Ep 186 Hypothermia Part 1: How it hurts

they were dead. If they resisted the craving for sleep, another passerby would help them along a little farther, thus prolonging their agony for a short while, but not saving them. For in this condition, the drowsiness engendered by cold is irresistibly strong. Sleep comes inevitably, and to sleep is to die. I tried in vain to save a number of these unfortunates. The only words they uttered were to beg me for the love of God, to go away and let them sleep.

To hear them, would have thought sleep was their salvation. Unhappily, it was a poor wretch's last wish. But at least he ceased to suffer without pain or agony. Gratitude and even a smile was imprinted on his discolored lips. What I have related about the effects of extreme cold and of this kind of death by freezing is based on what I saw happen to thousands of individuals. The road was covered with their corpses.

to live, and they don't let you forget it. Grabbing the wrong jacket before you step outside, losing a glove, a window that's lost its insulating ability. These things don't go unnoticed, at least not for very long. Whether immediately or eventually, the cold makes itself known. It insinuates itself into the nooks and crannies of your jacket, of your body, the tips of noses, toes, fingers, and it settles into your bones until you feel like you'll never be warm again.

But I think that many of us lower latitude dwellers have kind of a sense of awe, at least I do for those living in the Antarctic and Arctic regions of the world, because even with the warmest of jackets and the most insulated of shelters, polar life exists on a knife edge, where even the tiniest thing can tip the scales, turning a minor mistake or a minor accident

into a fatal outcome. I cruised the Wikipedia page for hypothermia related deaths, which is quite morbid, I know, and the one thing that really stuck out to me was just how easily it can happen. I went through and I like read different people's stories and it was just like and then on one wrong step, yeah, and that was it. That was it. And how powerless you are when the cold really sets in. And yet many species

call these polar regions their home, not just humans. Why would an animal live in a place that is so brutal, so unforgiving, although not all the time, as we'll see,

there are all sorts of reasons. Maybe it's more available, habitat, less competition for resources, escape from predators, escape from parasites, a combination, or something else entirely, But for this episode, the why isn't as interesting to me as the how, Like how can species live at the ends of the earth, not just like eking out a meager existence, but flourishing

despite the deadly cold. Humans have innovated incredible clothing, shelter, transportation, and tools to help protect from freezing temperatures, and animals have evolved a vast array of strategies anatomical, physiological behavioral to resist hypothermia and other harmful consequences of cold, like frostbite. Would you like to learn about some of these thrilled? Thrilled to learn about these one way is just to avoid it. Just migrate the heck out of it. Birds.

Birds love this, they're big fans of the migration.

the winter. Bears, ground squirrels, bats, some frogs. And then there's cold resistance, so like you keep operating mostly as normal during the cold months, but you just bump up your your own systems, your defense against Yeah, and that would be something like arctic foxes, polar bears and so on. And these strategies they're not mutually exclusive. You can have a little bit of this and a little bit of that.

And there's also a great variation within some of these, So like hibernating black bears only drop their body temperature by a few degrees celsius, while some mammals, small mammals drop temperatures twenty to thirty degrees celcish body temperatures. What oh it gets it gets better. Wood frogs, Oh, do you know about wood? Yes, I know about wood. Frogs. Who does it? But no, lots of people don't. I had I had to refresh my memory because the stats

are I was like, this can't be. I was like, I need to fact check this right multiple places.

keep swimming around. Other animals like polar bears, ptarmigan wolves and hares make simple burrows in the snow to help with insulation.

Bagel formation. And then other animals that live in colonies, like walruses and penguins, they'll huddle together for warmth, especially baby emperor penguins.

or become damaged. What I don't know. And then nasal cavities. I didn't realize that, like the shape of a nasal cavity could be so important, but it is.

nasal cavities. Oh that's fascinating. Yeah. Babies of Arctic animals are born well equipped with extra warm fur or feathers or brown adipose tissue that keeps them super warm, and mom will also often provision them with super fatty milk. One of my go to fun facts to share at a cocktail party is that some whale milk is so fatty, like thirty to sixty percent fat, that it has the consistency of toothpastete. That's one of my favorite things too. Yeah, just I love it.

this by cashing food. So like one arctic fox hoard had one hundred and thirty six seabirds and then yeah.

a lot scarier than it actually is. They just lose all their fur at once, and then they have to wait a while to grow back a new layer, and so during that time they can't go in the water for food because they'll get hypothermia, so they don't eat. Oh, they can go fifty two days without food or water.

doing for as long as we've been human. So even though I just spent a good deal of time in the polar regions with polar animals, you can get hypothermia anywhere on Earth. Some of the earliest references to hypothermia come from ancient Greece, which is certainly not arctic. Hippocrates, of course, noted the benefits of cold, but also the dangers quote cold is bad for the bones, teeth, nerves, brain,

and the spinal cord. In four point fifty BCE, the Greek historian Herodotus wrote about soldiers dying in a sea expedition. Quote some were seized by these sea monsters and so perished, while others were dashed against the rocks, and some of them did not know how to swim, and perished for that cause, others again by reason of cold end quote seamusters. War has always been a bad spot for hypothermia. In fact, most historical records of hypothermia come from various wars throughout history.

In two eighteen BCE, Hannibal's army of twelve thousand cavalry, ninety thousand infantry, and forty elephants was cut down to nineteen thousand men and some uncertain number of elephants during their march over the Alps, with many of them dying

of cold. During the American Revolutionary War, countless soldiers suffered frostbite and hypothermia, especially during the winter of seventeen seventy seven seventeen seventy eight, when nearly a fifth of the eleven thousand men who retreated into Valley Forge did not have shoes or boots at all. Oh, I just imagine that in the winter. No, I can't imagine that. And then there's Napoleon's army, this retreat from Moscow in eighteen twelve.

So he this is like where this is infamous, and we've talked about this in several other times of the podcast. Napoleon and his army started out in June with nearly half a million soldiers. By the time they had gotten to Moscow in late fall, numbers had dwindled pretty substantially by at least one hundred thousand. But when they arrived, they found a burned out, abandoned city, no opportunity to restock,

to refuel, no food, nothing. The Russian forces had adopted this like scorched earth tactic, and that would prove to be Napoleon's downfall. So he waited around a bit just trying to figure out what do I do here? Do we stay?

through their thin uniforms and worn shoes. Their wet clothing froze on them, and this icy shroud molded them their bodies and stiffen their limbs. The sharp wind made them gasp for breath and froze the moisture from their mouths and nostrils into icicles on their beards end. Quote. By the time they got back to France, all that remained of Napoleon's five hundred thousand troops was ten thousand. Oh my gosh. Yeah, some died in battle, others from their

injuries or infections. If you remember back to our Typhus episode, that was a major, major killer, but many succumbed to the cold. A frost bitten and constantly water logged foot turned gangrenous with the infections spreading to the rest of the body. A raid on a liquor store allegedly killed eight hundred soldiers who imbibed a bit too much and

fell asleep in the snow. At the time, it was thought that alcohol was warming and helped stave off the negative effects of the cold, although I'm not sure they were drinking it as medicine. And by the way, it is not warming. It is not what you should use to treat someone suffering from hypodermy.

and never saw daylight. More along the road, in the neighboring ditches of fields were perceived human carcasses, heaped up and lying at random in fives, then fifteens, and twenties of as had perished during the night end quote. No one was spared, not even the surgeons, who wrote how their brains had become so dulled by the cold that

they could barely recognize one another. So many dyed or suffered permanent injuries from the cold on this retreat, not just because of poor quality clothing and shoes or insufficient food, but also because no one really knew how to treat hypothermia or frostbite. Those words didn't even exist yet, a

practical thermometer that could be used clinically was still decades away. Instead, the effects of cold were kind of grouped together under the term asphyxia, partial asphyxia usually referring to frostbite, and

general asphyxia referring to hypothermia. Interesting, these were diagnosed from like subjective observation, so it was thought that like basically there was congealing in your body, fluids were congealing and blood in start at the at the extremity, right at your flick fingertips and nose, and then yeah, and then as it grew your whole if you're so, that was like frostbite, so you're like, okay, there's no it's all congealed. And then then hypothermia it was like your whole body.

It's not that far off. Yeah, yeah, I say, yeah and so. But because of this, treatment usually took the form of slowly rewarming to get everything to re liquefy, and you were supposed to start in reverse. So you start with snow, rubbing snow on your you know, frostbitten fingers, and then yeah, and then cold water and then cool water, then tepid water. You get the really okay, interesting go

slow yeah. Earlier physicians had learned their lesson the hard way not to use extreme heat, and revival efforts were occasionally successful during Napoleon's retreat, but they often weren't even attempted if someone looked dead, and it wasn't widely known at the time how many of the signs of hypothermia,

signs that mimicked death could be reversed. One of the surgeons, later learning of this, wrote quote how many resurrections might have been made on the retreat from Moscow, probably lots, and as later, medical advancements in the late nineteenth but especially the first half of the twentieth century revealed hypothermia did not always carry with it a death sentence, and doctors could more readily measure temperature thresholds beyond which recovery

was unlikely. And as the term hypothermia came into more usage in the first decades of the twentieth century and it became a distinct clinical entity, focused interest in prevention and treatment of the condition increased, especially during World War Two. So I don't know when exactly I tried to find when exactly the phrase you're not dead until you're warm

and dead you originated. Yeah, but it was likely in the last few decades of the twentieth century, showing the huge amount of progress made understanding hypothermia and reversing it. And so before I turn it over to you, Aaron, to tell us what exactly is happening when our body temperature dropped to dangerous levels and what we do about it, I want to end with one of the most amazing hypothermia revival stories that shows just how far we've come. Oh,

I love it. Like Napoleon's surgeon's minds would have been absolutely blown by learning of this story. Okay. In nineteen ninety nine, a twenty nine year old Swedish woman named Anna moved to a small town in northern Norway in the Arctic Circle to complete her medical residency or above the Arctic Circle, and part of the reason that she chose this location was because she was an avid and

very experienced backcountry skier. In May, she and a couple friends who also had medical training, went out skiing for the day. At six twenty pm, Anna or Anna maybe lost her balance and fell headfirst into a waterfall gully, where she became wedged in the ice and water. Her friends couldn't get her out. They tried to pull her out, and they couldn't get to her, and so they called

for help, and unfortunately help was slow to arrive. The only rescue helicopter available was on its way to transport a sick child, which was in the other direction from Anna. At seven pm, she stopped moving those forty minutes in the ice. At seven point forty a ground rescue team arrived and extracted her from the ice. She was clinically dead.

The helicopter arrived around eight pm and she was loaded onto it for transport to Tromso Hospital, which is about an hour's flight away, and with the adage you're not dead until you're warm and dead in mind, resuscitation efforts were started in transit and continued along with rewarming at the hospital. When she got there, doctors found that she was not breathing, She had no pulse, her pupils were widely dilated and unresponsive to light. Her EEG was flatline.

Nurses and doctors continued their chest compressions in ventilation as they prepped to put her on a heart lung machine. At nine fifty two pm, so this is three and a half hours after she went into the ice, her temperature, her body temperature was measured at thirteen point seven degrees celsius or fifty six point six degrees fahrenheit. Wow. At that point, yeah, she'd been three hours without a heartbeat.

But then at I guess I kind of spoiled it at the beginning by saying revival story, but I mean, you know where this is going. But then at ten fifteen pm something on the monitor a heart beat, then another, then a steady rhythm. She woke up ten days later and spent another couple of weeks in the intensive carry unit, and initially she showed signs of paralysis below the neck and struggled with various organ dysfunctions, but over time she made an almost complete recovery. After five months she was

like basically back to normal, back to skiing. It's an amazing story that shows what both the human body and modern medicine are capable of. And that being said, every year many people, especially those who are unhoused or struggle to keep their homes warm in the winter who can't

afford to do so, die of hypothermia. And most of these deaths are they represent a failure not of modern medicine but of our society in providing a safety net to prevent death in this way, because like stories like Annas show us, it is possible, and it can sometimes be reversed. But in a lot of these cases it should never have happened in the first place. Yeah, but now Erin, I'll turn it over to you to tell me more about how we deal with hypothermia today. I would love to.

point gets moved. Right. Our brain, specifically our hypothalamus controls our temperature set point, and so a fever is what happens when our hypothalamis is like, we need to get hotter, right, But most of the time, outside of a fever, we as humans seek to exist at about thirty seven degrees celsius ninety six or so fahrenheit, right, And that is that particular temperature is what our body is constantly maintaining.

And because we are endotherms like all mammals, we maintain this temperature by physiologic mechanisms within our own body.

the right temperature fail us. And that happens mostly when the environment is either just way too cold or it's just a little cold but for way too long for us to generate enough heat via our metabolism and all the things going on inside of our bodies, okay, and the external trappings that we use of course as humans, so we can pretty well maintain our body at a constant temperature without our bodies having to work very hard

to do it, even if we were totally naked. If we exist between like twenty five and thirty celsius, which is like seventy seven to eighty six fahrenheit, that's our like thermoneutral zone. Once you get above this or below this, our bodies are going to have to work harder to maintain our temperature. Now, that's seventy seven fahrenheit twenty five celsius. That's not cold, no, it's quite warm, it's quite warm. But below around that temperature means that our body is

having to do something to generate heat. Right if you were, if you were totally naked like, but we're off if you were totally naked those onto So that's that's behavioral adaptations. So what I want to talk about is less about the behavioral adaptations because those are obviously important, But I'm really going to focus on our bodies. How do we

typically deal with temperature stressors? What are we doing inside of our body to generate heat when we're exposed to cold, so that then we can understand what happens once those start to fail us. And then next week we're going to talk about kind of building off of that story that you told Aarin and what we know about what cold does to our bodies once it kicks in, and the ways that people have thought to maybe use this to their advantage to treat various conditions.

constriction of peripheral veins and arteries in our skin. And what that does is it keeps our blood, which is warm in our deeper circulation.

kind of sludgy when it gets that cold. And then you can also get blood clots in some of your small vessels, which might lead to more damage due to lack of blood flow there. And because of the actually freezing itself, the extracellular water freezes and that ice crystal formation can cause direct tissue damage. Right, So it's very multifactorial.

And in terms of treatment for frostbite, the treatment is to rewarm that area to try and increase blood flow to that area, But as likely happened during Napoleon's army, if there is a risk that things will refreeze, you cannot start to rewarm because freezing and then warming and then refreezing actually causes significantly more damage.

let's keep talking about cold, Okay. All we've said so far is that we start with vasoconstriction in our peripheral tissues and in our blood vessels. Sometimes that's not enough to maintain heat. So the next thing that our body does is to increase the production of heat inside of our bodies. Yeah, and there's two main ways that we

do that. One is shivering, so our skeletal muscle activity involuntarily starts to shiver and you have these repeated contractions and that increases metabolism, and so that increases heat production. But the downside of that is that it utilizes a lot of energy, right, Yeah, it's costly, it's costly. It's a very costly thing to do, but it can generate a lot of heat, so that can help to keep our bodies warm in some scenarios. There's another mechanism that

we use, which is brown fat, brown outapost tissue. You mentioned this, and brown fat is so fascinating to me because it generates only heat. So metabolism in all of the other tissues of our body just generates heat as like a byproduct. It doesn't it doesn't mean to, but it happens too. But brown fat doesn't generate any energy. It only generates heat.

the body if we cannot keep up? The first thing is that we see what's called a cold diarysis, which basically means that because all of our blood has been shunted into our core, it's flowing very quickly through our organs, including our kidneys, and so our kidneys are furiously filtering all of this blood and we start to see an increase in urine production.

will start to decrease. And as our core body temperature decreases, our energy expenditure also starts to decrease, and pretty dramatically actually, h I think for every one degree celsius decrease in core body temperature, our energy expenditure decreases by like thirteen percent. So there's no more shivering a lot of times. A

lot of times shivering will stop. Yeah, because things are just sort of slowing down, and all of our cellular functions start to slow down, and this eventually results in our central nervous system slowing down so much that we lose consciousness. Usually that doesn't happen until our central like our core body temperature drops to around thirty degrees celsius. Should have looked up what that is in fahrenheit, but

I didn't. It's cold, Yeah, it's cold. But what is usually lethal is not the effects on our central nervous system, but actually the effects on our heart. Because first you can get those acid base like and electrolyte disturbances from all of this diarysis that can affect the contractility of

your heart and it can lead to arrhythmias. Okay, And as our heart beat is slowing down and all of this metabolism is slowing down in our heart, the time between beats can prolong, so we get what's called breta cardia. Your heart beat is slowing down, and then the time that it takes for the electric signals to actually be conducted through the heart also gets affected, so you end

up with a rhythmias. There's a bunch of different types that you can get, but most often it's ventricular fibrillation, which is your heart just kind of quivering instead of contracting, and then eventually it stops completely. And that is how death usually happens with hypothermia.

age are more susceptible to hypothermia. So newborn babies and small babies and infants in general have a much greater surface area to volume ratio, So even though they have that great brown fat and everything, they just lose a lot more heat, and so they're at higher risk of core temperature drops and hypothermia people who are elderly, So as you get older, you have less efficient, we think,

thermoregulatory mechanisms. We also often see changes in like body mass composition during aging, and so that makes it so that you're less able to regulate your temperature. If you think about like your grandparents are cold all the time, right, they're just not as able to maintain their heat.

to put you at higher risk of hypothermia hugely. So, Yeah, but there's not like you can certainly see we see hypothermia here in San Diego, even in the winter, and it doesn't get very cold here, right, Yeah, In terms of how we treat it, it really depends on how severe it is, and then like the specifics of the person and the scenario themselves. But across the board, it's rewarming, rights, it is rewarming that person's body back to a normal temperature.

But whether that means just insulating them against any more heat loss, like if they're just mildly hypothermic, or if you need to actively rewarm somebody, and that might mean externally, like putting them in warm water or using we have in the hospital these things called bear huggers. Yeh, I'm pretty sure that's a brand name, Okay, But it's like these forced air it's like these blanket, paper, blankeant things

that you put over someone. We use them in surgery a lot too, but also in hypothermia, and they just force hot air, so then you're like insulated with this blanket of hot air that's moving over you. They're quite cute, uh huh. And then heated blankets. These are all like external ways that you could warm a person's body if they're mildly hypothermic. Okay, and then there's internal rewarming, which is of course much more invasive, and there's obsceeded on

er I'm sure you have many times. There's a lot of different ways that you can do it. You can do it with just like heated ivy fluids, so like just in you know, a peripheral line. You can do it via body like U body cavity levage, so like any of your body cavities. You can flush warm fluid through those body cavities and then drain it out, I know.

And then you also could use essentially like an ECMO machine that's extra extra corporeal rewarming machine that just takes your blood from your body, runs it through a machine, warms it up and oxygenates it, and then returns it back to your.

what it is. Yeah, yeah, I mean I don't We don't really have a great understanding of why and how that happens, but it is something that you can see, and we think that it's just due to Even though you might not lose consciousness until your body gets quite cold, like a core temperature of around thirty, the effects on your brain and your central nervous system can be pretty substantial, even at relatively mild hypothermia, which means that yeah, people

might not be like and we don't really know, like no one's thankfully today doing human experiments to figure out like what are you thinking about when your body is getting to be that cold? And so we don't have great data on like why do these types of things

but it can certainly complicate. I read a couple of like forensic examiner type papers where they were, like, hypothermia deaths if you're like investigating them as like a forensic medical person, can be really complicated because sometimes it is just hypothermia, but it can look like there's a lot of foul play involved, or it can look like really complicated scenarios and then it's ultimately determined that it's all

just due to hypothermia. But so it is. It's really fascinating. Yeah, okay, okay, And what I think is also so fascinating about hypothermia are the kinds of stories, like you told Aaron, of people actually being able to recover. Yeah, especially when you contrast it to heat stress, right, like hyperthermia, the way that extreme heat induces damage to our proteins, to our cell structures itself, that has a pretty poor prognosis if your body temperature gets way too hot.

I love it by Blicks from twenty sixteen. And it's just like such a fun, fascinating, just like a paper that talks a.

Is it is chilling and good and yeah, I clearly should have thought of more better adjectives before telling people to read it, but it is really it's it's I think it does a really good job of kind of taking you through how what hypothermia might feel like and sort of the one fault like one false step, one one miss misstep, one one bad move.