Environmental - Warming (hypothermia)

Indications

Hypothermia (core temperature <35 degrees)

Contraindications (absolute in bold)

None

Alternatives

Passive warming (remove cold wet clothes and provide warm blankets)

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

Arrythmia with risk of cardiac arrest (with patient movement or stimulation)

Thermal injury

Procedural hygiene

Standard precautions

PPE: non-sterile gloves

Area and monitoring

Resuscitation bay: temperature < degrees

Monitored bed: temperature >32 degrees

A rectal temperature probe is recommended for hypothermic patients

Non-invasive temperature readings are not reliable in hypothermia

Staff

Procedural clinician

Equipment

Dry towels and blankets

Forced-air warmer (e.g. Bair Hugger)

Warmed saline (40-42 degrees)

Positioning

Supine on bed

Sequence (external active rewarming)

Remove wet or cold clothing

Ensure the patient is dry

Cover the patient with warm, dry blankets

Deliver intravenous fluid resuscitation with warmed fluids

Apply forced-air warmer at maximum temperature (e.g. Bair Hugger)

Treat precipitant if known (e.g. sepsis)

Consider ECMO, coronary bypass or dialysis in refractory hypothermia

Post-procedure care

Minimise unnecessary interventions or transport until temperature >32 degrees

Diagnose and treat precipitant of hypothermia

Assess for complications of hypothermia (coagulopathy, electrolyte derangement, rhabdomyolysis)

Admit to intensive care or high dependency unit

Tips

Shivering stops <32 degrees making passive warming ineffective

Fatal dysrhythmias triggered by movement or invasive treatments are common <32 degrees

Transport and invasive treatments (other than rectal temperature monitoring) should be minimised until >32 degrees

Warm water (42 degrees) immersion is a highly effective way to treat hypothermia, but impractical in the emergency department

Discussion

Prolonged cardiac arrest second to hypothermia has a good prognosis, resuscitation and rewarming should continue until temperature >32 degrees. Practically, it is difficult to warm a patient in cardiac arrest. Intubation and mechanical CPR may provide a bridge to dialysis, bypass or ECMO.

There are case reports of successful peritoneal and thoracic cavity lavage. They might be considered in refractory hypothermia when ECMO dialysis or cardiopulmonary bypass are not available.

Classification of hypothermia:

Mild 32-35 degrees

Moderate 28-32 degrees

Severe <28 degrees

Rewarming rates by treatment

Passive rewarming with blankets: 0.5 degrees per hour in mild hypothermia

Forced-air rewarming: 2.5 degrees per hour

Warm fluids (42 degrees): No significant temperature rise but can prevent further falling temperatures

Dialysis: 3 degrees per hour

Cardiopulmonary bypass: 10 degrees per hour

ECMO: 10 degrees per hour

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.

Zafren K, Mechem CC. Accidental hypothermia in adults. In: UpToDate. Waltham (MA): UpToDate. 2020 May 13. Available from: https://www.uptodate.com/contents/accidental-hypothermia-in-adults

Rischall ML, Rowland-Fisher A. Evidence-Based Management Of Accidental Hypothermia In The Emergency Department. Emerg Med Pract. 2016;18(1):1-19.

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

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