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[Conditions](https://durgical.com/en/conditions/) · [Emergency medicine and toxicology](https://durgical.com/en/conditions/)

# Heat stroke and heat exhaustion

Heat illness ranges from exhaustion to heat stroke, a medical emergency in which body temperature soars and the brain is affected.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/)
- [Kidneys](https://durgical.com/en/anatomy/kidney/)
- [Cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/)
- [Skin](https://durgical.com/en/anatomy/skin/)
- [Liver](https://durgical.com/en/anatomy/liver/)

## In the clinical exam

- [Body temperature and fever patterns](https://durgical.com/en/clinical-exam/body-temperature-and-fever-patterns/)

## Why it happens

- [Disseminated intravascular coagulation: how consumption causes both clots and bleeding](https://durgical.com/en/general-pathology/disseminated-intravascular-coagulation-how-consumption-causes-both-clots-and-ble/)
- [Health effects of climate change](https://durgical.com/en/general-pathology/health-effects-of-climate-change/)
- [Thermal injury: burns, hyperthermia and hypothermia](https://durgical.com/en/general-pathology/thermal-injury-burns-hyperthermia-and-hypothermia/)
- [Causes of cell injury](https://durgical.com/en/general-pathology/causes-of-cell-injury/)
- [Heat exhaustion and heat stroke](https://durgical.com/en/physiology/heat-exhaustion-and-heat-stroke/)
- [Body temperature regulation](https://durgical.com/en/physiology/body-temperature-regulation/)

## Show 1 more

- [Fever](https://durgical.com/en/physiology/fever/)

## What it is

Heat-related illnesses caused when the body cannot lose enough heat. Heat exhaustion causes weakness and dehydration with normal brain function; heat stroke is a core temperature usually above 40 °C with central [nervous system](https://durgical.com/en/anatomy/system/nervous-system/) dysfunction and multi-organ injury.

## Who gets it

More frequent during heat waves and in hot, humid lowland regions; climate change is increasing exposure in Latin America, including Colombia's Caribbean coast and inter-Andean valleys. Exertional heat stroke affects young athletes, soldiers and outdoor workers; classic heat stroke affects older adults and people with chronic illness during heat waves.

## Causes

- Classic (non-exertional): high environmental temperature overwhelming thermoregulation
- Exertional: heat production from intense exercise or labour, often in heat and humidity
- Dehydration and salt loss from sweating (heat exhaustion)

## Risk factors

- Extremes of age, obesity, poor fitness and lack of acclimatisation
- Chronic heart, kidney or mental illness and limited mobility
- Medicines and drugs that impair sweating or increase heat (anticholinergics, diuretics, beta-blockers, antipsychotics, stimulants, alcohol)
- Heavy protective clothing or uniforms
- Living alone without cooling, and outdoor work without rest and water

## Pathophysiology

When heat gain exceeds loss, the hypothalamic set point is not changed (unlike fever), but cooling fails. High temperature denatures proteins and damages cells; gut ischaemia lets endotoxin enter the blood, triggering a systemic inflammatory response. The result is brain dysfunction, rhabdomyolysis, kidney and liver injury and disseminated intravascular coagulation.

## Classification

- Heat cramps and heat syncope
- Heat exhaustion: core temperature below about 40 °C, normal mental status
- Heat stroke: core temperature usually above 40 °C with neurological dysfunction (classic or exertional)

## Symptoms and signs

- Heat exhaustion: heavy sweating, thirst, weakness, headache, nausea, dizziness and fainting
- Heat stroke: confusion, abnormal behaviour, ataxia, seizures or coma
- Hot skin, dry in classic heat stroke but often sweaty in exertional
- Tachycardia, fast breathing and hypotension
- Muscle cramps

## Red flags

- Any change in mental status in a hot person (treated as heat stroke)
- Core temperature above about 40 °C
- Seizures or collapse during exertion
- Dark urine or low urine output
- Bleeding or bruising (coagulopathy)

## Diagnosis

**Clinical**
Clinical: heat exposure or exertion, a high core (rectal) temperature and neurological dysfunction. Oral or [skin](https://durgical.com/en/anatomy/skin/) thermometers underestimate core temperature.

**Tests**
Electrolytes, glucose, [kidney](https://durgical.com/en/anatomy/kidney/) and [liver](https://durgical.com/en/anatomy/liver/) function, creatine kinase, urinalysis for myoglobin, blood gases, coagulation tests and platelets.

**Imaging**
Head CT when another cause of coma is suspected; [chest](https://durgical.com/en/anatomy/region/chest/) X-ray if aspiration or pulmonary oedema.

## Differential diagnosis

- Sepsis or central nervous system infection
- Neuroleptic malignant syndrome, serotonin syndrome or malignant hyperthermia
- Anticholinergic or stimulant (cocaine, amphetamine) toxicity
- Thyroid storm
- Stroke or status epilepticus

## Goal of treatment

Lower core temperature as fast as possible ('cool first, transport second'), support organ function and treat complications.

## Treatment

**Acute**
Immediate whole-body cooling: cold-water immersion is fastest for exertional heat stroke; evaporative cooling (water spray and fanning) and ice packs to the neck, armpits and groin are alternatives. Cooling stops at about 38.5–39 °C to avoid overshoot.

**Conservative**
Heat exhaustion: rest in a cool place, remove excess clothing and oral or intravenous rehydration with salt replacement.

**Medical**
Intravenous fluids guided by circulation, benzodiazepines for shivering or seizures. Antipyretics such as paracetamol are not effective because the set point is normal.

**Follow-up**
Continuous core temperature, urine output, electrolytes, kidney and liver function and coagulation; nursing watches for rebound hyperthermia.

## Complications

- Rhabdomyolysis and acute kidney injury
- Acute liver injury
- Disseminated intravascular coagulation
- Seizures, cerebral oedema and lasting neurological damage
- Acute respiratory distress syndrome and multi-organ failure

## Prognosis

Heat exhaustion recovers fully with treatment. Heat stroke mortality rises with the time spent at high temperature; rapid cooling within the first 30 minutes greatly improves survival, especially in exertional cases.

## Prevention

- Gradual acclimatisation, scheduled rest and water for outdoor work and sport
- Avoiding heavy exertion in the hottest hours
- Checking on older and isolated people during heat waves and providing cool places

## Test yourself

Think of the answer, then tap the question to see it.

## What two features define heat stroke?

High core temperature (usually above 40 °C) and central nervous system dysfunction (confusion, seizures, coma).

## What is the most effective cooling method for exertional heat stroke?

Cold-water immersion, started on site as quickly as possible.

## Why are antipyretics not useful in heat stroke?

The hypothalamic set point is normal; the problem is failure of heat loss, not a raised set point as in fever.

## Which laboratory complications should be monitored in heat stroke?

Rhabdomyolysis (creatine kinase), acute kidney injury, liver injury and disseminated intravascular coagulation.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/heat-stroke-and-heat-exhaustion/)

## Related conditions

- [Rhabdomyolysis](https://durgical.com/en/conditions/rhabdomyolysis/)
- [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/)
- [Disseminated intravascular coagulation](https://durgical.com/en/conditions/disseminated-intravascular-coagulation/)
- [Dehydration (fluid volume deficit)](https://durgical.com/en/conditions/dehydration/)
- [Malignant hyperthermia](https://durgical.com/en/conditions/malignant-hyperthermia/)
- [Neuroleptic malignant syndrome](https://durgical.com/en/conditions/neuroleptic-malignant-syndrome/)
- [Serotonin syndrome](https://durgical.com/en/conditions/serotonin-syndrome/)
- [Anticholinergic toxicity (incl. scopolamine «burundanga»)](https://durgical.com/en/conditions/anticholinergic-toxicity/)
- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Thyroid storm](https://durgical.com/en/conditions/thyroid-storm/)
- [Acute liver failure](https://durgical.com/en/conditions/acute-liver-failure/)
- [Cocaine and sympathomimetic toxicity](https://durgical.com/en/conditions/cocaine-and-sympathomimetic-toxicity/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Heat emergencies](https://medlineplus.gov/ency/article/000056.htm) (MedlinePlus, US National Library of Medicine, 2026).

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Source: https://durgical.com/en/conditions/heat-stroke-and-heat-exhaustion/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/heat-stroke-and-heat-exhaustion/