Page 31 - JSOM Fall 2020

hyperthermia and severe trauma are also indicative of a poor Complications With an External Heat Source
patient outcome, as reported for both civilian and military ca- Cooling ischemic muscle has the potential to reduce muscle
sualties. A casualty should be treated on the basis of their damage. 88–90 When compared with baseline muscle tempera-
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core temperature; ambient temperature should not be relied ture, there is indirect evidence to suggest that a 2°C–3°C re-
on. During Operation Iraqi Freedom and Operation Enduring duction in muscle temperature may reduce muscle necrosis
Freedom, military surgical trauma teams frequently observed after extended tourniquet application. Furthermore, success-
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hypothermia in combat casualties even during extreme high ful limb salvage of a cool extremity after tourniquet appli-
temperatures in the Middle East deserts. 8,10,85 cations for 8 and 16 hours was reported in two cases. 92,93 A
Department of Defense medical panel recommended in 2003
Conclusion to take advantage of cool ambient temperatures when a tour-
With moderate to severe injuries, trauma-induced hypother- niquet is applied to an extremity. However, others do not
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mia can occur during combat operations in high ambient recommend packing snow or ice directly on an injured limb
temperatures and should be prevented or managed with an after tourniquet application, because of the risk of additional
HPMK or other active heating hypothermia wrap. With minor tissue trauma, such as frostbite. In 2015, a CoTCCC work-
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trauma, it is not recommended to use any active heating when ing group updated the recommendations for tourniquet use
there is evidence of moderate to severe heat illness in a combat and agreed with the recommendation made by Walters and
casualty. Level of Evidence: C Mabry that when a tourniquet is applied, keep the nonper-
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fused portion of the extremity exposed to cooler environmen-
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Safety of External Heat Sources tal temperature. This recommendation also has the added
Most external heat sources available in the field are safe, with advantage of allowing close observation of the limb for re-
a low chance of additional injury during hypothermia man- bleeding, but this 2005 recommendation needs to be consid-
agement; exceptions include a hot water bath or shower, fire, ered for each casualty on the basis of the severity of trauma,
fire-warmed rocks, and ovens. 24,57 It is generally safe to use and particularly if the casualty is hypothermic or at risk of
an RHB as part of the HPMK, but anecdotal reports from becoming hypothermic.
military trauma surgeons and published case reports show
these heating sources can cause first- to third-degree burns Conclusion
when applied directly to skin. 61,86,87 These injuries may occur For combat casualties with extremity trauma requiring a
through misuse or be the result of unexpected consequences to tourniquet to control hemorrhage, consider keeping the non-
application. Cold and underperfused skin is very susceptible to perfusing extremity distal to the tourniquet exposed to a
injury from pressure or heat. 17,87 The user should follow man- cooler environmental temperature. However, with moderate
ufacturer instructions and place a protective layer of material to severe trauma resulting in TIH, the priority is to prevent
between the heat source and the skin to prevent burns. 17 additional core cooling in an effort to decrease the compli-
cations of shock, hypothermia, coagulopathy, and acidosis.
Conclusion Consequently, in TIH cases, it is not advisable to expose any
There are three recommendations suggested to mitigate extremity with a tourniquet, through an exterior opening of
the risk of burns: (1) place a thin layer of material between the hypothermia wrap. Level of Evidence: C.
the skin and heat source; (2) avoid placing the heat in high-
pressure areas (e.g., the back of a supine patient) unless the See Table 3 for a summary of the indications, contraindica-
skin can be observed regularly; and (3) regularly monitor the tions, safety issues, and associated complications of hypother-
skin for burns. Level of Evidence: C mia wraps with external heat sources.

TABLE 3 Indications, Contraindications, Safety Issues, and Complications for Active Rewarming of Battlefield Casualties
Criteria General Comments
• Moderate to severe trauma Combat casualties with moderate to severe trauma
• Central nervous system trauma should be treated with active heating inside a
• Burn patients >33% TBSA with second- or third- hypothermia wrap as soon as possible.
Indications degree burns
• Altered level of consciousness/unresponsive; in cold
environment
• Impaired shivering; in cold environment
• None for TIH There are no restrictions to use active warming inside
• Only when a casualty presents with signs and a hypothermia wrap for TIH casualties.
Contraindications symptoms of hyperthermia (severe heat illness) It is contraindicated to use active warming for any
casualty who has heat exhaustion or exertional heat
stroke.
• First-, second-, and third-degree burns Never place any active heat source directly on skin.
Safety Follow manufacture directions for correct use of
heating source.
• Potential for enhanced muscle damage on an Increased temperature of nonperfused extremity distal
extremity distal to a tourniquet to a tourniquet can cause additional muscle damage.
Attempt to keep that part of the extremity from
Complications
increasing temperature.
Do not pack extremity with a tourniquet in ice
or snow.
Abbreviations: TBSA, total body surface area; TIH, trauma-induced hypothermia.

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