Heat Cramps, Heat Exhaustion, and Heat Stroke — Recognition and Response

Heat illness exists on a spectrum from uncomfortable (heat cramps) to fatal (heat stroke). The progression along this spectrum can be rapid — particularly in children, older adults, and people with underlying health conditions. Recognising where on the spectrum a person is, and responding appropriately to each level, is the difference between a minor incident and a preventable death.

The key distinction — between heat exhaustion and heat stroke — determines whether the situation requires immediate emergency services. Missing heat stroke and treating it as mere heat exhaustion has killed people.

The Heat Illness Spectrum

Level	Core Temperature	Mental Status	Skin	Sweating
Heat cramps	Normal	Normal	Normal	Yes
Heat syncope (faint)	Normal / slight rise	Brief loss of consciousness	Pale	Yes
Heat exhaustion	< 40°C (104°F)	Normal but may be anxious/confused	Pale, cool, clammy	Yes, heavy
Heat stroke	> 40°C (104°F)	Confused, disoriented, unconscious	Hot, red, possibly dry	May cease

The transition from heat exhaustion to heat stroke can happen quickly, particularly in:

• Children under 4 and older adults over 65
• People on diuretics, beta-blockers, or anticholinergics
• People with cardiovascular or renal disease
• People who are dehydrated before the heat exposure begins

Heat Cramps

Heat cramps are painful muscle spasms — typically in the legs, abdomen, or arms — caused by electrolyte loss through sweating during strenuous exercise or heat exposure.

Management:

1. Move to a cool area.
2. Rest.
3. Oral rehydration with water or a sports drink containing sodium.
4. Gentle stretching and massage of the affected muscles.
5. Do not return to exercise until cramps resolve completely.

Heat cramps are not dangerous in themselves but are a sign of significant electrolyte and fluid loss. They may indicate early stages of more serious heat illness if other symptoms develop.

Heat Exhaustion

Heat exhaustion is the most common heat illness. It is caused by sustained exposure to high temperatures with inadequate fluid and electrolyte replacement, leading to dehydration and mild cardiovascular stress.

Signs:

• Profuse sweating
• Pale, cool, clammy skin
• Rapid, weak pulse
• Nausea or vomiting
• Muscle cramps
• Dizziness, lightheadedness
• Headache
• Fatigue
• Core temperature below 40°C

The person is conscious and knows where they are.

Management:

1. Move to a cool, shaded, air-conditioned environment — the most important action.
2. Lie the person down and elevate their legs.
3. Cool the person: remove excess clothing; apply cool wet cloths to neck, armpits, and groin; fan them.
4. Encourage oral hydration — cool water or oral rehydration solution in small frequent amounts; do not force fluids.
5. Call 999 if symptoms do not improve within 30 minutes, or if any signs of heat stroke develop.
6. Monitor closely — heat exhaustion can progress to heat stroke rapidly.

Recovery from heat exhaustion typically occurs within 30 minutes with adequate cooling and hydration. A person who has had heat exhaustion should not return to exertion for at least 24 hours.

Heat Stroke

Heat stroke is a medical emergency. It is distinguished from heat exhaustion by neurological involvement — confusion, altered consciousness, or unconsciousness — combined with a core temperature above 40°C.

⚠️ Heat stroke is a medical emergency that can cause brain damage and death within minutes if not treated immediately. The core sign is neurological dysfunction — confusion, bizarre behaviour, loss of consciousness — in the context of heat exposure. Call 999 immediately and begin aggressive cooling while waiting.

Two types:

• Classical heat stroke: Typically in older adults during heat waves; develops over days; skin may be hot and dry
• Exertional heat stroke: Typically in young people during vigorous exercise; develops quickly; skin may still be sweaty

Signs of heat stroke:

• Core temperature > 40°C (104°F)
• Confusion, disorientation, slurred speech
• Bizarre behaviour or agitation
• Seizures
• Loss of consciousness
• Hot skin — red, possibly dry in classical; may still be sweaty in exertional
• Rapid, strong pulse initially; may weaken
• Nausea and vomiting

Signs that distinguish heat stroke from heat exhaustion:

• Confusion (heat exhaustion: person knows who they are and where they are; heat stroke: they do not)
• Temperature: if measured, > 40°C
• Skin hot vs. cool

Management — Heat Stroke:

1. Call 999 immediately.
2. Begin aggressive cooling NOW — do not wait for emergency services:
   • Move to coolest available environment
   • Remove all clothing
   • Apply ice packs to neck, armpits, and groin (highest-density blood vessel areas)
   • Cover with cool wet sheets and fan constantly
   • Immerse in cool water if possible and safe to do so (best method; target 39°C core temperature, then stop)
3. If conscious and able to swallow: offer small sips of cool water.
4. If unconscious and breathing: recovery position.
5. If not breathing: CPR.
6. Do not give paracetamol or aspirin — these do not lower heat stroke temperature and paracetamol can worsen liver damage in heat stroke.

The goal is to reduce core temperature below 39°C within 30 minutes. Rapid cooling is the treatment — everything else is supportive.

Prevention — Before Heat Illness Occurs

Measure	Benefit
Hydrate before activity	Starts exercise with adequate fluid
Regular fluid intake during heat	Replaces sweat losses; does not wait for thirst
Electrolyte replacement	Sports drinks, bananas, salted snacks for prolonged activity
Shade and cool resting periods	Reduces heat load
Acclimatisation	10–14 days of gradual heat exposure before strenuous activity
Cool environment during heat waves	Particularly for elderly; air conditioning access
Check on vulnerable people	During heat waves, regular welfare checks on elderly neighbours

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Quick Reference

Level	Key Sign	Treatment
Heat cramps	Muscle spasm; normal mental status	Rest; cool area; oral fluids with electrolytes
Heat exhaustion	Pale, sweaty; dizzy; conscious and oriented	Cool environment; cooling measures; oral fluids; monitor
Heat stroke	Confused or unconscious + hot	Call 999; aggressive cooling immediately; ice packs to neck/armpits/groin
Heat stroke vs. exhaustion	Mental status is key distinction	If confused: treat as heat stroke
Temperature > 40°C	Heat stroke territory	Emergency
Cooling target	Below 39°C	Stop cooling at 39°C to avoid overcooling