1. FROSTBITE

2. Definition & Pathophysiology
Localized, cold-induced injury due to freezing of tissue.
Frost nip: localized numbness or parasthesias which resolve with warming, and without residual damage
Two primary mechanisms
Direct cell death from freezing, formation of ice crystals, fluid / electrolyte shifts
Reperfusion injury
Once the tissue is warmed, return of blood flow triggers formation of reactive oxygen species and release of inflammatory cytokines

3. Classification Grade I Grade II Grade III Grade IV
Superficial; focal pallor, numbness, mild swelling
Grade II
Clear-fluid containing blisters, erythema, more swelling, but no tissue loss.
Grade III
Deeper injury, swollen, with hemorrhagic blisters. Can lead to tissue loss.
Grade IV
Complete tissue necrosis, involving muscle and bone, leading to mummification or auto-amputation.

8. From: Pandey P, Vadlamudi R, Pradhan R, Pandey KR, Kumar A, Hackett P
From: Pandey P, Vadlamudi R, Pradhan R, Pandey KR, Kumar A, Hackett P. Case Report: Severe Frostbite in Extreme Altitude Climbers-The Kathmandu Iloprost Experience. Wilderness Environ Med. 2018;29(3):

14. Risk Factors
Anything that increases conductive or convective heat loss
Wind, contact with water / metal / ground
Smoking
Previous cold injury
Diabetes, peripheral neuropathy
Intoxication
Maybe females < 20 yrs

15. Clinical Manifestations
Numbness, clumsiness of the affected extremity.
Before warming, skin may appear gray, dull yellow, and may feel hard or waxy
Any patient with cyanosis proximal to the distal phalanx of any digit after rapid rewarming is at risk for necrosis of the affected tissue and aggressive therapy (eg, thrombolysis in suitable candidates) may be needed.

16. Treatment (Prehospital)
Transfer patient to warm environment as soon as possible
Avoid walking on frostbitten feet
Remove wet clothing
Avoid rewarming if possibility exists of refreezing
Warm with body heat, clothing, or warm water
DON’T rewarm by rubbing or with heating elements, like a fire or stove

17. Treatment (Hospital) Rewarming: ideally using warm water, 37-39C.
Water warmer than 39C / 102F doesn’t result in faster warming, and can worsen tissue damage
Rewarming is complete when tissue is red or purple, generally min
Thrombolysis: Inflammation causes clot formation, which worsens perfusion
Severe frostbite presenting within hours are eligible for thrombolysis
Patients expected to require significant amputations due to tissue necrosis and who have undergone rewarming within 12 hours injury, without freeze- thaw cycles are eligible for thrombolysis in the absence of contraindications.

18. Does this actually work?
A single-center, retrospective review of 32 patients with severe frostbite reported that among the six patients (59 digits at risk for amputation) treated with intra-arterial tPA plus intra-arterial heparin within 24 hours of injury six digits (10 percent) required amputation, compared with 97 digits (41 percent) among patients with comparable injuries not treated with tPA
Another single center retrospective study involved 62 patients given thrombolysis with an overall digit salvage rate was 68.6 percent
A smaller single center retrospective study of 13 patients given thrombolysis showed a digit salvage rate of 83.4 percent

19. Wound care Usual aseptic technique
Let extremities dry after water bath
Non-adherent gauze for first layer
Loose dressings
Blisters: no clear answer
Clear blisters can be drained / debrided. Hemorrhagic blisters can be aspirated but NOT debrided.
Tetanus as needed
No need for prophylactic antibiotics

20. Complications: Usually due to subsequent neurovascular injury, and altered sympathetic tone
Short term complications
Pain (weeks)
Parasthesias / electrical shock sensation
Hyperhidrosis
Gangrene / infection
Compartment syndrome
Long term complications
Pain / sensory problems / neuropathy
Vasospasm
Hypersensitivity to cold -> increased susceptibility to recurrent cold injury

21. Prevention
Cold exposure is contraindicated 6 months after minor injury and 12 months after significant injury
Adequate calories and hydration
Avoid alcohol
Appropriate clothing (wicking layer / insulating layer / hard shell)
Remove wet clothing if possible

22. Primary source
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