Summary Frostbite is the extensive soft tissue damage associated with exposure to temperatures below freezing point. Diagnosis is made clinically with the appearance of a central whitish area with surrounding erythema and subsequent clear/cloudy blisters within 24 hours. Treatment involves prevention with prompt rewarming and potential surgical debridement depending on severity of soft tissue injury. Epidemiology Demographics males (M:F = 10:1) age 30-50 years Risk factors host factors alcohol abuse mental illness peripheral vascular disease peripheral neuropathy malnutrition chronic illness tobacco use race login to view 1 more bullet smoking login to view 2 more bullets environmental factors degree of cold temperature login to view 2 more bullets duration of exposure windchill login to view 2 more bullets altitude >17,000 feet contact with conductive materials (water, ice, metal) Etiology Pathophysiology with hypothermia (CBT <35°C) circulation shunted from periphery to maintain core body temperature (CBT) cardiac effects basal metabolic rate, HR and cardiac output drop myocardial irritability (abnormal EKG) neurological effects disorientation, coma shivering (anaerobic) until CBT drops below 30-32°C below 30-32°C, shivering stops and muscle rigidity ensures (like rigor mortis) login to view 2 more bullets limbs (4 phases) phase I (cooling and freezing) login to view 7 more bullets phase II (rewarming) login to view 6 more bullets phase III (progressive tissue injury) login to view 3 more bullets phase IV (resolution) login to view 3 more bullets cell biology leads to movement of water from intracellular location to extracellular location cellular dehydration leads to cell death biochemistry sensory nerve dysfunction occurs at -10°C ice crystal formation occurs within the extracellular fluid at -2 to -15°C Associated conditions frostnip mildest cold exposure injury only affects superficial layers of skin (blanching, numbness) but no dermis damage reversible chilblain (pernio) occurs in cold, nonfreezing temperatures in dry conditions burning sensation, with pruritus, swelling, erythema may have blisters, ulceration resolves in 2 weeks may leave chronic vasculitis esp in young/middle-aged women trench foot (immersion foot) military personnel prolonged wet nonfreezing condition <10°C frostbite results in localized/extensive tissue necrosis may require amputation hypothermia when core body temperature is affected can be fatal Presentation Physical exam hypothermia (mild, 32-35°C; moderate, 28-32°C; severe, <28°C) tachycardia followed by bradycardia, decreased cardiac output, arrythymia (atrial and ventricular fibrillation) decreased respiratory rate login to view 1 more bullet disorientation, comatose frostbite (similar to burns) traditional classification login to view 4 more bullets newer classification login to view 2 more bullets blisters form 6-24 hours after rewarming login to view 2 more bullets Imaging MRI T2-weighted images shows enhanced signal in necrotic muscles because of disrupted cell membranes and increased extracellular fluid Serial bone scans (99mTc) can be used to evaluate the severity of the soft-tissue damage 1st scan at 2 days after initial injury absence of uptake has poor prognosis but may not indicate necrosis 2nd scan at 5 days after initial injury normal blood/bone pool = treat expectantly diminished blood/bone pool = observation, with potential early debridement absent blood/bone pool = early debridement or amputation Treatment for Hypothermia protect patient from further exposure to freezing temperature rewarming only after confirmation that the patient can be maintained in a constant warm environment (avoid freeze-thaw cycles) external-surface rewarming (for mild hyperthermia) passive login to view 1 more bullet active login to view 2 more bullets internal-core rewarming (for moderate and severe hypothermia) warmed oxygen, warm IV fluid body cavity lavage (invasive) cardiac bypass login to view 1 more bullet continuous arteriovenous rewarming login to view 3 more bullets avoid alcohol/sedatives dulls shivering response and further lowers CBT Treatment for Frostbite Nonoperative prevention footwear thermal insulation is the most important factor for protection against cold-induced injury protect limb from mechanical trauma e.g. walking, rubbing pad/splint, wrap with blanket for transportation initial resuscitation with warm IV fluids, tetanus prophylaxis, NSAIDS, silver sulfadiazine ointment or topical antibiotics to open wounds, rapid rewarming indications login to view 1 more bullet water bath 40-42°C with mild antibacterial agent x 30min login to view 2 more bullets IV analgesia / conscious sedation wound care with topical aloe vera, extremity elevation and splinting IV antibiotics if secondarily infected rehabilitation whirlpool hydrotherapy PT and OT for preserve joint motion adjunctive (low molecular weight dextran, anticoagulants, tissue plasminogen activator) intravenous tPA within 24h reduces rate of digital amputations login to view 18 more bullets hyperbaric oxygen (anecdotal evidence) Operative immediate surgical escharotomy circumferentially constrictive lesion of digit fasciotomy for compartment syndrome debride clear blisters and apply aloe vera reduces high levels of prostaglandin F2 and thromboxane B2 drain/aspirate hemorrhagic blisters (represents deep injury) but leave intact prevents dessication of underlying dermis late debridement/amputation for necrosis “frostbite in January, amputate in July” after demarcation occurs at 1-3months surgical sympathectomy reduces duration of pain and time to demarcation of tissue does not reduce extent of necrosis Complications Adults persistent pain (50%) intolerable in 15% cold intolerance vasospastic disease (Raynauds phenomenon, cold sensitivity, persistent color changes, hyperhidrosis) treatment login to view 3 more bullets neuropathy (cold/heat hypersensitivity, hypesthesia, paresthesia) decreased motor/sensory NCV treatment login to view 1 more bullet musculoskeletal (osteopenia) subchondral bone loss (frostbite arthropathy), joint contractures esp in DIPJ > PIPJ of hands and feet treatment login to view 1 more bullet Children premature growth plate closure 1-2 years after exposure secondary to chondrocytic injury joint laxity, angular deformities, short digits, excess skin, degenerative joint changes seen after age 10 in patients with prior frost bite injuries treatment login to view 1 more bullet Prognosis Severity is increased with alcohol consumption/intoxication contact of skin with metal or ice elevated wind chill factor