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Immersion Foot
Prevention and Treatment of Immersion Foot
Joshua D. Caron
Department of Parks, Recreation, and Tourism
University of Utah
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As emphasized by our Instructor you must take care of your feet in the field. Your own
two feet are your best and sometimes your only way to reach definitive medical care. For the
purpose of this presentation I will define immersion foot, discuss the prevention, symptoms and
treatment of immersion foot and other Non-Freezing Cold Injuries (NFCI). In order to prevent
and treat immersion foot, you must first understand the causes and physiology of immersion foot.
Immersion foot is sometimes referred to as trench foot. Although immersion foot and
trench foot both present the same and have the same pathology they actually have different
etiologies. In Paul Auerbach’s book Wilderness Medicine, he explains that the term Trench foot
originated in World War I when our soldiers were engaged in trench warfare and wore their
boots and sock for long periods of time. The term immersion foot was first recorded during
World War II to medically document the shipwreck survivors who have been exposed to cold
wet conditions for long periods of time.
According to Merriam-Webster’s dictionary, immersion foot is a painful condition of the
feet marked by inflammation and stabbing pain and followed by discoloration, swelling, ulcers,
and numbness due to prolonged exposure to moist cold with actual freezing. With that definition
in mind, the easiest way to prevent immersion foot is to keep your feet warm and dry. For
adventurers, that may not always be an easy task in a field setting.
Some common causes of immersion foot in the backcountry may be extended
river crossings, multiple hours of hiking in wet conditions or multiple hours with cold, wet feet
without rewarming. There are some misconceptions that because immersion foot is technically
considered a cold injury that you must be in cold conditions in order to get immersion foot.
Actually the temperature in which people are most susceptible ranges from 32 degrees to 59
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degrees Fahrenheit. For many people temperatures in the 50s are ideal conditions for prolonged
backpacking, trekking and hiking.
NFCI progresses from initial onset of exposure through 3 distinct phases. The phases
may overlap and have variable time courses depending on many factors to include the
temperature of exposure and overall vascular health of the patient. Increased risk factors include
diabetes, smoking and high blood pressure. NFCI injuries may range from mild to severe. In the
most severe cases patients are hyper sensitive to cold and may not be able to work outside and
some result in amputation of the affected limb. The three distinct phases are the pre-hypermic
phase, the hypermic phase and the post-hypermic phase.
The pre-hypermic phase begins after the initial exposure. In this phase the exposed limb
will appear blanched, yellowish white or mottled. During this phase there is typically no pain, if
the affected limbs are the feet the patient may have a feeling of “walking on air”. This is a sign
that the patient is losing sensation in their feet. Continued exposure will lead to an altered gait
and a decrease in palpable pedal pulses. Extreme vasoconstriction is the predominant causative
factor.
The hypermic phase begins within several hours of rewarming. At this point is when the
patient will begin to feel extreme pain as they begin to regain sensation in the exposed limbs.
Palpable pulses can now be detected and the extremities will become warm or hot to the touch.
This is due to vasodilation. The hypermic stage may carry on for 7-10 days with the most
intense pain around the 24-36 hour mark. Milder cases will peak at 24 hours and in the most
severe cases may take 6-10 weeks. There may also be blistering redness and peeling of the skin
in this phase.
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The post-hypermic phase can vary greatly depending on the severity of the injury. Mild
cases may show no physical signs while the most severe patients may develop gangrene and
severe tissue loss ultimately requiring amputation of the affected area. Typically the sharp
stabbing pain associated with the hypermic phase becomes a dull aching pain. Patients will
experience a cold sensitivity to the affected area and may sweat excessively. These symptoms
may last several weeks to years. Ongoing disabling problems may continue to affect the limb
much like a person with diabetes.
The best treatment for immersion foot is prevention. The most effective way to do that in
the field is to wear wool or synthetic socks, change them often and wear a waterproof, breathable
boot. Hiking and other strenuous activities may cause your feet to sweat regardless of the
outside temperature. That is why wearing synthetic material or wool, which wick sweat away
from your skin is vital. Cotton fabrics will absorb sweat. Eventually when your body cools it
will hold that now cold moisture next to your skin, contributing to early immersion foot.
If despite your best efforts, you or someone in your party develops immersion foot in the
field the optimal treatment is at a definitive care facility. In the field you will be limited to
warming and drying the feet, which will be extremely painful. Rewarming also creates a greater
metabolic demand of the damaged cells. This will lead to vasodilation, fluid transudation and
edema, which will only increase pain. Since pain management is limited in the field, it is
imperative to transport the patient quickly. Walking the patient is contraindicated since it may
cause further tissue damage, so again prevention is paramount.
As mentioned, it does not have to be extremely cold to develop immersion foot.
People have developed NFCIs from prolonged exposure to wet conditions in temperatures in the
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50s. You also don’t have to be hiking through water or rain to develop immersion foot. Simply
sweating in your boots for prolonged periods makes you susceptible. The best treatment of
immersion foot is prevention, however if you or someone does experience immersion foot it is
very important to transport them to a medical treatment facility promptly. Immersion foot can
potentially have life changes impacts on patients, from amputations to severe cold sensitivity.
The best prevention technique is to change socks every 8 hours, massage your feet twice a day to
encourage blood flow and to sleep without socks if possible to allow your feet to air dry. Lastly,
remember that cotton kills, always wear wool, polypropylene or another synthetic material that
will not absorb moisture. Happy hiking.
Immersion Foot
References
Auerbach P. (2014). Trench Foot (Immersion Foot). Wilderness Medicine 6th Edition.
Retrieved from. https://www.inkling.com/read/wilderness-medicine-auerbach-6th/chapter7/trench-foot-immersion-foot
Merriam-Webster. (2014). Immersion foot definition. Retrieved from. http://www.merriamwebster.com/medical/immersion%20foot
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