Hypothermia/Cold Exposure

Table of Contents

Aliases

Hypothermia, frost bite, cold induced injuries

Patient Care Goals

  1. Maintain hemodynamic stability
  2. Prevent further heat loss
  3. Rewarm the patient in a safe manner
  4. Appropriate management of hypothermia induced cardiac arrest
  5. Prevent loss of limbs

Patient Presentation

  1. Patients may suffer from hypothermia due to exposure to a cold environment (increased heat loss) or may suffer from a primary illness or injury that, in combination with cold exposure (heat loss in combination with decreased heat production), leads to hypothermia
  2. Patients may suffer systemic effects from cold (hypothermia) or localized effects (e.g. frostbite)
  3. Patients with mild hypothermia will have normal mental status, shivering, and may have normal vital signs while patients with moderate to severe hypothermia will manifest mental status changes, eventual loss of shivering and progressive bradycardia, hypotension, and decreased respiratory status
  4. Patients with frostbite will develop numbness involving the affected body part along with a “clumsy” feeling along with areas of blanched skin – later findings include a “woody” sensation, decreased or loss of sensation, bruising or blister formation, or a white and waxy appearance to affected tissue

Inclusion Criteria

Patients suffering systemic or localized cold injuries.

Exclusion Criteria

  1. Patients without cold exposure
    OR
  2. Patients with cold exposure but no symptoms referable to hypothermia or frostbite

Patient Management

Assessment

  1. Patient assessment should begin with attention to the primary survey, looking for evidence of circulatory collapse and ensuring effective respirations
    1. The patient suffering from moderate or severe hypothermia may have severe alterations in vital signs including weak and extremely slow pulses, profound hypotension and decreased respirations
    2. The rescuer may need to evaluate the hypothermic patient for longer than the normothermic patient (up to 60 seconds)
  2. History – Along with standard SAMPLE-type history, additional patient history should include:
    1. Attention to any associated injury or illness
    2. Duration of cold exposure
    3. Ambient temperature
    4. Treatments initiated before EMS arrival
  3. There are several means to categorize the severity of hypothermia based on either core body temperature readings or clinical evaluation – If possible and reliable, EMS providers should perform core body temperature measurements and categorize patients into one of the three follow levels of hypothermia:
    1. Mild: normal body temperature 35-32.1°C/95-89.8°F
    2. Moderate: 32°-28°C / 89.7°-82.5°F
    3. Severe: 28°-24°C / 82.4°- 75.2°F
    4. Profound: less than 24°C (75.2°F)
  4. Equally important is the patient’s clinical presentation and the signs or symptoms the patient is experiencing – the above temperature based categorization should be balanced against these clinical findings
    1. Mild: vital signs not depressed normal mental status, shivering is preserved; body maintains ability to control temperature
    2. Moderate/Severe: progressive bradycardia, hypotension, and decreased respirations, alterations in mental status with eventual coma, shivering will be lost in moderate hypothermia (generally between 31-30° C), and general slowing of bodily functions; the body loses ability to thermoregulate

Treatment and Interventions

  1. Maintain patient and rescuer safety – the patient has fallen victim to cold injury and rescuers have likely had to enter the same environment. Maintain rescuer safety by preventing cold injury to rescuers
  2. Manage airway per the Airway Management guideline
  3. Mild hypothermia:
    1. Remove the patient from the environment and prevent further heat loss by removing wet clothes and drying skin, insulate from the ground, shelter the patient from wind and wet conditions, and insulate the patient with dry clothing or a hypothermia wrap/ blanket. Cover the patient with a vapor barrier and, if available, move the patient to a warm environment
    2. Hypothermic patients have decreased oxygen needs and may not require supplemental oxygen
    3. Provide beverages or foods containing glucose if feasible and patient is awake and able to manage airway independently
    4. Vigorous shivering can substantially increase heat production – shivering should be fueled by caloric replacement
    5. Consider field-rewarming methods such as placement of large heat packs or heat blankets (chemical or electric if feasible) to the anterior chest or wrapped around the patient’s thorax if large enough – forced air warming blankets (e.g. Bair Hugger®) can be an effective field rewarming method if available
    6. Monitor frequently – if temperature or level of consciousness decreases, refer to Severe Hypothermia, below
    7. Consider IV access
      1. Indications for IV access and IV fluids in the mildly hypothermic patient are similar to those of the non-hypothermic patient
      2. IV fluids, if administered, should be warmed, ideally to 42°C
      3. Bolus therapy is preferable to continuous drip
      4. The recommended fluid for volume replacement in the hypothermic patient is normal saline
    8. If alterations in mental status, consider measuring blood glucose and treat as indicated (treat per Hypoglycemia or Hyperglycemia guidelines) and assess for other causes of alterations of mentation
    9. Transport to a hospital capable of rewarming the patient
  4. Moderate or severe hypothermia:
    1. Perform ABCs, pulse checks for patients suffering hypothermia should be performed for 60 seconds, and obtain core temperature if possible for patients exhibiting signs or symptoms of moderate/severe hypothermia
      1. Core temperatures are best measured by esophageal probe, if one is available, the patient’s airway is secured, and the provider has been trained in its insertion and use.
      2. If esophageal temperature monitoring is not available or appropriate, use an epitympanic thermometer designed for field conditions with an isolating ear cap
      3. Rectal temperatures may also be used, but only once the patient is in a warm environment – rectal temperatures are not reliable or suitable for taking temperatures in the field and should only be done in a warm environment (such as a heated ambulance)
    2. Manage airway as needed
      1. Care must be taken not to hyperventilate the patient as hypocarbia may reduce the threshold for ventricular fibrillation in the cold patient
      2. Indications and contraindications for advanced airway devices are similar in the hypothermic patient as in the normothermic patient
    3. Prevent further heat loss by removing the patient from the environment and removing wet clothes and drying skin, insulate from the ground, shelter the patient from wind and wet conditions, and insulate the patient with dry clothing or a hypothermia wrap/ blanket. Cover the patient with a vapor barrier and, if available, move the patient to a warm environment
    4. Initiate field-rewarming methods such as placement of large heat packs or heat blankets (chemical or electric if feasible) to the anterior chest or wrapped around the patient’s thorax if large enough
      1. Chemical or electrical heat sources should never be applied directly to the skin
      2. Use a barrier between the skin and heat source to prevent burns
      3. Forced air warming blankets (e.g. Bair Hugger®) can be an effective field rewarming method if available
    5. Handle the patient gently
      1. Attempt to keep the patient in the horizontal position, especially limiting motion of the extremities to avoid increasing return of cold blood to the heart
      2. Once in a warm environment, clothing should be cut off (rather than removed by manipulating the extremities)
      3. Move the patient only when necessary such as to remove the patient from the elements
    6. Apply cardiac monitor or AED if available
    7. Establish IV and provide warmed NS bolus – Repeat as necessary
    8. If alterations in mental status, consider measuring blood glucose and treat as indicated (treat per Hypoglycemia or Hyperglycemia guidelines) and assess for other causes of alterations of mentation
    9. Transport as soon as possible to a hospital capable of resuscitation – if cardiac arrest develops consider transport to a center capable of extracorporeal circulation (ECMO) or cardiopulmonary bypass (if feasible)
    10. Warm the patient compartment of the ambulance to 24°C (75.2°F) during transport
  5.  Frostbite:
    1. If the patient has evidence of frostbite, and ambulation/travel is necessary for evacuation or safety, avoid rewarming of extremities until definitive treatment is possible. Additive injury occurs when the area of frostbite is rewarmed then inadvertently refrozen. Only initiate rewarming if refreezing is absolutely preventable.
      1. If rewarming is feasible and refreezing can be prevented use circulating warm water (37 – 39°C / 98.6 – 102°F) to rewarm effected body part, thaw injury completely. If warm water is not available, rewarm frostbitten parts by contact with non-affected body surfaces. Do not rub or cause physical trauma.
      2. After rewarming, cover injured parts with loose sterile dressing. If blisters are causing significant pain, and the provider is so trained, these may be aspirated, however, should not be de-roofed. Do not allow injury to refreeze. Treat per the Pain Management

Notes – Hypothermia/Cold Exposure