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Hi. So I'm Alex. Um I'm an emergency medicine registrar, um who works in the seven. I'm going to be talking to you today about heat illness. So, heat related illnesses are a group and spectrum of illnesses. They are caused by exposure to excessive environmental temperatures that surpass compensatory limits of thermoregulation. So, what would be an example of heat related illnesses? So, um there are two that I can think of. Um one is um the brownie brothers, um who were running a race, I think in the UK um several years back and um they're approaching the end of the race and one of them um begins to develop signs of a heat, heat illness. Um It's a clip that's really, really worth watching if you'd like to see some of the neurological symptoms that can occur as this illness progresses. The other story that's quite famed in the media is um love some wood walking the Nile. Um And this is actually quite a tragic story and just to highlight the severity of heat illness because I think it can be underestimated at times. Um and he had a cameraman that was on this trip um he was called um Matt Power and Power was seen clearly suffering in the heat and was collapsed on the floor as he struggled to push on. Um Levison Wood explained that they had no choice but to continue with the next village closer than the last. But while they were erected a shelter in the heat and used all of their drinking water to cool and attempt to cool him down. Wood revealed um that they believed he was suffering from heat stroke. And with the rangers two hours away and their emergency helicopter four hours away, he added, we're running out of options and Matt's fading fast. Um Unfortunately, um Matt passed away as a result of heat illness. Um So and love and we had this quote that he said afterwards. Um So Matt just died, he died from severe heat stroke. We tried to get a helicopter but they couldn't get here in time and he died just right there in front of me. I saw him take his last breath, what a tragedy, what an absolute tragedy. And I know that's a bit of a shocker to start your talk with. But I just feel it's really important that we highlight um the real drama that can be and how severe heat illness can be. Um And how suddenly it can come on. Um They were out walking in a sort of jungle environment um in part of Africa. Um And it wasn't something that I think they had anticipated up until the point that it happened. And this isn't just something that happens solely out in the wilds of Africa. So there was a case with some of the soldiers who were training in the Brecon Beacons when there was a particularly hot spell. So it is a risk in the UK. We do definitely see people presenting to emergency departments with heat related illnesses, primarily, obviously heat exhaustion during hot weather. So what methods do we have of heat loss? Um So there are, there are four. So I'll give you a moment just to have a think about them and you can pause here if you'd like to like to write a little brainstorm list. Um But to give the game away, um we have evaporation which is where sweat is vaporized the surface of the skin. Um and then just takes off. Um we have convection which is a transfer of heat from the body to moving air or liquid. So this is what you get when you have fans or a breeze blowing over you, you have conduction. So that would be your transfer of any heat into your ground source. You probably see this most prominently in hypothermia. Um casualties quite often lose quite rapidly lose heat into the earth. Um and radiation which is a transfer of heat via electromagnetic waves. So the most common form of this is um just the the radiation of the sun on the earth surface and on us, we're outside, but probably the one of the most imperative things to think about when we think about heat related illness. So what is the difference between these two environments and the predominant feature? Um is the humidity? Um And that actually makes a really big difference to us. Um And one of the methods we've got of quantifying this is the wet ball globe temperature um which is an indicator of heat related stress on the human body at work or play in direct sunlight. Now, this will be represented in a graph that looks like this. Um and it can be graded based on the severity or the risk to the individuals. And it takes into account variables like um temperature, humidity, wind speed, sun angle and cloud cover. And it is a method of determining um what the kind of levels of activity we should be undertaking in these environments are and they use it quite often in sporting activities for that reason. Um It helps us to determine rest times, activity times and what protective equipment should be using and precautions to protect people to make sure that they don't contract heat related illnesses. However, so there's been this suggested cut off of 35 degrees as the maximum that we can tolerate and a limit which we cannot further acclimatize beyond. And this isn't a specific temperature in every environment. So, and if you are environment of 40 degrees and your community is 75 per cent that equates to a temperature roughly of 35 degrees. However, this limit, which was suggested in one of our previous research papers done in 2010 has been scrutinized since that paper was produced. And it's now been shown in other research papers that this limit may be even around 30 to 31 degrees in quite young healthy individuals. So a lot of individual risk factors that alter what that individual can tolerate. And we can see environment variability a bit more than this graph here. So the suggestion is along the line in the center, the heat and humidity combination becomes too dangerous for humans to be able to acclimatize. The suggestion is that you can tolerate temperatures of up to the high forties provided that the humidity is low. But the point which the humidity starts to increase the temperatures that you can tolerate are a lot lower. So why do we need to worry about this from a global perspective? Well as climate change increases and areas are seeing rises in temperature and instability in weather conditions, the inhabitable areas that are safe and not at risk of heat illness will decrease. And we will expect to see more migration as a result of this. To give an example of this, the number of times that the wet bulb temperature of 30 degrees has reached, which is still considered an extreme humidity and heat event. And we know from the earlier study that we mentioned that may be as high as some individuals can tolerate. And this more than doubled between 1979 and 2017. And there were about 1000 occurrences of 31 degrees wet bulb temperature and about a dozen above 35 in countries such as Pakistan, India, Saudi Arabia, Mexico, and Australia. But locally, what does this look like for us? Well, they have this concept in medicine of the iceberg of illness where the visible sort of effect of an illness or a disease we see above the surface and then the hidden sort of impacts we see below the water level. So the visible effects we would see would be things like heat stroke and death or heat illness and exacerbation of heat sensitive diseases with increase in hospitalizations. But the lower down things would be things like an increased risk of accidents, an increase in transmission of food borne and water borne diseases and just a general impact on the healthcare system overall. So it's important to appreciate that this isn't a collection of conditions to belittle. They will very much increase in prominence as climate change goes on. And when we look at what our body's response to thermal stress is, um so we have an area in our brain called the hypothalamus. And this detects temperature change. And when it finds that we have increased in temperature, it um diverts blood to the skin and this dissipation of heat um allows convection to take place and um helps us with um sweating and evaporation and all of our kind of heat loss by stopping us holding that heat in the center of our body, we also change our behavior. So we may seek shade, we may drink, we may slow down if we're engaging in rigorous activities. And to allow the blood to divert to the skin, we reduce blood flow to the gut. This has a side effect in that if you're digesting meals and taking sustenance and things your absorption of this is reduced because your blood has been redirected. But ultimately, acclimatization depends on body shape. It depends on severity of the heat stress. So the and the temperatures you're in the environment that you're in and it depends on your preexisting physical fitness. Um So there can be quite a lot of variability between individuals and some of the ways in which the body does acclimatize can be seen here. Um So your plasma volume will steadily increase. Um before platter off, um your heart rate um will steadily decrease as we acclimatize your core temperature and skin temperature will alter your sweating rate steadily increases. Um And in your thermal comfort will steadily increase and then it will plateau. We also see in the climatisation, increased sweat loss and blood flow. And that can allow us to increase our heat loss up to 20 times. We find that two hours a day of exercise helps, but it has to be done at cool times of day and that should speed the acclimatization process. It should be noted that it's harder in humid environments to acclimatize. But if you have acclimatized and humid environment, this will transfer to a dry environment, but that doesn't work the same the other way round. A climatisation persists for 20 to 40 days. Um and then you revert back to your back to your baseline. With regard to sweat, we can sweat up to 15 L a day as we go through our process of acclimatization and the salinity of that depends on the sweat rate and whether you're not, you were already partially acclimatized because in a climatized individuals, kidneys are better at conserving salt and they start to sweat at lower temperatures and sweat glands more readily conserve salt to retain water. We find that initially when people arrive in hot environments, they need to take additional salt to make up for this as your body's adjusting. Um And it should be noted that sweating is not effective in high humidity environments because the capacity for water to be lost into air that's already saturated is obviously less than if the air is dry and doesn't contain very much water. So when we think about the differences in the different types of heat illness, um there are sort of three categories that spring to mind. The first is a classical heat related illness. So this often happens to individuals who are more at risk for whatever reason, they may be elderly, they may be more frail, they may be mobile or injured. We then have a category of exertional heat related illness. So this will be people who are exercising in hot or humid environments, putting their own bodies in strain. Um and that increases their risk of heat related illness. We then have this concept of hyperthermia. Um I've put a selection of medicines in there because it's a raft of ways in which this can occur, but probably the most frequent that we see um relates to drugs, medicines. Um and some of those patients will come into hospital with a high body temperature for those reasons. So, the first step in heat related illness is heat exhaustion. Um And in this, we see cardiac output. Um so um the blood volume that your heart has the capacity to pump over one minute and this is insufficient to meet demands to meet the blood supply needed to the skins, muscle and the vital organs, low plasma volume will compound this. So, um by this, I mean, um the volume of kind of blood and fluid in your blood vessels, um which is obviously directly to related to how much you're hydrated. Um This will further make it difficult for your heart to generate enough um enough blood flow to these areas of the body. However, we don't see any organ damage. And if you recover well from this, um then you can resume activities in roughly 24 to 48 hours. So it doesn't have any long lasting side effects by contrast, exertional heat stroke. So the definition of this is a core body temperature over 40 degrees caused by exercise or environmental heat exposure. So that can be classic or exertional heat related illness and um central nervous system dysfunction and multisystem organ failure. I'll explain in detail in a sec what this looks like. But essentially, um if you suspect your patient is looking unwell or behaving abnormally in a hot environment, then heat stroke becomes a possibility, particularly um if they're a bit unsteady, if they're um a bit drowsy like any of these things that come from, that come from the brain, then we'd start to worry that they might be um suffering from a heat stroke, but the symptoms are quite diverse. Um And this is what the symptoms of heat related illness can look like. And there's obviously a huge spectrum in there. Things to watch out for the sorts of things that I'd worry more about heat stroke would be anything as we said that affects the brain. So things like anxiety, confusion, delirium. Um but even dizziness, um headaches, irrational behavior, there are um other things in there that would make me concerned, but probably less. So. So, so many things like weakness can obviously be hard to judge in exertion environments, but any of these um symptoms, I would be starting to consider whether or not my patient may have um heat stroke, but it's not always obvious if your patient has heat stroke and there are a selection of other things to consider. And in medicine, we call this a differential. Um So I'm going to put this up as just a list of other things that may be possible. Um So, acute fever from just a viral illness. Um if we're thinking about things like dizziness and stroke as a possibility, um and just when you get may get a blood clot or a blood bleed to the brain, probably more common in older adults. Um drugs we've talked about as a possibility. Um You may see seizures from epilepsy um or um effects to the brain because of head injury. If you have a low blood sugar, you can get some effects of the brain. Um and low sodium, we will talk about that again in future, even things like um ischemic heart disease. So, um things like um angina, which is um a restriction of blood supply to the heart um or a complete blockage of that blood supply when we get um a heart attack um can cause nausea. Um and some of these other symptoms that you, that we may see, there's a very specific condition called exertion collapse associated with sickle cell trait. Um You can sometimes see some of these things with um arrhythmias, um which is an irregular heart rhythm, um or with hyperthermia, which is a high high blood temperature. So, the take home message, if the core body temperature remains persistently, elevated metabolism becomes deranged and enzymes de nature and there is a cascade of cellular and systemic responses. Um So, in essence, your body's ability in the cells and in its make up to cope with these high temperatures, completely breaks down And that results in sort of inflammation throughout the body. And a breakdown of these of these responses that aren't necessary to allow your body to continue to function. And when we look at the different things that might pose a risk from heat illness, so there's a whole range of things in there and we can split these into lifestyle factors, health factors and work factors. Um Not all of these are modifiable, but many of them are. Um So it's worth just examining if you're going on any trips or in an environment that may be hot. If there's any of these, you could adjust or tweak to protect people that are on the trip with you. And one of the areas I'd like to particularly highlight is medication. Um So there are a huge volume of medications that can cause trouble for participants for all manner of reasons. Um Alcohol probably a particularly significant one to note but any sorts of recognition drugs, um antihistamines, many BP tablets, um laxatives, it's worth noting that around about 25% of the population are on BP tablets. So, um there's a really big risk to quite a significant number of people who engage in trips and hot environments. And with this in mind, answer prevention is worth a pound of cure. So if you can adapt things to help protect individuals, it's infinitely better than suddenly trying to work out. Is this heat illness is not heat illness. How much time have I got? How concerned do I need to be? And how do I call this individual down? We have lots of ways of trying to prevent heat illness. So probably the first thing to do would be to identify individuals you think are particularly at risk and try and modify some of the risk factors that we talked about in the earlier slide to help prevent them from suffering from a heat illness, you can monitor environmental heat stress environments that you're in which obviously quite difficult. But the idea is that if anybody's resting heart rate exceeds 75 per cent of an age adjusted maximum, then the next working period is reduced by a third. So that's a heart rate measured at the point at which your individuals are doing whatever it is that you're supposed to be doing in that environment. So um be that running or walking. Um and if it is exceeding that limit, um then you need to reduce the period of time that you are working for in order to protect the whole group. Um You can also adjust daily exposition activities accordingly without measuring any of that. So you can just make an assessment that you feel that you need to reduce that for the safety of the group. Um It's important to educate everyone about what signs and symptoms to look for, so they know what to expect. Um and when to seek help and when to cool down and when to engage in kind of protective behaviors, make sure that you provide adequate water shade and the trains. And this is probably of most significance for younger groups. Um particularly um young people who might be a bit stressed about going to the toilet in unfamiliar environments and maybe restricting their water intake and make sure that you've got a robust evacuation plan to be able to protect individuals who are on the trip from the perspective of fluids. Um We used to say um to drink to thirst, but we now know that that's probably the point at which you've already lost a reasonable amount of your fluids. So we now say pre emptive drinking, not excessive but just pre emptive. And you're aiming for this kind of like champagne colored urine, um which we talk about with participants sometimes. Um this is obviously dependent upon they need to have a safe and secure water supply. Um The water supply needs to be palatable because I know many young people struggle with, um, with just plain water or water with kind of flavorings in from um, sort of iodine or chlorine tablets. Um, which it's worth considering because you may consider taking um some sort of the Robinsons fruit shoot, um, kind of squirts that you can put into drinks. Um, the trees have to be accessible and they have to know how to use them and how to get to them and not be afraid to use them and you need to replace initial salt losses. And that helps with that sweating process. It's worth mentioning um when people overcook fluid maintenance. So, um by this, it's most commonly seen in sort of exercise environments where people who have just really, really tried to preemptively hydrate and have taken far too much. Um The complexity with this is um some of the symptoms that you get look very much like heat related illness that can be quite hard to determine if this is somebody that needs cooling and water or who's taking too much water. Um Symptoms that we normally would see would be things like stomach bloating, weakness collapse. Um But they can get unconsciousness. Um they can have seizures. Um So it's important to evacuate people because um cerebral edema, by which we mean, brain swelling is a risk. Fluid balance is really important to know what the ingoing and outgoings are and avoid giving them any further water. If it's really necessary, then medical professionals might consider something like hypertonic saline, which is basically just a really high salty concentration um given to a patient over 20 minutes um to try and reduce that risk of brain swelling. So how do we know for definite that our patient has a heat related illness? Well, a lot of it is clinical um but we can try and measure temperature. It used to be thought that the best way to do this was to take a core temperature of which probably the most easy and variable and environmental condition situation is to put a temperature in the rectum ie up somebody's bottom to measure their core temperature. Unsurprisingly in a confused um sick, um muddled or um you know, a patient who's struggling with some of the brain effects of heat related illness. This is not always the most favorable option um and can be quite difficult for us to achieve with some of the equipment we've got. Um So I think it's worth saying that an ear temperature is completely acceptable. Um and not to delay um treatment for heat related illness. If you think that this is what your patient's got, even if you're struggling to get a temperature. So the take home message overall is your goal is to rapidly call the patient. And that is the most important thing that you can do to protect your patient if you think they've got heat related illness. So the methods that you've got um are things like cold water immersion. So um 2 to 15 degrees of water should lower the body temperature by 3 to 4 degrees over 15 to 20 minutes, which is really actually quite quick. Um Your other suggestions if, if that's not immediately available are um icy wet towels, so cover the patient's body and then change them every 2 to 3 minutes. You can consider running water. Obviously, there's a bit of convection with that. So that will help draw heat away from the individual. Um You can also get um get wet fan, get the patient wet and then fan them. Um which again is um a convection and just allows some of that heat to dissipate if you don't have these options. We used this the other day with a patient hospital, but you can give cold ivy fluids and ice packs supplied to the axilla and the groins just to make sure that the patient cools down as rapidly as you can manage, but be careful not to cause any sort of cold injury to your patient. So, summary of treatment, aggressive cooling, cooling, cooling, cooling. Um but um you would then also do your um assessment from top to toe. So we in medicine, we call that AC ABCD E um basically stands for um have they got any catastrophic bleeding? Um is their airway? Ok. Are they breathing? All right. Um What does their circulation seem to be like? So the heart rate the peripheries and this probably comes under. Are they hydrated? Are they not what their BP and heart rate? Um D is when we start to think about things like they awake? Are they asleep? Um, can we wake them up? What are their sugars? What do their pupils look like? And are they doing the right things we'd want ie are they constricting to light? And then is everything else? I mean, usually we throw temperature underneath this underneath e but in this situation, we'd raise it sooner. If we think the suspicion of hate related illness, you need to make sure you've removed your patient from the heat source. Um You need to manage any seizures, although I can appreciate that that's harder for individuals that don't have um medical familiarity with it, but just be aware that they can happen. Um and how to put your patient into the recovery position to protect airway. Um Make sure you monitor some kind of some of their vital signs if you can. So checking the heart rate, checking their breathing rate. Um and just seeing how that alters over the time you're giving treatment. Um you can make sure you keep tabs on their it is urine output. Um and predominantly, I guess make sure that somebody somewhere was making an evacuation plan to get them out of the hot environment that they're in. Um because your body temperature remains unstable for several days after the acute severe episode and it's really important to avoid further stressors. Um And you want to make sure that your patients in a protected environment, um in case they have any further um complexities as a result of their heat related illness. It is actually a picture here of one of the stress management um that they gave um for the Olympics in Japan where if they had any athletes that suffered from heat related illness. So there are other conditions. So I sort of given this as a bit of a um a bit of an example. Um but um you're on expedition to the Atacama Desert and one of your participants approaches you and tells you that they have developed this rash. So this is actually um a heat rash and it just comes from irritation and blockage of the sweat glands um in the heat. Um And one of the ways that we can mitigate against this is to wear loose clothing um and to keep kind of clean and dry where we can stop blockage of those sweat glands. But there are so there are a selection of other heat related illnesses that can occur. Um And I'm going to run through those now. Um one is heat syncope. So, syncope basically means fainting and this happens when the blood pools in your lower legs and it therefore does not deliver to the brain to the same extent that it was previously and this causes you to faint it's self limiting but can be exacerbated by medications. So, again, another reason to have a look at what your participants are taking and see whether or not you can tweak or adjust those. Um for the hot environments you're going into heat edema. Probably quite a lot of us have experienced is when you get swelling um of your kind of fingers and toes and your peripheries, um just as a result of um hot environments, um it's self limiting, meaning that it should just spontaneously resolve of its own accord, exercise associated muscle cramps. Um So this is thought to be due to um a kind of dilutional hyponatremia. So when you get a sort of lower sodium level um as a result of um fluid or um with inadequate salt replacement, um and with salt replacement, it should resolve and if it's not doing so you need to think about additional illnesses or other options like um kind of muscle breakdown. Um And get your participant reviewed. He tetany happens when um you have patients or people who hyperventilate. Um And that hyperventilation causes a fluctuation in calcium levels. Um All you need to do is coach the um breathing back down to a normal rate. Um And that should resolve this. Um We call it a relative hypocalcemia. So the relative change in calcium levels driven by their breathing. Um and that allows um the tetany which look like kind of little muscle flickers to settle malaria rubra um is the prickly heat that we've just, we've just covered as heat rash. Um when you get blocked sweat glands, which may cause itching. Um And we've talked about guidance on how to prevent that and then sunburn, um which again, not to be underestimated, you can still end up with significant um burns from sunburn. Um and it is very, very uncomfortable. So another thing that we would strongly advise against this is a list of three of the most useful references that I used when I was putting care this presentation. And I hope you might find them helpful as well. Thank you for listening to this talk on heat related illness and I hope you've enjoyed it and found it informative. If you have any questions, do feel free to email me at this email address. I'm very happy to answer them um or to get in touch with Endeavor medical and they can forward them on to me. I hope you enjoy your course.