Heat stroke is a medical emergency. Clinical features include a core body temperature >40°C and central nervous system dysfunction (e.g., altered level of consciousness ranging from confusion to coma [encephalopathy], seizures) in the context of passive exposure to severe environmental heat (classic heat stroke) or strenuous exercise (exertional heat stroke).
Use a rectal thermometer to measure core body temperature and monitor continuously. In practice, consider using an oesophageal probe in intubated patients.
Start rapid active cooling immediately, based on clinical suspicion regardless of degree of hyperthermia and measuring technique. Aim to achieve a target temperature of no less than 39°C. Stop cooling once this temperature is reached.
Cold or ice water immersion is the preferred method for patients with exertional heat stroke. Use wetting and fanning the skin in patients with classic heat stroke and consider wetted ice packs or chemical cold packs as adjunctive cooling.
Patients are at risk of multi-system organ failure, so careful monitoring is essential even after return to normothermia.
This topic covers the management of both heat stroke and heat exhaustion in adults
Heat stroke is defined as a core temperature >40°C with central nervous system dysfunction (e.g., altered level of consciousness ranging from confusion to coma [encephalopathy], seizures). Heat stroke is generally divided into classic heat stroke (due to passive exposure to severe environmental heat) and exertional heat stroke (due to strenuous physical exercise).
Heat exhaustion is a mild to moderate heat illness. The patient presents with a normal or slightly elevated core temperature (37°C to 40°C), mild neurological symptoms (e.g., intense thirst, weakness, anxiety, dizziness, syncope), and an intact mental status. If untreated, heat exhaustion can progress to heat stroke. Heat stroke, however, can occur without preceding heat exhaustion.
History and exam
Key diagnostic factors
- history of exposure to severe environmental heat or strenuous physical exercise
- central nervous system dysfunction
- hyperthermia (>40°C)
- risk factors
Other diagnostic factors
- intense thirst (heat stroke or heat exhaustion)
- weakness (heat stroke or heat exhaustion)
- anxiety (heat stroke or heat exhaustion)
- dizziness (heat stroke or heat exhaustion)
- syncope (heat stroke or heat exhaustion)
- headache (heat stroke or heat exhaustion)
- nausea/vomiting (heat stroke or heat exhaustion)
- sinus tachycardia
- muscle tenderness
- bruising and skin bleeding
- older age
- impaired cognition
- patients unable to care for themselves
- lack of acclimatisation to hot environments
- pre-existing dehydration
- poor physical condition
- environmental factors
- young, active people exercising intensely under hot, humid conditions
1st investigations to order
- rectal temperature
- liver function tests
- renal function tests
- arterial blood gases
- creatine kinase
- clotting profile
Alexander Alexiou, MB, BS, BSc, DCH, FRCEM, Dip IMC RCSEd
Greater Sydney Area Helicopter Emergency Medical Service
New South Wales
AA declares that he has no competing interests.
BMJ Best Practice would like to gratefully acknowledge the previous expert contributor, whose work is retained in parts of the content:
James L. Glazer, MD, FACSM, CAQSM
Tufts University School of Medicine
Helen Small, FRCEM, MSc Sports and Exercise Medicine
Consultant in Emergency Medicine
Royal Free London
HS declares that she has no competing interests.
Section Editor, BMJ Best Practice
HDC declares that she has no competing interests.
Lead Section Editor, BMJ Best Practice
TAO declares that she has no competing interests.
Lead Section Editor, BMJ Best Practice
RW declares that she has no competing interests.
Comorbidities Editor, BMJ Best Practice
AS declares that she has no competing interests.
Drug Editor, BMJ Best Practice
AM declares that he has no competing interests.
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