EM · Hypothermia
Hypothermia
Also known as Accidental hypothermia · Primary hypothermia · Environmental hypothermia
Accidental hypothermia is an involuntary core temperature below 35 C. ANZCOR stages mild 32-35, moderate 28-32, severe below 28. Revised Swiss HT I-IV uses consciousness, not shivering. Check signs of life for up to one minute. If VF persists after three shocks, delay further shocks until the core is above 30 C; withhold adrenaline below 30 C and give it every 6 to 10 minutes from 30 to 34 C. ECLS/VA-ECMO for hypothermic arrest. HOPE for in-hospital ECLS triage. ANZCOR avalanche: burial over 35 minutes plus obstructed airway, or potassium above 12 mmol per litre. ACEM-primary.
Checked against its sources on 4 Sept 2026
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Red flags
- Accidental hypothermia is an involuntary core below 35 C; measure with a low-reading thermometer (tympanic, rectal, or oesophageal)
- Handle the cold patient gently — rescue collapse and afterdrop (further cooling after rewarming starts) can precipitate arrest
- In hypothermic VF, if three shocks fail and the core is below 30 C, delay further shocks until the core is above 30 C; withhold adrenaline and amiodarone below 30 C
- Check for signs of life for up to one minute (pulse, respiration, ECG, EtCO2, ultrasound) before declaring arrest
- HOPE (age, sex, core temperature, potassium, asphyxia mechanism, CPR duration) outperforms potassium-only ECLS triage; do not use HOPE in children
- ANZCOR avalanche: burial over 35 minutes with cardiac arrest and an obstructed airway, or potassium above 12 mmol per litre — not a universal potassium-of-10 cease rule
Meet the patient
A 67-year-old man is brought to a regional emergency department by ambulance after being found collapsed in a Tasmanian national park in winter, having been missing for 18 hours in wet clothing at 2 degrees ambient. On arrival he is unconscious (GCS 8), pale and cold. Heart rate 42 in sinus bradycardia, blood pressure 78 over 44, respiratory rate 8 and shallow. A low-reading bladder probe records a core of 28.2 degrees. The ECG shows sinus bradycardia with prominent Osborne J waves and a prolonged QT. Capillary glucose is 3.1. The nearest ECMO-capable centre is 90 minutes away.[1]
Three questions decide the next hour, and they are the three that decide every hypothermia: how cold is he really? (a low-reading probe is the only instrument that finds the severe case), which rung of the rewarming ladder? (active internal for HT III, with ECMO on the horizon), and what must I not do? (rough-handle him — a cold myocardium fibrillates with a single jolt).[1]
References13ShowHide
- [1]Brown DJA, Brugger H, Boyd J, Paal P. Accidental hypothermia N Engl J Med, 2012.PMID 23150960
- [2]Dow J, Giesbrecht GG, Danzl DF, et al. Wilderness Medical Society Clinical Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2019 Update Wilderness Environ Med, 2019.PMID 31740369
- [3]Lott C, Truhlář A, Alfonzo A, et al. European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances Resuscitation, 2021.PMID 33773826
- [4]Wanscher M, Agersnap L, Ravn J, et al. Outcome of accidental hypothermia with or without circulatory arrest: experience from the Danish Præstø Fjord boating accident Resuscitation, 2012.PMID 22634431
- [5]Pasquier M, Rousson V, Darocha T, et al. Hypothermia outcome prediction after extracorporeal life support for hypothermic cardiac arrest patients: An external validation of the HOPE score Resuscitation, 2019.PMID 30940473
- [6]Paal P, Pasquier M, Darocha T, Lechner R, Kosinski S, Wallner B, Zafren K, Brugger H. Accidental Hypothermia: 2021 Update Int J Environ Res Public Health, 2022.PMID 35010760
- [7]Pasquier M, Hugli O, Paal P, Darocha T, Blancher M, Husby P, Silfvast T, Carron PN, Rousson V. Hypothermia outcome prediction after extracorporeal life support for hypothermic cardiac arrest patients: The HOPE score Resuscitation, 2018.PMID 29481910
- [8]Lott C, et al. European Resuscitation Council Guidelines 2025 Special Circumstances in Resuscitation Resuscitation, 2025.PMID 41117569
- [9]Musi ME, et al. Clinical staging of accidental hypothermia: The Revised Swiss System Resuscitation, 2021.PMID 33675869
- [10]Reed RL 2nd, et al. The disparity between hypothermic coagulopathy and clotting studies J Trauma, 1992.PMID 1404519
- [11]Eastwood GM, et al. A pilot assessment of alpha-stat vs pH-stat arterial blood gas analysis after cardiac arrest J Crit Care, 2015.PMID 25449882
- [12]Australian and New Zealand Committee on Resuscitation Guideline 11.10 Resuscitation in Special Circumstances ANZCOR, 2026.Source
- [13]Australian and New Zealand Committee on Resuscitation Guideline 9.3.3 First Aid Management of Hypothermia and Cold-Related Injuries ANZCOR, 2026.Source