Frostbite is injury due to freezing of tissue. Initial manifestations may be deceptively benign. Skin may appear white or blistered and is numb; rewarming causes substantial pain. Gangrene may develop. Severely damaged tissue may autoamputate. Treatment is rewarming in warm (37 to 39° C) water, local care, and pain management. Surgical amputation may occasionally be indicated. However, surgical intervention, often guided by imaging results, is usually delayed until definitive demarcation of necrotic tissue occurs.
(See also Overview of Cold Injury.)
Frostbite usually occurs in extreme cold, especially at high altitude, and is aggravated by hypothermia. Distal extremities and exposed skin are affected most often.
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Ice crystals form within or between tissue cells, essentially freezing the tissue and causing cell death. Adjacent unfrozen areas are at risk because local vasoconstriction and thrombosis can cause endothelial and ischemic damage. With reperfusion during rewarming, inflammatory cytokines (eg, thromboxanes, prostaglandins) are released, exacerbating tissue injury. The depth of tissue loss depends on the duration and depth of freezing.
Symptoms and Signs of Frostbite
The affected area is cold, hard, white, and numb. When warmed, the area becomes blotchy red, swollen, and painful. Blisters form within 4 to 6 hours, but the full extent of injury may not be apparent for several days.
Blisters filled with clear serum indicate superficial damage; superficial damage heals without residual tissue loss.
Blisters filled with blood indicate deep damage and likely tissue loss.
Gangrene, when it occurs, can be dry or wet. Dry gangrene, due to freezing of deep tissue, results in a hard black carapace over healthy tissue. Wet gangrene is gray, edematous, and soft and is less common. Wet gangrene is characterized by infection; dry gangrene is less likely to become infected.
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Severely damaged tissue may autoamputate. Compartment syndrome may develop. All degrees of frostbite may cause faulty nail growth and long-term neuropathic symptoms: sensitivity to cold, excessive sweating, and numbness (symptoms resembling those of complex regional pain syndrome).
Diagnosis of Frostbite
HJistory and physical examination
Diagnosis is based on clinical findings. Many early characteristics of frostbite (eg, coldness, numbness, white or red color, blisters) are also characteristic of nonfreezing cold injuries; thus, the definitive diagnosis of frostbite may require repeated observation until more specific characteristics (eg, black carapace) develop.
Treatment of Frostbite
Rewarming in warm (37 to 39° C) water
Supportive measures
Local wound care
Sometimes surgery
Prehospital care
In the field, frostbitten extremities should be rewarmed rapidly by totally immersing the affected area in water that is tolerably warm to the touch (37 to 39° C). Rewarming with an uncontrolled dry heat source (eg, fire, heating pad) should be avoided because the affected area is numb and at risk of burns. Rubbing, which may further damage tissue, should also be avoided.
The longer an area remains frozen, the greater the ultimate damage may be. However, if a patient must walk any distance to receive care, it may be necessary to delay thawing the feet. Thawed tissue is particularly sensitive to the trauma of walking and, if refrozen, will be more severely damaged than if left frozen. If thawing must be delayed, the frozen area is gently cleansed, air dried, and protected in sterile and dry bulky compresses. Patients are given analgesics, if available, and the whole body is kept warm.
Acute care
Once the patient is in the hospital, core temperature is stabilized and extremities are rapidly rewarmed in large containers of circulating water kept at about 37 to 39° C; 15 to 30 minutes is usually adequate (1). All jewelry must be removed. Pain may be severe during rewarming. Parenteral analgesics, including opioids, are often required.
Patients are encouraged to move the affected part gently during thawing. Large, clear blisters generally are left intact or aspirated using sterile technique. Hemorrhagic blisters are left intact to avoid secondary desiccation of deep dermal layers. Broken vesicles are debrided.
2, 3). If the injury is deep and there is a risk of amputation, intra-arterial or intravenous thrombolytic (fibrinolytic) therapy should be considered within the first 24 hours of the injury (4
5).
Preventing infection is fundamental; empiric prophylaxis is not indicated, unless there is gross contamination, crush injury, or wet gangrene. If wet gangrene is present, broad-spectrum antibiotics are administered. Tetanus toxoid is given if the status of tetanus vaccination is unknown or not up to date. If tissue damage is severe, tissue pressure is monitored for indications of compartment syndrome (see Compartment Syndrome: Diagnosis, How To Measure Compartment Pressure in a Forearm, and How To Measure Compartment Pressure in the Lower Leg).
Ongoing care
Adequate nutrition is important to sustain metabolic heat production. Consider using Doppler ultrasound to assess pulses and tissue status.
Other imaging tests include radionuclide scanning, MRI, microwave thermography, and laser-Doppler flowmetry to help assess circulation, determine tissue viability, and thus guide treatment. MRI, and magnetic resonance angiography in particular, may establish the line of demarcation of viable tissue before clinical demarcation and thus make earlier surgical debridement or amputation possible. However, whether earlier surgery improves long-term outcome is unclear. Usually, surgery is delayed as long as possible because the black carapace is often shed, leaving viable tissue. Advise patients with severe frostbite hat many weeks of observation may be required before demarcation and the extent of tissue loss become apparent.
Optimal long-term management includes whirlpool baths at 37° C 3 times a day followed by gentle drying, rest, and time. No totally effective treatment for the long-lasting symptoms of frostbite (eg, numbness, hypersensitivity to cold) is known. Chemical or surgical sympathectomy for late neuropathic symptoms is not advised.
Treatment references
1. McIntosh SE, Freer L, Grissom CK, et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2024 Update. Wilderness Environ Med. 2024;35(2):183-197. doi:10.1177/10806032231222359
2. Iloprost (Aurlumyn) for frostbite. Med Lett Drugs Ther. 2024;66(1707):114. doi:10.58347/tml.2024.1707b
3. Vampola C-L, Fahrbach K, Davis C. Risk of Amputation in Severe Frostbite - A Systematic Literature Review and Meta-analysis to Evaluate Iloprost and Standard of Care. Wilderness Environ Med. 2023;34(4):e4. https://doi.org/10.1016/j.wem.2023.08.016
4. Hickey S, Whitson A, Jones L, et al. Guidelines for Thrombolytic Therapy for Frostbite. J Burn Care Res. 2020;41(1):176-183. doi:10.1093/jbcr/irz148
5. Lorentzen AK, Davis C, Penninga L. Interventions for frostbite injuries. Cochrane Database Syst Rev. 2020;12(12):CD012980. Published 2020 Dec 20. doi:10.1002/14651858.CD012980.pub2
Key Points
Depth of injury is difficult to recognize initially, although blood-filled blisters indicate deep damage.
Thaw frostbitten tissue as soon as possible using water that is tolerably warm to the touch (37 to 39° C); analgesia is usually required.
Avoid thawing and refreezing.
Keep affected areas uncovered, clean, dry, and elevated.
Black tissue may represent a black carapace that will be shed or gangrene that will require amputation; surgery is usually delayed until the demarcation is clear.
Neuropathic symptoms (eg, sensitivity to cold, numbness) may persist indefinitely.
