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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022
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1 of 19Image courtesy of Bureau of Land Management – Nevada.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
In the above image, firefighters simulate the evacuation of a fellow firefighter suffering from heat illness.
Heat illness encompasses a spectrum of disorders caused by environmental heat exposure, including minor conditions—such as heat rash, heat cramps, heat syncope, and heat exhaustion—as well as the most severe condition, heat stroke. Heat stroke is generally defined as a body temperature exceeding 40.5°C (104.9°F) due to environmental heat exposure with lack of thermoregulation. It results in multiple organ dysfunction or central nervous system (CNS) abnormalities.[1,2] Approximately 700 deaths are attributable to heat illness each year in the United States.[3,4]
2 of 19Image from Wikimedia Commons | Nickt.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
People at risk for heat-related illness include those who are often exposed to hot climates without enough shade or water or without proper clothing. Individuals who are poorly hydrated because of illness, poor fluid intake, or excess alcohol consumption are also at risk. Obesity is an independent risk factor,[5] and it should be noted that females do not tolerate heat as well as men do during exercise.[6]
The chance of developing heat illness is especially high for nonathletes or "weekend warriors" who engage in strenuous physical activities and tend to be less prepared for heat exposure. However, even seasoned athletes may succumb to heat illness.
Some drugs and medications increase the risk of heat illness, including alcohol, antihistamines, beta blockers, diuretics, and laxatives.[7] Vasoconstrictors and beta blockers prevent appropriate thermoregulation and can exacerbate the effects of heat. The initial signs of heat illness are frequently neurologic because the brain is highly susceptible to hyperthermia.[8]
Compensatory techniques for engaging in hot-weather physical activity include drinking electrolyte-balanced fluid and wearing lightweight, moisture-wicking fabric.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
The typical symptoms of heat cramps, heat exhaustion, and heat stroke are shown. Two forms of heat stroke exist[9]:
Exertional
Classic nonexertional
Exertional heat stroke generally occurs in young individuals who engage in strenuous physical activity in a hot environment for a prolonged period. It develops when heat generated by muscular activity builds up faster than the body can release it through cutaneous vasodilation and sweating.[10]
Classic nonexertional heat stroke generally affects sedentary older individuals, people who are chronically ill, and the very young; this type of heat stroke occurs during environmental heat waves. Both types of heat stroke are associated with high morbidity and mortality, especially when therapy is delayed.[9]
4 of 19Image courtesy of Environmental Protection Agency (EPA).
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Between 1979 and 2014, the US heat-related death rate remained in the vicinity of about 0.5 deaths per million population (shown) for much of the time, though figures spiked in some years.
In the above graph, heat was the main cause of the deaths represented by the orange line; the blue line represents deaths only from May to September, with heat being the main or contributing cause of mortality.[11] Because of revisions in the international codes used by the World Health Organization (WHO) to classify causes of death, it is difficult to compare pre-1999 mortality data with mortality data from or after 1999.
Every year, an average of 21.5 visits to emergency departments (EDs) per 100,000 people occur for heat illness.[12] Heat exposure is considered to be responsible for approximately 700 deaths in the United States per year, with victims more likely to be male.[4,13] It is vital to recognize and treat heat illness expeditiously; the sequelae, which can be deadly, include neurologic damage, cardiovascular collapse (eg, prolonged tachycardia in an elderly patient), pulmonary damage, gastrointestinal issues, hepatic failure, renal failure, and rhabdomyolysis.[14]
5 of 19Image from Wikimedia Commons | Sentient Planet.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Heat rash (miliaria rubra; shown) appears as small pinkish pimples and is usually found on body areas covered by clothing.
Heat rash is caused by blockage of the sweat ducts, which results in the leakage of eccrine sweat into the epidermis or dermis.[15] The lesions develop within minutes or hours after the stimulation of sweating and resolve quickly (usually < 1 hour after removal of the stimulus that led to sweating).
Individuals with heat rash are at particularly high risk for heat exhaustion during exertion in hot weather because their ability to dissipate heat by means of sweat evaporation is impaired.[16] Treatment for heat rash involves supportive care and topical steroids.[17]
6 of 19Image from Wikimedia Commons | James Heilman, MD.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
The image shows myoglobinuria, often described as "Coca-Cola" urine, resulting from rhabdomyolysis, a symptom of heat stroke.
Heat exhaustion may be a precursor of heat stroke; its symptoms include the following:
Profuse sweating
Rapid breathing
Fast, weak pulse
Symptoms of heat stroke include the following:
Severely elevated temperature, often greater than 40.5°C (104.9°F)
Vomiting
Hot/dry skin
Tachycardia
In the later stages of heat stroke, CNS symptoms such as confusion, ataxia, seizures, and delirium can occur. Other severe symptoms include, as mentioned, rhabdomyolysis, resulting in renal failure and coagulopathy. Heat stroke–related mortality approaches 10%, but it increases to 33% in patients presenting with hypotension.[18]
7 of 19Image courtesy of Mark Silverberg, MD.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Multiple cooling techniques are available for the treatment of hyperthermia.[14,16] Evaporative cooling, which is often the most readily available method, reduces core body temperature in heat stroke by approximately 0.05-0.09°C (0.09-0.16°F) per minute.[16] After removing all clothing from the patient, continuously mist the individual with tepid water while directing a large fan at him/her. An alternative (and less time-consuming) evaporative cooling method is to place a wet sheet on the patient (shown).
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Strategic ice packing (shown), another simple technique, is often used in conjunction with evaporative cooling,[16] with ice packs placed on the patient's groin, in the axillae, and around the anterior and posterior neck. However, the data to support this cooling strategy are poor, and the other listed cooling methods are significantly more effective at lowering a patient's core temperature.[10]
9 of 19Image courtesy of United States Air Force Medical Service.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
When available, ice-water immersion (illustrated above), with the patient placed in a large container of ice water, is the treatment of choice for whole-body cooling.[19] Ice-water cooling acts faster than evaporative cooling in reducing core temperature,[10] lowering it by approximately 0.15-0.35°C (0.27-0.63°F) per minute.[16] Circulating the water can also increase the rate of cooling. This is the most effective means of lowering body temperature.[20] Ice-water immersion should be used with caution in the elderly, children, and persons with comorbid conditions, who have a higher mortality risk.
10 of 19Image courtesy of Mark Silverberg, MD.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Whole-body ice packing is similar to ice-water immersion and can be used when a large tub is not available.[16] After the patient's clothing has been removed, position him/her on plastic covers or sheets. Ensure that the patient's chest and extremities are covered with crushed ice (shown). A cadaver bag may be used to contain the patient (excluding his/her head), along with the ice and water. The bag is usually readily available in the ED, is easy to set up on a stretcher, and is nonporous or leakproof.
Another strategy, the use of a cooling blanket, can be employed in conjunction with other techniques to rapidly lower core body temperature. These blankets are made of materials that allow sweating and absorb body heat and are typically filled with cold fluid or gel.[21]
11 of 19Image courtesy of United States Air Force 59th Medical Wing.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Invasive core cooling can be used in conjunction with external cooling techniques.[16] Intravenous (IV) administration of cooled fluids can be used as a first-line treatment, especially when heat illness is combined with dehydration.
Oral and IV fluid therapy have been shown to be equally effective for hydration in cases of heat illness, but if the patient's mental status is altered, IV administration has the advantage of minimizing the risk of aspiration.[10] Fluids must be administered carefully because aggressive hydration can result in pulmonary edema. Note that it can be extremely difficult to establish IV access in a dehydrated patient, especially a baby; in such cases, intraosseous access can be used (shown).
12 of 19Image courtesy of Nicole E Cimino-Fiallos, MD, FAEEM.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
As mentioned, complications of IV fluid administration for rapid cooling include pulmonary edema (shown).[16] If providing fluids, administer normal saline (NS) or lactated Ringer solution. Avoid free water, because it can cause hyponatremia and cerebral edema.[16] Patients with altered mental status may benefit from a trial of glucose administration.
13 of 19Image from Medscape.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
More invasive techniques, such as gastric lavage (equipment setup shown), have demonstrated effectiveness in the rapid cooling of patients. The gastric mucosa is a particularly effective surface to cover with cool liquid, in that it does not vasoconstrict and can rapidly respond to treatment.[22]
14 of 19Images from Medscape (main) and Wikimedia Commons | National Institute of Diabetes and Digestive and Kidney Diseases (inset).
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Bladder irrigation can also be used for rapid cooling (setup shown). Although the bladder has a limited surface area, its proximity to the peritoneum and relative safety of access make it a good target for adjunctive treatment.
Peritoneal lavage is also effective for cooling, by virtue of the peritoneum's large surface area.[22] Whereas the data on this method have shown significant reductions in patient core temperature, most of the studies were performed in post–cardiac arrest scenarios, using patients with a different physiologic starting point from that in patients experiencing hyperthermia. This must be considered if the clinician is planning to use peritoneal lavage for cooling.
15 of 19Image courtesy of United States Air Force.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
For severe, refractory hyperthermia, even more invasive techniques should be considered if the necessary resources and staffing are available. Methods that have been effective include hemodialysis (shown), cardiopulmonary bypass, and intravascular cooling.[23] Patients with severe hyperthermia may require admission to an intensive care unit (ICU) for initial cooling and for treatment of subsequent complications, including, potentially, disseminated intravascular coagulopathy (DIC).
16 of 19Image from Wikimedia Commons | James Heilman, MD.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Consider using short-acting benzodiazepines, such as midazolam (shown), to reduce shivering and agitation in patients while instituting rapid cooling.[16] These medications are also useful in treating hyperthermia due to certain drugs and toxins (eg, sympathomimetics). When using benzodiazepines, make sure to carefully monitor the patient's airway and provide symptomatic support.
17 of 19Image courtesy of YouTube | cymcarvalho.
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Burning Up? A Guide to Treating Heat Illness
Zina Semenovskaya, MD, FAWM; Sage Wiener, MD | July 21, 2022 | Contributor Information
Dantrolene (shown), a muscle relaxant that binds to ryanodine receptors and prevents calcium release, is a highly effective antidote for malignant hyperthermia, a condition caused by medications.[24,25] However, it has not been shown to be effective in treating other types of heat illness. Antipyretics (eg, acetaminophen and ibuprofen) are also ineffective at decreasing core body temperature.
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Benign prostatic hyperplasia (BPH) occurs when an increased number of prostatic stromal and epithelial cells lead to enlargement of the prostatic tissue. Learn more about the evaluation of BPH and the different medical and surgical modalities used to treat it.Medscape Reference Slideshow, August 2020
Heat illness may be viewed as a continuum of illnesses relating to the body's inability to cope with heat. It includes minor illnesses, such as heat edema, heat rash (ie, prickly heat), heat cramps, and tetany, as well as heat syncope and heat exhaustion.Diseases/Conditions, Aug 2019
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Contributor Information
Authors
Zina Semenovskaya, MD, FAWM
Assistant Professor
Department of Emergency Medicine
Mount Sinai St Luke's-Roosevelt Medical Center
New York, NY
Disclosure: Zina Semenovskaya, MD, FAWM, has disclosed no relevant financial relationships.
Sage Wiener, MD
Assistant Professor
Attending Physician, Emergency Medicine
Director, Medical Toxicology
NYC Health + Hospitals/Kings County
SUNY Downstate Health Sciences University
Brooklyn, NY
Disclosure: Sage Wiener, MD, has disclosed no relevant financial relationships.
Editor
Lars Grimm, MD, MHS
Associate Professor
Department of Diagnostic Radiology
Duke University Medical Center
Durham, NC
Disclosure: Lars Grimm, MD, MHS, has disclosed no relevant financial relationships.
Reviewer
Nicole E Cimino-Fiallos, MD, FAAEM
Assistant Medical Director, Emergency Department
Meritus Medical Center
Hagerstown, MD
Disclosure: Nicole E Cimino-Fiallos, MD, FAAEM, has disclosed no relevant financial relationships.
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