Head and Torso Rewarming Using a Human Model for Severe Hypothermia
Condition: Hypothermia
MeSH terms: Hypothermia
Study type: Interventional

Summary: 
      This Clinical trial is being conducted to study the effectiveness of heat donation through
      head or torso in hypothermic rewarming efficacy using a human model for severe hypothermia.
      The purpose of the study is to compare the core rewarming effectiveness of the same amount of
      heat donation through the head or torso in treatment of hypothermia using a human model for
      severe hypothermia. The information obtained from this study will give a better understanding
      of heat-transfer mechanisms. This might help in the ongoing research in hypothermia
      treatment.
    

Detailed description: 
      Procedure:

      Eight healthy, non-pregnant participants between 18 and 45 years old will be cooled in 8°C
      water, for 60 minutes or to a core temperature of 35ºC on three occasions and then warmed by
      each of three warming conditions.

      The study will include following specific procedures:

      Anthropometric data which includes age, weight, height, and measurements of skinfold
      thickness at four sites- biceps, triceps, subscapularis, and suprailiac will be collected.
      Participant's heart rate and electrocardiogram will be monitored continuously throughout the
      experiment.

      Conditions: The three treatment methods are as follows. A. Spontaneous rewarming (Shivering
      inhibition) In this control condition, Demerol will be infused through the arm or hand vein.

      The first 1.5 mg/kg will be slowly injected in five equal doses (of 0.3 mg/kg) at 2 minute
      intervals during the last 10 minutes of cold water immersion. After removal from the water,
      further aliquots of 0.3 mg/kg (at minimum of 2-minute intervals) will be given only as
      necessary to inhibit any shivering that may develop, to a maximum cumulative dose of 3.2
      mg/kg body weight.

      After towel drying the subject will lie on a mattress under an insulated cover without any
      extra heating modality. Spontaneous rewarming will be the first condition for every subject,
      the results will be used to determine the dosage schedule for demerol in the active warming
      conditions below.

      B. Head warming:

      Charcoal Heater applied to the Head (CH-H) - A charcoal heater (HEATPAC Personal Heater,
      Emergco Tech. Solutions, Vancouver) consists of a combustion chamber, a canister containing
      the charcoal fuel, and a branched heating duct that produces 250 W of heat. The canister is
      placed inside the combustion chamber and the charcoal fuel is ignited. Heated air is blown
      through the impermeable heating ducts by a fan within the charcoal heater above the
      combustion chamber. The combustion chamber will be placed on right side of the face/head with
      ducts wrapping around the dorsum of the head, anteriorly over the forehead, nose, chin and
      the neck, not covering the eyes or the mouth. The participant will be breathing ambient air
      (̴ 22˚C).

      C. Torso warming:

      Charcoal Heater to the Torso (CH-T) - The same charcoal heater as above will be used. The
      combustion chamber will be placed on the subject's anterior chest with a towel in between.
      The flexible ducts will be applied to the areas of high heat transfer i.e. over the
      shoulders, neck, and then anteriorly under the axillae to cross over the lower anterior
      chest. Participant will be breathing ambient air at room temperature (~22˚C).

      Rewarming procedures will be administered either for a period of 60 minutes or until core
      temperature returns to normal values ( ̴ 36.5-37˚C). Following that, participants will be
      placed in a warm water bath (40-42˚C) until they wish to exit or core temperature reaches
      37°C.

      Research Design:

      Each of the three experimental trials will be separated by at least 48 hours. On each of the
      three trials, participants will be immersed up to the level of the sternal notch in 8˚C for
      up to 60 minutes or until the core temperature falls to 35˚C. Demerol will be administered by
      a licensed physician during the final 10 minutes of immersion to suppress shivering.
      Participants will then exit the water, be dried off and rewarmed with either head or torso
      warming techniques. After removal from the water, an extra dosage of demerol might be given
      to suppress shivering only if its necessary. The rewarming will be administered for 120
      minutes or until the core temperature returns to normal values (̴36.5-37˚C). The order of
      warming methods will follow a modified balanced design with control being first and the two
      active warming conditions being balanced.
    

Intervention name(s): Charcoal Heater (STK Heatpac, Emergco Tech Solutions, B.C.); No heat
Intervention type(s): Device; Other
Intervention description(s): A heater (STK Heatpac) will be used in the active warming arms of the study.; No active heating provided post cooling
Intervention MeSH terms: Charcoal
Allocation: Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: hypothermia; rewarming; non-shivering