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Frost Bite

- Pathophysiology:
    - effects of cooling:
           - temperature of the hands and feet is partially determined by ateriovenous regulation of blood flow;
           - vascular effects:
                  - severe vasoconstriction 2nd to increased sympathetic tone;
                  - direct endothelial injury causing thrombus formation
           - when temperature in the extremities drops below - 2 deg celcius, crystallization begins in the extracellular spaces, and cell death 
           - direct cellular injury (freezing of involved tissue) thru formation of crystals in the extra cellular space;
    - effects of rewarming:
           - rewarming causes shifts in osmotic gradients and cell swelling which can lead to further cellular necrosis;
           - repeated freezing and re-warming causes recurrent cellular injury and increases necrosis

- Clinical Features:
           - Images in Clinical Medicine. Digital Frostbite
    - partial thickness:
           - mild partial thickness injuries will lead to skin erythema and edema, in addition to with transient
                     tingling or burning;
           - skin demonstrates mottled blue/grey/red colors and may become hot and dry;
    - deep partial thickness:
           - more significant injury leads to clear blister formation and/or skin desquamation w/ in 24 hours;
           - blisters may appear on the dorsum of the hands and feet;
           - clear blisters are a sign of partial thickness injury versus hemorrhagic blisters which indicate full thickness injury;
           - may see parathesias, tenderness, and necrosis of the pressure points of the feet;
           - there will be increased sensitivity to cold and hyperhydrosis with repeated cold exposure;
    - full thickness injuries:
           - damage extends into the subcutaneous tissues;
           - hemorrhagic blister formation, skin necrosis which is replaced by a black, hard, dry eschar;
           - more signficant injury includes involvement of the subcutaneous tissues, muscle, tendon, and bone;
           - remember that the skin is most tolerate of ischemia - as compared to the bone, tendons, and nerves;
                   - skin will often be the last tissue to show signs of necrosis;
           - compartment syndromes may occur with deep injury;    
           - w/ deep injury, line of demarcation is evident at 3-4 weeks and demarcations extends into the bone in 60 or more days;
           - late sequelae includes extreme cold sensitivity;

- Treatment of Frostbite:
    - acute treatment:
           - specific treatment for deep frostbite should be delayed until adequate medical care can be provided because rewarming will
                   cause severe pain and tissue loss will be much greater if re-freezing occurs;
           - restore body heat;
           - rapid re-warming of frozen extremity 40 - 42 deg water bath for 15-30 min;
                   - rapid re-warming may be controversial when frost bite has been present for more than 24 hours;
           - medications:
                   - tetanus prophylaxis;
                   - antibiotics:
                           - risk of infection increases with depth of injury;
                   - ASA and/or NSAIDS may be useful to prevent thrombosis formation and may be useful to retard a deliterious
                           inflammatory response;
                   - controversial agents:
                           - tissue plasminogen activator;
                           - hemodilution;
                           - vasodilators: ketanserine, buflomedil;
                           - references:
                                     - Reduction of the incidence of amputation in frostbite injury with thrombolytic therapy.
                                     - An open-label study to evaluate safety and efficacy of tissue plasminogen activator in severe frostbite.

           - dressing and debridement protocols: keep blebs intact, debride torn blisters;
                   - in some respects, wound management is similar to burn management;
                   - typically expect to see blisters on day two;
           - bone scan:
                   - in the report by Cauchy E, et al (2000), the authors note the prognostic value of a 2 phase technetium 99 bone scan in 92
                            patients with severe frostbite;
                           - initial bone scan (day 3) has excellent specificity in evaluating the severity of frost bite injury;
                           - there was direct correlation between the demarcation zone of uptake in the phalanges and eventual level of
                           - a second bone scan on day 7 was even more informative and sensitive;
                                   - blisters were excised prior to the bone scan;
    - late treatment:
           - consider regional sympathectomy to prevent late sequelae;
           - mummified digits:
                   - surgical debridement & amputation should be delayed 60 to 90 days unless infection supervenes;
           - late complications:
                   - intrinsic muscle atrophy;
                   - epiphyseal destruction in skeletally mature
                   - OA of the IP joints;
                   - vasospastic syndromes 2nd to increased sympathetic tone:
                          - severe pain
                          - hyperhydrosis
                          - coldness and or edema (patient will be less able to tolerate cold temperatures);
                          - trophic changes: decreased nail and hair growth;
                          - raynaud's

- Outside Links:

  • Cold Injury: NAVMED P-5052-29, US Navy
  • Medical Aspects of Cold Weather Operations: A Handbook for Medical Officers, USARIEM
  • Prevention and Managment of Cold Weather Injuries, USARIEM 
  • Sustaining Health and Performance in The Cold: Environmental Medicine Guidance for Cold Weather Operations 
  • Textbook of Military Medicine: Medical Aspects of Harsh Environments - Volume 1, US Army

    The effects of frostbite in childhood.    
    Frostbite: an orthopaedic perspective.      
    The value of tech 99 scintigraphy in prognosis of amputation in severe frost bite injuries of  extremities: a retrospective study of 92 severe frosbite injuries.
    Case records of the Massachusetts General Hospital. Case 41-2009. A 16-year-old boy with hypothermia and frostbite.