Definition

Non-freezing injury is a condition that occurs when body tissues are exposed to cold temperatures that are near freezing for an extended period. This condition commonly affects the feet or hands, particularly in wet environments and in temperatures just above freezing. It is often seen in soldiers who endure prolonged exposure to these conditions.

This injury happens due to damage to the small blood vessels (microvascular damage), blood flow stagnation, and vascular occlusion. Initially, the affected tissue may feel numb or cold, but within 24 to 48 hours, it progresses to hyperemia, a condition where blood accumulates in the tissue. This stage is often accompanied by intense pain, a burning sensation, wounds, redness, and possible blistering. Non-freezing injury is also referred to as immersion foot or trench foot.

Causes

Non-freezing injury is caused by prolonged exposure to cold and wet conditions, even when temperatures do not reach freezing. For example, trench foot can occur in wet, cold environments even at temperatures as high as 16°C.

When cold and moisture combine, the small blood vessels (capillaries) can weaken, leading to damage in the surrounding tissue. The restricted blood flow also affects circulation and nerve function. In some cases, excessive sweating of the feet can contribute to the development of trench foot. It can take anywhere from 10 to 14 hours of exposure to cold and damp conditions for a non-freezing injury to develop.

Risk Factor

The primary risk factor for non-freezing injury is exposure to cold and moisture. Several environmental and situational factors can increase the likelihood of developing this condition:

• Military Occupation
  
  • Military personnel are at high risk, particularly during training and field duties, where they may experience prolonged exposure to cold, wet conditions.
• Homelessness
  
  • People without permanent housing often lack proper footwear or multiple pairs of socks and are exposed to cold, humid conditions for extended periods.
• Outdoor Activities
  
  • Events such as music festivals, which expose participants to cold and damp weather for multiple days, can increase the risk of non-freezing injury.
  • Additionally, mountain climbing or hiking, especially if socks and shoes are not changed regularly, also pose a risk.
• Water-Related Professions
  
  • Workers in ports, fishing, or any profession requiring prolonged exposure to water have a higher likelihood of developing non-freezing injury due to their constant contact with wet conditions.

Symptoms

The initial symptoms of non-freezing injury include a tingling or itchy sensation, which may progress to stiffness or numbness. The affected area, usually the feet or hands, may feel heavy or immobilized, as if it were a block of wood, making movement difficult. The skin might initially appear bright red but will soon turn pale or white as blood vessels constrict. When the person moves out of the cold, the affected area may change color. For lighter-skinned individuals, the skin may appear bluish or purplish due to poor blood circulation. For those with darker skin, these color changes may not be as visible, but the skin may still feel cold and bumpy.

The affected area may also become swollen, with severe cases causing the tissue to double in size. As the area warms up, the redness may return, and the person might feel sharp pain or unusual sensations as the blood flow resumes.

Diagnosis

To diagnose non-freezing injury, the doctor will carry out a medical interview, a physical test, and supporting tests.

Medical Interview

During the medical interview, the doctor will ask a series of questions, including:

• Current symptoms

• Previous medical history

• Occupational history

• Family medical history

The doctor will also inquire about any recent activities, such as whether you have been exposed to cold or damp conditions in the hours leading up to your symptoms.

Physical Examination

Next, the doctor will perform a physical test. This will involve both a general and specific examination. During the general examination, the doctor will check your blood pressure, respiratory rate, pulse, and body temperature. They will also perform a targeted physical test on your feet to ensure that the symptoms are not caused by an infection or conditions like frostbite.

Diagnostic Tests

• Laboratory Tests
  • A complete blood test will be performed to check for any infections that could be causing your symptoms.
• Imaging Tests
  • An X-ray will be taken to evaluate the condition of the bones and to rule out the possibility of bone infections.

Management

Non-freezing injury can be effectively treated if caught early. The primary treatment is to rewarm the affected feet slowly. Rapid warming can cause severe pain and swelling. The first step is to remove the individual from the cold, wet environment and gradually warm the affected areas. The doctor will ensure that the feet are cleaned, kept dry, and kept warm.

Additional treatments include rest and elevating the feet above the level of the heart. To prevent infection, antibiotics will be prescribed. A tetanus booster injection may also be administered. For pain management, Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) or acetaminophen may be prescribed, and in some cases, amitriptyline might be used.

Some steps you can take to care for your feet during recovery include:

• Wear clean, dry socks daily.

• Avoid wearing socks while sleeping to keep your feet dry.

• Check your feet every day to ensure symptoms aren’t worsening or developing into an infection.

• Avoid smoking or nicotine products, as these can restrict blood flow to your feet.

• Consume a high-protein diet to aid in the healing process.

Complications

If left untreated, complications such as cellulitis (skin infection) or gangrene (tissue death) can develop. In severe cases, gangrene may necessitate amputation to prevent further deterioration. Other potential complications include sepsis (blood infection), which can be life-threatening, and in the worst cases, death.

Prevention

Non-freezing injury can be prevented by taking certain precautions:

• Change wet socks and shoes or boots as soon as possible.

• Ensure your feet stay dry at all times.

• Change socks at least once a day to maintain foot hygiene.

• Wear shoes or boots that are appropriate for the conditions.

• Do not sleep with wet socks.

• If you wear socks while sleeping, make sure they are loose to allow proper air circulation.

When to See a Doctor?

If you experience symptoms of non-freezing injury that interfere with your daily activities, consult a doctor immediately. It is important to discuss the condition and any recommended treatments with your healthcare provider.

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