Frozen Flesh: Understanding Frostbite

0:00This is A.W.L.S. Podcasts on Wilderness Medicine from the University of Utah School of Medicine. This is Wilderness Medicine from the University of Utah School of Medicine. Thank you for tuning in to our Podcast today as we study wilderness medicine to keep people in our friends safe as we explore this beautiful world in which we live. Remind you always to go to www.wildmedu.org to see the free resources that are available for you, your family and friends to study wilderness medicine. As we move from season to season, we always tackle different outdoor issues. One of the most famous and infamous diseases that we have in the back country has always been that of frostbite.

1:08And while most people have heard of frostbite, most people don't know exactly what it is. It is a very famous disease and it, well they say frostbite, it's not really frost, it is freezing. This occurs when tissue and that is typically in the extremities become so cold that ice crystals form in and around the cells. You can almost say that the tissue is freeze and micro circulation which is out in the extremities or wherever the frostbite occurs. And this causes a complete loss of blood supply to that area. And of course any time you get that you have serious problems. After you get the loss of blood supply, you get this inflammatory cascade that follow. And when you're in the back country and in the wilderness, evacuation may take hours to occur or days depending upon where you're at. And so the prevention and the early field-based care is absolutely critical to improving outcomes.

2:12When you freeze tissue, that tissue could easily die and need to be amputated or you have other very serious consequences. Beyond the back country, back in hospital settings, there has been modern advancements in pharmacologic and interventional therapies. And these are changing what is possible when you get to the hospital. One of the most important recent developments in the United States, the U.S. Food and Drug Administration's approval of ILEPROST, which is the treatment for severe frostbite. This is the first time in the United States that the first drug specifically approved for this indication has been approved, although it's been used around the world quite extensively. I want to make a comment about the details I'm just going to go through about frostbite so that you'll know them. You can park these into the back of your head, but when we talk about how to treat frostbite, it will become important.

3:14So the development of frostbite is typically conceptualized in these overlapping sort of these broad phases. The first is what they call the pre-freeze or the cooling phase. So when the tissue cools, the blood vessels constrict and there is reduced blood supply, and this is when it starts. This is when cellular metabolism slows, tissue becomes what we call a schematic. But ice crystals haven't formed yet. The second phase is the freezing phase or the freezing thaw phase. This is where ice crystals may form in and around the cells. This causes mechanical damage. You get dehydration in the cells, and kind of this weird thing where electrolytes and salts shift and move around. The third phase is they dub as the vascular stasis or the re-perfusion injury phase. This is where damage occurs. After thawing you get this inflammation and the endothelial injury where you get tiny little micro thrombi or little tiny clots forming, which lead to further decrease in blood supply.

4:29And then you get the vasospasm, the constriction of the blood vessels on their own. Platelets clump or aggregate, and you get this occlusion which impairs profusion and you get more damage. And then you get this late ischemic, what they call the necrosis phase, where you get the irreversible damage to the tissue. This is often over days and the full extent in the necrosis may actually take weeks to delineate. When you're out in the wilderness, you never worry about whether it's first, second, third or fourth. And in fact, you can't do that until the frostbite is recovering. And then you kind of grade it. It has been done first degree or superficial, second degree or superficial with blistering, third degree, which they say is deep, fourth degree, which is full thickness or deep tissue. Again, you don't do that until after the fact and you're starting to recover.

5:30The risk factors that predispose humans to frostbite include cooler or cold temperatures with the windshield. Moisture and wetness because moisture and wetness will cause conductive heat loss. This is when you sweat or have soaked clothing. Tight clothing, which constrict blood supply, which would be like constrictive footwear or tight fitting gloves or things which would prevent blood supply, immobility or very prolonged exposure. One of the ones that we kind of overlook is dehydration and malnutrition. These are a much bigger factor in frostbite than we usually think about. It's important in the winter time to make sure you're hydrated and you're maintaining good nutritional status. And then other things like underlying bascular diseases, which people who smoke, rain outs, phenomenon and, of course, diabetes.

6:30When you get to altitude, you have less oxygen to begin with. And as a consequence, this will cause it. And then exhaustion or cold-induced lethargy will impair judgment. So I always like to say that the prevention of frostbite is actually the treatment of frostbite. And you always hear prevention is far more effective than cure in wilderness environments. So when you get out into the back country with your family and friends, especially young people who don't know the dangers of this, a very comprehensive prevention strategy that includes equipment, behavior monitoring and planning needs to be undertaken long before you get out there. And of course, education is insanely important, especially to people who are unaware of the horrible dangers of freezing our tissues. Well, there are some strategies that you can use that are already known like don't let your tissues freeze or go out of the cold. But the problem is we do go skiing, we do go back country hiking and snowboarding and snow-shoeing and things like this.

7:35So here are some ideas that are helpful and are the prevention as being the cure. One of the best things is to use moisture wicking base layers, marino wool or synthetics or combined that pull sweat off the skin. This will help you on insulating mid layers like fleece, synthetic down, synthetic fill that will trap the heat. You want an outer windproof and waterproof shell that protects against convective heat losses. And avoid cotton or fabrics that soak these will keep water next to the skin and make your skin cold. You want to carry sparse, dry gloves, socks, bootliners so that you can change wet items before damage begins. You want to protect hands, feet, face, head, ears and exposed skin with hats, boxlava, mittens, preferable when possible, overboots, gators. You can use chemical warners or electric heated insoles that help but must be used carefully not directly against the skin.

8:42One thing you can do is frequent movement to maintain circulation. You can wiggle fingers, toes, like ankles. You should avoid sustained resting cold conditions. If a group stops for any reason, ensure warm change of dry gear and body checks. Body checks is probably one of the most important things in the backcountry medicine and anything, whether it's hypothermia, hypothermia or in frostbite. So you should have regular visual and tactile inspection of each other's extremities. Look for the color, the numbness stiffness because one may not directly know their own frostbite onset. You should plan around weather and terrain. Avoid the long exposure and conditions with very low windshield and use travel strategies that limit exposure time. Make sure you're hydrated and that you're well fed and not put on constrictive clothing or boots which impede arterial flow. One of the things that we see a lot in frostbite, and this is something you should watch in others, is to avoid alcohol or substances that impair judgment or peripheral perfusion.

9:47Recognize the early warning signs. These are going to be things like frost nip, which is numbness and tingling and stinging before the full frostbite sets in. That stage, immediate warning or projective action can support the progression. When the thing about frostbite is that it doesn't come on like a thunderclap. It can come on very slowly. So if you're looking at signs and things like frost nip will help. You want a monitor and an interpret windshield, which indicates problems. You want to track individuals and group signs. The summit begins to complain of cold numbness or loss of dexterity. Then you want to act early on that. For eye, altitude tricks allow a climatization and watch for combined effects of hypoxia and cold on circulation. Because when you go up in altitude, you get go down in temperature. And many people listening to this podcast are going to go very high. So this is something you want to be very careful of.

10:49And by layering smartly, staying active, monitoring and having a good buddy check and using good judgment. Many frostbite cases can be prevented. So in the field, there are some things that you need to do almost immediately. But be aware that even with excellent preventive measures, frostbite is probably going to occur in some situations. The principles of field care revolve around what we call stabilization protection. And then rewarming if it is safe, pain control because this is going to hurt and wound protection and evacuation. So as always, treat life threatening conditions first, like hypothermia and trauma. Remove from the cold environment, find shelter or windbreak. Remove wet clothing, jewelry, constrictive items that will help prevent injury. Protect the frozen injuries from further mechanical trauma. Whatever you can think that that means. Never rub or massage frozen parts, this can worsen the injury.

11:51That's an old thing that people say is rub cold, but that is something you really don't want to do. Friction does increase heat, but that can cause damage to the skin and underlying tissues. And you want to keep the injured parts dry and protected from the wind because that will protect conductive and convective losses of heat. One of the most critical decisions is whether to rewarm in the field. And you think that that's like a no brainer, but here's the deal. And here are the general guidelines. If you are confident that once thought that tissues will not refreeze, proceed with rewarming. If refreezing is a realistic possibility that is during the travel through the colder time to evacuation is short, it is often smarter to delay the thawing until in a controlled environment. And then refreezing is extremely harmful. If ambient transport time is short, like under a couple of hours, and rewarming is not reliably maintainable, passive rewarming or keeping the tissue frozen can be preferable.

12:53Now, if you do active rewarm, and you're in a place where it will not refreeze, then it is safe to attempt. Remember, you cannot refreeze. It should be done incredibly rapidly, but we're going to use the word gently. So the best thing you can do if you can find it, but it's hard maybe in the back countries to mostly affect it area in warm water. That would be like 37 to 39 degrees centigrade or about 100 degrees Fahrenheit until the tissue becomes soft and pliable. This will take 15 to 30 minutes, maybe a little bit longer. And this is going to be really painful. We don't like to use a fire stove or heating pad since the numb tissue is a high risk of burns. If you maintain the water temperature by circulating or replenishing the warm water, that's better. So you boil water, get it at about 100 degrees, that chakuzi temperature water, 38 degrees. You put it in a void thawing if you suspect refreezing will occur. Now we've talked about that.

13:54No, pain control is a big deal. Rewarming is going to be painful. You want to use analgesics. You can use antsets, narcotics if you have them. Ibupropin is typically good, is recommended to reduce inflammation and inhibit thromboxine, which is a thromboxine mediated data constriction. You can use things like aloe vera, which is recommended, because it is also has anti thromboxine in local anti-inflammatory measures. And you can use systemic hydration nutrition support, which is insanely important. You can dry the area, don't rub, exercise thought areas and loose sterile dry dressings. Use non-unherit gauze, wrap loosely to allow for swelling, avoid tight constrictive dressings. Blister's form, they may be carefully aspirated with sterile techniques, like you have done. Elevate the limb above the heart of possible to reduce the edema they can form. And after thawing avoid walking on freshly thought lower extremities as much as possible.

14:58Unless only toes are involved. And then you want to evacuate as quickly as possible while you're trying to maintain immobilization and stability. Once you get to a hospital, cunning more aggressive therapies are probably going to be done, at least going to be considered, especially this more of the deep grade that is the grade three and four frostbite injuries. A lot of this, smaller ones, I mean going to the hospital is always a very good idea, but probably not a lot more it's going to be done. One of the most significant recent advances is elopros, which is a prostocycline analog that induces vasodilation. And this also inhibits platelet aggregation, which is very, very important. And thereby it improves micro-circulation and thawed tissue. This was approved in the United States in February of 2024, though it's been used around the world for some time. Typically, this is administered intravenously, so it's definitely not field treatment.

16:02There are some side effects to it, which are minor compared to the frostbite. Evidence and studies indicate that this is quite effective. There are other things that have been done, but those are the best. I think in the hospital, sometimes they use hyperbaric oxygen, and like it's very serious wound care with the breathing and sometimes amputation. But the best thing, as we said now, is going to be prevention. A useful way to conceptualize frostbite management is to think of it as a stage continuum from prevention through field care to advance care in a hospital and the field. The priority is preventing further damage, especially from re-freezing, protecting tissue, assessing whether warming is safe, and stabilizing for evacuation. If you're in the field, you should be cautious about re-warming, if there is a risk of the re-freeze. Rapid transfer is really important to medical care, if essential for severe injuries.

17:05Once independent of care providers can choose between therapies, like the nuins, based on timing and complications and other things. And remember, not every frostbite warrants aggressive therapies. Supervisual injuries, like the grade ones, the two, often recover with supportive field care alone. The wind of a therapies is short, like if you use TPA, which they use in hospital. ILaPros may have a more extended window, so if you get up there in a couple days, you're fine. Bleeding risks, comorbidities, logical constraints, must factor heavily. And remember that ultimately combining your clinical judgment and things that are done in the hospital are, give us the best outcome. Well, that's kind of the story of frostbite. You know, it remains a challenging cold injury, especially in more wilderness setting. The pillars of success are meticulous prevention, layering, hydration, movement, monitoring, planning, nutrition.

18:06Then, of course, sound field care decisions, protecting the tissues where you warm only when safe and really good and aggressive pain control. Advanced therapies are done in the hospital. And then patient tailored decisions, meaning that every single case must be weighed differently, found severity, resources that are available to you. Now, as our knowledge grows and protocols refine, the divide between wilderness first response and hospital level care is narrowing in terms of what is possible. But prevention and early field care remains the list pins of the treatment of frostbite. This ends the update on frostbite management with the new therapies, medicines, and hospital. And as always, we say thank you for listening.

19:08Thank you.