Page 73 - 2021 Advanced Ranger First Responder Handbook

Hyperthermia
Heat Injuries
Heat injuries fall into a continuum of heat cramps to heat exhaustion to heat stroke. While the mechanism of heat
cramps is not fully understood, there is convincing evidence to suggest it is the result of sodium depletion or over hydra-
tion. Heat exhaustion and heat stroke represent a spectrum of disorders, which range in intensity and severity of tissue
damage. The pathophysiology of heat exhaustion and heat stroke are so similar that they may represent a continuum of
disease rather than separate, distinct diseases and both are characterized by sodium and water depletion. Heat cramps,
heat exhaustion, and heat stroke are all illnesses related to a failure of the body to maintain fluid and electrolyte balance
to the challenge of adapting to added heat loads. These conditions may develop over several days, allowing adequate
time for effective intervention. The maintenance of adequate diet and fluid intake is essential. The use of dietary supple-
ments can lead to dehydration and increased likelihood of heat injury. When faced with increased heat loads, the body
is dependent on sweating to maintain a constant body temperature. The sources of the heat load may be external (a hot
day), internal (a road march with 50 pounds of gear) or both (a road march in the desert sun). If the heat load exceeds
the body’s ability to lose heat, a heat injury will result.
Heat Cramps
The term “heat cramps” is actually a misnomer, as muscle cramping more likely results from sodium depletion during
intense activity, not from heat. In fact, cooling of a fatigued muscle is often a contributing factor. Heat cramps typically
occur in individuals undergoing prolonged, intense activity in a hot and humid environment. Heat cramps are brief,
intermittent, and very painful but can largely be prevented by maintaining an adequate salt and fluid balance prior to
and during exertion.
S/Sx: Painful, tonic contractions of skeletal muscles frequently preceded by palpable or visible muscle twitching. Fa-
tigue, dizziness, nausea, and vomiting are common.
Management: Obtain hydration and diet history to guide management and identify likely electrolyte cause. Oral elec-
trolyte rehydration and foods are the initial management of choice. IV crystalloid solution is indicated if more rapid
treatment is needed. Mild stretching and massage of the contracting muscle will provide some relief for the intense dis-
comfort. May return to activity after symptoms resolve but patient is at risk for return of heat cramps or other heat injury.
Heat Exhaustion/Stroke
Heat exhaustion is the most common heat illness. Although heat exhaustion in a military setting often manifests after
extreme exertion, in reality, it likely develops over several days. It is a result of cardiovascular strain as the body tries
to maintain normothermia in a hot environment. Heat exhaustion occurs when the demands for blood flow (to the skin
for temperature control through convection and sweating, to the muscles for work, and other vital organs) exceed the
heart’s ability to pump blood. A body that has developed a state of salt depletion over several days, in combination with
extreme exertion, is at risk for heat exhaustion.
S/Sx: Profound fatigue, chills, nausea/vomiting, tingling of the lips, shortness of breath, dizziness, headache, syncope,
hyperirritability, anxiety, raised skin hair, heat cramps, heat sensations in head and upper torso. Casualty may or may
not feel thirsty. Tachypnea, tachycardia, hypotension may be present. Core temperature may be normal or > 104°F. Heat
stroke can be defined as a heat injury with central neurologic symptoms such as altered mental status (AMS) or seizures.
Management: Heat Exhaustion: Reduce the load on the heart with rest and cooling. Place casualty in shade and re-
move heavy clothing. Apply cool water to the skin, if available. Correct water and electrolyte depletion by administering
oral or IV fluids. IV fluids replenish the volume and correct symptoms quickly. Patients with resting tachycardia or hypo-
tension should initially receive up to 1–2L boluses of crystalloid solution and monitored for these vital signs to correct. If
patient can tolerate oral fluids, use an oral electrolyte solution or sports drink. Ranger should limit activity for minimum
of 24 hours and ease into return in activity, in a slow stepwise approach.
Management: Heat Stroke: Heat stroke is a true emergency and needs to be managed by rapid active cooling (ice bath
immersion or rotation of ice sheets). In a patient with an undefined heat injury and temperature > 104°F, or hyperthermia
and AMS, treat as heat stroke per the protocol. Do not rely solely on temperature to diagnose but have a high index of
suspicion with appropriate risk factors and clinical setting and treat presumptively.
Hyponatremia
In addition to these standard heat injuries, hyponatremia, or emergently low blood levels of sodium, may be classified
as a heat injury. Hyponatremia in our population most commonly occurs due to excessive water consumption that over-
whelms the body’s ability to maintain a normal blood electrolyte concentration. This excessive water leads to a dilution
of the blood sodium and can have central nervous system effects such as seizures or AMS.
Treat all apparent heat injuries with primary concern for heat stroke. In a patient thought to have a heat injury due to
environmental factors with AMS or seizures with a core temperature < 104°F attempt to gain history of excessive water MISC
consumption or recurrent clear vomiting. With a negative evaluation for heat stroke in patient with AMS or seizures, treat
for presumptive hyponatremia. Treatment includes continuing emergent evacuation and administering IV fluids. Ensure
large IV access for administration.
2021 ADVANCED RANGER FIRST RESPONDER HANDBOOK 63