| Author: Victoria Wilson
|
| Author: Victoria Wilson
|
A Look at Heat-Related Health Alterations
Heat-related health alterations are a major cause of preventable deaths worldwide, especially in regions with high temperatures. Heat-related health alterations develop when the body can't offset its rising temperature, thus retaining too much heat (hyperthermia). Heat-related health alterations can occur when the body gets too hot (temperature above 99° F [37.2° C]) too quickly and is unable to cool itself.
Just cool it!
Although the body initially tries to cool itself down when it's exposed to too much heat, the mechanisms that regulate body heat can fail if the stress becomes too great. Normally, the body adjusts to excessive temperatures through complex cardiovascular and neurologic changes coordinated by the hypothalamus. Heat loss offsets heat production to regulate body temperature.
To and fro
Heat transfer to and from the body occurs in four ways:
If you can't take the heat . . .
In hot temperatures, the body loses heat mainly by radiation and evaporation. However, when air temperature is higher than 95° F (35° C), radiation of heat from the body stops and evaporation becomes the only means of heat loss. Sweat is the body's primary way to rid itself of extra heat. When a person sweats, water evaporates from the skin. The heat that makes this evaporation possible comes from the heat created by blood flowing through the skin. As long as blood is flowing properly, extra heat from the core of the body is “pumped” to the skin and removed by sweat evaporation.
Weather forecast
The effectiveness of sweat sometimes depends on the weather. If the air is humid (a condition in which there is significant water vapor in the atmosphere), it's harder for sweat to evaporate. If humidity reaches 100%, evaporation of sweat is no longer possible and the body loses its ability to lose heat. This means it's easier to sweat (and for the body to rid itself of excess heat) when it's relatively dry than when it's humid.
Don't sweat the small stuff
Because the evaporation that occurs during sweating causes water loss, it's important for a person to replenish by drinking water when sweating. If the body doesn't have enough water, dehydration can occur. This condition makes it harder for the body to cool itself because less water is available for the body to use during evaporation.
Heat-related health alterations are easy to prevent with adequate hydration. Teach your patients the importance of drinking water and other nonalcoholic fluids, especially when exerting themselves in hot weather (U.S. Department of Labor, n.d.).
What causes heat-related health alterations
Heat-related health alterations result when the body's production of heat increases at a faster rate than the body's ability to dissipate (get rid of) it (heat loss). Heat production increases with exercise; fever; infection; and the use of certain medications, such as amphetamines. Heat loss is more difficult in the presence of high temperatures or humidity, lack of acclimatization, lack of air conditioning or proper ventilation, excess clothing, obesity, decreased fluid intake, dehydration, extensive burns, cardiovascular disease, skin diseases, sweat gland dysfunction, endocrine disorders (such as hyperthyroidism, diabetes, and pheochromocytoma), ingestion of alcohol, and use of certain medications. (See Most common medications that can cause heat-related health alterations.)
When the body uses all its mechanisms and still can't keep its temperature down, the excess heat is retained and heat-related health alterations can develop.
Preventing heat-related health alterations
Prevention of heat-related health alterations is possible. Encourage your patient to stay well hydrated and be sensible about exertion in hot, humid weather. Remember to emphasize that water is the best fluid to drink when sweating, not an electrolyte drink. (See Teaching about heat-related health alterations.)
What to look for
Signs and symptoms of heat-related health alterations vary depending on the severity of the syndrome. (See each type of heat-related health alteration for specific information.)
Risks of heat-related health alterations
The presence of certain fluid and electrolyte imbalances is associated with increased risk of heat-related health alterations. These imbalances include dehydration, hyponatremia, and hypokalemia.
Dry idea
Signs and symptoms of dehydration include thirst; dry mucous membranes; hot, dry skin; decreased urine output; confusion; dizziness; postural hypotension; tachycardia; and eventually anhidrosis (absence of sweating).
Pass the salt, please
Signs and symptoms of hyponatremia (decreased serum sodium levels) include lethargy, nausea and vomiting, muscle cramps and weakness, muscle twitching, and seizures.
Special K
Signs and symptoms of hypokalemia (decreased serum potassium levels) include fatigue, paresthesia, hypoactive reflexes, ileus, cardiac arrhythmias, and electrocardiogram changes (flattened T waves, the development of U waves, ST-segment depression, and prolonged PR intervals).
Who's at risk?
Patients who are most at risk for fluid and electrolyte loss with heat-related illness include older adults, young children, people with chronic or debilitating diseases, those not acclimated to heat, those who frequently drink alcohol, and people taking certain medications (such as anticholinergics, diuretics, and beta-adrenergic blockers). (See Age-related heat-related health alteration risk.) Fluid and electrolyte loss also occurs in healthy people who work or exercise in extreme heat and humidity and in those who don't increase their fluid intake accordingly. Football players are prone to heat-related health alterations because their uniforms cover nearly all of the body and practice takes place in late summer, when the temperature outside is highest. Athletes should pay careful attention to the fluids they drink and lose, and should wear lightweight clothing when possible.
What tests show
These test results indicate heat-related health alterations. Depending on their actual value, severity is determined.
Other laboratory tests are used to detect end-organ damage (especially in patients with heatstroke) or to rule out other disorders.
Types of heat-related health alterations
Heat-related health alterations fall into five categories: heat rash, heat cramps, heat exhaustion, heat syncope, and heatstroke (Centers for Disease Control and Prevention, 2022d).
Heat rash
Heat rash is a skin irritation that can develop from excessive sweating during hot weather. It is usually found on the neck or upper torso, or in skin folds such as the axillae, elbow, groin, or breast creases and looks like a red cluster of pimples or tiny blisters (Centers for Disease Control and Prevention, 2022c). Teach your patient to stay in cooler environments with low humidity whenever possible. The body should be kept as dry as possible, and the patient can apply corn starch to areas at highest risk for heat rash. Creams and ointments should be avoided because these attract moisture.
Heat cramps
Heat cramps are muscle contractions that typically occur in the abdomen, arms, or legs. These painful contractions are caused by a deficiency of water and sodium and are generally attributed to dehydration and poor muscle conditioning. Cramps usually occur after exertion in high temperatures (> 100° F [37.8° C]) with profuse sweating and water intake without adequate electrolyte replacement. Heat cramps are common in manual laborers, athletes, and skiers who overdress for the cold as well as in those who aren't used to hot, dry climates in which excessive sweating is almost undetected because of rapid evaporation.
Hospitalization for heat cramps is rare, and the signs and symptoms are usually self-limiting. Symptoms usually improve with rest, water consumption, and a cool environment. Clothing can be removed or loosened, and stretching or direct pressure on the muscles may decrease cramping. Teach your patients to refrain from taking salt tablets while recovering and encourage them to choose a healthy snack with water instead (Centers for Disease Control and Prevention, 2022a). If the patient can't eat or drink, an IV infusion of normal saline solution may be needed (U.S. Department of Labor, n.d.).
Heat exhaustion
Heat exhaustion is caused by heat and fluid loss from excessive sweating without fluid replacement. Symptoms include headache, nausea, dizziness, weakness, thirst, heavy sweating, increased body temperature, decreased urine output, and irritability (Centers for Disease Control and Prevention, 2022b). Older adults, those with hypertension, and people working outside in hot weather are at highest risk for heat exhaustion (Centers for Disease Control and Prevention, 2022b). Rest, water, ice packs, and a cool environment are helpful when treating mild heat exhaustion. More severely exhausted patients may need IV fluids, especially if vomiting keeps them from drinking enough. Circulatory collapse may occur if this condition isn't promptly treated.
Hospitalization usually isn't necessary for heat exhaustion. It's typically treated by having the patient rest in a cool location and drink water, slightly salty fluids, or electrolyte-rich sports drinks every few minutes. Clothing can be removed or loosened, and the feet can be elevated 12" (30.5 cm). For severe cases, isotonic IV fluids may be given if available and if necessary. Rarely, cardiac stimulants and plasma volume expanders (such as albumin and dextran) are given; these should be used cautiously to avoid volume overload. Untreated heat exhaustion may lead to heatstroke (U.S. Department of Labor, n.d.).
Heat syncope
Heat syncope (fainting or dizziness) occurs when a patient stands up quickly or has been standing for a prolonged period of time. Dehydration and lack of acclimatization are often to blame for heat syncope (Centers for Disease Control and Prevention, 2022f).
Teach your patient to stay hydrated, to avoid being in direct sunlight for long period, to alternate between standing and sitting (so that prolonged standing is avoided), and to rise slowly when standing. Heat syncope can be treated by having the patient sit or lie down in a cool area and providing water or a replenishing sports drink. Depending on the circumstances, some patients who experience heat syncope may need hospitalization or medical attention, particularly if they have sustained an injury during the syncopal episode (U.S. Department of Labor, n.d.).
Heatstroke
Heatstroke, also known as sunstroke, is the most severe form of heat-related health alteration; it can be fatal if left untreated. It commonly occurs in patients who exercise in hot weather. Older adults and patients taking certain medications are also at risk for heatstroke in hot weather, even in the absence of exercise (Mayo Clinic, 2022). Signs to look for include hot, dry skin or profuse sweating (Centers for Disease Control and Prevention, 2022e), and symptoms that resemble a regular stroke, such as slurred speech, changes in level of consciousness, confusion, or dizziness.
Whether exercise related or not, a person with heatstroke usually has a very high temperature (104° F [40° C] or higher) and may be delirious, experience a seizure, or become unconscious.
Cool moves
Patients with heatstroke need to have their temperature reduced quickly (often with ice packs on the neck, armpits, and groin) and must also be given IV fluids for rehydration. Treatment of heat-related health alterations involves more than just balancing fluids. Sponge bathing with water, spraying with tepid water, or dabbing with wet towels and allowing a fan to blow cool air (evaporative cooling) over the patient can help to lower the body temperature. Spinal body cooling units may also be used (Mechem, 2022). Because many body organs can fail during heatstroke, patients are often hospitalized for observation. The body's attempt to regulate its temperature during heat-related health alterations causes a loss of excessive amounts of water and electrolytes. These must be replaced to counteract the hyperthermia. For these reasons, cool IV fluids may be used. Other ways to support the cooling process may include oxygen therapy and, in severe cases, endotracheal intubation. If the patient has uncontrollable seizures, IV diazepam and barbiturates may be prescribed (U.S. Department of Labor, n.d.).
Other options for cooling include covering the patient with ice and/or providing immersion in an ice bath, although these are used less often than the interventions mentioned earlier. Covering the patient with ice and using an ice bath rapidly lower body temperature, yet these methods can create complications such as peripheral vasoconstriction, which can lead to less heat dissipation. These techniques are uncomfortable for the patient, limit the ability to monitor the patient's vital signs and cardiac status, may result in hypothermia, and eventually may cause the patient to shiver. Shivering slows the cooling process because it increases core body temperature.
Recapping how you intervene
Treatment of heat-related health alterations requires frequent monitoring of laboratory values (central venous and pulmonary wedge pressures), instituting rehydration measures, replacing sodium and potassium, and starting cooling measures to decrease body temperature. You will also institute the interventions listed here:
For heat-related health alterations
For heatstroke
Say no to (these) drugs
For all types of heat-related health alterations, patients shouldn't take salicylates to decrease body temperature because salicylates increase the risk of coagulopathy. Patients shouldn't also take acetaminophen because it doesn't reduce body temperature during heat-related health alterations. Taking acetaminophen may actually worsen existing hepatic damage because the liver metabolizes acetaminophen.
If you answered all five questions correctly, grab a bottle of water! You're hot, hot, hot!
If you answered four questions correctly, good job! You've worked up a sweat in this chapter. Now move onto the next one.
If you answered fewer than four questions correctly, don't worry! You're sure to hit a hot stroke—err, streak—soon.
References
Centers for Disease Control and Prevention. (2022a, May 13). Heat cramps. https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html#_Heat_Cramps
Centers for Disease Control and Prevention. (2022b, May 13). Heat exhaustion. https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html#_Heat_ Exhaustion
Centers for Disease Control and Prevention. (2022c, May 13). Heat rash. https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html#_Heat_Rash
Centers for Disease Control and Prevention. (2022d, May 13). Heat stress. https://www.cdc.gov/niosh/topics/heatstress/default.html
Centers for Disease Control and Prevention. (2022e, May). Heatstroke. https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html#_Heat_Stroke
Centers for Disease Control and Prevention. (2022f, May 13). Heat syncope. https://www.cdc.gov/niosh/topics/heatstress/heatrelillness.html#_Heat
Mayo Clinic. (2022, June 25). Heatstroke. https://www.mayoclinic.org/diseases-conditions/heat-stroke/symptoms-causes/syc-20353581
Mechem, C. (2022). Severe nonexertional hyperthermia (classic heatstroke) in adults. UpToDate. https://www.uptodate.com/contents/severe-nonexertional-hyperthermia-classic-heat-stroke-in-adults
U.S. Department of Labor. (n.d.). Heat-related illnesses and first aid. https://www.osha.gov/SLTC/heatstress/heat_illnesses.html
In this chapter, you'll learn: