Heat-Related Illnesses

 

Am Fam Physician. 2019 Apr 15;99(8):482-489.

  Patient information: A handout on this topic is available at https://familydoctor.org/condition/heat-exhaustion-heatstroke.

Author disclosure: No relevant financial affiliations.

Heat-related illnesses comprise a spectrum of syndromes resulting from disruption of thermoregulation in people exposed to high environmental heat. Symptoms range from heat edema and exercise-associated muscle cramps to exercise-associated collapse, heat exhaustion, and life-threatening heat stroke. Athletes, outdoor laborers, and military personnel are at greatest risk. Several intrinsic and extrinsic factors increase the risk of heat-related illness, including medical conditions, environmental factors, medication use, and inadequate acclimatization. Proper recognition and treatment are effective in preventing adverse outcomes. Management of the mildest forms of heat-related illness (e.g., heat edema, exercise-associated muscle cramps) is largely supportive, and sequelae are rare. Heat exhaustion is characterized by cardiovascular hypoperfusion and a rectal core temperature up to 104°F without central nervous dysfunction. Mild cooling, rest, and hydration are recommended. Heat stroke is a medical emergency in which patients present with rectal core temperature of 105°F or greater, multiorgan damage, and central nervous dysfunction. Ice water or cold water immersion is recommended. Patients adequately cooled within 30 minutes have excellent outcomes. Patients with heat stroke generally require hospitalization to monitor for medical complications despite rapid cooling. People diagnosed with heat stroke or severe heat-related illness should refrain from physical activity for at least seven days after release from medical care, then gradually begin activity over two to four weeks. Acclimatization, adequate hydration, and avoidance of activities during extreme heat are the most effective measures to reduce the incidence of heat-related illnesses.

Heat-related illness is a physiologic insult that occurs when the body is unable to dissipate heat adequately, which leads to dysfunctional thermoregulation. It includes a continuum of syndromes ranging from heat edema and exercise-associated muscle cramps to exercise-associated collapse, heat exhaustion, and life-threatening heat stroke.1,2 The latter two conditions typically manifest with an elevated core body temperature.3 Athletes, military personnel, and outdoor laborers (e.g., farmers, construction workers, firefighters) are at greatest risk. Heat-related illness is largely preventable.4,5

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferences

Ensuring adequate acclimatization, physical fitness, and hydration, and assessing wet bulb globe temperature or heat index before outdoor activity or work reduces the risk of heat-related illness.

C

14

Patients with heat stroke should be cooled to a core body temperature of 101°F (38.3°C) within 30 minutes after recognition of symptoms.

C

25

Rectal temperature is the recommended method for obtaining core body temperature to assist in diagnosing heat stroke.

C

14, 15

Ice water and cold water immersion are the most effective cooling modalities in the treatment of heat stroke.

B

25, 26, 28


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferences

Ensuring adequate acclimatization, physical fitness, and hydration, and assessing wet bulb globe temperature or heat index before outdoor activity or work reduces the risk of heat-related illness.

C

14

Patients with heat stroke should be cooled to a core body temperature of 101°F (38.3°C) within 30 minutes after recognition of symptoms.

C

25

Rectal temperature is the recommended method for obtaining core body temperature to assist in diagnosing heat stroke.

C

14, 15

Ice water and cold water immersion are the most effective cooling modalities in the treatment of heat stroke.

B

25, 26, 28


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.

Risk Factors

Heat accumulation is the effect of combined environmental exposure, metabolic demands, and restricted or impaired cooling mechanisms. When the ability to cool the body is inadequate, core temperature rises, resulting in clinical symptoms. Major risk factors include strenuous exercise, exposure to high temperatures and/or humidity, lack of acclimatization, poor physical fitness, and excessive clothing,

The Authors

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ROBERT GAUER, MD, is an assistant professor in the Department of Family Medicine at Uniformed Services University of the Health Sciences, Bethesda, Md., and a hospitalist at Womack Army Medical Center, Fort Bragg, N.C....

BRYCE K. MEYERS, DO, MPH, is a brigade surgeon/chief medical officer in the Headquarters Company, 505th Parachute Infantry Regiment, 3rd Brigade Combat Team, 82nd Airborne Division, and primary care manager at Robinson Health Clinic, Fort Bragg.

Address correspondence to Robert Gauer, MD, Womack Army Medical Center, Family Medicine Residency Clinic, Bldg. 4-2817, Riley Rd., Fort Bragg, NC 28310 (e-mail: robertgauer@yahoo.com). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

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