Non-freezing cold injury
Tissue damage from cold, wet conditions above freezing.
Non-freezing cold injury (NFCI) happens when tissue is damaged by long stretches in cold, wet conditions where the temperature stays above freezing. It mostly hits the hands and feet, harming small blood vessels and nerves, which can lead to pain, changes in feeling, and a lasting sensitivity to cold. Different types of NFCI are often named after the situations where they’re common or were first noticed—trench foot, for instance, got its name from trench warfare.
The damage comes from injury to the lining of tiny blood vessels, blood flow slowing down or stopping, and blocked vessels, which causes nerve damage in the limbs. It usually affects soldiers, but also outdoor workers and divers. The condition can come on slowly, making it hard to spot and treat. At first, the area feels cold and numb, but within a day or two, blood flow increases, bringing intense burning pain, blisters, redness, and sometimes ulcers. Long-term effects can include numbness, tingling, and chronic pain—the exact cause of which isn’t fully understood—along with a lasting sensitivity to cold.
To reduce the impact, the focus is on identifying who’s at risk, limiting time in cold conditions, and using proper protective gear. Symptoms can look like those of decompression sickness or hand-arm vibration syndrome, and NFCI can happen in settings where those conditions are also possible, such as diving in cold water or logging and construction in cold environments.
NFCI is a type of local cold injury that doesn’t involve freeze-thaw damage. Cold injuries are divided into systemic (hypothermia) and local. Local injuries split into freezing (frostbite) and non-freezing. Types of NFCI include trench foot, immersion foot, and NFCI from cold water diving.
The condition goes through four stages. First, during cold exposure, blood vessels narrow, reducing blood flow, and the tissue gets cold and numb. This can affect touch and sense of position, leading to clumsiness, loss of strength, and trouble walking. Skin may first look flushed, then pale. Second, after rewarming starts, there may be a short phase of mottled bluish skin, still cold and numb, with swelling and weak pulses. Third, a hyperemia stage can last weeks, with swelling, hot red dry skin, poor microcirculation but full pulses, plus tingling, pain, and possible areas of dead skin.
Quick Facts
- Onset
- following exposure
- Duration
- indefinite
- Causes
- prolonged exposure to low temperatures above freezing<!-- or
- Risks
- occupational, social
- Diagnosis
- based on symptoms and history of exposure
- Differential
- Decompression sickness, hand-arm vibration syndrome
- Prevention
- personal protective clothing
- Treatment
- rewarming
- Medication
- analgesic
- Prognosis
- variable
Facts from the source article.
Lore & Background
Non-freezing cold injury has several forms, with common names often referring to the circumstances in which they occur or were first described, such as trench foot, named after its association with trench warfare. Other types include immersion foot and NFCI due to cold water diving exposure. The condition is caused by microvascular endothelial damage, stasis and vascular occlusion, and is characterised by peripheral neuropathy. It generally affects the hands or feet during exposure to temperatures just above freezing, often wet, and is typically found in soldiers.
Development may be gradual and difficult to recognize and treat. Initially the affected area is cold and numb, but this changes to hyperemia within a day or two, along with an intense, painful, burning sensation, blisters, redness, and in some cases ulceration. Four distinct stages occur: during cold exposure, vasoconstriction reduces perfusion and the tissue becomes cold and numb; after cold exposure, a short phase of mottled cyanosis may occur; the third stage of hyperaemia may last for several weeks; and the final stages may last for weeks to years, even indefinitely.
Risk factors include exposure of the extremities to cold and wet for prolonged periods, with fatigue, malnutrition, immobility, poor environmental protection, inadequate fluid or caloric intake, and stress often contributing. Pre-existing conditions such as circulatory problems, diabetes, smoking, older age, mental illness, and alcohol use may increase susceptibility, though data on some factors are inconclusive. The mechanism is poorly understood, involving reduced control of circulation and damage to the microcirculation, with evidence suggesting a combination of temperature and duration determines tissue damage.
Reader's Guide
Non-freezing cold injury is significant as a cause of substantial morbidity in military personnel and civilians who work in cold conditions, mountaineers, fishermen, homeless people, and underwater divers. Its legacy includes lifelong effects such as numbness, paraesthesia, chronic pain, and hypersensitivity to cold, the etiology of which is not yet adequately demonstrated. Persistent symptoms can continue long after the original injury and may have long-term psychological and financial effects, forming the basis of a significant number of military legal claims. Diagnosis can be complicated by overlap with decompression sickness and hand-arm vibration syndrome, as NFCI may occur in conditions where these are possible, such as diving in cold water and logging or construction work in cold environments. Strategies to reduce impact focus on recognizing those at risk, limiting exposure, and using suitable personal protective equipment. Treatment prioritizes systemic cold injury first, then freezing cold injury, followed by non-freezing cold injury; isolated NFCI should be allowed to rewarm gradually with rest and elevation, as rapid rewarming increases pain and edema.
Did You Know?
- NFCI can occur at temperatures up to 21 °C (70 °F) if exposure lasts about 8 days.
- The 'hunting response' or cold-induced vasodilation occurs in 5 to 10 minute cycles and may improve resistance to NFCI, though evidence is not conclusive.
- Tissue loss in severe cases is thought to be caused by pressure injury or compartment syndrome, not by the cold itself.
- Symptoms of NFCI can be similar to those of decompression sickness and hand-arm vibration syndrome.
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