Recommendations
Urgent
Suspect heat stroke in a patient with:[1]
A history of passive exposure to severe environmental heat (classic heat stroke) or strenuous exercise (exertional heat stroke)
An elevated core body temperature (>40°C)
Central nervous system dysfunction (e.g., altered level of consciousness ranging from confusion to coma [encephalopathy], seizures).
Assess and stabilise the patient using the Airway, Breathing, and Circulation (ABC) approach.[1][2]
Assess the patient’s temperature with a rectal thermometer.[1][2] In practice, consider using an oesophageal probe in intubated patients.
Remove excess clothing and start rapid active cooling immediately based on clinical suspicion (regardless of the degree of hyperthermia or measuring technique).[1][2][9] See the Management section.
Discuss the patient with a senior colleague.
Move the patient to a cooler place
Remove excess clothing and start rapid active cooling immediately (before the patient is transported to hospital). See the Management section
Arrange immediate transfer of the patient to hospital.
Key Recommendations
Monitor the patient's temperature while cooling. The target core temperature should be no less than 39°C to avoid overshoot hypothermia.[1] Stop cooling at this point. See the Management section.
In practice, order and monitor serial bloods (particularly potassium levels, renal function, arterial blood gases, clotting profile, creatine kinase) at least once daily in all patients with heat stroke, and more frequently in patients who are critically ill or who have signs of organ failure.
Be aware that older adults are at particular risk for heat stroke.[2] Other risk factors include:[1][2][10]
Poor physical condition
Pre-existing dehydration
Obesity
Lack of acclimatisation to hot environments
Environmental factors (e.g., absence of adequate breaks, absence of shelter or shade, high humidity, high temperatures, lack of access to water)
Certain medical conditions (e.g., diabetes, cardiovascular disease, anhidrosis)
Certain medications (e.g., diuretics, anticholinergics, antidepressants).
Heat exhaustion is a mild to moderate heat illness. Patients present with:[1][2]
A normal or slightly elevated core temperature (37°C to 40°C)
Mild neurological symptoms (e.g., intense thirst, weakness, anxiety, dizziness, syncope)
An intact mental status.
If untreated, heat exhaustion can progress to heat stroke.[1] Heat stroke, however, can occur without preceding heat exhaustion.[1]
Heat stroke is a medical emergency. Patients with heat stroke may develop life-threatening multi-organ dysfunction syndrome with shock, acute respiratory failure, acute kidney injury, disseminated intravascular coagulopathy, and intestinal ischaemia.[1]
Assess and stabilise the patient using an Airway, Breathing, and Circulation (ABC) approach.[1][2] See the Management section.
If the patient presents in the community, move them to a cooler place.[1][2][9]
Suspect heat stroke in a patient with:[1]
A history of passive exposure to severe environmental heat (classic heat stroke) or strenuous physical exercise (exertional heat stroke)
An elevated core body temperature (>40°C)
Central nervous system dysfunction (e.g., altered level of consciousness ranging from confusion to coma [encephalopathy], seizures).
Be aware that in older adults (>65 years old) the presentation may be subtle and non-specific.
Suspect heat exhaustion in a patient with:[1]
A history of passive exposure to high environmental heat or strenuous physical exercise
A normal or slightly elevated core temperature (37°C to 40°C)
Mild neurological symptoms (e.g., intense thirst, weakness, anxiety, dizziness, syncope).
Heat exhaustion is a mild to moderate heat illness. If untreated, however, it can progress to heat stroke.[1] Heat stroke can occur without preceding heat exhaustion.[1]
A patient with heat stroke has a history consistent with exposure to:[1]
Passive severe environmental heat (classic heat stroke), particularly in at-risk patients (e.g., older people) during a heat wave, or
Strenuous physical exercise (exertional heat stroke), particularly in younger adults, athletes, and people who exert themselves in the heat (e.g., firefighters, soldiers, construction workers).
Consider important risk factors for heat stroke:
Age <15 or >65 years old (children are not covered in this topic)[2][7]
Older adults are at particular risk for heat stroke, as they may be less able to recognise and respond to thermal loading.[7] Older people tend to have more cognitive comorbidities (e.g., dementia, Parkinson's disease) than younger people, and may take medicines (e.g., diuretics, antihypertensives) that predispose them to heat stroke
Poor physical condition[2]
Pre-existing dehydration[2]
Obesity[2]
Environmental factors (e.g., absence of adequate breaks, absence of shelter or shade, high humidity, high temperatures, lack of access to water).[2]
Other risk factors include:[1][2][10]
Medical conditions (e.g., diabetes, cardiovascular disease, anhidrosis, skin abnormalities [e.g., deep burns, psoriasis, extensive scarring of the skin], recent or acute illness, recent heat injury)
Congenital disorders (e.g., ectodermal dysplasia, idiopathic anhidrosis)
Drug (e.g., amphetamines) and alcohol misuse
Certain medications (e.g., diuretics, beta blockers, anticholinergics, antidepressants, antihistamines, antipsychotics).
Perform a physical and neurological examination.
Look for clinical findings consistent with heat stroke, which include:[1][2][10]
An elevated core body temperature (>40°C)
Central nervous system dysfunction:
Altered level of consciousness ranging from confusion to coma (encephalopathy)
Agitation
Lethargy
Seizures
Ataxia
Irritability
Other neurological symptoms such as headache, anxiety, dizziness, weakness, syncope, and nausea/vomiting
Vital sign abnormalities
Sinus tachycardia
Tachypnoea
Hypotension
Hot skin, that is dry or wet (i.e., sweating may be absent or present)
Profuse sweating and wet skin are typically seen in exertional heat stroke
The skin is commonly dry in classic heat stroke (as the sweat gland response and output is classically decreased in older adults under heat stress)
Additionally, the skin may be flushed (due to excessive peripheral vasodilation) or pale (a sign of vascular collapse)
Jaundice
Caused by hepatic injury due to thermal stress, tissue hypoperfusion, and indirect effects of heat stroke
Liver failure may occur
Muscle tenderness
Rhabdomyolysis may develop. Patients may report muscle tenderness and have hypo- or hypertonic muscles
Bruising and skin bleeding
Coagulopathies may manifest as bleeding from intravenous sites or as epistaxis
Endothelial damage may present as peripheral or pulmonary oedema
Disseminated intravascular coagulation may develop.
Findings consistent with heat exhaustion include:[1][2]
A normal or slightly elevated core temperature (37°C to 40°C)
Mild neurological symptoms, which may include:
Intense thirst
Weakness
Anxiety
Dizziness
Syncope
Headache
Nausea/vomiting.
Profusely sweating, cold, clammy skin
Practical tip
The presence of neurological dysfunction (e.g., an altered level of consciousness [encephalopathy], seizures), together with hot, dry skin, helps to distinguish heat stroke from heat exhaustion (though it is important to be aware that heat stroke can also present with hot, wet skin, especially exertional heat stroke, where heavy sweating is common).[2][10]
In patients with heat exhaustion mental status remains intact and profusely sweating, cold, clammy skin is seen.[2]
Rectal temperature
Measure rectal temperature in all patients with suspected heat stroke.[1][2]
Rectal temperature provides a more accurate measurement of core hyperthermia than axillary, oral, or aural thermometry.[1][2]
In practice, consider using an oesophageal probe in intubated patients.
Do not delay treatment in hyperthermic patients with an altered level of consciousness whose temperature is below the diagnostic threshold of 40°C.[2] See the Management section.
Practical tip
Be aware that patients who present with a normal temperature can have heat stroke, either because of inaccurate measuring techniques or from the effects of prior cooling (e.g., in the community). Continue to monitor the patient's temperature while cooling. See the Management section.
General investigations
Blood tests
Order blood tests in all patients with suspected heat stroke including:[10]
Full blood count
Neutrophilia, anaemia, and thrombocytopenia may be present
Liver function tests
Elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST) due to heat-induced liver damage
Renal function tests
Elevated creatinine and urea due to reduced renal perfusion
Glucose
Hypoglycaemia may occur in patients with exertional heat stroke and in patients with fulminant hepatic failure
Electrolytes
Hyper/hyponatraemia and hyper/hypokalaemia due to volume depletion
Arterial blood gases
Metabolic acidosis and respiratory alkalosis are the most common abnormalities due to poor peripheral perfusion
Creatine kinase
Elevated in rhabdomyolysis, a frequent complication of heat stroke
Clotting profile
Prolonged clotting times are due to heat-induced liver damage and disseminated intravascular coagulation, a frequent complication of heat stroke.
In practice, order and monitor serial bloods at least once daily (particularly potassium levels, renal function, arterial blood gases, clotting profile, and creatine kinase; see the Diagnosis section). If the patient is critically unwell or there is evidence of organ failure, consider repeating bloods more frequently.
Urinalysis
Order urinalysis to detect rhabdomyolysis (myoglobinuria) and other evidence of renal injury.[10]
ECG
Perform an ECG and monitor continuously for possible arrhythmias.[10]
Other ECG changes may be non-specific and include conduction abnormalities and non-specific ST/T wave changes.[10]
Use of this content is subject to our disclaimer