Page 25 - JSOM Fall 2020

TABLE 1 Core Temperature Thresholds for Primary (Accidental) It was not until recently that the HPMK’s effectiveness was
Versus Secondary (Trauma-Induced) Hypothermia Classification 43 evaluated using human volunteers in a cold (−22°C [−7.6°F])
Accidental Trauma-Induced chamber study. Five active, heated hypothermia enclosure
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Classification Hypothermia Hypothermia systems (also known as hypothermia wraps) were compared.
32°C–35°C 34°C–36°C The results indicated that the HPMK (noninsulated), as com-
Mild hypothermia (89.6°F–95.0°F) (93.2°F–96.8°F) pared with three other commercial, insulated, active heated
Moderate 28°C–32°C 32°C–34°C hypothermia enclosure systems and one user-assembled, insu-
hypothermia (82.4°F–89.6°F) (89.6°F–93.2°F) lated, active heated hypothermia enclosure system, was ranked
Severe hypothermia <28°C (<82.4°F) <32°C (<89.6°F) the lowest in both subjective ratings and objective physiologi-
cal heat transfer and balance indices. 22
components. 12,29,30,50 A lack of warm IV fluids is an iatrogenic
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contributor to the lethal triad, particularly when administer- These findings by Dutta et al. and feedback from the field
ing large fluid volumes. In a prospective multicenter study regarding HPMK limitations resulted in the CoTCCC under-
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of trauma patients who required massive transfusion, it was taking a comprehensive literature review to update the current
reported that hypothermia on arrival was an independent recommendations for treating casualties with hypothermia.
predicator of mortality. Furthermore, the authors reported The following are specific questions addressed by the CoTCCC
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that every decrease of 1.0°C (1.8°F) in core temperature below in 2019 regarding the battlefield (prehospital) management of
36°C (96.8°F) resulted in a 10% increase in red blood cell all-cause hypothermia:
(RBC) consumption in the first 24 hours of admission. These
authors and others concluded that hypothermia (<36°C) is (1) Is adding an external heat source to a hypothermia wrap
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associated with increase in blood-product consumption and effective?
mortality. These data emphasized the need for effective hy- (2) Is an improvised, user-assembled, heated hypothermia
pothermia prevention at the point of injury (POI) and contin- wrap effective?
ued patient warming during massive transfusion with warmed (3) What is the most effective method to apply an active heat
(38°C–42°C [100.4°F–107.6°F]) whole blood. source to the casualty in a hypothermia wrap to prevent
and/or treat hypothermia?
Commercial, battery-powered, in-line IV warming devices, as (4) What are the indications, contraindications, safety is-
well as improvised IV warming methods, inconsistently warm sues, and complications associated with applying an ex-
blood to the target temperature from cold ambient tempera- ternal heat source inside a hypothermia wrap during field
tures. 53–56 Also, battery-powered, in-line IV warming devices management?
do not have equal performance characteristics or easy set-up (5) What are the required characteristics of a portable IV
methods for IV delivery of blood. 55–59 warming device for infusion of fluids and blood products?
(6) What are the relevant safety concerns for a portable, bat-
One basic requirement for managing cold-stressed (>35°C tery-operated, IV warming device? 11
[95°F]) or hypothermic (<35°C) combat casualties is the
ability to enclose them in a hypothermia wrap consisting of Overview of Prehospital
an enclosure, insulation, vapor barrier, and an external heat Hypothermia-Wrap Systems
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source. Wool blankets have been the standard for treating
hypothermic combat casualties dating back to World War The evidence for both passive and active external rewarming
I. 4,11,20 This long-standing hypothermia management approach treatment options has been discussed for decades 23,24 and was
did not advance significantly after many wars and conflicts un- recently reviewed for treating hypothermic patients in the pre-
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til the implementation of the use of the HPMK. The HPMK hospital environment. The authors concluded that prehospital
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was one component of the Joint Theater Trauma System’s warming inside a hypothermia wrap is safe and advantageous,
(JTTS) theater-wide strategy to address hypothermia in battle- especially for a nonshivering hypothermic patient with or with-
field casualties and was recommended in the clinical practice out injuries. This review revealed that hypothermia enclosure
guidelines. This JTTS strategy demonstrated the need for a systems that include more insulation and active heat sources
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systematic approach to performance improvement, which in- perform better for patient treatment. Table 2 lists relevant pre-
cludes research and development, clinical practice guidelines, hospital passive 62–66 insulation and active 22,56,57,61,67–69 rewarm-
education, training, and monitoring outcomes for care at the ing enclosure systems, graded by the level of evidence. The
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POI during medical evacuation, and at each role of care in prevention of heat loss should begin aggressively soon after
the operational environment to decrease TIH mortality. 8,11,60 injury, as should active external heating, if possible.
However, a survey of battlefield medical care from 2009 and
2011 revealed that wool blankets, not the HPMK, were still Rewarming hypothermic patients can be passive, using the
being used in some cases for managing and preventing hypo- casualty’s own heat production from shivering, or active, pro-
thermia. 19,20 The decision to add the HPMK to the CoTCCC viding external heat to the casualty. Active warming is rec-
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Guidelines was supported by the findings of Allen et al., who ommended, especially for trauma patients; it will warm the
evaluated three passive and five active hypothermia-warming skin; decrease shivering (without negative effects on core re-
systems. Even though there were good results with the HPMK, warming) and, therefore, decrease the work of the heart; and
this study was not conducted with human volunteers; the re- increase the casualty’s comfort level and general psychological
searchers measured heat flux changes in warmed fluid blad- outlook. Although active warming may not be necessary, it
ders as a method to simulate a human torso. These authors will do no harm in hypothermic patients and will be helpful. 57
noted this was a study limitation and made a recommendation
that future studies on hypothermia enclosure systems be con- An improvised rewarming method is used to create a hypo-
ducted with human volunteers. thermia wrap (also known as a “burrito wrap”). This consists

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