Hypothermia

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Hypothermia is a medical emergency characterized by a core body temperature below the normal range of 95°F (35°C).

Causes of Hypothermia:

  1. Increased heat loss

    • Homeless population

    • Elderly patients

    • Submersion injuries

    • Drugs, EtOH, CO poisoning can all cause increased vasodilation, leading to increased heat loss

  2. Decreased heat production

    • Endocrine (hypothyroidism, hypoadrenalism, hypoglycemia)

    • Erythrodermas (psoriasis, exfoliative dermatitis, eczema, burns)

    • Impaired shivering

    • Impaired thermoregulation

    • Sepsis

Swiss Hypothermia Staging System:

Stage 1: Mild (32-35°C) - Shivering, mild confusion, awake

Stage 2: Moderate (28-32°C) - Severe shivering, altered mental status

Stage 3: Severe (20-28°C) - Loss of consciousness, bradycardia, shivering may cease

Stage 4: Profound (<20°C) – Unobtainable vital signs

Associated Complications:

  1. Cardiac dysfunction

    1. Dysrhythmias can occur when body temperature drops below 30°C

    2. There is typically a drop in temperature and MAP after rewarming is started due to vasoconstriction

  2. Cold injuries (frostbite, etc. Maybe there will be more on this at a later date)

  3. Coagulopathy (patient may be coagulopathic despite normal labs because the lab rewarms the sample)

    1. Impaired clotting function

    2. Thromboembolism (due to hemoconcentration and poor circulation)

    3. DIC

  4. Impaired pharmacology

    1. Protein binding increases when temperature drops, rendering drugs ineffective

    2. Oral meds are not absorbed well due to decreased GI motility

    3. IM route is impaired due to vasoconstriction

  5. Rhabdomyolysis

General Management:

  1. Airway, Breathing, Circulation (ABCs)

    • Hypothermia causes a leftward shift in oxygen curve so support with oxygen, and prepare for intubation depending on how profound the hypothermia is

  2. ECG Findings

    • Patients usually have sinus bradycardia, can progress to a fib with slow ventricular response

    • Severe cases can develop v fib

    • Osborn or "J" waves (associated with moderate to severe hypothermia)

  3. Remove Wet Clothing - Prevent further heat loss

  4. Passive External Rewarming - Insulate the patient, provide warm blankets

  5. Active External Rewarming (should be done for moderate hypothermia)

    • Use forced warm air blankets or radiant heaters – our ED uses the Bair Hugger

  6. Active Internal Rewarming (for severe hypothermia)

    • Warmed intravenous fluids (warmed to 38-42°C)

    • Heated humidified oxygen

    • Various lavages (Thoracic, peritoneal, bladder, GI)

Management during Cardiac Arrest:

  1. CPR – initiate if patient does not have a pulse (should also assess if patient is still breathing)

    • It is challenging to assess vital signs in hypothermic patients - use end tidal or POCUS to help assist to see if patient is breathing and has cardiac function

    • Starting CPR if the patient does have a pulse may precipitate ventricular rhythms

    • Hypothermic patients have higher chances of improved neurological outcome and survival than normothermic patients that arrest

  2. Defibrillation

    • Use defibrillation if indicated, but note that hypothermic patients may not respond to defibrillation until adequately warmed

  3. ECMO

    • Patients with refractory hypothermia should be considered for ECMO

    • Patients with out-of-hospital-cardiac-arrest that are hypothermic should ideally be transported to an ECMO center

    • If patient is unstable (dysrhythmia, severe hypothermia, etc) ECMO teams should be contacted early in the ED visit

 

Stay warm out there this weekend!

 

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 Jan 3;19(1):501. doi: 10.3390/ijerph19010501. PMID: 35010760; PMCID: PMC8744717.

Baumgartner EA, Belson M, Rubin C, Patel M. Hypothermia and other cold-related morbidity emergency department visits: United States, 1995-2004. Wilderness Environ Med 2008;19:233-237

Brown et al., Accidental Hypothermia. N Engl J Med 2012; 367:1930-1938