Updated: 5/16/2021


Review Topic
https://upload.orthobullets.com/topic/12105/images/frostbite of hand_moved.jpg
https://upload.orthobullets.com/topic/12105/images/blisters clear.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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(OBQ12.26) A 22-year-old college student presents with significant finger pain after coming into contact with liquid nitrogen in his chemistry lab. A clinical photo of the affected finger in shown in Figure A. What is the most appropriate next step in treatment?

QID: 4386

Blister debridement and hyperbaric oxygen therapy



Drainage of the blister with the overlying skin left intact



Full thickness blister and skin debridement with local flap coverage



MRI scan of the digit to assess degree of soft tissue damage



Wet to dry twice-daily dressing changes to the digit



L 4 C

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