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Hyperthermia

Rapidly cool the person to reduce their body temperature.

Hyperthermia is a condition in which the body reaches abnormally hightemperatures because it cannot regulate its internal temperature. It is caused whenthe body produces or absorbs too much heat or both. Hyperthermia can be mild(heat exhaustion) or severe (heatstroke). A person can experience hyperthermiathrough intense physical activity or from being in a very hot environment. Childrenand the elderly are most at risk. If left untreated, heatstroke can lead to a Seizureor a coma, and be life-threatening.

Guidelines

In the case of an adult experiencing hyperthermia due to intense physicalactivity, the first aid provider should consider immersing the person from theneck down in cold water (1-26° C/33.8-78.8° F) until a core body temperatureof less than 39°C (102.2° F) is reached. If this is not possible, they may coolthe 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 hotenvironment to a cool place.For people with hyperthermia due to intense physical activity, first aidproviders can also consider using any other immediate active or passivecooling techniques available to them (e.g. cold-water immersion of hands orfeet, icepacks, cold showers, fanning, ice-sheets and towels).If the person has hyperthermia due to intense physical activity and they areresponsive enough, they may have something cool to drink. This may includewater or a water and sugar and salt solution (e.g. homemade oral rehydrationsolution or sports drink). See Dehydration.

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The first aid provider should access emergency medical services (EMS) if theperson:> 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.

Guideline classifications explained

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 makecooling methods available so there is no delay in first aid when hyperthermiaoccurs.

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.

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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 place1.and to remove any excess clothing.If the person is showing signs of severe hyperthermia, (see signs above),2.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 droppedto less than 39°C (102.2°F). If this is not possible (e.g., cold water isunavailable or the person is confused and refuses), cool the person using anyother active cooling technique (e.g., place a cool, wet sheet on the person orwet them with cold water and place ice packs on their neck and groin areas).Fanning them may also increase the cooling action.Access EMS.3.If the person is showing signs of mild to moderate hyperthermia, (see signs4.above), cool them off using any technique available such as immersing theirhands 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 somewater to drink. Sports drinks or cold tea may also be helpful.Monitor the person’s temperature and level of response. Try to reduce their5.temperature to less than 39°C.

Access help

If the person shows signs of severe hyperthermia, access emergency medicalcare immediately. Severe hyperthermia can be life-threatening.

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A person with mild to moderate hyperthermia will usually recover withoutmedical care. Monitor them closely in case their condition does not improve orworsens. And access medical care if in any doubt.

Recovery

Keep the person cool and encourage them to rest. In most cases, people with mildto moderate hyperthermia will recover fully.

Education considerations

Context considerations

Programme designers should consider any cultural or legal implicationsinvolved with removing the person’s clothing and emphasise the importance ofdignity to learners.In areas where ice or cold water is not readily available, identify the coolingmethods that may be available to them such as removing the person from theheat, wetting them, fanning them, encouraging rest and removing any excessclothing.

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 higherrisk of hyperthermia.

Facilitation tips

Focus on prevention and help learners to recognise the warning signs ofhyperthermia so they can take preventative action before it happens.The key action is to cool the person quickly, so the first aid provider needs toprioritise readily available cooling methods.Emphasise the temperature that the body should be reduced to 39 °C(102.2°F) and not less.

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Learning connections

Combine this topic with other first aid emergencies (such as Breathingdifficulties or Seizures) so learners can recognise and differentiate thesymptoms of hyperthermia.Dehydration is common in people with hyperthermia.

Scientific foundation

Systematic reviews

The International Liaison Committee on Resuscitation (ILCOR) first aid task forcecompleted a systematic review on different techniques for cooling of heatstrokeand exertional hyperthermia (Douma, 2020), and the Centre for Evidence-basedPractice (CEBaP) developed evidence summaries about the reduction of activityand drinking (2020).

Coldwater immersion (14°C–15°C/57.2°F–59°F)

The following studies all relate to adults with exertional hyperthermia. In sevennon-randomised controlled trials, a faster rate of core body temperature reductionwas found with cold water immersion of the torso compared with passive cooling(low certainty of evidence). In three controlled trials, no significant meandifference in the rate of core body temperature reduction was found with coldwater 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 showedno significant mean difference in the rate of body temperature reduction with theuse of cold water immersion (14°C/57.2°F) of the torso compared with the use ofcolder-water immersion (8°C/46.4°F) (low certainty evidence). Two controlled trialsshowed no significant mean difference in the rate of body temperature reductionwith 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).

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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 foundwith cold water immersion of hands and/or feet (10°C-17°C/50.0-62.6°F) comparedwith passive cooling in adults with exertional hyperthermia (moderate certaintyevidence).

Colder-water immersion (9° C–12° C/48.2° F–52.6° F)

The following studies in this paragraph relate to adults with exertionalhyperthermia. In three non-randomised controlled trials, a faster rate of core bodytemperature reduction was found with the use of colder-water immersion of thetorso (9°C-12°C/48.2°F-52.6°F) compared with passive (moderate certaintyevidence). One controlled trial did not show a significant mean difference in therate 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 certaintyevidence). One controlled trial showed a faster rate of core body temperaturereduction 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 bodytemperature 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 thetorso (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 normalsaline at room temperature 0.9% were compared with applying ice-packs to thearmpits in adults with exertional heatstroke, showed no deaths in either group(very low-certainty evidence). In four non-randomised controlled trials in adultswith exertional hyperthermia and one cohort study on people with exertionalheatstroke, a faster rate of core body temperature reduction was shown whencomparing ice-water immersion of the torso (1°C-5°C/33.8°F-41°F) with passivecooling (low-certainty evidence). The same was found in two non-randomised

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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). Inone small cohort study in adults with exertional heatstroke where ice-waterimmersion (5°C-10°C/33.8°F-41.0°F) combined with the administration ofintravenous 0.9% normal saline was compared with applying icepacks to thearmpits (low certainty evidence).

Evaporative cooling (mist and fan)

Two controlled studies in adults with exertional hyperthermia showed nosignificant mean difference in the rate of core body temperature reduction withevaporative cooling compared with passive cooling (low-certainty evidence). Twocontrolled trials showed no significant mean difference in the rate of core bodytemperature reduction with evaporative cooling compared with the use of ice-packsapplied to the neck, armpit and groin (one trial, low-certainty evidence), orcompared with the use of commercial ice-packs applied to the neck, armpit andgroin (one trial, low-certainty evidence). One controlled trial showed no significantmean difference in the rate of core body temperature reduction with the use ofevaporative cooling and commercial icepacks to the neck, armpit and groincompared with evaporative cooling alone (low-certainty evidence). One controlledtrial showed no significant mean difference in the rate of core body temperaturereduction with the combined use of evaporative cooling and commercial icepacks tothe neck, armpit and groin, compared with passive cooling (low-certaintyevidence).

Commercial icepacks

Two controlled trials in adults with exertional hyperthermia showed no significantmean difference in the rate of core body temperature reduction with the use ofcommercial icepacks to the neck, groin and armpits compared with passive cooling(low-certainty evidence). One controlled trial in adults with exertionalhyperthermia showed no significant mean difference in the rate of core bodytemperature reduction with the use of commercial icepacks to the whole bodycompared with passive cooling (low-certainty evidence).

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One controlled trial in adults with exertional hyperthermia showed a faster rate ofcore body temperature reduction when applying commercial ice-packs to thecheeks, palms, and soles compared with passive cooling, as well as when comparedwith 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 significantmean difference in the rate of core body temperature reduction with the use offanning 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, afaster rate of core body temperature reduction was found with cold showerscompared with passive cooling (moderate-certainty evidence).

Hand-cooling devices

Three controlled trials in adults with exertional hyperthermia showed no significantmean difference in the rate of core body temperature reduction with the use ofhand-cooling devices compared with passive cooling (low certainty evidence).

Cooling vests and jackets

Two controlled trials in adults with exertional hyperthermia showed no significantmean difference in the rate of core body temperature reduction with the use of theArctic Heat cooling jacket compared with passive cooling (low certainty evidence).Five controlled trials in adults with exertional hyperthermia compared the use ofvarious cooling vests with passive cooling. None of the studies showed a significantmean difference in the rate of core body temperature reduction when comparedwith passive cooling (very low certainty evidence).

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Reflective blankets

One controlled trial in adults with exertional hyperthermia showed no significantmean difference in the rate of core body temperature reduction with the use ofreflective blankets compared with passive cooling (low certainty evidence).

Physical activity

There is limited evidence from one observational case-control study in favour ofreducing physical activity. The study showed that decreasing activity resulted in astatistically significant decrease in the risk of heatstroke during heat waves.Evidence is of very low certainty and results cannot be considered precise due tolack of data (CEBaP, 2020).

Drinking fluids

There is limited evidence from one observational case-control study in favour oftaking in extra liquids. The study showed that taking in extra liquids resulted in astatistically significant decrease in the risk of heatstroke during heat waves.Evidence is of very low certainty and results cannot be considered precise due to alack of data (CEBaP, 2020).

References

Systematic reviews

Centre for Evidence-Based Practice, Belgian Red Cross-Flanders. (2020). Evidencesummary Heatstroke – Reduction of activity. Availablefrom: https://www.cebap.org/knowledge-dissemination/first-aid-evidence-summaries/

Centre for Evidence-Based Practice, Belgian Red Cross-Flanders. (2020). Evidencesummary Heatstroke – Drinking. Available from:

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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 thePrevention and Treatment of Heat Illness: 2019 Update. Wilderness &Environmental Medicine, 30(4), S33-S46. Retrievedfrom: 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/

Related topicsBreathing difficultiesSeizureDehydration

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