- 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 ensues;
- 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:
-
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 frosbite 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.
- 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 E. Cauchy et al JHS 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 amputation;
- 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 (PDF)
Medical Aspects of Cold Weather Operations: A Handbook for Medical Officers, USARIEM (PDF)
Prevention and Managment of Cold Weather Injuries, USARIEM (PDF)
Sustaining Health and Performance in The Cold: Environmental Medicine Guidance for Cold Weather Operations - Overview - also in PDF
Textbook of Military Medicine: Medical Aspects of Harsh Environments - Volume 1, US Army
The effects of frostbite in childhood. DR Bigelow et al. JBJS 45-B. 1963. p 122-131.
Frostbite: an orthopaedic perspective. TR McAdams MD et al. The American Journal of Orthopedics. Jan 1999. p 21.
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.
E. Cauchy MD et al. J. Hand Surg. 2000; 25-A. 969-978
