Heat exhaustion and heatstroke

Also called Sunstroke, Heat illness

Heat exhaustion is treatable at home in 30 minutes. Heatstroke is a 999 call, and confusion is the line between them.

What it is

Two stages of the same problem. **Heat exhaustion** is the body struggling to cope with heat: hot, sweaty, weak, headachy, but the person is still themselves. It responds to cooling and fluids within about 30 minutes.

**Heatstroke** is when the temperature control system fails. The core temperature rises above 40C, and the person becomes confused, stops sweating, or loses consciousness. It damages the brain, kidneys, liver and heart, and it kills. It is a medical emergency exactly like a stroke or a heart attack.

**Confusion is the line.** Somebody hot and unwell who is still lucid has heat exhaustion; somebody hot and confused has heatstroke until proven otherwise.

UK heatwaves now cause thousands of excess deaths, concentrated in older people, people living alone, people with dementia or heart failure, people who cannot move or drink independently, and people in top-floor flats and care settings.

Medicines increase the risk substantially: diuretics, ACE inhibitors, antipsychotics, anticholinergics, antihistamines and lithium all impair heat regulation or fluid balance, and lithium levels become dangerous in dehydration.

Babies and young children left in cars are a specific and rapidly fatal risk.

Signs you might notice

Heat exhaustion: tiredness, dizziness, headache, nausea, feeling sick, excessive sweating, pale clammy skin, cramps in the arms legs or stomach, fast breathing, a fast weak pulse, being very thirsty, and a temperature up to 40C.

Heatstroke, all of which mean 999: still unwell after 30 minutes of cooling; a temperature above 40C; confusion, disorientation or odd behaviour; loss of consciousness or a seizure; hot skin that is no longer sweating; very fast breathing or breathlessness.

In an older person the first sign is often confusion or a fall, not a complaint of heat.

In a baby: unusually sleepy, floppy, refusing feeds, and fewer wet nappies.

How it can affect day-to-day life

Older people feel thirst less, sweat less and often restrict fluids deliberately because of continence worries. That combination is what makes heat lethal indoors.

Care settings need a plan before the heat arrives: fluids offered hourly, curtains closed by day, windows opened at night, activities moved to the cool part of the day, and identifying which residents are most at risk.

Fans do not cool a room and, above about 35C, blowing hot air over skin can make things worse. Damp cloths, cool showers and moving to the coolest room work.

Medication reviews before summer are worth doing for people on diuretics and psychotropics.

Never leave anybody, or any animal, in a parked car. Interior temperatures rise dangerously within minutes even on a moderate day.

Supporting someone well

Move the person somewhere cool, lie them down, raise their feet, remove excess clothing, and cool the skin with cool water on the skin, cold packs in the armpits and neck, and fanning.

Give plenty of water, or a rehydration or sports drink.

Reassess after 30 minutes. Improving means heat exhaustion; not improving, or confused, means 999.

Call 999 for confusion, unconsciousness, seizure, hot dry skin, or a temperature over 40C. Keep cooling while waiting.

Prevent: offer fluids regularly rather than waiting to be asked, keep rooms shaded and ventilated at night, avoid the middle of the day, and check on people living alone.

Review medicines before summer for anyone on diuretics, antipsychotics, anticholinergics or lithium.

Never leave anyone in a parked car.

Where to get help

999 for heatstroke: confusion, unconsciousness, seizure or a temperature over 40C.

NHS 111 for advice on heat exhaustion that is improving slowly.

A GP practice for a medication review before summer for anybody at risk.

Age UK on 0800 678 1602 for hot weather advice for older people.