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Environmental - Cooling (hyperthermia)

Indications

Hyperthermia (core temperature ≥40 degrees)

and

Altered mental status

Contraindications (absolute in bold)

None

Alternatives

None

Informed consent

Medical emergency

Consent is not required if the patient lacks capacity or is unable to consent

Brief verbal discussion is recommended if the situation allows

Potential complications

Hypothermia (overcooling)

Skin damage (direct contact with ice)

Shivering (with temperature increase)

Procedural hygiene

Standard precautions

PPE: non-sterile gloves

Area

Resuscitation bay

A rectal temperature probe is recommended for hypothermic patients

Non-invasive temperature readings are not reliable in hyperthermia

Staff

Procedural clinician

Equipment

Ice packs

Water to spray on patient or wet towels

Fan

Positioning

Supine

Medication

Diazepam 2.5-5mg IV, repeat every 3-4 minutes until shivering stops

Sequence (active cooling)

Remove sheets and clothing except underwear

Mist or wet the patient with tepid water repeatedly (evaporative cooling)

Place a large fan at the foot of the bed close to the patient (increases evaporation)

Apply ice packs around the large blood vessels of the axillae, groin, neck and head (replace and rotate frequently)

Administer 1000ml cold saline bolus

Sequence (refractory hyperthermia, with shivering and agitation)

Diazepam 2.5-5mg IV, repeat every three to four minutes until shivering stops or required sedation is obtained

Consider intubation and paralysis if unable to control agitation and shivering with diazepam

Consider ECMO or coronary bypass in refractory hyperthermia

Consider toxicological causes of hyperthermia and administration of antidote

Post-procedure care

Diagnose and treat precipitant of hyperthermia

Assess for complications of hyperthermia (arrythmia, electrolyte derangement, rhabdomyolysis)

Admit to intensive care or high dependency unit

Stop active cooling once core temperature reaches 39 degrees (to avoid hypothermia)

Tips

Severe agitation with hyperthermia (heat stroke) has a high mortality and requires aggressive cooling

Agitation or shivering refractory to diazepam may require intubation and paralysis to facilitate treatment

Active cooling by cold water immersion is highly effective but impractical in the emergency department

Always consider drug-induced hyperthermia, toxicology discussion and administration of antidote

Discussion

The aim of cooling is to reduced temperature below 40 degrees within 30 minutes. Evaporative cooling is the most effective method available in the emergency department.

Cooling rates by treatment:

Cold water immersion at 8 degrees: 0.25 degrees per minute

Fan and mist: 0.1 degrees per minute

Ice packs: <0.1 degrees per minute

Antidotes to common toxicological causes of hyperthermia:

Serotonin syndrome: chlorpromazine 25mg in 100ml sodium chloride 0.9% by slow IV

Anticholinergic syndrome: physostigmine 2mg IV, repeated if only a partial response

Neuroleptic malignant syndrome: bromocriptine 2.5mg orally or via nasogastric tube 8-hourly

Malignant hyperthermia: dantrolene 2.5mg/kg every five minutes (total dose 10mg/kg/day)

Aspirin: urinary alkalinisation or haemodialysis

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

Please direct feedback for this procedure to ACI-ECIs@health.nsw.gov.au.

References

Roberts JR, Custalow CB, Thomsen TW. Roberts and Hedges’ clinical procedures in emergency medicine and acute care. 7th ed. Philadelphia, PA: Elsevier; 2019.

Dunn RJ, Borland M, O’Brien D (eds.). The emergency medicine manual. Online ed. Tennyson, SA: Venom Publishing; 2019.

Murray L, Little M, Pascu O, Hoggett KA. Toxicology handbook. 3rd ed. Sydney: Elsevier Australia; 2015.

eTG complete. Melbourne: Therapeutic Guidelines; 2012 Jul (updated 2018 Jul). Toxicology: general approach. Available from: https://tgldcdp.tg.org.au/viewTopic?topicfile=toxicology-general-approach

Santelli J, Sullivan JM, Czarnik A, Bedolla J. Heat illness in the emergency department: keeping your cool. Emerg Med Pract. 2014;16(8):1-22.

NSW Agency for Clinical Innovation NSW. Temperature measurement for critically ill adults: a clinical practice guideline. Sydney: ACI; 2014. Available from: https://www.aci.health.nsw.gov.au/__data/assets/pdf_file/0004/240178/ACI14_Temperature-1-4.pdf

© Agency for Clinical Innovation 2021