Page 39 - JSOM Spring 2025

and management of EHI, including prevention, prehospital which can be measured with a rectal thermometer, prefera-
care, emergency department care, inpatient hospital care, and bly an indwelling rectal thermistor. In addition to providing
return to duty guidelines. The CPG represents the first Joint the most accurate temperature reading in the setting of EHI,
Service collaborative effort to establish consensus around EHI a thermistor provides the additional benefit of being able to
management while recognizing the diverse missions of the remain in place during management and provide continuous
branches of the Armed Forces. The EHI CPG has been dissem- monitoring of core temperature during rapid cooling. Mea-
inated through the Defense Health Agency (DHA) and can be surement of core temperature at other anatomic locations is
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found on the Joint Trauma System website. not advised. A lack of ability to obtain a core temperature
should not delay rapid cooling in the setting of a patient who
The CPG is a broad document, integrating service-specific collapses during or immediately following exertion (especially
guidance, that covers valuable information on the manage- in hot weather), coupled with signs and symptoms of CNS dys-
ment of EHI, to include return to duty, in a wide variety of function. This clinical scenario should be considered an EHS
medical settings. While much of this is relevant to the Special until proven otherwise. Of note, it is common for core tem-
Operations community, the most pertinent section for medical perature to plateau or even rise during initial cooling, a physi-
personnel to be familiar with is early recognition and prehos- ologic response likely due to extremity vasoconstriction. 25
pital care. This article introduces the recommended practices
from the CPG, which are most relevant to the Special Opera- Pre-Mission Planning
tions community.
One of the key strategies for reducing EHIs is mitigating the
threat via prevention. Best practices and recommendations
Early Recognition and Universal Training
for this are discussed in detail in the “prevention” section of
Early recognition of the signs and symptoms associated with the CPG. However, even with the best prevention strategies in
EHI is paramount to rapidly treat patients and mitigate the im- place, EHI can still occur. This necessitates medical personnel
pact and long-term sequelae of heat injury. Prolonged hyperther- to appropriately plan and coordinate for EHI incidents. Key
mia can result in significant morbidity and mortality; between steps in pre-mission planning include awareness of variables
one and three military Servicemembers die each year from heat- in weather such as ambient temperatures and humidity, iden-
6
related illnesses. The duration of hyperthermia is often more tifying personnel and phases of the operation at greatest risk
consequential than the severity of peak core temperature. 5,10–21 for heat-related injuries, coordinating available treatment per-
sonnel, and developing strategic areas for treatment and rapid
Medical personnel are not always present with all elements cooling to occur.
during all facets of operations. Cross-training is imperative to
function as a medical force multiplier to preserve the fighting Rapid Treatment
force. Annual training on how to identify and provide initial
aid for EHI should be conducted for all personnel in the orga- “Cool first, cool fast” is the mantra emphasized by the
1
nization. When altered mental status or other signs of EHI are CPG when it comes to treating EHS. The overarching strat-
present, prompt action should be taken. These actions include egy should be cooling to a goal temperature of 39.0–39.2°C
calling for medical support, initiating rapid cooling methods (102.0–102.5°F) as soon as possible, ideally not exceeding 30
(discussed further below) as clinically indicated, and appropri- minutes from the time of injury. EHS is one of the few medical
ately moving the patient to a secure location with air condi- emergencies in which EMS transport should be delayed prior-
tioning if available. itizing rapid on-site treatment unless aggressive enroute cool-
ing using proven strategies is possible. This may be seen as a
point of divergence from other existing protocols, where evac-
Differential Diagnosis
uation is stressed over initial treatment. Active cooling should
The spectrum of heat injuries can be difficult to distinguish ini- be stopped when the goal core temperature of 39.0–39.2°C
tially. HE, HI, and EHS often share common clinical features (102.0–102.5°F) is achieved. Different rapid cooling strategies
and are accordingly initially managed in similar ways. The will be discussed in the “clinical best practices” section below.
clinical picture can often be further complicated by other con-
founding diagnoses such as sudden cardiac arrest, exertional Clinical Best Practices
rhabdomyolysis, exertional collapse associated with sickle-cell
trait, hypoglycemia, and exercise-associated hyponatremia. Rapid cooling, as opposed to evacuation with delayed rapid
When EHI is coupled with these conditions, the morbidity and cooling, improves overall morbidity and mortality. 5,10–21 On-
mortality rate increases, necessitating early recognition and site cooling prevents delays in treatment. Whole-body cooling
prompt treatment. 5,10–14,22–37 It is crucial that medical personnel serves multiple purposes by reducing organ and tissue tempera-
are familiar with the clinical presentations of these conditions tures (most important) and supporting tissue perfusion by va-
to be able to initiate appropriate management in a timely man- soconstricting blood vessels in the skin and superficial tissues,
ner. For further discussion of these conditions, see the WHEC thereby moving intravascular volume from the peripheral to
website for additional CPGs and treatment algorithms. 28 the central circulation. The primary goal of prehospital cooling
is to rapidly lower the body core temperature out of a severe
range, which reduces the area under the excessive temperature
Core Temperature Assessment
curve (degree-minutes) and protects the most heat-sensitive
When a Servicemember has a suspected EHI in a field setting, body organs. A minimum cooling rate for achieving favorable
the first step of the treatment algorithm (Figure 1) is to check clinical outcomes has not been established, but cooling rates
the body core temperature. The most practical and accurate greater than 0.15°C/min (0.27°F/min) are desirable to further
method to measure core temperature is via rectal temperature, reduce both morbidity and mortality. 5,10–12,14,16,18,19,30

Clinical Practice Guideline for Exertional Heat Illness | 37