Dr Abigail Wrathall / EM Registrar / North of Scotland
In 2013, Adventure Medic published this review of frostbite, with a detailed breakdown of the condition and the evidence for its identification and management. This is an update to that article, with thanks to the original authors.
Frostbite is a vascular injury, as a result of exposure to cold temperatures. Risk increases with reductions in temperature, and so as expedition and extreme medicine providers we must be aware of the condition, especially the avoidance, recognition and early management whilst out in the field. As humans push further into wild environments and sadly as large numbers of people become unhoused due to socio-economic circumstances, politics, and war; frostbite is set to become an increasingly frequent presentation, and has significant long term effects on quality of life and function.
How, why and where?
Frostbite most commonly affects the feet and hands, however can be identified in many other places across the body: nose, ears, chin, buttocks, and the penis. These reflect the activities undertaken in cold environments: mountaineers and adventurers exercising in extreme cold and high altitude; and sitting on cold surfaces, especially in people experiencing homelessness.
There are four phases to frostbite:
Pre-freeze: where the tissues cool, vessels vasoconstrict and blood flow is reduced leading to ischaemia. There may be paraesthesia at this stage.
Freeze-thaw: ice crystals form during the freeze, causing deranged proteins, lipids and electrolytes, disruption of cell membranes and eventually cell death. During thaw, there is further ischaemia with reperfusion injury & massive inflammatory response.
Vascular stasis: blood vessels cycle between vasodilation and -constriction, with fluid & protein leaking due to vessel wall damage and intravascular coagulation.
Late ischaemic: inflammatory cascade leads to progressive tissue ischaemia and infarction, intermittent vasoconstriction and vasodilation results in continued reperfusion injury, and emboli & coagulation in downstream vessels.
The inflammatory cascade is responsible for much of the damage caused by frostbite. This is mediated by a number of factors, including histamine, bradykinin, thromboxane A2 and prostaglandin F2alpha. The disruption of vascular function and destruction of microcirculation results in cell death. If repeated exposure to freezing is experienced, the damage is compounded.
Prevention and avoidance
Before discussing identification and treatments, it is important to note that there are several things that can be done to avoid frostbite all together. As ever, prevention is the best cure. The core of prevention is a combination of maintaining perfusion and reducing heat loss. The use of exercise to avoid frostbite is a recommendation to be applied with caution. There is ongoing research into chemoprophylaxis for frostbite.
Perfusion
There are several ways to maintain perfusion. Ensuring adequate core temperature; good hydration and nutrition; reducing exposure by covering all skin and avoiding restrictive clothing, including too-tight footwear and tight cuffs on jackets. There is also some evidence for using supplemental oxygen in high altitude environments to improve perfusion & oxygenation of peripheral tissues – this appears to be predominantly due to an inability with hypoxia to maintain a sufficient core temperature. In addition, mountaineers not using supplemental oxygen for summit attempts are breathing more rapidly and deeper, leading to increased volume of cold air exposure.
Reducing heat loss
Simple tactics can make the biggest difference in terms of safety in extreme cold. Ensuring appropriate clothing is being used by individuals; replacing clothing – especially gloves – which become wet (including with perspiration); avoiding sweating by using appropriate layering for the environment; encouraging individuals to avoid the use of alcohol and drugs; recognising signs of hypoxaemia that may alter behaviours; use of electrical and chemical warming devices, including heated socks/gloves, and hand/foot warmers (with caution to avoid direct skin exposure and reduced blood flow due to tight footwear). Recognition of early signs of frostnip/frostbite is also key to avoiding further damage.
Exercise
There is no doubt that exercise raises core body temperature, and therefore can increase blood flow and perfusion of extremities. However, exercise often causes perspiration, leading to increased heat loss as detailed above. It also increases energy use and in extremes can lead to exhaustion, exacerbating rapid heat loss. It can be a helpful method to avoid cold injury in moderation.
Chemoprophylaxis
The use of prophylactic medication is not commonplace, and is still an area lacking in research. There have been mouse studies into ‘antifreeze’ proteins, however as it stands there are no available or recommended medications for preventing frostbite in humans.
Classification and recognition
Frostnip
This is a superficial cold injury, with vasoconstriction in areas of skin exposed to the cold air, usually on the face. There may be frost visible on the skin surface. Rewarming leads to recovery of blood flow and therefore resolution of the symptoms of numbness and skin pallor. It can precede frostbite, and when frostnip is identified indicates that there is high risk of developing frostbite.
Frostbite
The longstanding 4-tiered classification system for frostbite is based on both clinical and radiological findings. There is a more recent 2-tiered classification, more appropriate for use in the field. This describes the prognosis following rewarming, but prior to imaging, which represents a more common realistic scenario in the world of extreme & expedition medicine.
- Superficial: represents no or minimal tissue loss
- Deep: anticipated tissue loss (corresponding to 3rd- and 4th- degree injury)
The Cauchy classification system can be used at day 2 post-injury to predict prognosis and therefore plan for evacuation, if required. The full details of this can be read here. However in brief, the more proximal the lesion is and/or the presence of haemorrhagic blisters, are both negative prognostic indicators and increase the risk of amputation, systemic involvement and sepsis. The use of bone scanning in these patients is beneficial, but obviously unavailable in a remote context.
Signs & Symptoms
Initially, the individual will experience sensory loss of the affected extremity or digit. Often described is the feeling of clumsiness, as a result of a loss of proprioception. There can be severe pain, especially during the thaw cycle and the resulting reperfusion. Some experience paraesthesia in the days following the injury.
Clinically, skin is often pale but otherwise can appear relatively normal during the freeze stage however following this, blisters can appear, which are haemorrhagic in severe cases. On re-warming, tissues can appear blue, yellow-white, or waxy. If the extremity undergoes rapid rewarming, then erythema can occur.
Management
This will be divided into treatment options in the field (with the caveat that ability to provide these interventions may be variable based on resources), followed by hospital-based management. The Gold Standard for treating cold injuries remains the State of Alaska cold injuries guidelines.
Field management
Thawing: The first decision to be made is whether to thaw the tissues. While it may seem like the obvious start, if the extremity cannot be adequately protected from the risk of refreezing occurring, then it is not recommended to commence thawing. Instead, protect from physical injury by avoiding use, and remove restrictive jewellery and constrictive clothing. The extremity should not be placed in ice or snow, and there is no evidence that dressings have any therapeutic benefit. Any dressings which are applied should not be restrictive or damaging to the skin.
The following treatments can be applied whether the intention is to thaw the tissue or not. Most frostbite will spontaneously thaw. Do not rub the extremity or directly expose to heat.
Treat hypothermia: Moderate to severe hypothermia should be managed prior to treating a cold based injury; mild hypothermia can be treated concurrently. See our hypothermia article for more details on this.
Rehydration: Good hydration status reduces the risk of developing frostbite, however there is little evidence of treatment once the injury occurs. Maintain fluid intake orally, or if unable to drink then with (ideally prewarmed) boluses of IV fluids targeted based on urine output.
Ibuprofen/Aspirin: There is poor quality evidence to recommend these therapies, which in theory may improve circulation, however aspirin can inhibit prostaglandins necessary for wound healing. Commencing ibuprofen at 12mg/kg/day (max 2400mg/24hr) is the current recommendation.
Low Molecular Weight Dextran: No longer recommended.
If the intention is to rewarm/thaw, then the following treatments can also be applied in the field. If rapid rewarming is not available, then spontaneous thawing & rewarming should be allowed.
Rapid rewarming: The ideal way to do this is by warm bath immersion; other methods have increased risk of heat injuries. The water should be heated to ~37 to 39 degrees centigrade, ideally using a thermometer to maintain this range. This can be checked without a thermometer by immersing the hand of someone other than the casualty for 30 seconds to ensure the temperature is tolerable. Water should be stirred and regularly reheated to maintain the adequate temperature, although reheating water should be avoided while the extremity is immersed. Alternating between two containers is one way to avoid this. The rewarming process is normally completed within 30 minutes, and the extremity will appear red or purple with tissues being palpably soft. Following this, gentle drying should take place, taking care not to cause damage to the skin.
Antiseptics: If available, addition of an antiseptic solution to the rewarming water may reduce the risk of developing cellulitis, however there is no evidence for its use in frostbite.
Topical Aloe Vera: May theoretically be beneficial, and if being used should be applied prior to any dressings.
Analgesia: Based on the WHO pain ladder and the patient’s symptoms.
Debridement of blisters: This is not recommended in the field due to risk of infection. If there is a tense blister at risk of rupture, then aseptic aspiration can be performed, however deroofing should not be carried out. Haemorrhagic blisters should not be aspirated or debrided.
Dressings: Dry gauze dressings should be applied to the affected areas, with care not to wrap circumferential dressings tightly due to progressive oedema. Any such dressings should be checked regularly to ensure they are not restrictive.
Elevation: Raising the affected area above the level of the heart to reduce tissue oedema is recommended.
Ambulation: Use of the affected extremity should be avoided unless absolutely necessary for safe evacuation, as it can worsen tissue damage and increase the risk of amputation.
Oxygen: As discussed in the prevention section, hypoxia worsens tissue perfusion. However, it can also cause vasoconstriction. The recommendation is to apply supplemental oxygen in cases of hypoxia or at high altitude, but to avoid otherwise, however the evidence for this is weak.
Additional field management options are currently under research, including peripheral nerve blocks. There is currently no evidence for their use in frostbite.
Hospital management
Some treatments remain the same once hospital is reached: treatment of hypothermia, hydration, low molecular weight dextran, ibuprofen, aloe vera, and rapid rewarming. If thaw has been achieved, further rewarming is not of benefit.
The Helsinki Frostbite management protocol can be useful if in a centre with access to angiography, as a stepwise approach to management in tertiary care.
Blisters: As in the field, haemorrhagic blisters should not be aspirated or deroofed. Clear or cloudy blisters can be reduced by needle aspiration once in hospital, however there is limited evidence of benefit to carrying this out. Application of sterile dressings to open blisters reduces the risk of secondary infection.
Antibiotics: Prophylaxis is not routinely recommended; initiate if major trauma, high risk of infection due to other causes, or evidence of cellulitis or sepsis.
Tetanus prophylaxis: Should be administered, see Green Book guidelines for use of booster vaccine vs immunoglobulin depending on patient’s vaccination history.
Iloprost: This is the mainstay of drug treatment for frostbite, and its use is now widespread across the world. It is a vasodilator that reduces inflammation and platelet aggregation. There is a randomised controlled trial that demonstrated it was more effective than combination therapy with tPA, or alpha blocker monotherapy, at reducing amputation rate. Its use is also supported by case series in Canada, Finland and the Himalaya. It should be considered the first line treatment where available; where it is not then thrombolysis with tPA is second line.
Thrombolysis therapy: Tissue plasminogen activator (tPA) administered IV or intra-arterial may be of some benefit in the first 24 hours following tissue thawing. The standard risks of thrombolysis accompany the treatment, with the addition of increased risk of compartment syndrome. There is no high level evidence for its use, however the available evidence suggests a reduction in amputation rates.
Vasodilators: The use of vasodilators is restricted to adjuvant therapy, rather than first or second line monotherapy.
Long term management
There are various longer term treatments that have variable evidence supporting their use in reducing the morbidity and sequelae of frostbite. These include:
- Hydrotherapy
- Hyperbaric oxygen therapy
- Imaging (for prognostication and surgical planning)
- Sympathectomy
- Fasciotomy (to treat compartment syndrome)
- Surgical debridement or amputation (should be delayed until definitive demarcation of necrotic tissue, unless sepsis requires more urgent intervention)
These interventions should only be undertaken in specialist centres with expert advice taken.
Telemedicine
There is advice available via phonecall/email from anywhere in the world via three UK experts in frostbite. See here for details. Any decisions for surgery or repatriation should ideally be discussed with one of the experts here prior to action undertaken.
Conclusions
Frostbite is a predominantly avoidable condition with significant sequelae affecting morbidity and quality of life. Early recognition, prompt effective field management, and appropriate hospital transfer and treatments can all reduce the individual’s risk of amputation, and improve their level of function following the injury. Whilst there is gradually increasing research into novel treatments, by knowing the basics and getting them right, as a medic providing care in extreme environments, we can make a difference.
Useful Resources
Canadian Frostbite Care Network (CFCN)
“Frostbite injury can have significant functional impacts on affected individuals, including the possibility of amputation, increased risk of future cold injuries, chronic pain, and challenges in wound healing in severe cases. Our research has identified a pressing need for easily accessible, evidence-based information on frostbite treatments and protocols. Community hospitals see the majority of frostbite cases, which frequently includes marginalised and homeless populations, who stand to benefit the most from improved awareness and treatment protocols. To address this need, the Canadian Frostbite Care Network launched in October 2024, providing an information and collaboration hub for the public and healthcare professionals to enable timely access to high-quality frostbite care. The Canadian Frostbite Care Network is dedicated to improving frostbite treatment across Canada by promoting best practices, fostering expert collaboration, and supporting ongoing research and education.”
Adventure Medic would like to thank the CFCN for the use of their photographs in this article. The CFCN resources can be accessed here: https://frostbitecare.ca
Dr Chris Imray in The Alpine Journal
“In the UK, the British Mountaineering Council Frostbite Service has been operating for 20 years. This service, which is run by Dave Hillebrand, Paul Richards and myself, offers expert advice over satellite phone or by email to those dealing with frostbite. All three of us hold the UIAA Diploma in Moun- tain Medicine and have practical expedition experience. We provide remote advice for affected individuals both locally in the UK and on expeditions abroad. The aim is to support and advise local providers or offer to take over care where appropriate. Contact details for all three of us are available via the BMC website.
However, even the best advice will be of little use if you can’t access the right treatments. Throughout this article, I’ve repeatedly mentioned the frostbite drugs iloprost and rTPA. In recent years, these drugs have revolutionised the care of those with more serious frostbite. Time is crucial and treatment with them should ideally be started within 24 hours of injury. The longer the delay, the less effective the treatment becomes as the frostbitten extremities die without a blood supply. Doctors use the phrase ‘time is tissue’ to indicate that the longer something is left untreated, the more tissue will be lost.
Speed is not the only consideration. It is also very important to go to a unit familiar with these modern treatments. Sadly, there have been a number of cases recently where climbers have been taken to units that do not offer iloprost, despite the presence of units offering the treatment within the same city. Because this information was not volunteered, digits were lost when they needn’t have been.
To try and get around this issue, the recently set up International Freezing Cold Injury Working Group is establishing a worldwide database listing the units that offer iloprost and other complex frostbite treatments as well as a second database of clinicians who regularly advise on cold injuries.
Until recently, this first database would not have included sites in the USA as iloprost was not approved for use there. This changed in February 2024, when the US Food and Drug Administration (FDA) approved the use of iloprost for the treatment of severe frostbite. You can now visit Alaska safe in the knowledge that, should you face a case of severe frostbite, regulation will not prevent you from receiving the best treatment currently known to science.
Dr Imray’s article can be found here,
UK Frostbite Care
“At UK Frostbite, we are a dedicated team of medical doctors and researchers focused on providing accurate and comprehensive information about frostbite prevention and treatment. Our expertise ensures that you receive reliable guidance to protect yourself and others from frostbite-related issues.”
The UK Frostbite Care site can be accessed here.
References
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