Trench Foot and Immersion Foot Syndrome

Other Names

• Peripheral vasoneuropathy
• Nonfreezing Cold Injury (NFCI)
• Acute trench foot
• Chronic trench foot
• Immersion foot
• Sea boot foot
• Bridge foot

Pathophysiology

• General
  • Trench foot is a type of nonfreezing cold injury; moisture is required to produce an NFCI
  • It is typically accompanied by moisture, sometimes infection, resulting in a peripheral vasoneuropathy
  • NFCI is affected the nerves, microvasculature, and soft tissue of the distal limbs, most often the feet
  • Overall, the pathophysiology is poorly understood and described
• Acute trench foot
  • Thrombi form, causing vascular occlusion and tissue death, nerve fiber inflammation
• Chronic trench foot
  • Partial recanalization of vessels may occur, but residual symptoms persist
  • Chronicity tends to follow repeated episodes of acute trench foot, resulting in ‘chronic trench foot’
  • This leads to increasing severity, necrosis and potentially cellulitis, sepsis
• Natural history
  • Most cases described with cold, wet extremities for at least one to three days
  • but NFCI can develop after 14 to 22 hours of exposure to seawater at 0 to 8 °C
  • Typically occurs in wet, cold conditions in patients who are unable to remove their shoes or boots whilst they are relatively immobile.
  • Patients are also usually fatigued and calorie-depleted.

Causes

• Nonfreezing cold injury (NFCI)
  • Exposure to cold temperatures just above freezing
  • Predominant manifestations are dysfunction of circulatory control and injury to the microcirculation
  • If sufficient duration and severity result in neurovascular changes, leading to peripheral vasoneuropathy
  • Combined with moisture and pressure, drives reactive hyperemia with subsequent edema and destruction of capillaries
  • This impairs tissue perfusion, leading to the destruction of nerves and tissue necrosis
  • Blood flow is reduced in the toes due to a reduction in arterial diameter
  • Reduced blood flow leads to ischemia and subsequently reperfusion injury, which can result in long-term tissue damage
• Nerve conduction
  • Among UK servicemen, nerve conduction was normal, however intra-epidermal nerve fiber density was markedly reduced in 91% of patients
  • Animal models show a reduction in nerve conduction, distal degeneration of nerve fibers after cold exposure
  • Cold exposure primarily affects sensory fibers, with 95% of patients with NFCI experiencing neuropathic pain
• Frostbite
  • Trench foot, a non freezing cold injury, should be distinguished from frostbite, a freezing cold injury
• Tinea Pedis
• Cellulitis
• Occupations (with risk of cold, wet feet)
  • Military
  • Fish processers
  • Harbor workers
• Sports/ Recretional
  • Diving^[10]
  • Hiking
  • Mountaineering
  • Festival attendees
• Military Training^[11]
  • Winter training exercises
  • Younger, unseasoned soldiers
  • Afro-Caribbean troops
• Socioeconomic/ Other
  • Homelessness
  • Alcoholism
  • Inability to dry socks, boots
  • Immobility
  • Wet clothing or footwear
  • Poor caloric intake

• General
  • Hypothermia
• Freezing
  • Frostbite
• Non-Freezing
  • Chilblains (Pernio)
  • Cold Induced Urticaria
  • Trench Foot
• Cold Injury Mimics
  • Pressure Necrosis including Acute Compartment Syndrome
  • Cellulitis

Diagnosis

• History
  • Diagnosis is clinical
  • History of exposure to wet cold for at least several hours in temperatures near freezing
    • Or an exposure for days with higher temperatures, as high as about 15 °C
  • History of losing feeling for at least 30 min and having pain or abnormal sensation on rewarming
  • Most commonly occurs in the feet, but can occur elsewhere in the body, including hands
• Physical Exam: Physical Exam Foot
  • Red, edematous hands or feet
  • Demarcations are not sharp between diseased and non-diseased tissue (unlike frostbite)
• Special Tests
• The diagnosis of NFCI is made clinically
• Imaging and laboratory testing are not helpful in most cases

Classification

• Stages of Trench Foot^[13]
  • Length varies widely
  • Some stages may be very short, easy to miss
  • Transition times vary
• Stage 1 (cold exposure)
  • Characterized by complete loss of sensation
  • Patients report numbness, hands or feet feel like blocks of wood
  • May have trouble walking due to loss of sensation
  • Limbs may appear bright red, then become pale or white due to vasoconstriction
  • Stage is painless
• Stage 2 (pre-hyperemic or post-exposure)
  • Starts when the victim is rescued from cold, placed in warm environment
  • Takes place during and following rewarming
  • Duration is extremely variable (hours to days)
  • Light skin: appears mottled and pale blue, indicating mild return of circulation
  • Dark skin: difficult to see color changes
  • Pulse is weak, but may become strong later, slow capillary refill
  • Limb is cold and insensate, with or without swelling
• Stage 3 (hyperemic)
  • Starts suddenly then persists for days or weeks
  • Limb is bright red, swollen with strong pulses
  • Capillary refill remains delayed due to injury to the microcirculation
  • Hyperalgesia replaces numbness, although some distal areas may still be diminished or insensate
  • There is usually no tissue damage
  • Blisters may arise in injured areas that have suffered pressure injury or infection.
  • Blistering or discoloration may signify incipient necrosis.
• Stage 4 (post-hyperemic)
  • Last for weeks to years or be permanent
  • Appearance is normal except in rare cases where tissue has been lost
  • Limbs are cool and are usually exquisitely cold-sensitive, vasoconstrict when exposed
  • Limbs may stay cold for hours, even after very brief cold exposure
  • Chronic pain in response to cold is common
  • Hyperhidrosis: often complain of excessive sweating
  • Victims may develop symptoms that resemble complex regional pain syndrome (CRPS)
  • Amputation is rare, but can occur with tissue necrosis

Treatment

Prevention

• Primary treatment is prevention
  • Not well studied or published
• General
  • Avoid wet-cold environments
  • Some recommendations are from warm water immersion injuries
  • Clothing should be warm, even when wet
  • Material: Synthetic materials are preferred over wool, avoid cotton as it gets very cold when wet
  • Remain active to encourage circulation
  • Elevate feet when possible
  • Education and training for cold to prevent, minimize stress and risk
  • Rotate personal in and out of cold environments
• Dry feet
  • Air dry feet >8 hours a day is effective in preventing warm water immersion foot
  • Recommend to dry feet for a day after every 2 days of immersion^[14]
• Soldiers guide from WWI^[15][3]
  • Paired with battle buddy, responsible to check each others feet
  • Increase rations, provide dry socks in waterproof bags
  • Change socks regularly, keep warm, avoid friction blisters
  • Inspect for blisters, signs of gangrene
  • Raise feet to prevent venous edema
  • Rotation schedules to avoid prolonged periods in wet, muddy trenches
  • Wraps around the calf and ankle above boots
  • Remain as active as possible to prevent vasoconstriction
  • Gum boots with foot powder instead of using oils (which probably increaser risk)

Prehospital

• Patient moved to warm environment quickly
• Patient may need to be carried
• Wrapped in vapor barrier with insulation, over wet clothing as needed
  • Can remove wet clothing in warm environment

Emergency Department/ Acute Management

• Correct hypothermia, if present
  • Use core temperature to identify
• Rewarming limbs
  • If frostbite is present, rewarm affected limbs in water at 37-39 °C
  • If frostbite is absent, limbs do not need to be rewarmed
  • Rewarm gradually with rest, elevation, gentle pat drying
  • Rapid rewarming can cause severe pain, increased oedema, and increased tissue ischemia
• Hydrate to address fluid losses
  • Recommend warming to ~42 °C
• Avoid
  • Rubbing affected limb due to damaged skin
• Tetanus Booster should be administered
• Antibiotics are not routinely needed
• Pain control
• Consider prophylaxis for Venous Thromboembolism

Hospital Management/ Acute Management

• Limb care
  • Elevate above level of heart
  • Dressings, if necessary, should be loose to protect circulation
• Stage 3/ hyperemic
  • Sensation returns, limb becomes hyperalgesic
  • Recommend cool limbs using a fan at room temperature to 15-18 °C
  • Analgesics are generally ineffective including opioids
• Amitriptyline
  • Initiate at the onset of pain^[16]
  • 50 to 100 mg orally at bedtime
  • Higher doses for breakthrough pain
• Gabapentin
  • Can be added or substituted if Amitriptyline is insufficient
• Mild fever in the first 12 to 36 hours is common and usually transient
• If cellulitis is present, antibiotics to cover staphylococci, streptococci, and pseudomonas
• Surgical consultation if there are signs of tissue necrosis (hemorrhagic blisters)
• Not helpful
  • Vasodilators including Nifedipine

Long Term Care

• Pain management
  • Neuropathic pain and CRPS are common
  • Often require pain management specialist
• Occupation
  • Outdoor work only if minor symptoms without numbness
  • Some soldiers can return to full duty if the normal response to cold
• Peripheral neuropathy
  • Should see a neurologist for further investigation
• Prostaglandin Analogue
  • Iloprost (a synthetic prostaglandin I2 analog), temporarily reduced pain and increased mobility in a case report^[17]
• Nicotine tartrate
  • Demonstrated improved symptoms in 16 (44%) of 36 patients, with particular improvement in pain, paraesthesia, and exercise capacity.^[18]
• Ineffective drugs
  • Aminophylline
  • Papaverine
• Future research
  • Thromboxane and prostaglandin inhibitors have shown increased tissue survival in frostbite^[19]
• Tinea Pedis
  • If present should be treated with systemic or topical antifungals

Operative

• Indications
  • Unclear
  • Recommend surgical consult if evidence of significant necrosis
• Technique
  • Lumbar Sympathectomy (obsolete, not recommended)

Complications 

Complications

• Acute tissue necrosis
• Infection
• Difficulty ambulating
  • Patients may have a ‘slapping, flat-footed, springless gait’ which often resolves in about 1 week^[20]
• Cold feet
  • Limbs often feel cold with persistent vasoconstriction, especially after cold expsure
  • This can cause pain, even when walking
• CRPS/ Chronic Pain/ Hyperalgesia
  • Occurs frequently
• Nail pathology
  • Intermittent nail loss
• Severe arthropathy of major joints
• Hyperhydrosis
  • In response to cold, heat, or emotional stimuli
  • Can lead to recurrent Paronychia, Onychodystrophy
• Raynauds Syndrome
• Chronic fungal infections
• Psychiatric/ behavioral
  • Including Depression, suicidal thoughts
  • Substance and alcohol abuse
• Occupation
  • Inability to work outdoors
  • Soldiers may be unable to redeploy
    • In one study, NFCI was career ending for 25/42 soldiers and career altering for the remaining 17