• Exertional heat illness (EHI) is the leading cause of morbidity and mortality among young athletes in North America.
• Other subgroups who exert themselves in or around heat (e.g. firefighters, soldiers, and outdoor labourers) are also at increased risk of EHI.
• EHI manifests via a spectrum of disease from minor (e.g. heat cramps) to severe (e.g. heat stroke):

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• While the pathophysiology of EHI is largely unclear, morbidity and mortality are a direct result of ischemia and oxidative and nitrosative stress. This leads to a culmination of thermoregulatory failure, heat stroke, and circulatory shock.
• Quick recognition and management are crucial as prognosis is worse when cooling is delayed and the core temperature is allowed to remain above the critical threshold of 40.5 to 41.0°C (105 to 106°F) for any period of time.

Management

• Remove from heat source.
• Initial assessment (e.g. ABCs, vitals, rectal temperature).
• Large bore IV access, supplemental oxygen if needed, cardia telemetry.
• For mild heat illness (e.g. heat cramps), provide oral fluid replacement.
• For moderate heat illness (e.g. heat syncope, heat exhaustion), provide oral IV fluids and initiate cooling measures (see below).
• Severe heat illness (e.g. heat stroke), rapidly cool (within 30 minutes) initiate cooling measures including ice bath immersion (see below).
• Consider benzodiazepines to manage agitation and shivering.
• Cooling Methods:
  • Should be initiated as soon as possible.
  • Remove all clothing/equipment.
  • If performing cold water immersion, ideally immerse as much of the body as safely possible in ice water with temperature between 2 to 15°C (35 to 60°F) and stir the water vigorously during cooling.
  • Ensure rectal thermometer is in place for continuous measurement.
  • Continue cooling until the patient’s rectal temperature reaches 39°C (102°F).
  • If ice water immersion is not feasible, cool the patient using the best available means such as:
    • Placing patient in a cold shower.
    • Dousing them with cold water and facilitate cooling with fans.
    • Moving them to a cool shaded area and applying cold wet towels to as much of the body surface as possible.
    • Placing wet ice packs all over the body, especially over skin covering major vessels (e.g. groin, axilla).
    • Placing chemical cold packs over cheeks, palms, and soles.

Source: Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update.

• Reassess (e.g. vitals, rectal temperature, urine output, cardiac telemetry).
• Order relevant bloodwork given the clinical context. (e.g. electrolytes, liver function, cardiac biomarkers, creatine kinase, ECG).
• Supportive measures (e.g. cooling, fluid resuscitation, correct electrolyte disturbances).
• No role for pharmacologic therapy (e.g. acetaminophen) in exertional heat stroke.

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Patients suspected to have a severe heat illness (i.e. heat stroke) and/or signs of hemodynamic instability should be admitted for a period of observation and monitoring for complications.

Dependent on local guidelines.

Will depend on clinical presentation and patient’s progress during hospitalization. Relevant specialties may be required depending on the nature of the patient’s complication (e.g. internal medicine for acute kidney injury).

• Will depend on clinical presentation and patient’s progress during hospitalization.
• For healthy patients at baseline who recover rapidly from exertional heat stroke with cooling and have no residual symptoms, common practice at many major endurance events involves discharge after observation for up to six-hours. This also includes a thorough reexamination prior to discharge and arrangements made for appropriate follow-up (e.g. family physician).

1. Atha, W. F. (2013). Heat-related illness. Emergency medicine clinics of North America, 31(4), 1097-1108.

   
   

2. Cheshire Jr, W. P. (2016). Thermoregulatory disorders and illness related to heat and cold stress. Autonomic Neuroscience, 196, 91-104.

   
   

3. Grubenhoff, J. A., du Ford, K., & Roosevelt, G. E. (2007). Heat-related illness. Clinical Pediatric Emergency Medicine, 8(1), 59-64.

   
   

4. Lipman, G. S., Gaudio, F. G., Eifling, K. P., Ellis, M. A., Otten, E. M., & Grissom, C. K. (2019). Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update. Wilderness & Environmental Medicine.

   
   

5. O’Connor, F. G., Casa, D. J. (2019). Exertional heat illness in adolescents and adults: Management and prevention. In J. Grayzel (Ed.), UpToDate. 

   
   

6. Pryor, R. R., Casa, D. J., Holschen, J. C., O’Connor, F. G., & Vandermark, L. W. (2013). Exertional heat stroke: strategies for prevention and treatment from the sports field to the emergency department. Clinical Pediatric Emergency Medicine, 14(4), 267-278.