Environmental Injuries / Exposures
- Accidental hypothermia (HT) = involuntary core body temperature < 35o
- Primary HT is due to environmental exposure.
- Secondary HT is a result of predisposing factors (e.g., alcohol/drug intoxication, trauma, shock, endocrine/metabolic, medications, burns etc.).
- Approximately 26 HT-related deaths per year in BC (1998-2012).
- Highest mortality rates in rural areas, lower socioeconomic status, and elderly in BC.
- The neuroprotective effect of HT translates to the potential for the good neurologic outcomes if HT precedes brain hypoxia, even in the context of prolonged CPR and transport.
- “No one is dead until warm and dead” still applies.
Hypothermia can be assumed if the following 2 conditions are met:
- Cold exposure OR predisposing factor to HT, AND
- Trunk is cold to touch OR core temperature < 35oC
- Core temperature needs to be measured with a low-reading thermometer.
- Intubated patients – esophageal probe (lower third of esophagus).
- Non-intubated patients – rectal probe (15 cm deep) or bladder probe.
- HT I (Mild) – the patient is conscious and shivering with a core T between 35-32o
- HT II (Moderate) – the patient has an impaired level of consciousness, they may be shivering, and their core T is <32-28o
- HT III (Severe) – the patient is unconscious but vital signs are present with a core T <28o
- HT IV (Hypothermic cardiac arrest) – no vital signs, and core T <28o
- Clinical features do not always align with specific core temperatures; consider secondary causes or alternative processes when significant discrepancies.
Labs selection will depend on the clinical situation but usually order:
- Point-of-care glucose testing (all HT patients)
- ECG (HT II-III)
- Blood samples are warmed before analyzed – masks coagulopathy of HT.
- Blood gas analyzers warm sample to 37oC – Alpha stat strategy recommended: titrate ventilation to a PCO2 of 40mmHg (do not apply correction factors but be aware that the cold patient has a higher pH and lower partial pressures compared with the results from your warmed samples).
Patients in Cardiac Arrest
- HT can be ruled out as the cause of cardiac arrest when:
- Absent vital signs and normothermic cardiac arrest prior to cooling.
- Absent vital signs, asystole, and core temperature >32oC.
Handle hypothermic patients carefully throughout assessment due to risk of arrhythmias.
- Assess signs of life for 60 seconds through clinical examination and other modalities if available (ECG, EtCO2 and ultrasound).
- Check central pulse.
- Do not assume death or poor neurologic prognosis in hypothermic patients with fixed dilated pupils, absent corneal reflexes, signs of rigor mortis, areflexia, and/or respiratory arrest.
- Look for other injuries (e.g., frostbite, trauma).
See BC guidelines, Appendices: A. Management of Accidental Hypothermia, B. EPOS Triage Tool for Stage IV Accidental Hypothermia, C. EPOS Triage Tool for Stage III Accidental Hypothermia, D. Provincial ECMO Provider Map.
- HT I – manage on-site or transport to hospital particularly if suspected secondary HT.
- HT II – transport to hospital (ideally ECMO/Cardiopulmonary bypass (CPB) center).
- HT III, IV – contact Emergency Physician Online Support (EPOS) – BC Patient Transfer Network (BCPTN) or BCAS dispatch for consideration of transfer to ECMO/CPB-capable center or a portable ECMO team may be dispatched.
- If history suggests cardiac arrest prior to hypothermia – Either use local Termination of Resuscitation Protocols (BCAS – EPOS) or transport to nearest hospital.
- Consider a mechanical CPR device if in cardiac arrest.
- Prevent further heat loss.
- If transport time to ECMO/CPB is >6 hours, the patient will likely be managed locally.
- Passive rewarming: prevent heat loss and support self-rewarming.
- Warm environment, dry clothes, insulation, warm drinks, active movement
- Active external and minimally invasive rewarming: provide heat to body surface.
- Heating blankets (e.g., forced-air), hot packs, warm environment, insulation, “hypothermia burrito” (See BC Guidelines, Appendix E: Practical Tips for Rewarming HT II & III)
- IV fluids: warm (38-42oC) crystalloids titrated to clinical volume status (Consider 10-20mL/kg per ~3oC raise in core temp if needed).
- Active internal/invasive rewarming: provide heat to body’s interior. Examples:
- Extracorporeal life support (VA-ECMO or CPB)
- Warm (38-42oC) lavage (e.g. bladder, thoracic, peritoneal)
- Indications for invasive vascular rewarming techniques that do not support circulation are not well established.
- Hot showers/baths are not recommended as risk of hypotension.
Management Based on Stage
- HT I – passive rewarming
- Treat as HT II in cases of trauma, comorbidities, or possible secondary hypothermia.
- HT II – active external and minimally invasive rewarming; cardiac and core temp monitoring.
- HT III – active external and minimally invasive rewarming; cardiac and core temp monitoring; +/-airway management; +/- bladder lavage.
- Cardiac stability – invasive rewarming not recommended
- Refractory cardiac instability – consider ECMO/CPB
- HT IV – CPR; airway management; ECMO/CPB (ideally).
- There is a lack of consensus in various guidelines (ERC, AHA, BC) but BC guidelines recommend up to three doses of epinephrine and defibrillation with additional doses guided by response.
- Alternative to ECMO/CPB – continue CPR; rewarm to 32oC with active external and internal rewarming (+/- bladder lavage, +/- thoracic lavage, +/- peritoneal lavage).
- Do not apply heat to the patient’s head.
- Rewarming will likely correct the following:
- Acid-base disturbances (bicarbonate in not recommended unless other indications are present)
- Benign arrhythmias (atrial fibrillation and flutter, bradycardia, AV blocks, nodal rhythms, QRS prolongation)
- Mild hypotension
- Vasopressors – increased risk of arrhythmias with early administration. Consultation recommended.
- Sedatives, analgesics – suppress adaptive physiologic responses (e.g., shivering, vasoconstriction).
- Risk of drug toxicity in hypothermic patients due to reduced metabolism of drugs.
- Keep central venous catheter tips away from heart.
- If inadequate response to rewarming, think of secondary causes.
Prognostication and Resuscitation Termination
- European Resuscitation Council (ERC) Guidelines 2021 recommend using either the HOPE or ICE score for prognostication of successful extracorporeal life support (ECLS) rewarming. ERC advises against the use of these scores in children.
- ICE Survival Score – calculated based on gender, asphyxiation, serum potassium.
- Hypothermia Outcome Prediction after ECLS (HOPE) Score – calculated based on age, sex, core temperature, serum potassium, asphyxiation, duration of CPR.
- Termination of resuscitation may be considered in patients with HT IV if serum potassium is >12mmol/L, or if the patient is rewarmed to ≥32oC and on-going asystole and no other causes of reversible cardiac arrest.
- Serum potassium – may be less reliable than HOPE or ICE scores; risk of false elevations with comorbidities or certain medications.
Complications of hypothermia
- Cardiac – dysrhythmias (e.g. VF), cardiac arrest
- Neurologic – CNS impairment
- Metabolic – cold diuresis, rhabdomyolysis, pseudo-rigor mortis
- Hematologic – coagulopathy, hypercoagulable state
- Extracorporeal life support-related complications
- Respiratory – pulmonary edema, infection, respiratory arrest
- Cardiac – hypotension, dysrhythmias, cardiac stunning
- Neurologic – seizures, peripheral neuropathy, impaired cognition, coma
- Multi-organ failure
Quality Of Evidence?
We are highly confident that the true effect lies close to that of the estimate of the effect. There is a wide range of studies included in the analyses with no major limitations, there is little variation between studies, and the summary estimate has a narrow confidence interval.
We consider that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. There are only a few studies and some have limitations but not major flaws, there are some variations between studies, or the confidence interval of the summary estimate is wide.
When the true effect may be substantially different from the estimate of the effect. The studies have major flaws, there is important variations between studies, of the confidence interval of the summary estimate is very wide.
Indications for the administration of epinephrine in hypothermic cardiac arrest patients – Mostly based on animal studies and conflicting recommendations among various guidelines. – Low.
The HOPE Score – Derived from a systematic literature review (18 studies, 237 patients) and unpublished hospital data (49 patients). This score has been externally validated. – Low.
ICE Survival Score – Derived from an individual patient data meta-analysis of observational studies (44 retrospective cohort studies, 40 case reports). This model has not been validated. – Low.
Brown DJA. Hypothermia. In: Tintinalli JE, Ma OJ, Yealy DM, Meckler GD, Stapczynski JS, Cline DM, Thomas SH, eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 9th McGraw-Hill; 2020. Accessed April 21, 2021.
Lott C, Truhlář A, Alfonzo A, et al. European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances. Resuscitation. 2021;161:152-219. doi: 10.1016/j.resuscitation.2021.02.011.
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;139:321-328. doi: 1016/j.resuscitation.2019.03.017.
Pasquier M, Hugli O, Paal P, et al. Hypothermia outcome prediction after extracorporeal life support for hypothermic cardiac arrest patients: The HOPE score. Resuscitation. 2018;126:58-64. doi:10.1016/j.resuscitation.2018.02.026.
Saczkowski RS, Brown DJA, Abu-Laban RB, Fradet G, Schulze CJ, Kuzak ND. Prediction and risk stratification of survival in accidental hypothermia requiring extracorporeal life support: An individual patient data meta-analysis. Resuscitation. 2018;127:51-57. doi:10.1016/j.resuscitation.2018.03.028.
OTHER RELEVANT INFORMATION
The purpose of this document is to provide health care professionals with key facts and recommendations for the diagnosis and treatment of patients in the emergency department. This summary was produced by the BC Emergency Medicine Network and uses the best available knowledge at the time of publication. However, healthcare professionals should continue to use their own judgment and take into consideration context, resources and other relevant factors. The BC Emergency Medicine Network is not liable for any damages, claims, liabilities, costs or obligations arising from the use of this document including loss or damages arising from any claims made by a third party. The BC Emergency Medicine Network also assumes no responsibility or liability for changes made to this document without its consent.
Last Updated May 11, 2021
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