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Heat exhaustion
Last reviewed: 07.07.2025
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Heat exhaustion is a non-life-threatening clinical syndrome characterized by general weakness, malaise, nausea, fainting, and other non-specific symptoms associated with heat exposure. Thermoregulation is not impaired.
Heat exhaustion develops as a result of water and electrolyte disturbances associated with heat exposure, with or without physical exertion.
Symptoms of heat exhaustion
Symptoms of heat exhaustion are often non-specific, and patients may not understand what caused them. General weakness, headaches, nausea, and sometimes vomiting are possible. Fainting associated with prolonged exposure to heat (heat syncope) is characteristic of heat exhaustion and may resemble manifestations of cardiovascular pathology. Upon examination, the patient appears weakened, with increased sweating and tachycardia. Mental status is usually normal, unlike heat stroke. Body temperature is usually within normal limits, and when elevated, it is usually no higher than 40 °C.
Diagnosis of heat exhaustion of the body
The diagnosis is established based on clinical data; in most cases, it is necessary to exclude other causes of loss of consciousness (for example, hypoglycemia, acute coronary syndrome, various infectious diseases). Laboratory tests are needed only for differential diagnosis.
[ Treatment of heat exhaustion
The patient should initially be moved to a cool place and kept in bed. Treatment involves intravenous fluids and electrolyte replacement, usually with 0.9% saline; oral rehydration does not provide adequate electrolyte replacement. The rate and volume of rehydration depend on the patient's age, underlying medical conditions, and clinical response. Generally, 1–2 L of fluid given at 500 mL/h is sufficient. Elderly patients and those with cardiovascular disease may require slightly lower rates; if hypovolemia is suspected, more rapid infusion is necessary initially. External cooling (see appropriate section) is usually unnecessary. Rarely, severe heat exhaustion following vigorous exercise may be complicated by rhabdomyolysis, myoglobinuria, acute renal failure, and disseminated intravascular coagulation.