Page 30 - JSOM Fall 2020

FIGURE 2 Four commercial and one User-assembled hypothermia the charcoal heater (0.6°C/h) tended to be higher than that
enclosure systems with heat source locations. (A) User-assembled for the chemical heating pads (0.2°C/h); all were significantly
(control); (B) Doctor Down Wrap; (C) Wiggy’s Victims Casualty higher than the spontaneous warming rate (0.1°C/h). The
Hypothermia Bag; (D) MARSARS Hypothermia Stabilizer Bag;
(E) Hypothermia Prevention, and Management Kit. 22 authors recommended the use of charcoal heaters, chemical
heating pads, or hot-water bags in that order of preference,
based on effectiveness, when applied to cold-stressed or hypo-
thermic patients in the field or during transport. Although the
hot- water bags (55°C [131°F]) are effective, there is a logisti-
cal challenge to maintain a warmed-water supply, particularly
when moving during transport.
Small chemical heat packs, as commonly used inside gloves
and shoes for hand and foot warming, are not recommended
for hypothermia management. These low-volume units do not
provide sufficient heat to affect core temperature, although
they may provide warm comfort and prevent local cold injury
(A) (B)
of the hands and feet.
Conclusion
There is evidence to support application of a heat source to
the upper torso of a hypothermic casualty sufficient to transfer
heat to the body core and provide comfort to the patient. Level
of evidence: B

Q4. What are the indications, contraindications,
safety issues, and complications when adding an
external heat source inside a hypothermia wrap
during field management?
(C) (D) Indications for Active Heating
For decades, the indications for, and benefits of, an active ex-
ternal heating source placed inside a hypothermia wrap have
been well accepted. 17,23–25 With traumatic injury, hypothermia
must be actively prevented starting at the POI, because of the
increase in mortality risk from hypothermia that begins at a
temperature of 35.6°C (<96°F). 13,43,44 Other indications for ac-
tive warming are central nervous system trauma, shock, acute
(E)
spinal cord transection, altered level of consciousness, unre-
sponsiveness, opioid administration, and impaired shivering
in a cold environment. 82
environment and is reasonable to transport by backpack in
many situations. This evidence-based method for making a Conclusion
hypothermia wrap is described by Giesbrecht. 78 For all cold patients with the potential for TIH, hypothermia
prevention is of utmost importance and should be accom-
Conclusion plished by using all available resources to stop core heat loss
There is evidence that an improvised hypothermia wrap is ef- after serious injury. Insulation should be maximized, and a
fective when high-quality insulation with a cold-rated sleeping heat source should be added to the torso as soon as possible. It
bag is combined with a heat source, an internal vapor barrier, is recommended to prepare and train for TIH on the battlefield
and an outer impermeable enclosure. Level of evidence: B with an HPMK or insulated, active rewarming hypothermia
wrap. Level of Evidence: B
Q3. What is the most effective method to apply an
active heat source to the casualty in a hypothermia wrap Contraindication for Active Heating
to prevent and/or treat hypothermia? For TIH, there is no absolute contraindication for using an
External heat sources are most effective if concentrated on the HPMK or other active rewarming hypothermia wraps. The
upper torso and not on the extremities, in the following order only relative contraindication would be a scenario on the bat-
of preference: (1) axillae, (2) chest, and (3) back. These are tlefield when someone has minor trauma and presents with
the areas with the highest potential for heat transfer to the signs and symptoms of moderate to severe heat illness (i.e.,
core. 17,57,79,80 heat exhaustion and exertional heat stroke). 83,84 In this sce-
nario, there is no ongoing noncompressible hemorrhage or de-
Lundgren et al. evaluated the differences among three ex- rangement of thermoregulation with core heat loss at the POI.
81
ternal heat sources applied in combination to the chest and This casualty would not benefit from active heating, which
back of volunteer subjects whose shivering was pharmacolog- actually may exacerbate the severity of heat illness.
ically suppressed. Two chemical heat pads, two flexible hot
water bags, and a charcoal heater (HeatPac) were assessed. Although it is accepted that hypothermia, as an outcome of
The core rewarming rates for the hot-water bags (0.7°C/h) and trauma, results in increased mortality, it is less known that

28 | JSOM Volume 20, Edition 3 / Fall 2020