis of heat exhaustion is made by circumstantial evidence:
- history (exercising or working in a hot environment)
- symptoms (excess sweating, headache, weakness, nausea and vomiting)
- physical examination (signs of dehydration)
Laboratory tests are not mandatory unless the health care practitioner is concerned about electrolyte imbalance or significant dehydration.
However, it is important for the health care practitioner 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. Careful history and physical examination may be all that is needed.
How is heat exhaustion treated?
Cooling and rehydration are the cornerstones for treating heat exhaustion. The affected individual should stop their activity and then move 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 the 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 and acetaminophen.
What are the complications of heat exhaustion?
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.
How can heat exhaustion be prevented?
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 a cooler areas, adequate fluid intake, and slowing the pace of work to decrease heat generation within 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 very hot environment quickly increases the risk of developing heat related-illness symptoms.
It is important to look after 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 centres 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.
What is the prognosis for heat exhaustion?
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 affected individuals is cooled and hydration begins, the greater the likelihood that complications will not occur.