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Updated: May 16 2021

Frostbite

Images
https://upload.orthobullets.com/topic/12105/images/frostbite of hand_moved.jpg
https://upload.orthobullets.com/topic/12105/images/blisters clear.jpg
https://upload.orthobullets.com/topic/12105/images/hemorrhagic.jpg
  • 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
          • African descent more likely to sustain frostbite than Caucasians who have better cold induced vasodilatation
        • smoking
          • reduces nitric oxide (vasodilator)
          • potentiates thrombosis by increasing fibrinogen levels and platelet activity
      • environmental factors
        • degree of cold temperature
          • risk of frostbite is low at > -10°C
          • risk of frostbite is high at < -25°C
        • duration of exposure
        • windchill
          • tissues at -18°C freeze in 1h at windspeed of 10mph
          • tissues at -18°C freeze in 10min at windspeed of 40mph
        • 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)
          • resembles death (absent respirations, dilated pupils, muscle rigidity)
          • must be rewarmed before pronounced dead (“no one is dead until warm and dead”)
      • limbs (4 phases)
        • phase I (cooling and freezing)
          • vasoconstriction/vasospasm followed by transient arteriovenous shunting (hunting response) of cycles of vasodilatation/vasoconstriction every 10min
            • those who do not have this response are more prone to cold injury
            • with persistent cold, cycles cease and temperature in tissue drops to freezing point of tissue (<-2°C)
            • intracellular ice crystals destroy cell membranes
            • extracellular ice crystals causes sludging/stasis and intracellular dehydration (because of osmotic gradient)
            • interstitial crystallization is exothermic, maintains latent heat to keep limb above freezing temperature
            • when crystallization is complete, limb temperature falls to ambient temperature
        • phase II (rewarming)
          • reverses freezing process
          • limb absorbs heat, intra/extracellular ice crystals melt
          • intracellular swelling occurs
          • endothelial cells of capillaries become permeable
            • fluid extravasation leads to blisters/edema
            • important to prevent re-freezing (freeze-thaw has severe effects on tissues)
        • phase III (progressive tissue injury)
          • inflammation, stasis/thrombosis, tissue necrosis
          • diminished prostaglandin E2 (vasodilator, antiplatelet)
          • elevated prostaglandin F2a and thromboxane B2 (vasoconstrictors, platelet-aggregating)
        • phase IV (resolution)
          • complete healing with no symptoms
          • healing with sequelae
          • early tissue necrosis/gangrene
      • 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
          • CO2 retention leads to hypoxia/respiratory acidosis
        • disorientation, comatose
      • frostbite (similar to burns)
        • traditional classification
          • 1st degree – central whitish area with surrounding erythema
          • 2nd degree – clear/cloudy blisters within 24h
          • 3rd degree – hemorrhagic blisters / hard black eschars
          • 4th degree – tissue necrosis
        • newer classification
          • superficial (1st and 2nd degree) has good prognosis
          • deep (3rd and 4th degree) has poor prognosis
        • blisters form 6-24 hours after rewarming
          • superficial lesions present as clear blisters
          • deeper lesions form hemorrhagic blisters which may be painless
  • 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
          • dry clothes and warm room
        • active
          • disadvantage is too-rapid vasodilatation leads to metabolic waste rushing to core, leading to paradoxical drop in core temperature (“afterdrop”) that can worsen arrythmia
          • heat lamps, radiant heaters, heating blanket, immersion in warm water with cardiac monitoring
      • internal-core rewarming (for moderate and severe hypothermia)
        • warmed oxygen, warm IV fluid
        • body cavity lavage (invasive)
        • cardiac bypass
          • requires systemic heparinization
        • continuous arteriovenous rewarming
          • blood from femoral arterial catheter into fluid heat exchanger
          • returns to body through subclavian venous catheter
          • achieves 1°C every 15min
      • 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
          • superficial frostbite
        • water bath 40-42°C with mild antibacterial agent x 30min
          • successful when skin becomes pliable and red-purple
          • avoid repetitive freeze-thaw cycles
        • 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
          • indications
            • no blood flow on bone scan
            • 2nd or 3rd degree (NOT superficial frostbite)
          • contraindications
            • general contraindications
              • alcoholic patients (risk of bleeding from concomitant head injuries)
              • active internal bleeding
              • intracranial hemorrhage/surgery within past 3 months
              • concurrent trauma
              • major surgery within previous 14 days
              • known aneurysm or vascular malformation
              • known bleeding diathesis
              • pregnancy
              • labile hypertension
            • cold-related contraindications
              • > 24 hours of cold exposure
              • warm ischemia times >6h
              • multiple freeze-thaw cycles
        • 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
          • calcium channel blockers, vasodilators, beta blockers, surgical sympathetectomy
            • indications
              • late, persistent vasospastic disease
      • neuropathy (cold/heat hypersensitivity, hypesthesia, paresthesia)
        • decreased motor/sensory NCV
        • treatment
          • decompression e.g. carpal tunnel release
      • musculoskeletal (osteopenia)
        • subchondral bone loss (frostbite arthropathy), joint contractures esp in DIPJ > PIPJ of hands and feet
        • treatment
          • joint arthroplasty, resection arthroplasty
    • 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
          • physeal arrest, osteotomy, arthrodesis
  • Prognosis
    • Severity is increased with
      • alcohol consumption/intoxication
      • contact of skin with metal or ice
      • elevated wind chill factor
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