This module will focus on the prevention and treatment of hypothermia with techniques that are appropriate for the Tactical Field Care phase.
As a combat medic/corpsman, the first medical provider to care for the casualty and initiate more advanced treatments in the continuum of prehospital care, it is important that you understand the roles and responsibilities of the nonmedical personnel (All Service Members (ASM) and Combat Lifesaver (CLS)) who may be assessing casualties and providing care/assisting in the prevention and treatment of hypothermia in the prehospital environment.
There are 2 cognitive learning objectives and 1 performance learning objective for the hypothermia module.
The cognitive learning objectives are to identify the progressive strategies, indications, and limitations of hypothermia prevention of a trauma casualty in Tactical Field Care (TFC), and to identify passive hypothermia prevention measures on a trauma casualty.
The performance learning objective is to demonstrate active and passive external warming hypothermia prevention measures on a trauma casualty.
It is critical for a combat medic/corpsman to recognize hypothermia, understand it is a serious problem for a trauma or burn casualty, and be able to successfully prevent and/or treat it.
Hypothermia prevention and management is the “H” in the MARCH PAWS sequence (which also includes head injuries).
Remember, you are now in TFC, which affords the relative safety and time to expand the focus of assessment and management beyond immediate life-threatening hemorrhage control to treatment of other injuries and prevention of potentially life-threatening complications including the prevention and treatment of hypothermia.
Hypothermia poses a significant risk to combat trauma and burn casualties and is an independent predictor of mortality. It can occur regardless of ambient temperature and aggressive prevention and treatment is an essential element of the care of all combat casualties.
Simple interventions have proven effective in decreasing the incidence of hypothermia in the prehospital environment. Remember, hypothermia prevention and treatment is not just about keeping the casualty warm and comfortable, it can help save their life.
Hypothermia is a decrease in core body temperature. This can result when the body’s ability to produce heat is overcome by excessive or prolonged exposure to cold ambient air or water. Alternatively, in trauma patients, it results from derangement of body thermoregulation secondary to hemorrhage, and shock and can be seen even in very warm environments
Hypothermia results from a combination of environmental factors and physiologic responses to blood loss.
The physiologic impact of even a small decrease in core body temperature (below 36 degrees C or 96.8 degrees F) has been well documented and can significantly increase mortality in trauma and burn casualties.
Acidosis, coagulopathy, and hypothermia occurring together in a trauma casualty is referred to as the lethal triad.
As mentioned previously, the functions of the clotting cascade are impaired in hypothermia, and further blood loss from coagulopathy leads to increasing hypothermia.
The early recognition and prevention of hypothermia are essential during trauma assessment and care. Maintain a high index of suspicion when operating in a cold, wet, windy environment.
Hypothermia affects every organ system of the human body. Even with mild hypothermia, brain function and mentation are affected. A hypothermic casualty may be confused or disoriented and have slurred speech.
During mild hypothermia, casualties can shiver. Shivering will generate heat for the body. In moderate to severe hypothermia, when the core body temperature reaches around 32 degrees C or 90 degrees F, the body loses the ability to shiver.
Mild and moderate hypothermia leads to diuresis, which can result in dehydration.
In moderate and severe hypothermia, breathing slows, and in severe hypothermia, the respiratory drive from the brainstem is shut down.
Remember that ALL trauma casualties in shock or at risk of shock are at risk for trauma-induced hypothermia even when operating in a warm environment.
Hypothermia is one leg of trauma’s “lethal triad”. Bleeding and shock lead to tissue hypoperfusion causing hypothermia, acidosis, and coagulopathy resulting in increased blood loss and worsening hemorrhagic shock. This vicious cycle results in increased mortality in trauma casualties. Casualties with burns are also at increased risk of hypothermia.
In other words, prevent and/or treat hypothermia!
Environmental factors (wind, cold ambient air temperatures, precipitation, etc.) contributing to hypothermia only make things worse.
Due to the physics of heat transfer, it is much easier to prevent hypothermia than to treat it. Take early and aggressive steps as soon as possible after wounding to prevent hypothermia. Prevention of hypothermia in casualties is an essential element of care, and simple interventions have proven effective in decreasing the incidence of hypothermia during trauma assessment, treatment, and prolonged evacuations.
In addition to aggressive steps taken early to prevent further loss of body heat, when possible, trauma and burn casualties should be actively warmed (by adding external heat). Minimize casualty’s exposure to cold ground, wind, and air temperatures. Place insulation material between the casualty and any cold surface as soon as possible. Keep protective gear on or with the casualty if feasible. Replace wet clothing with dry clothing, if possible, and protect from further heat loss.
Prevention of hypothermia in casualties is an essential element of care, and simple interventions have proven effective in decreasing the incidence of hypothermia during trauma assessment, treatment, and prolonged evacuations.
Hypothermia Indications
ALL trauma casualties in shock or at risk of shock are at risk for trauma-induced hypothermia even when operating in a warm environment. For 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).
When hypothermic patients (core temperature <28°C [82.4°F]) are below the thermoregulatory threshold for shivering (~30°C [86°F]), shivering heat production ceases. Thus, these primary hypothermic patients will continue to cool, and they cannot warm up spontaneously without external heat, even if they are well insulated from the environment; this is especially true for trauma patients.
During prehospital trauma management, the administration of pain medications, such as ketamine, opioids, and benzodiazepines, per TCCC guidelines, may abolish shivering, which can further exacerbate the magnitude of hypothermia.
Possible active hypothermia limitations may include:
Hypothermia Prevention
In addition to aggressive steps taken early to prevent further loss of body heat, when possible, trauma and burn casualties should be actively warmed (by adding external heat).
If using a hypothermia kit, place the casualty centered on the vapor barrier shell.
If a commercially available vapor barrier shell is not available, place the casualty centered on an improvised impermeable vapor barrier (space blanket, survival blanket, plastic tarp, poncho liner, waterproof sleeping bag shell, body bag, etc.).
If an active warming device is available, open the active warming device package, remove the device, and expose to air (per manufacturer’s guidance) to activate. Apply the active warming device on the casualty’s anterior torso and under the arms in the axillae. The active warming device should not be placed directly on the skin to prevent burns.
Wrap the entire vapor barrier shell (or other improvised impermeable vapor barrier materials) completely around the casualty, including the head, and secure using tape if necessary taking care not to cover up the casualty’s face.
As soon as possible, any improvised vapor barrier should be upgraded to a well-insulated enclosure as additional materials become available. Seek to improve adding to the hypothermia prevention management.
As a mission planning factor, an insulated hypothermia enclosure system with external active heating should be pre-staged for transition from non-insulated hypothermia enclosure systems.
It is important to continue to monitor the casualty closely for life-threatening conditions and to protect the casualty from further exposure to wind and precipitation while awaiting evacuation.
CAUTION: Do not apply active warming blanket directly to bare skin to prevent burns. Active heating sources can cause first- to third-degree burns when applied directly to skin. These injuries may occur through misuse or be the result of unexpected consequences to application. Cold and under-perfused skin is very susceptible to injury from pressure or heat. The user should follow manufacturer instructions and place a protective layer of material between the heat source and the skin to prevent burns.
Passive hypothermia management keeps the casualty’s body heat contained and insulates to prevent further loss. It does not reverse the hypothermic process.
Place the casualty centered on the vapor barrier shell. If a commercially available vapor barrier shell is not available, place the casualty centered on an improvised impermeable vapor barrier (space blanket, survival blanket, plastic tarp, poncho, waterproof sleeping bag shell, wool blankets, body bag, etc.).
If an active warming device is not available, wrap passive warming materials (blanket, poncho liner, sleeping bag, etc.) under and around the casualty, including the head.
Wrap the entire vapor barrier shell (or other improvised impermeable vapor barrier materials) completely around the casualty, including the head, and secure using tape if necessary, taking care not to cover up the casualty’s face.
As soon as possible, passive warming materials and any improvised vapor barrier should be upgraded to active warming and a well-insulated enclosure as additional materials become available.
As a mission planning factor, an insulated hypothermia enclosure system with external active heating should be pre-staged for transition from non-insulated hypothermia enclosure systems.
It is important to continue to monitor the casualty closely for life-threatening conditions and to protect the casualty from further exposure to wind and precipitation while awaiting evacuation.
«There is evidence that an improvised hypothermia wrap is effective when high-quality insulation with a cold-rated sleeping bag is combined with a heat source, an internal vapor barrier, and an outer impermeable enclosure». (Bennett 2020)
As noted by the authors of the Allen paper, however, the testing conditions used were not a severe model of cold stress – and the success of all improvised devices is contingent on the quality of the improvisation materials and the skills of the improviser.
PDF Active/Passive Hypothermia Prevention and Management Skills Card
In summary, you should now be able to define hypothermia and discuss active and passive hypothermia prevention and management.
Hypothermia is decreased core body temperature secondary to external environmental factors and/or hemorrhage and shock.
Hypothermia in trauma patients is an independent predictor of mortality.
Hypothermia is a consideration even in hot operational environments as hemorrhage and shock can cause significant hypothermia in trauma patients.
Active hypothermia management/prevention is preferred, when available, and involves external heating of the casualty.
Passive hypothermia management/prevention can be used when active warming is not available. It does not reverse the hypothermic process.
Above all else, remember that hypothermia can kill a trauma casualty (even in a hot operational environment) and it is easier to prevent than treat. Don’t let your casualty get cold!
To close out this module, check your learning with the questions below (answers under the image).
Answers
Why is it important to prevent/manage hypothermia in a trauma casualty?
Even a small decrease in body temperature can interfere with blood clotting and increase the risk of bleeding to death. Casualties in shock are unable to generate body heat effectively. Avoid the “lethal triad”
True or False? Hypothermia is not an issue in hot operational environments?
False. Even in a hot environment, a trauma or burn casualty can become hypothermic due to hemorrhage and shock. Hypothermia prevention and management is a consideration for all trauma casualties.
What is the difference between active and passive hypothermia management?
Active hypothermia treatment uses an external heating source to warm the casualty. Passive hypothermia management strategies will keep the casualty from losing more heat, but will not warm the casualty or reverse the hypothermic process.
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