Hyperthermia is a condition in which the body reaches abnormally high temperatures because it cannot regulate its internal temperature. It is caused when the body produces or absorbs too much heat or both. Hyperthermia can be mild (heat exhaustion) or severe (heatstroke). A person can experience hyperthermia through intense physical activity or from being in a very hot environment. Children and the elderly are most at risk. If left untreated, heatstroke can lead to a Seizure or a coma, and be life-threatening.
Guidelines
- In the case of an adult experiencing hyperthermia due to intense physical activity, the first aid provider should consider immersing the person from the neck down in cold water (1-26° C/33.8-78.8° F) until a core body temperature of less than 39°C (102.2° F) is reached. If this is not possible, they may cool the person using any other active cooling technique (e.g. with a wet sheet, water or icepacks placed in the armpits, neck and groin area). *
Good practice points
- The person should stop all physical activity and be removed from the hot environment to a cool place.
- For people with hyperthermia due to intense physical activity, first aid providers can also consider using any other immediate active or passive cooling techniques available to them (e.g. cold-water immersion of hands or feet, icepacks, cold showers, fanning, ice-sheets and towels).
- If the person has hyperthermia due to intense physical activity and they are responsive enough, they may have something cool to drink. This may include water or a water and sugar and salt solution (e.g. homemade oral rehydration solution or sports drink). See Dehydration.
- The first aid provider should access emergency medical services (EMS) if the person:
> shows unusual behaviour, confusion or becomes unresponsive
> has a seizure
> has a body temperature above 39°C (102.2°F)
> stops sweating
> cannot drink without vomiting.
Chain of survival behaviours
Prevent and prepare
- Wear appropriate clothing for the temperature and activity.
- Limit physical activities during the hottest part of the day.
- Take frequent breaks to drink water.
- In places where there is a high risk of hyperthermia, consider how to make cooling methods available so there is no delay in first aid when hyperthermia occurs.
Early recognition
The person’s condition will depend on how much the body has overheated.
Mild to moderate hyperthermia (heat exhaustion)
- Normal or mildly higher temperature.
- Cool, pale, clammy skin.
- Excessive sweating.
- Thirsty.
- Headache.
- Muscle cramps.
- Rapid, weak pulse.
- Fainting or dizziness.
Severe hyperthermia (heatstroke)
- The person has stopped sweating (indicating they are severely dehydrated).
- High body temperature (above 40°C/104°F).
- Dry, flushed, hot skin.
- Nausea.
- Muscle spasms.
- Pain throughout the body.
- Unusual behaviour or signs of confusion.
- Seizure or possible loss of responsiveness.
First aid steps
- Advise the person to stop all physical activity. Help them to rest in a cool place and to remove any excess clothing.
- If the person is showing signs of severe hyperthermia, (see signs above), immediately start cooling them down. Immerse them in cold water (1-26° C/33.8-78.8°F) for around 15 minutes, or until their temperature has dropped to less than 39°C (102.2°F). If this is not possible (e.g., cold water is unavailable or the person is confused and refuses), cool the person using any other active cooling technique (e.g., place a cool, wet sheet on the person or wet them with cold water and place ice packs on their neck and groin areas). Fanning them may also increase the cooling action.
- Access EMS.
- If the person is showing signs of mild to moderate hyperthermia, (see signs above), cool them off using any technique available such as immersing their hands and feet in cold water, applying ice-packs to their neck and groin area, encouraging them to have a cold shower, or fanning them. Give them some water to drink. Sports drinks or cold tea may also be helpful.
- Monitor the person’s temperature and level of response. Try to reduce their temperature to less than 39°C.
Access help
- If the person shows signs of severe hyperthermia, access emergency medical care immediately. Severe hyperthermia can be life-threatening.
- A person with mild to moderate hyperthermia will usually recover without medical care. Monitor them closely in case their condition does not improve or worsens. And access medical care if in any doubt.
Recovery
Keep the person cool and encourage them to rest. In most cases, people with mild to moderate hyperthermia will recover fully.
Education considerations
Context considerations
- Programme designers should consider any cultural or legal implications involved with removing the person’s clothing and emphasise the importance of dignity to learners.
- In areas where ice or cold water is not readily available, identify the cooling methods that may be available to them such as removing the person from the heat, wetting them, fanning them, encouraging rest and removing any excess clothing.
Learner considerations
- Athletes and older adults are important learner audiences on which to focus. Athletes may have greater exposure to heat and older adults are at a higher risk of hyperthermia.
Facilitation tips
- Focus on prevention and help learners to recognise the warning signs of hyperthermia so they can take preventative action before it happens.
- The key action is to cool the person quickly, so the first aid provider needs to prioritise readily available cooling methods.
- Emphasise the temperature that the body should be reduced to 39 °C (102.2°F) and not less.
Learning connections
- Combine this topic with other first aid emergencies (such as Breathing difficulties or Seizures) so learners can recognise and differentiate the symptoms of hyperthermia.
- Dehydration is common in people with hyperthermia.
Scientific foundation
Systematic reviews
The International Liaison Committee on Resuscitation (ILCOR) first aid task force completed a systematic review on different techniques for cooling of heatstroke and exertional hyperthermia (Douma, 2020), and the Centre for Evidence-based Practice (CEBaP) developed evidence summaries about the reduction of activity and drinking (2020).
Coldwater immersion (14°C–15°C/57.2°F–59°F)
The following studies all relate to adults with exertional hyperthermia. In seven non-randomised controlled trials, a faster rate of core body temperature reduction was found with cold water immersion of the torso compared with passive cooling (low certainty of evidence). In three controlled trials, no significant mean difference in the rate of core body temperature reduction was found with cold water immersion of the torso compared with temperate-water immersion (20°C-26°C/68°F-78.8°F) (very low certainty evidence). One controlled trial showed no significant mean difference in the rate of body temperature reduction with the use of cold water immersion (14°C/57.2°F) of the torso compared with the use of colder-water immersion (8°C/46.4°F) (low certainty evidence). Two controlled trials showed no significant mean difference in the rate of body temperature reduction with the use of cold water immersion (14°C/57.2°F) of the torso compared with ice-water immersion (2°C-5°C/35.6°F-41°F) (very low certainty evidence).
Coldwater immersion (10° C–17° C/50.0° F–62.6° F) of hands and feet
In six controlled trials, a faster rate of core body temperature reduction was found with cold water immersion of hands and/or feet (10°C-17°C/50.0-62.6°F) compared with passive cooling in adults with exertional hyperthermia (moderate certainty evidence).
Colder-water immersion (9° C–12° C/48.2° F–52.6° F)
The following studies in this paragraph relate to adults with exertional hyperthermia. In three non-randomised controlled trials, a faster rate of core body temperature reduction was found with the use of colder-water immersion of the torso (9°C-12°C/48.2°F-52.6°F) compared with passive (moderate certainty evidence). One controlled trial did not show a significant mean difference in the rate of core body temperature reduction with the use of colder-water immersion (9°C/48.2°F) up to the waist compared with passive cooling (low certainty evidence). One controlled trial showed a faster rate of core body temperature reduction with the use of colder-water immersion of the torso (11.7°C/53.0°F) compared with temperate water (23.5°C/74.3°F) (moderate certainty evidence). One controlled trial showed no significant mean difference in the rate of core body temperature reduction with the use of colder-water immersion of the hands or feet (10°C-12°C/50.0°F-52.6°F) compared with the use of colder-water immersion of the torso (low-certainty evidence).
Ice-Water Immersion (1° C–5° C/33.8° F–41.0° F)
In one small cohort study where ice-water immersion of the torso (5°C-10°C/33.8°F-41°F) together with the administration of intravenous normal saline at room temperature 0.9% were compared with applying ice-packs to the armpits in adults with exertional heatstroke, showed no deaths in either group (very low-certainty evidence). In four non-randomised controlled trials in adults with exertional hyperthermia and one cohort study on people with exertional heatstroke, a faster rate of core body temperature reduction was shown when comparing ice-water immersion of the torso (1°C-5°C/33.8°F-41°F) with passive cooling (low-certainty evidence). The same was found in two non-randomised controlled trials comparing ice-water torso immersion (2°C/35.6°F) with temperate-water immersion (20°C– 26°C/68.0°F –78.8°F) (moderate-certainty evidence). In one small cohort study in adults with exertional heatstroke where ice-water immersion (5°C-10°C/33.8°F-41.0°F) combined with the administration of intravenous 0.9% normal saline was compared with applying icepacks to the armpits (low certainty evidence).
Evaporative cooling (mist and fan)
Two controlled studies in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with evaporative cooling compared with passive cooling (low-certainty evidence). Two controlled trials showed no significant mean difference in the rate of core body temperature reduction with evaporative cooling compared with the use of ice-packs applied to the neck, armpit and groin (one trial, low-certainty evidence), or compared with the use of commercial ice-packs applied to the neck, armpit and groin (one trial, low-certainty evidence). One controlled trial showed no significant mean difference in the rate of core body temperature reduction with the use of evaporative cooling and commercial icepacks to the neck, armpit and groin compared with evaporative cooling alone (low-certainty evidence). One controlled trial showed no significant mean difference in the rate of core body temperature reduction with the combined use of evaporative cooling and commercial icepacks to the neck, armpit and groin, compared with passive cooling (low-certainty evidence).
Commercial icepacks
Two controlled trials in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with the use of commercial icepacks to the neck, groin and armpits compared with passive cooling (low-certainty evidence). One controlled trial in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with the use of commercial icepacks to the whole body compared with passive cooling (low-certainty evidence).
One controlled trial in adults with exertional hyperthermia showed a faster rate of core body temperature reduction when applying commercial ice-packs to the cheeks, palms, and soles compared with passive cooling, as well as when compared with applying commercial ice-packs applied to the neck, groin and armpit (moderate certainty evidence).
Fan alone
Two controlled trials in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with the use of fanning alone compared with passive cooling (low-certainty evidence).
Cold shower (20.8° C/69.4° F)
In one non-randomised controlled trial in adults with exertional hyperthermia, a faster rate of core body temperature reduction was found with cold showers compared with passive cooling (moderate-certainty evidence).
Hand-cooling devices
Three controlled trials in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with the use of hand-cooling devices compared with passive cooling (low certainty evidence).
Cooling vests and jackets
Two controlled trials in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with the use of the Arctic Heat cooling jacket compared with passive cooling (low certainty evidence). Five controlled trials in adults with exertional hyperthermia compared the use of various cooling vests with passive cooling. None of the studies showed a significant mean difference in the rate of core body temperature reduction when compared with passive cooling (very low certainty evidence).
Reflective blankets
One controlled trial in adults with exertional hyperthermia showed no significant mean difference in the rate of core body temperature reduction with the use of reflective blankets compared with passive cooling (low certainty evidence).
Physical activity
There is limited evidence from one observational case-control study in favour of reducing physical activity. The study showed that decreasing activity resulted in a statistically significant decrease in the risk of heatstroke during heat waves. Evidence is of very low certainty and results cannot be considered precise due to lack of data (CEBaP, 2020).
Drinking fluids
There is limited evidence from one observational case-control study in favour of taking in extra liquids. The study showed that taking in extra liquids resulted in a statistically significant decrease in the risk of heatstroke during heat waves. Evidence is of very low certainty and results cannot be considered precise due to a lack of data (CEBaP, 2020).
References
Systematic reviews
Centre for Evidence-Based Practice, Belgian Red Cross-Flanders. (2020). Evidence summary Heatstroke – Reduction of activity. Available from: https://www.cebap.org/knowledge-dissemination/first-aid-evidence-summaries/
Centre for Evidence-Based Practice, Belgian Red Cross-Flanders. (2020). Evidence summary Heatstroke – Drinking. Available from:
https://www.cebap.org/knowledge-dissemination/first-aid-evidence-summaries/
Douma, M. J., Aves, T., Allan, K. S., Bendall, J. C., Berry, D. C., Chang, W. T., … Lin, S. (2020). First aid cooling techniques for heat stroke and exertional hyperthermia: A systematic review and meta-analysis. Resuscitation, 148, 173-190.
Non-systematic reviews
Lipman, G. S., Gaudio, F. G., Eifling, K. P., Ellis, M. A., Otten, E. M., & Grissom, C. K. (2019). Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2019 Update. Wilderness & Environmental Medicine, 30(4), S33-S46. Retrieved from: https://doi.org/10.1016/j.wem.2018.10.004.
Wasserman, D. D., & Healy, M. (2017). Cooling techniques for hyperthermia. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK459311/
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