Hypothermia

[00:00:07] Hello. Welcome back to another episode of the Code 321 podcast. As I was walking out to get my gear last night leaving work, I noticed that I think I saw a little bit of snow flurry starting to come down. It got me thinking about some time pertinent topics, and one of the ones I wanted to spend a little time on is the idea of hypothermia. Most people have probably had some level of hypothermia training or education, especially if you're up here in the northeast. It's pretty common. But I thought I'd do something a little different and talk about an article that I read last year that I really enjoyed. It's called the management of accidental hypothermia in the emergency department. And what it does is it actually has these risk management pitfalls. And I'll include the citation below so you can read the entire piece of literature, but it's by Rashal and Roland. It was in emergency medical practice. And what we're going to do is we're going to kind of blend a little bit of hypothermia education with these risk management pitfalls. So hopefully I'm going to be able to correlate the two and add a little bit of background and you can walk away with something pretty interesting. So welcome back. Um, what we're going to start with is the idea that hypothermia is isolated to a specific location. One of the common pitfalls we run into is just like in Vermont. I don't do a lot with diamondback rattlesnakes because we don't have a tremendous amount of diamondback, diamondback rattlesnake bites in the area that I work in. But when I flew down to Utah with my family last week, that was a pretty common outcome. I mean, they had signs everywhere. So, so when we change our environment, sometimes we change the types of emergencies we go to. And so the first pitfall that we're going to study is a nurse is talking about working in Florida, not Alaska, and not expecting any hypothermia. And this can really happen anywhere. A great example is the trip I took down in Utah. You know, it's actually in a biome called a hot desert, almost on a cold desert, depending on what part of Utah you go to. But the idea behind that is you might have daytime temperatures of over 100, 2130 degrees fahrenheit, and then at night itll be below freezing. [00:02:18] So a lot of times what happens is people will go outside and theyll take a look at the Weather Channel or theyll pull up their phone and ill say, you know, high above 120 degrees or 110 degrees today, and theyre like, oh, cool. So I can just wear a t shirt and shorts. And then, you know, the hike takes a little longer than theyre thinking. Or maybe they hike down into, like a crevasse or valley or narrows, and all of a sudden they don't have that bright sunshine directly on them. And these temperatures can get below freezing at night. I mean, there can be frost. There can be all kinds of significant cold temperatures that we can run into based on where the sun is hitting, what the wind is doing, what the water is doing, and then, obviously, if it's daytime or nighttime. So making sure that everybody is trained on hypothermia and hypothermia, even if you're not in an area where you think that's going to be common. So we want to make sure that we are doing a robust training program that's going to be inclusive of anything we might see. And so that can be hard to really think of those outliers if you're kind of focused on the same in and out patient that you see regularly. [00:03:24] The next one is pretty common, both in pre hospital systems and in hospital systems is the human use of equipment. And what happens is sometimes people will use, let's say, a thermometer, and they'll use the thermometer on a thousand patients. And every one of those patients is in between, you know, 95 and 105 degrees fahrenheit. And so the thermometer works great. [00:03:51] And then you have a really significantly sick, critical hypothermia patient that comes in that may have temperatures in the seventies, eighties, low nineties. And all of a sudden the thermometer is not really working very well. If anyone has ever been to a hypothermia patient, sometimes this can be the hardest challenge, is actually trying to determine what temperature you have. And here's a little hint. Your axillary and tympanic and skin temperatures are probably not going to be very effective because they may not reflect the actual core temperature of the individual. Typically, what we talk about here is a rectal temperature or an esophageal temperature, but getting the actual reading is one thing. [00:04:28] Now, integrating the piece of equipment is a whole nother. Uh, one of the places I used to work use life pack 15. And there's actually a very specific way that that machine is set up to read abnormal temperatures. And ill just give you a quick example. You need to go to your manual of your own, monitor if youre using a monitor to take temperatures to determine what the actual readings are going to be. So remember, it might be in Celsius and it might be in fahrenheit. So youre going to be responsible for knowing those two values and being able to change from one to the other just so you can be fluid with your documentation and your clinical decision making, because it might not be what youre typically used to. [00:05:04] So with a life pack, the thing is it has a valid range and it has an invalid range. So the valid range is about 88 degrees to about 106 degrees. And the vast majority of our patients are going to fit in there, right. And we talked about that, where you might take, you know, might work ten years with a life pack 15 and use that thermometer and never have a weird reading because you're always between 88 degrees and 106 degrees. But what happens if you get to a patient and all of a sudden they're 84 degrees or 83 degrees? And so what this particular device is going to do, Lifepack 15, is it's going to show the value. So it's going to say, hey, you have 84 degrees, but it's also going to give you a message that says check sensor. And what it's doing is there's not actually anything wrong with the sensor, but it's telling you that that value is lower than it expected it to be. And they want to make sure that all of the parts and components are correctly set up and you're in the right spot and enough of the probe is inserted so that you can get the most accurate value. [00:06:09] Now, if you go to a patient, let's say you're in the backcountry, you know, the patient's been climbing on Mount Everest and they've been buried in snow for a while, and you put the probe in and you see temp check sensor, that same message, but you only have dashes in the place of where the temperature would be. [00:06:25] A lot of us, our first instinct would be like, well, it's a broken, it's a broken monitor. It's a broken temp sensor. Like, give me a new sensor, like dashes. It's not reading. It's, I can't get a reading. Right. Think of like your spo two, right? If you were to plug in your spo two and have dashes all across the screen, your first thought is, I have no pleth, I don't have a reading. So I need to swap the sensor or change the site in this particular situation with the Lifepack 15, that's not what it's telling you to do. It's telling you that that range is too low. So anything below 76.6 degrees, you're going to have dashes, and you have temp check sensor. So just make sure you understand how your monitor works. And this is different for a zol. It's different for a tempest or whatever other device you're using, but you want to make sure that you understand what it's telling you, because if you have a patient in front of you that could actually be below 76.6 degrees, then, and you're getting dashes, that might be an accurate reading. And as you start to increase that patient's temperature, you might start to get those, those other messages and an actual number. A good tip that I learned from another provider is when you're setting up your monitor and you're setting up your temp probe, put the end of the temp probe in your hand. So take it out of the package and put it in your hand while you're setting the monitor up and plug it in, because the inside of your hand is probably going to be between 76.6 degrees and 113 degrees, and that's going to give you at least a number. And then, you know, the probe is working. So if you insert the probe and now you have dashes, you know that that's an accurate outcome. So I think, you know, understanding how your monitor works and then using it properly is really helpful. If you have access to a manual in real time, that can really bail you out of a lot of situations. So whether it's your ventilator, you know, or if it's your life pack or your monitor, your zole, having access to that manual, especially if you have multiple medics or multiple providers on a scene and you get something weird that can sometimes just bail you out for the moment. And you can do a quick lookup, um, you can do like a control laugh or do a quick search and find the information looking for pretty quickly. [00:08:28] So the next one that we ran into is this idea of, I couldn't feel a pulse. We started CPR. [00:08:34] And so most people have heard of this. You've read it in a textbook that hypothermic patients are really difficult to palpate pulses on. They have a decreased vascular tone. They have a profound bradycardic rhythm sometimes. Sometimes they're in atrial fibrillation, sometimes they're in v fib. And, um, you may not be able to palpate any peripheral pulses because they have that peripheral shunt as the body cools. It's going to bring all that blood into the center, into the core, to try to protect their brain, their heart and their lungs. So you might not actually have any palpable pulses out in the peripheral areas that we would normally check, like your, you know, your radial arteries. Um, some people don't do a great job at checking the femoral artery, and, and some of that's just lack of practice, and some of it is body habitus. It's just difficult to get in there and check that. So this would be a good idea if you had ultrasound available to you to look for cardiac activity that's going to correlate with the. With the electrical activity you're seeing on the monitor, and that might be your best metric. Um, dysrhythmias are. Are super common, you know, as these patients start to drop in temperature, really, with, um, any temps between, like, 83 and 90 degrees, the most common arrhythmias you're going to see are atrial fibrillation and sinus bradycardia. And these can be really profound bradycardia. So some state protocols will actually tell you, you know, take a full 60 seconds to palpate a pulse, rather than that 10 seconds, because really want to be sure that they dont have any sort of cardiac activity. And one of the reasons for that is because if they are in a profound bradycardia, they may be meeting their metabolic demand to a certain degree. And the minute we start manipulating them, especially with something like defibrillation or CPR, that can put them into ventricular fibrillation, where they are now not having any ability to meet their metabolic demand. [00:10:28] So these patients are really, are really tenuous, and they're really sensitive, and we want to be careful and make sure that we're not manipulating somebody too aggressively when they actually do have a perfusing rhythm. And sometimes that can be hard to check. So ultrasound's a great tool. Um, if you're kind of uncertain about that, especially if you're trying to decide between, uh, pulses, electrical activity, and some sort of other profusing rhythm, that ultrasound is really to be a great tool for you to kind of see if there's any sort of perfusing rhythm and movement of the cardiac chambers. [00:11:01] Pitfall four is this quote a nurse says, where she says, I started rewarming the patient, and then they got admitted to the ICU, as they should. Right. These patients should be going to the ICU. And as the patient, patient was going upstairs, he arrested in the elevator. So I think a really important piece to think about is the timing of how these things happen. You know, we know that this patient needs to go to the ICU. We're aware of that. But moving them when they're in their most tenuous phase can sometimes be the thing that causes an arrest. Think of all of the things that go into packaging a patient, putting them on telly, moving them. Even you in the field, you know, think about every stretcher transfer, you know, calling a flight service if you're going to be moving them from one stretcher to another, and then taking off and jostling them in the helicopter, all these other things that are going to agitate the patient. And really, anything below that normal range, you know, below 90, 92 degrees, is going to be really, really sensitive to any movement. So really, the safest thing that we can do is continue to treat that patient in a stable environment and get their temperature up, at least closer to a normal range before we actually move them. And when we do move them, we need to be aware that if we see any of those arrhythmias or we see any abnormal activity during the movement, it's too early. We got to wait. We got to just keep them calm in the bed there and try to continue to treat the patient as best we can. [00:12:27] This is another case where we might run into a situation called after drop, which, not to be confused with circum rescue collapse, which I can talk about in another podcast later, but after drop really talks about how as the body cools, your blood is moving from the periphery to the core. You're getting this shunt where all your extremities are kind of just completely drained of blood. And when they're completely drained of that warm blood, they're going to cool even faster. So now you have these, like basically big four icicles attached to your body, and you have all of this blood in your core that's trying to stay warm because it's trying to kind of, uh, constrict itself to a smaller area. [00:13:07] But as we start to rewarm the patient, your bodys like, oh, yeah, those icicles. I gotta start perfusing those and getting some, some blood back into there. But what it does is its like the opposite of a fluid, warmer. Now, were taking blood thats already pretty cold and were cycling it through these giant icicles that are attached to our extremities. And then as the blood moves in and out of the arteries and veins in those areas, its gonna not only pick up a lot of the, um, incomplete products of, uh, metabolism, but it's also going to pick up it a lot of, like, cold, um, it's going to cold energy, so it's going to release a lot of its heat energy as it goes through those freezing cold extremities and returns back to the core. [00:13:47] And the blood is really the primary thing that's warming us at this point, once we get that cold. So if that blood temperature drops, even though you started warming, the patient may continue to get cold. And one of the things we want to think about is, like we mentioned that atrial fibrillation is sinus bradycardia, right around, like, 83 to 90 degrees. And really, anything below, like, 86 degrees, you're starting to get the renal failure, you're starting to get really high risk for ventricular fibrillation. And if you think of a patient that's, let's say they're like 84 degrees, and all of a sudden we start warming them, and we have this after, after drop effect, even a drop of two degrees celsius or two, you know, two degrees fahrenheit, may put them into that arrest range where now they can't tolerate even a drop of one to two, um, one to two degrees. So we want to be prepared for that and recognize that even as soon as we start warming, it's not going to immediately get better. It's going to take a little bit for us to recover and get those extremities warm enough to keep that blood temperature where we want it. Some things to think about. Um, there was a really good study that they did, um, in a wilderness, uh, in a wilderness magazine. I can send the link in the show notes as well, too. Actually fascinating how they did this study, but essentially, the purpose of it is that an esophageal temperature is more accurate and quicker responding than a rectal temperature. So a rectal temperature continues to lag as we start to warm. They trend pretty similarly as the patients are cooling. But once we start to warm the patient and the patient's temperature starts to respond, the esophageal temperature is going to. Is going to reflect the value quicker and more accurately than a rectal temperature. So just food for thought if you have both options, especially if your patient's intubated. The AHA actually says that it is appropriate to intubate a patient in hypothermia for a couple reasons. One, obviously for the aspiration risk. Two, to make sure that we're not, um, creating extra intrathoracic pressure by over ventilating with a BVM. And also because warm humidified oxygen can contribute to the warming process. So by actually putting that warm humidified oxygen directly into the trachea through a ventilator, we might be able to kind of contribute to some of that, um, recovery, which I think is, like, pretty helpful. [00:16:09] Number five is this nurse talks about, you know, I put warm blankets on him and started iv fluids, but I don't know why his temperature isn't improving. [00:16:17] And so if you read this article by the AHA about the management of hyperthermia, they talk about the idea of passive cooling versus active cooling. And passive cooling is going to be those peripheral, um, things that we're using, like a warm blanket or, you know, putting them in a warmer room or trying to take the wet clothes off them. And some of those even, like, intravenous fluids. Warmed intravenous fluids is still kind of passive. It's not really as aggressive as some of the other methods. And if these patients core temperatures are, you know, 84, 80, 78 degrees, these, like, almost unsustainable with life temperatures, you're going to run into problems where it's just not enough. You know, putting a warm blanket on someone that has a core temp of 82 degrees is just not going to do much to warm them up. There's been a bunch of studies that show that pre hospital passive warming techniques really don't do anything. Even warmed iv fluids really don't do anything to actually increase the patient's temperature. We need to do some more aggressive interventions. Like, sometimes they'll put chest tubes in and they'll circulate warm fluids through the chest tubes. They'll do gastric lavage, they'll do, um, ECMO, you know, intubation with warm humidified oxygen, bear hugger, you know, those types of things where they're actually moving these warm fluids from the inside out, because remember, that core is really what we care about. The extremities will kind of take care of themselves after that initial, after drop period. So making sure you're using the right technique and making sure that you understand that, um, you know, this passive rewarming technique pre hospitally generally doesn't make a huge difference when patients are hypothermic. It is important, but usually in mild, and kind of the more mild end of moderate hypothermia is where that's going to be super effective. [00:18:02] Number six is very common in EMS. I've actually heard this from providers, and I've been trying to go around and reeducate and help people understand that shouldn't be a metric we use but, you know, folks say his pupils were fixed and dilated, so I thought he would have a bad outcome. You know, I remember someone once telling me, you know, about a cardiac arrest. Oh, his pupils are fixed. You know, he's not going to be, he's not going to be resuscitated. So in hypothermia, really anything below, like, 80 degrees, you're not going to have that response. The pupillary response is just a physiological thing. So even if their pupils are fixed and dilated, there have been many patients that have recovered from hypothermia, even with core temps below 80. So we shouldn't be using the fixed and dilated pupils as a clinical correlation until we actually get that temperature into the normal range. And even that, that's a neurology thing. There's all kinds of things with, you know, decreased cerebral perfusion and your temperature, your acid base balance, all of those pieces of it are going to come into play when they start to make those decisions. But the initial phase and the initial assessment, fixed and dilated pupils just know that that can be expected below 80 degrees. So it, it's not really anything super important. We need to just warm them up and then make an assessment. And kind of the common theme between all of these points is that these patients are abnormal for what we're used to in terms of our assessment. And so until we get them into that normal range, you know, above 90 degrees, above 95 degrees, whatever your protocols say, we really can't make an accurate assessment. So don't get sucked in about the pupils. It's, it's okay. Right? [00:19:42] So the next thing we want to talk about here is going to be this idea that, you know, I didn't see any evidence of hyperkalemia on the EKG. And so one of the things to remember is that your ekgs are going to be all over the place. You have, you have this acute renal failure because anything below 86 degrees, you're going to start to run into renal failure, which is going to cause a hyperkalemia. [00:20:06] You may not have the peak t waves because the electrolactivity is blunted just by the mechanism of hyperthermia itself, just from that process. [00:20:14] Um, you might see, like, osborne waves is pretty common. But remember, your most common arrhythmias are going to be atrial fibrillation and sinus bradycardia if youre within that, like, 83 to 90 degrees range, and then its going to be, you know, vf below that, and we can easily stimulate vf. So youre already having abnormal EKG, um, findings, just. Just from the fact that they are hypothermic. So trying to make an assessment on, like, potassium just from the EKGD is probably not going to be ideal. We should infer that they do have a hyperkalemia and then confirm that with lab results. Just by what we know about the way that patients respond during hypothermia. Uh, but don't put too much onus on the pupils or, um, the ekgs. I mean, we're going to correlate that, uh, clinically with the lab results as well, too. [00:21:00] Um, it can be quite a process to try to get lab results on a patient like that. Just remember that, you know, by all of the. All of the fluid and blood being pushed into the core and those extremities just getting significantly colder and colder. Sometimes you can't even. You can't even place, like, a peripheral needle and even get like, an art line or an ABG or any sort of stick in that peripheral area. So you might have to start thinking about more central access, if that's in your scope. [00:21:26] Number eight is going to be. I don't think he needed fluids because his heart rate was normal. [00:21:31] As the patients start to start to get colder, one of the things that we run into is these patients start to have this, like, peripheral vasodilation, this, like, profound basal dilation, because they just lose their vascular tone. Um, and you can kind of think about this as that, um, oxyhemoglobin dissociation curve. So as patients temperature starts to cool, you know, they start to lose some of their abilities to properly regulate their enzymes and have this, like, vasoactive response. So they're going to have this peripheral profound vasodilation. Um, they. They can also have, like, a relative heart rate change. So when we think about a hypothermic patient, we expect them to have a bradycardia. So if you have a patient that's. That is hypothermic, maybe they're 82, 84, 86 degrees, and their heart rate is 50 or 60, you might say, oh, well, that's in the normal sinus rhythm. You know, this. The 60 is, like, starting to get closer to normal sinus rhythm. But in reality, we expect that patient to be bradycardic. So that's a relative tachycardia, given the clinical situation. And we want to start thinking about what stressors are causing that patient to have that tachycardia, especially with a reduced metabolic demand. Even though they have, um, you know, reduced metabolic output, they don't really require as much because of the way that the body's reacting in the cold temperatures. So thinking about not only your heart rate, but your heart rate in terms of the patient's clinical situation, and then making sure that we don't put too much onus on one thing, and that could be said for really all of these debrief points, is you want to look at the full picture and use all of your diagnostic tools. You dont want to get sucked into one thing, like the pupils or the heart rate or the EKG. We want to kind of put all of those things together to really understand what were looking at here with the number nine. Were going to talk about looking at patients potential for ventricular fibrillation, especially when theyre at those really dangerous levels. We talked about like 83, 84, 85 degrees starting to get into that window where were really worried about any sort of manipulation or physical movement causing ventricular arrest. [00:23:33] One of these, um, nurses is talking about just after I examined the patient's extremities for frostbite, he had a ventricular fibrillation arrest. And so what we're talking about is, you know, timing on these interventions and assessments is just as important as actually doing them. So when we think about checking a patient's extremities for frostbite, if they're at 83 degrees, does it really matter that their fingers are frostbitten? Right. That that's going to be there in, you know, a couple hours when we come back and this patient's in a more stable range. You know, doing those assessments when they're, you know, 88, 92 degrees is going to be a lot safer, just like not moving the patient, you know, remember number four, we talked about, you know, trying to move the patient too early. We really want that patient to get back into that safe window before we do anything that's not critical to the actual warming of the patient back into that window. [00:24:25] Finally, number ten, this one is a quote. I don't know if this is from a provider in nurse, but says the patient was in a systole and didn't respond to multiple rounds of Epi, so we called the code. [00:24:36] So remember that with patients who are hypothermic, there's a high potential for the vasoactive drugs and even the antiarrhythmic drugs to be either less effective or not effective at all, just solely on the. On the fact that they cannot circulate properly. So think about if you had a peripheral line and this patient was shunting and had all the cold blood in the extremities and then the warm blood that was circulating closer to the core. If we introduce these potent medications into the periphery, they may not have actually have much biouptake by the actual blood that's circulating to get to the brain, the heart and the lungs, or the target tissues that we're looking for. So we want to make sure that we recognize, um, they can also. They can also accumulate to toxic levels. So if you think about like, oh, you know, three doses of cardiac epi or five doses of cardiac epi or whatever your protocol says, if that medication is not being, uh, accepted by the body and it's not being processed and used, um, the way that it should be and affecting the actual, you know, alpha one beta one beta two, all that stuff that we're looking for, it's just going to continue to sit there and just like a crush injury, if we introduce all those medicines and say we do get a return of spontaneous circulation, and now were going through that after drop phase and were starting to recirculate those extremities, they may get hit with like, you know, five, six milligrams of epi at once. And remember how I told you that the. The dysrhythmias and the cardiac irritability is highest right after resuscitation, or right in that lower window, especially as we go through after drop, these patients are not going to respond well to, like, five milligrams of epi when they're already at a sustained risk of ventricular fibrillation. So making sure that you recognize there are changes that happen to the BLS and ACLs algorithm specific to hypothermia, you should be able to find those in your local protocols. If you go under your hypothermia, under your hypothermia guideline, you can also locate a lot of this information right through the American Heart association or a lot of other wilderness programs will talk a lot about how to actually, uh, treat a patient properly that's going through an emergency like this. I will attach the references that I've used for this particular show in the bottom so you can read a little bit more. If you're like me and you like to go to the root document and really just comb through it. But the purpose here is, I hope that you got something from all of these points. I hope that you recognize that these actually come from people who have dealt with real hypothermic emergencies in the emergency department, that we're really going through challenges. And the idea here is to take a real situation and then go into the science behind why that happened and learn a little bit more about it. So I wanted to make sure that we added something above and beyond just what your EMT textbook would say if you were to turn it to the hypothermia page. So hopefully this was valuable. [00:27:26] Please let me know. Get a hold of me. You can go to precisiontrainingusa.com and get ahold of me if you have feedback on this episode, if there's anything else you'd like to see, if there's a new study that you've run into and you want me to dive into it, I really enjoy that process. Um, and again, I encourage all of you to get out of your local bubble. Try to access information from people that you don't normally talk to. It's. It's really healthy. You know, the biodiversity of information is super healthy for everyone as they start to grow. Um, if anyone will be at vital signs over in Rochester, I'm going to be flying out later tonight and I'll be there through the weekend, so please connect with me. Let me know what you like and what you don't like, and I hope that you all stay very safe and bundle up. Getting cold out there.