Immersion FootMANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

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422 items

☷ Legend

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Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Acute Mountain Sickness Arterial Gas Embolism Bee-Wasp Sting (Anaphylaxis)Chilblains Ciguatera Fish Poisoning Coral Cut Decompression Sickness Electrical Burn Injury Envenomation (snake, spider, insect)High Altitude Cerebral Edema (HACE)High Altitude Pulmonary Edema (HAPE)High-altitude illness Hypothermia Hypothermia (Mild)Hypothermia (Severe)Immersion Foot Lightning Strike Injury Scombroid Fish Poisoning Scorpion Envenomation Sea Urchin Injury Shark Bite Snake Envenomation Spider Bite (Black Widow)Spider Bite (Brown Recluse)Stingray Spine Injury Tick paralysis White Phosphorus Burn

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp37

Immediate priorities

›Life threats requiring immediate action

›Concurrent hypothermia

›Core temperature < 35°C requires active management separate from foot injury

›ECG for Osborn (J) waves, bradycardia, prolonged QT, atrial fibrillation

›Continuous cardiac monitoring until normothermic

›Signs of systemic sepsis

›Fever, leukocytosis, hypotension from secondary cellulitis or wound infection

›Lactate >= 2 mmol/l as organ hypoperfusion marker

›Broad-spectrum antibiotics within 1 hour if septic shock

›Tissue necrosis or gangrene

›Surgical consultation for debridement or amputation assessment

›Compartment syndrome evaluation if severe swelling present

Rewarming and stabilization

›Key intervention: passive rewarming only

›Remove from cold and wet environment immediately

›Remove wet footwear, socks, constricting garments

›Allow feet to rewarm passively at room temperature — do NOT apply heat

›Active rewarming (warm water baths) is contraindicated and worsens injury

›Elevate affected extremities to reduce edema

Monitoring and targets

›Monitoring bundle

›Core temperature monitoring if hypothermia concern

›Rectal or esophageal probe for accurate measurement

›Axillary temperature unreliable in cold injury

›Peripheral perfusion assessment

›Hourly capillary refill, skin color, and temperature reassessment

›Peripheral pulse documentation (dorsalis pedis, posterior tibial)

02History/hx35

Exposure history

›Cold-wet exposure details

›Duration of continuous wet foot exposure — typically >= 12 hours to days

›Water temperature range — cold NFCI defined as 0–15°C (32–59°F)

›Continuous wearing of wet socks or footwear without removal

›Ability to change socks or access dry shelter during exposure

›Constricting footwear — tight boots, puttees, or wraps impairing circulation

Symptom progression

›Staged symptom timeline

›Initial numbness lasting > 30 minutes — most common early symptom

›Clumsiness or gait disturbance during exposure phase

›Burning, tingling, or intense pain on rewarming — hyperemic phase

›Chronic cold sensitivity and neuropathic pain in posthyperemic phase

›Prior episodes of NFCI — increases susceptibility to recurrence

Risk factors

›Population and social determinants

›Homelessness — up to 20% of medical complaints in homeless populations are foot-related

›Military deployment — prolonged field operations in cold-wet environments

›Outdoor occupation or recreation with prolonged exposure

›Prolonged immobility in wet conditions

›Malnutrition — risk factor for NFCI development

›Medical risk factors

›Peripheral vascular disease

›Diabetes mellitus — impaired circulation and sensation

›Venous insufficiency or lymphedema

›Raynaud phenomenon — increased cold-induced vasoconstriction

›Prior NFCI or frostbite — sensitizes to future injury

›African descent — military data suggest increased susceptibility to cold injury

03Physical Exam/exam31

Vitals and general

›Stability assessment

›Core temperature — rectal preferred if hypothermia suspected

›Heart rate — bradycardia suggests hypothermia; tachycardia suggests infection or pain

›Blood pressure — hypotension suggests sepsis or hypothermia

›Respiratory rate — tachypnea in sepsis or concurrent pulmonary infection

›General appearance

›Altered mental status — hypothermia or intoxication

›Nutritional status — cachexia, signs of malnutrition

›Signs of systemic illness — diaphoresis, rigors, toxicity

Staged foot examination

›Stage-dependent findings

›Stage 1 — During exposure: pale/white, cold, numb feet; diminished peripheral pulses; proprioception loss

›Stage 2 — Prehyperemic: mottled cyanotic appearance; cold and numb; mild edema

›Stage 3 — Hyperemic: erythematous, warm, swollen feet; intense pain; brisk capillary refill; blistering possible

›Stage 4 — Posthyperemic: chronic cold sensitivity, cyanosis with cold exposure, persistent neuropathic pain

›Key exam maneuvers

›Dorsalis pedis and posterior tibial pulse palpation

›Capillary refill time — both feet for symmetry

›Skin temperature — compare bilateral and proximal-to-distal gradient

›Sensory testing — light touch, pinprick, proprioception

›Skin inspection — maceration, bullae, ulceration, necrosis, fungal infection

Infection screen

›Signs of secondary infection

›Cellulitis — erythema, warmth, induration

›Lymphangitis — streaking proximal to wound

›Inguinal lymphadenopathy

›Purulent or malodorous wound drainage

04Differential Diagnosis/ddx33

Freezing cold injuries

›Frostbite

›ICD-10 T33–T35 range

›Tissue temperature below 0°C — ice crystal formation distinguishes from NFCI

›Hemorrhagic bullae and demarcated necrosis more prominent

›History of sub-zero temperature exposure

›Treatment: rapid rewarming — opposite of NFCI management

Nonfreezing cold injury spectrum

›Chilblains (pernio)

›ICD-10 T69.1

›Superficial erythrocyanotic papules after brief cold-wet exposure (1–5 hours)

›Pruritic; self-limited; does not progress through NFCI stages

›Warm water immersion foot

›Water temperature 15–32°C

›White wrinkled plantar surfaces; resolves in 2–3 days with drying

›Tropical immersion foot

›Warm water > 22°C for > 3 days

›Bright red, swollen feet; pitting edema; may have fever and lymphadenopathy

Vascular and dermatologic mimics

›Peripheral arterial disease

›ICD-10 I73.9

›Chronic ischemic changes; absent pulses; claudication history; no cold-wet exposure

›Venous stasis dermatitis

›ICD-10 I83.10

›Chronic bilateral lower extremity edema and skin changes; no acute exposure event

›Cellulitis

›ICD-10 L03.115 (lower leg)

›Usually unilateral; well-demarcated erythema; warmth; NFCI is bilateral

05Laboratory Tests/lt23

Core labs

›Diagnostic approach

›NFCI is a clinical diagnosis — no labs are diagnostic

›Labs directed by clinical concern for infection, hypothermia, or comorbidities

›Infection markers

›Complete blood count — leukocytosis in secondary cellulitis or sepsis

›C-reactive protein or ESR — inflammation quantification; limited specificity

›Blood cultures — if systemic infection or sepsis suspected, prior to antibiotics

›Wound culture — if purulent discharge or ulceration present

Metabolic and organ function

›Electrolytes and renal function

›Basic metabolic panel — especially if hypothermic (cold diuresis and electrolyte shifts)

›Glucose — screen for diabetes in at-risk populations

›Lactate — if concern for sepsis; >= 2 mmol/l indicates organ hypoperfusion

›Muscle injury

›Creatine kinase — if prolonged immobility or concern for rhabdomyolysis

›Urinalysis — myoglobinuria screen if CK elevated

›Nutritional status

›Prealbumin and albumin — assess nutritional status in malnourished or homeless patients

›Limited direct impact on acute management but informs disposition and recovery

Cardiac and hypothermia labs

›If concurrent hypothermia suspected

›Thyroid stimulating hormone — exclude hypothyroidism as contributing factor

›Coagulation panel — coagulopathy common with hypothermia

›Fingerstick glucose — hypoglycemia may accompany hypothermia

›Arterial blood gas — assess pH and metabolic acidosis

06Diagnostic Tests/dt44

Scoring Systems

›NFCI severity classification

›No validated single scoring system exists specific to NFCI

›Clinical staging system (Stages 1–4) is the primary classification

›Stage 1: cold phase with pallor and numbness during exposure

›Stage 2: prehyperemic with cyanosis and persistent numbness post-exposure

›Stage 3: hyperemic with erythema, edema, intense pain, possible blistering

›Stage 4: posthyperemic with chronic cold sensitivity and neuropathic pain

›Severity determined by extent of blistering, tissue loss, and pain intensity

›Wilderness Medical Society Classification

›WMS 2023 guidelines provide management framework but no numeric score

›Identifies mild (no skin breakdown), moderate (blistering), and severe (necrosis) categories

MRI

›MRI indications in NFCI

›Rarely needed for acute uncomplicated immersion foot

›Consider for suspected deep tissue involvement in severe cases

›Muscle or tendon involvement assessment

›Differentiation from pressure necrosis or osteomyelitis

›MRI superior to plain radiographs for soft tissue injury characterization

›Unlike frostbite, MRA (magnetic resonance angiography) is not routinely indicated for NFCI

›CT indications in NFCI

›Not routinely indicated for isolated immersion foot

›Plain radiographs preferred as first-line if bony concern

›Osteomyelitis assessment if chronic ulceration

›Foreign body detection

›CT angiography — consider if arterial thrombosis or vascular insufficiency suspected

›Particularly if peripheral pulses absent despite rewarming

07Disposition/dispo29

Discharge criteria

›Appropriate for discharge

›Stage 1 or Stage 2 injury with intact skin

›No signs of secondary infection

›Pain controlled with oral medications

›Adequate social support and ability to maintain dry, warm environment

›Access to follow-up within 2–3 days

›Able to ambulate safely

Admission indications

›Requires inpatient management

›Significant edema, blistering, or skin breakdown

›Signs of secondary infection — cellulitis, lymphangitis, wound infection

›Inability to ambulate or bear weight

›Concurrent hypothermia requiring active management

›Severe pain requiring IV analgesia

›Homelessness without access to shelter or dry footwear

›Social work consultation mandatory for housing plan

›Failure of outpatient pain management

›Uncontrolled comorbidities — decompensated diabetes, severe PVD

High-acuity and surgical admission

›Conditions requiring specialized care

›Tissue necrosis or gangrene — surgical consultation within hours

›Sepsis or septic shock from secondary infection

›ICU admission if hemodynamic instability

›Suspected compartment syndrome — emergent surgical evaluation

›Vascular surgery consultation for arterial thrombosis or absent pulses

Follow-up

›Outpatient follow-up plan

08Treatment/t54

Immediate wound care

›Passive rewarming protocol

›Remove from cold and wet environment — mandatory first step

›Remove wet footwear, socks, and any constricting bandages

›Allow passive rewarming at room temperature

›Do NOT apply warm water baths or heating pads — contraindicated

›Do NOT rub or massage affected tissue

›Elevate affected extremities above heart level to reduce edema

›Light, loose, non-constrictive dry dressings

›Keep toes separated with dry gauze to prevent maceration

Pain management

›Stepwise analgesic approach

›Mild pain — NSAIDs first-line

›Ibuprofen 400–600 mg PO every 6–8 hours with food

›Naproxen 500 mg PO twice daily as alternative

›Neuropathic pain — amitriptyline first-line

›Amitriptyline 50–100 mg PO at bedtime

›Start as soon as neuropathic pain develops — most effective analgesic for NFCI

›Titrate based on response and tolerability

›Inadequate response — gabapentin add-on

›Gabapentin 300 mg PO three times daily — titrate to effect

›Maximum 3600 mg/day in divided doses

›Reduce dose for renal impairment

›Severe acute pain — opioids as rescue

›Opioids generally ineffective as sole therapy for NFCI neuropathic pain

›May be required for acute pain not controlled by above regimen

›Short course only; reassess at each visit

›Agents to avoid

09Special Populations/sp46

Pregnancy

›Physiologic considerations

›Peripheral vasodilation of pregnancy may modify cold injury presentation

›Edema of pregnancy may confound staging assessment

›Fetal monitoring if systemic hypothermia or sepsis present

›Medication safety

›Amitriptyline — Category C; weigh benefit vs risk in pregnancy; avoid in first trimester if possible

›Gabapentin — Category C; limited data; avoid unless no alternatives

›NSAIDs — avoid after 20 weeks gestation (risk of premature ductus arteriosus closure)

›Acetaminophen 500–1000 mg PO every 6 hours preferred analgesic

›Tetanus prophylaxis — safe in pregnancy; update if needed

›Antibiotics for infection — cephalexin and cefazolin are safe in pregnancy (Category B)

›Disposition considerations

›Lower threshold for admission given fetal monitoring needs with systemic illness

›Obstetrics consultation if hypothermia, sepsis, or hemodynamic instability

Geriatric

›Physiologic vulnerability

›Reduced peripheral vascular reserve and impaired thermoregulation

›Decreased pain perception may delay presentation — injuries often more advanced at diagnosis

›Polypharmacy — diuretics and beta-blockers impair cold compensation

›Baseline peripheral neuropathy may confound sensory exam

›Medication considerations

›Amitriptyline — high falls risk; START LOW (10–25 mg at bedtime) and titrate slowly

›Gabapentin — reduce dose for age-related renal impairment; sedation risk

›NSAIDs — increased GI and renal risk; use minimum effective dose with PPI

›Opioids — increased sedation and fall risk; use with caution

›Comorbidity burden

›Peripheral vascular disease and diabetes common — higher tissue loss risk

10Background/b41

Epidemiology

›Incidence and affected populations

›Predominantly affects homeless, military personnel, and outdoor-exposed populations

›Up to 20% of medical complaints in homeless individuals are foot-related

›WWI — trench foot incapacitated over 75,000 British soldiers in winter 1914–1915

›Improved rations and dry socks rotations nearly eliminated the disease

›Still encountered in modern military operations, disasters, and urban homeless populations

›Incidence in homeless populations correlates with local temperature and housing availability

›Morbidity and outcomes

›Tissue loss from NFCI alone is rare — most resolve with conservative management

›Chronic neuropathic pain and cold hypersensitivity persist in up to 50% of severe cases

›Long-term sequelae may last months to years and significantly impair quality of life

›Prior NFCI increases susceptibility to future cold injury

Pathophysiology

›Mechanism of injury

›Prolonged cold-wet exposure causes intense peripheral vasoconstriction

›Tissue temperature remains above 0°C — no ice crystal formation distinguishing from frostbite

›Vasoconstriction leads to ischemia of peripheral neurovasculature

›Ischemia-reperfusion injury occurs on rewarming

›Reactive hyperemia generates free radicals and inflammatory mediators

›Endothelial injury and increased vascular permeability cause edema

›Nerve injury is the primary long-term morbidity driver

›Small fiber neuropathy predominates — affects pain, temperature, and autonomic fibers

›Proprioceptive loss from large fiber involvement

›Contributing factors

›Constricting footwear compounds venous and lymphatic obstruction

›Immobility prevents normal muscle-pump venous return

›Malnutrition impairs tissue repair mechanisms

11Patient Discharge Instructions/pdi29

copy discharge instructions

›What is immersion foot?

›Immersion foot (also called trench foot) is a cold injury to the feet caused by prolonged exposure to cold, wet conditions

›It is not frostbite — the skin does not freeze, but the nerves and blood vessels are damaged

›Most mild cases recover fully with proper care, but severe cases can cause long-term nerve pain and cold sensitivity

›Home care instructions

›Keep your feet dry and warm at all times

›Change into clean, dry socks at least once daily — more often if feet become wet

›Do not apply heating pads, hot water bottles, or soak feet in warm water — this can worsen the injury

›Elevate your feet above heart level when resting to reduce swelling

›Do not rub or massage the affected feet

›Wear well-fitting, non-constricting footwear

›Inspect feet daily for any new blisters, sores, or skin breakdown

›Medications

›Take prescribed pain medications as directed — amitriptyline or gabapentin may be prescribed for nerve pain

›Do not stop medications abruptly without talking to your doctor

›Over-the-counter ibuprofen or naproxen can help with mild pain if no contraindication

›Return to emergency department immediately if

›Worsening pain despite medication

›New or spreading redness, warmth, or swelling in the legs

›Fever or chills

›Foul-smelling discharge or pus from the skin

›Inability to bear weight or walk

›New blisters or open sores developing

›Skin turning black or developing a dark color (gangrene concern)

›Signs of whole-body illness — confusion, very rapid heart rate

›Follow-up

›Return for a wound check and pain reassessment in 2–3 days

12References/r20

Guidelines and key sources

›Zafren K. Nonfreezing Cold Injury (Trench Foot). International Journal of Environmental Research and Public Health. 2021. PMID 34639782

›Primary evidence base for staging, diagnosis, and management of NFCI

›Supports amitriptyline as first-line analgesic for NFCI pain

›Zafren K, Hollis S, Weiss EA, et al. Prevention and Treatment of Nonfreezing Cold Injuries and Warm Water Immersion Tissue Injuries. Wilderness and Environmental Medicine. 2023

›Wilderness Medical Society Clinical Practice Guidelines supplement

›Recommends passive rewarming; defines management of NFCI subtypes

›Rathjen NA, Shahbodaghi SD, Brown JA. Hypothermia and Cold Weather Injuries. American Family Physician. 2019. PMID 31790182

›Broad cold injury overview including NFCI; management principles

›Cappaert TA, Stone JA, Castellani JW, et al. National Athletic Trainers' Association Position Statement: Environmental Cold Injuries. Journal of Athletic Training. 2008. PMID 19030143

›Discusses susceptibility factors including racial differences and prior injury sensitization

›Castellani JW, Young AJ, Ducharme MB, et al. ACSM Position Stand: Prevention of Cold Injuries During Exercise. Medicine and Science in Sports and Exercise. 2006

›Prevention evidence base; footwear and sock change recommendations

›Olson Z, Kman N. Immersion Foot: A Case Report. Journal of Emergency Medicine. 2015. PMID 26004855

›Emergency department management perspective

›Mistry K, Ondhia C, Levell NJ. A Review of Trench Foot: A Disease of the Past in the Present. Clinical and Experimental Dermatology. 2020. PMID 31309614

›Historical context and contemporary clinical review

›To MJ, Brothers TD, Van Zoost C. Foot Conditions Among Homeless Persons: A Systematic Review. PloS One. 2016. PMID 27936071

›Epidemiology in homeless populations; up to 20% foot-related complaints

›Backer HD, Freer L. Heat and Cold Illness in Travelers. CDC Yellow Book. 2025

›Travel medicine perspective; warm water and cold immersion foot distinction

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