Therapeutic Guidelines Wilderness Medicine

Why the Therapeutic Guidelines are focused on some of the points around prevention and preparation is to ensure that, in the unlikely event that these issues occur, that you're best prepared to manage them.

[Music] Welcome to the Australian Prescriber Podcast. Australian Prescriber – independent, peer-reviewed and free.

Hi, and welcome to this Australian Prescriber podcast on wilderness medicine. I'm Dr Justin Coleman. I live on the Tiwi Islands, just north of Darwin in what you would have to describe as a vast and fairly flat wilderness. The Tiwi Islands are the second largest islands in Australia, the largest being Tasmania of course, and there's another large island to our east, and that is called New Zealand.

And we are very lucky to have with us today the Chief medical officer of the New Zealand Defence Force, who lives in Wellington, Charmaine Tate. Welcome, Charmaine.

Thanks, Justin. Lovely to be here.

I do think this podcast will suit not only doctors and pharmacists who are our usual listeners, but there's actually not a lot of specific drug information on this, and therefore it will actually suit hikers or trampers. Is that the word? We're going to run through today a wide variety of topics, and we'll start with bites and stings and all those nasty things in Australia and New Zealand that can make your life a bit of a misery when you’re out bush. And then we are going to run through hot and cold, if you overheat or if you get freezing. And we're going to talk about the highs and lows of wilderness medicine, so altitude sickness and drowning. And we'll talk a bit about electrical injury to finish things off. Does that sound like a decent smorgasbord of things that might go horribly wrong when you're out bush, Charmaine?

It sounds like a good start, Justin.

And we're talking now about the Wilderness Medicine guide, which is the Therapeutic Guidelines' new edition with lots of updated stuff. And we're concentrating on what is different in the updated edition compared to the previous. For bites and stings, I do notice that despite the fact that our continents do have plenty of the nasties on the planet, such as the most venomous snakes in the world, most bites you get tend to be things like scorpions, millipedes, caterpillars, and leeches. And in fact, we can reassure ourselves that most of those sorts of bites do not cause systemic effects, even though of course some are very painful or look worrying.

Yeah, that's right, Justin, I have to say the bulk of these troublesome creatures do seem to be on your much larger island. And this section is really not dealing with the snake and spider bites, those are covered elsewhere in the Toxicology and Toxinology sections of the guidelines. However, it's really things that are more common. So the common things that hikers and trampers might present with, either at the time that they're away or later on.

So we talk about tick bites. As with a lot of sections in the new guidelines, we talk a lot about prevention of these types of events in the wilderness and then some really basic principles around management.

Obviously, one of the key ones around ticks is how you remove them or more how you don't remove them. And then there's discussion of some of the rarer but interesting systemic effects that can occur after a tick bite, paralysis being one if you have a tick attached for a longer time. It has to be attached for four or five days.

And then some interesting conditions, one such as the mammalian meat allergy, around which tick venom creates a sensitisation to an allergen known as alpha-gal. That is a substance that can be present in meat products and milk products, things like gelatin-coated medication. It's obviously a delayed presentation, but it can be kind of concerning and something that you wouldn't automatically think about relating to a wilderness exposure, but well worth asking when you get strange presentations after a period of time in the wilderness.

And some basic advice for people who get ticks, obviously we want to remove it so that we don't squeeze anymore substance into our bloodstream and also retain the tick mouth parts. How do we remove ticks?

Yeah, it's a bit tricky. We just think the best place to remove a tick is in hospital. Trying to remove a tick off yourself, one it's a bit awkward with positioning, and two is trying to use sort of gadgets, tweezers, and things. If you squeeze the head, it can result in the tick releasing the venom or leaving parts behind. So we really say that the best place is a medical facility, and most general practices and medical clinics in most parts of Australia will know how to get rid of them. Often it's by freezing, so with an ether spray, and that causes the tick to drop off. Permethrin cream can also be dabbed onto the tick as another method to remove them.

I've done that on a few occasions, and I find the permethrin doesn't seem to upset the tick nearly as much as I wished it would. I've found a good old punch biopsy of a retained tick head at just 2 or 3 mm, it certainly gets rid of that whole zone, and you don't have to go poking around for its proboscis and other horrible tick parts that are left inside the skin.

It's hard to, even with the naked eye, to see what's left behind. So that's a good way to make sure.

Just moving on now to heat-related illness. So we'll go from hot first and then cold. If someone has been in a hot exposed area for some time and has any sort of neurological symptom, we really do need to keep a high degree of suspicion.

Yeah, the challenge with heat-related illness is that, the textbooks talk through looking for core body temperature, which is difficult to achieve in a wilderness environment. And really instead we focused on considering the environment. So what are the possible differentials? And then what are the key clinical signs that you're looking for? And any sort of altered mental state or neurological sign in a warm environment has to have you thinking of heatstroke until proven otherwise. The challenge is, for every degree of rise in core temperature, you start to move towards more trouble. And so, the amount of damage that's caused is related to time that your body spends at that elevated core temperature. So the most important thing is recognising it early and then starting treatment as soon as possible.

So just to clarify, by the word ‘core temperature’ you're referring here to things you could do in hospitals, where you put probes inside body parts and take their actual central temperature. But of course, we don't have those things outside hospitals. So you're saying that, skin thermometers and perhaps mouth and rectal temperatures are unreliable?

Yeah, so it's the same with hypothermia. So the challenges in those environments, when you're looking for a specific number to decide on your clinical diagnosis, that number can be affected by all sorts of things when you are further away from the core and measuring temperature. And you don't need the core temperature to make the diagnosis. If it is a hot environment, the person is presenting with those neurological signs, then this really is a diagnosis you want to include and start responding to quite quickly. Along with other differentials going through your mind, you can start to treat this.

And unlike cold injury, where we have to have some caution about reverting towards normal temperature, I take it with heat-related illness we really, really just have to get the core temperature down pretty rapidly. Is that right?

Yeah, absolutely that intracellular dysfunction is really damaging. And so this is about rapidly cooling, and the challenge of that obviously is you're in that wilderness setting, so cooling someone is not as simple as it is in a hospital setting. And finding an efficient way to do that is really the key.

And I guess using shade but also water as much as possible would be your tools out in the bush?

Yeah. So the gold standard for this is something that looks like an ice bath, but obviously not many of those are sitting around. A method that I've used before is something called a taco slurry, which is essentially using a tarp, placing the person in the tarp, and then tipping over them as cold a water as you can while oscillating the tarp. And so it's sort of a pseudo cold water bath with a bit of air for evaporation while the oscillation process is taking place. Cooling and sprayed water and fanning is another way to do it, but really the taco ice bath is one of the really useful tools.

And I believe in Australia, we call it taco, although let's face it, I think in Mexico they'd probably call it something else again, but, okay. So the idea is you have that tarpaulin raised on each side with ice flushing around in them.

Let's move on to cold-related illness. Again, you mentioned that we have to be a bit suspicious or skeptical, I guess, of any specific temperature we are measuring using an external measurement tool. The clinical signs I've got listed here, something called the umbles, which are fumble, mumble, grumble and stumble. I note they sound like me in the morning before I've had my first coffee, but what clinical signs are we looking for for a cold-related injury?

Yeah, not knowing you well, Justin, but that's probably a good comparison. So it is using something to trigger your mind into looking at whether somebody's physical and mental state is deteriorating. And that ‘umbles’ is a way to think through someone who's unable to use their fine motor skills and might be tripping over themselves, not able to walk properly. They tend to get that semi-drunk incoherent mumbling, and they are sort of genuinely upset or almost grumpy, but complaining about what's occurring. So it's a gradual deterioration in the cold, but picking up those little signs early starts you thinking about the fact that the person is cooling down. The guidelines really talk a lot about prevention. So recognising this condition early and doing things to prevent someone getting colder is really much more easy to achieve than trying to warm someone up later.

One of the things I do love about Wilderness Medicine is that they tend to think you won't have a book necessarily with you, so they come up with these great little mnemonics, like fumble, mumble, grumble, and stumble. And another one that appears for the first time in this book is the phrase, "no one is dead until they are warm and dead". Tell me about that, Charmaine.

Yeah, well really again, this is acknowledging the challenges of clinical assessment in the field. It is very challenging when presented with someone who's profoundly hypothermic to even detect a pulse. And so we talk through critical points around just taking that minute extra to try and detect a carotid pulse. Often these patients are quite bradycardic, very peripherally shut down, and can appear quite metabolically slowed. So the real importance here is recognising that they're not dead and that they can still be warmed up, and occasionally you have some pretty good results from that.

All right, so I do think of the two topics we're covering today, yeah, certainly the cold injury and the drowning injury, they are two things where you can sometimes get the risk of calling off a resuscitation too early, because in fact the person is still alive, even though there may not be the obvious signs of life.

Getting on towards rewarming now. So we mentioned that if you are cooling someone down, you do it as rapidly as possible. But tell us about rewarming someone who's hypothermic.

Yeah, rewarming is a much slower process. One, it's actually harder to achieve. So rewarming someone in the field is actually quite challenging. We talk through in the guidelines, your initial phase is really trying to at least stop cooling. So you're trying to prevent any further loss in core temperature, and then a number of practical tips around different styles of wrapping patients to slowly start to increase their core temperature. One of the critical factors is trying to keep the patient as still as possible due to the risk of arrhythmias as cold blood circulates through the cardiovascular system. So this is a much more gentle process, but again, stopping them getting colder and then starting the rewarming process as much as you can with what you have in the field.

Okay, which is usually going to be, I guess, insulation from the cold perhaps and removing wet gear?

Yeah, so we talk about something again, weirdly related to food, but the burrito wrap, which is a concept of essentially a vapour barrier on the outside of a sleeping bag and a source of heat on the inside. But for that type of wrap, when you have a vapour barrier, you don't need to remove wet clothing, for example, because often, even that means they're getting cooler while you're doing that. So really it's about using what you have at hand, and that should help people too, to even pack what they're taking with them. So if you're going in cold environments, you make sure that you have the kind of equipment you might need to warm someone up, which may include all the components of a wrap that's effective in warming someone.

Well, the Therapeutic Guidelines are famous for never being sponsored by any vested interests. I do wonder though, with burrito wraps and tacos, whether we've allowed a Mexican food company to sponsor this guideline.

Yeah although I'm not sure that they have the cold conditions there. But whatever helps us to remember things, as you said before, Justin,

That's wonderful. We'll talk to a topic dear to your heart as a New Zealander. Although in Australia, I literally don't think it can occur while our feet are touching the ground, which is altitude illness. I used to always think of it as altitude sickness, but I gather it's a bit broader than that.

So again, I think New Zealand, you do have to come across the Ditch to get that gain in altitude, but you can see it even reasonably low. So 2,500 m, I’ve seen it present in patients just a bit lower than that as well. And usually with altitude illness, you have time and hopefully plenty of planning to consider this as a mechanism that you might be worried about. And again, a lot of focus in the Therapeutic Guidelines on the rules around preventing this problem from occurring.

And can you just briefly outline the three syndromes that altitude illness covers?

Yes. We talk about acute mountain sickness or AMS, which is the most common form of altitude sickness. And that really is a mixture of symptoms that are part of the body's physiological response to hypoxia. There is a normal process of acclimatisation, and AMS really represents the start of that, but they’re not achieving that acclimatisation. That can progress to a much more dangerous form of illness that is the high-altitude cerebral oedema or HACE. And also occasionally, there's a high-altitude pulmonary oedema. So primarily, a respiratory illness that occurs again because of that hypoxic effect.

And there's a printable patient information sheet, which I think is very handy in this new edition called Go Slow and Sleep Low is a Safe Way to Ascend. Certainly both in prevention and treatment of altitude illness it is really all about ascent versus descent.

Yeah, absolutely. And again, these guidelines really are most useful when you can prevent the conditions from occurring. Yeah, there's very good studies that show what the safe rates of ascent are. So sticking to those at least gives you a starting environment, which means you have a lower likelihood of experiencing this.

But of course we all live in the grey zone. At the extremes, decision making is easy. But in the middle, decision making can be complex. So if someone has a mild symptom, for example, but has spent months preparing for this ascent and have many other people of their group with them, we don't want to err too much on the side of just cancelling the entire event. So I think there is also a recommendation on how urgent the descent is, according to the severity of presentation.

Yeah, you're right, Justin. And I think if you think about these guidelines being useful for any health person who's on these types of expeditions, descending is not always easy. So descending can introduce its own risks. Certainly descent is the answer for any altitude-related illness. But where that descent introduces its own hazards, there are some thoughts that might help people make those decisions.

For the prescribers amongst us, is there any medication with evidence base behind it involved in the prevention of altitude illness?

Yeah, certainly. So we talk through the use of acetazolamide as a prophylactic for acute mountain sickness and for high-altitude cerebral oedema, and we discuss some of the practicalities around that, one of which is patients trialling the medication at sea level. It can give you a few side effects that can be uncomfortable, and some people don't like taking it. And then that can be used quite well to essentially speed up the acclimatisation process and again reduce but not eliminate your likelihood of having problems at altitude.

Let's move from the highs to the lows. So we'll talk about now being in the water and underwater, what's new in the guidelines around diving medicine?

The previous sections were quite focused on a couple of specific areas, mostly related and linked to respiratory conditions. In this version, we have tried a little bit more to appeal to the general practitioner who might be dealing with a patient involved in particular with recreational diving.

Diving is a very unforgiving environment. It's a lot of complex physiological and psychological challenges in the environment. And the environment doesn't support respiration, so multiple hazards and extreme consequence. And most diving-related illnesses and injuries can be prevented certainly by good diving practice. So having somebody who really has the state of mind at the time and in general to do the right thing when diving.

And then too, by having health professionals to understand what they're looking for in terms of determining if someone has a clinical condition, which means that they shouldn't be placed in that environment. So again, an emphasis on prevention and not trying to get too much into the complex physiology of diving, but enough there so that if you are a GP and you have someone who's presenting to you, either pre- or post-diving as a recreational diver, you have a few things you can look out for and at least have a bit more knowledge and particularly know when to refer them to a diving medicines specialist who can do the clearances required.

Diving is something, which I guess if you are into you're reasonably likely to look up, particularly if you're a professional involved. Whereas drowning, water lung injury and hypoxia is something of course any one of us may come across at any time. There are terms such as near drowning, wet or dry drowning. They're no longer the case. So drowning involves now not necessarily death, but describes the process of the immersion underwater. Is that right?

Yeah, that's right. So those more common terms haven't been particularly useful in terms of guiding clinical response in the past. So simply, the term ‘drowning’ refers to any impairment caused by being submersed in a liquid or immersed in a liquid. And, in both of our countries, it's a very common cause of injury and mortality.

Can you take us through briefly some of the emerging information about that situation, starting from how to get the person out of the water?

Yeah, so there's a few principles, particularly when the water's a bit cooler. One of them being the removal from the water is ideally done with a patient in a horizontal position. It's quite common to see a sort of circulatory collapse if someone has been in the water for some time and is lifted out vertically, as they pool all their blood into their boots as they get pulled out. And so removing someone from the water horizontally is a good thing to think about where that's practical. And then again, much like hypothermia and now hyperthermia, it's about the practicalities of assessing someone who's in a drowned state and the difficulty that can come with that to discern exactly how unwell they are. They can often appear dead or near dead, but again, good resuscitation can help these patients. And so the guidelines really focused on taking that bit longer to assess people and to then optimising the ways that CPR is conducted to give the patient the best chance of survival.

And resuscitation for people who have drowned is often under less-than-ideal conditions on a slippery beach or side of a river or something. How much should we be thinking about things like cervical spine injury, which I guess can impede resuscitation attempts if we have to consider it too much?

A common fear I think of particularly lay rescuers where that's being bandied around in the onlooking crowd. But again, it's about considering that mechanism of injury but not delaying or impeding resuscitation effort if it's because of it. That injury occurs at the moment of impact. And if you can remove the patient from the water in a reasonably horizontal position just with manual in-line stabilisation, that's enough to then make sure that you commence good CPR on them.

And we move finally now to electrical injury. And of course in the wilderness, this is largely going to be lightning strikes. Although, I guess increasingly with people out camping with all sorts of powerful batteries, charging their fridge etc., there are also opportunities for DC and AC electrical injuries. Talk me through what's new in lightning strikes.

Yes, Justin, a little bit more common than you would think. Our stats show that over 100 people are injured by lightning in Australia every year. And about 5 to 10 deaths occur, with a high number of injuries actually resulting from simply the use of landlines during thunderstorms, the landlines being sort of a conductor in themselves. And then again, that clinical presentation after lightning strike can be quite varied. Patients who are unconscious can seem quite unwell and can seem deceased. You can get pupil dilation. So fixed dilated pupils in a transient time after lighting strikes. The patient can appear dead, but actually what we promote is a prolonged period of resuscitation.

Just taking it back to that prevention, and I'm asking a silly question on behalf of any of my silly listeners who also don't know the answer: logically thinking, using a mobile phone could not possibly increase your risk in any way out bush, is that right?

I think that there's some evidence that it can, Justin. So I think it's just those metal components acting as conductors.

Okay.

What we say is just sort of being aware of the types of metal things you have in your hand. Even things like jewelry or rings can create burns where those metal pieces are. It's just really having a think about what might place you slightly more at risk.

Okay, and everyone for a long time has known that if you're in a field with one tree, you don't go and shelter under the tree. Is there any particular advice about what to do, where to shelter in certain situations?

Certainly inside buildings is a good option. Traditionally people have thought that tents might be a good option, but the metal poles in tents can be quite a conductor, and simple wooden shelters like basic huts can also be not particularly good protection. Hard topped cars are good protection. Being inside buildings is good. And then we talk about the lightning position, which is if you are caught in the open, that really minimal contact with the ground as possible. So sitting on a pack or even a dry rope or an insulated foam mat or something, and the smallest amount of contact with the ground as you can is the key to that.

I think that's been a fascinating run through all sorts of perils that can happen to us when we're out bush, and I do remind our listeners, and I'm sure most are on board already, that of course this isn't to scare us away from spending time in the wilderness. But in fact, to just make us a bit safer while we're out there, because I'm sure both you and I would strongly encourage the physical, mental and spiritual health effects of spending time out bush.

Yeah absolutely, Justin. And I think when these events happen in the wilderness, they are rare events, and the majority of people really enjoy their time in the wilderness and don't have catastrophic problems occurring. But why the Therapeutic Guidelines are focused on some of the points around prevention and preparation is to ensure that, in the unlikely event that these issues occur, that you're best prepared to manage them.

Charmaine Tate, it's been a pleasure talking to you on this Australian Prescriber podcast. Thanks very much.

Thanks, Justin.

[Music]

My guests’ views are their own and don’t represent Australian Prescriber and my views are certainly all mine.