Computer generated transcript

Warning!
The following transcript was generated automatically from the content and has not been checked or corrected manually.

So what I'm going to talk about is some about chemical weapons in particular. And then I'll briefly talk about biological, radiological and nuclear weapons and I'm going to concentrate on chemical weapons that have been used in the recent past, predominantly in the Middle East. A very small bit of history of these weapons. Um, the key thing is that quite a few countries had very large supplies of chemical weapons. So Russia in particular had 40,000 tons of chemical weapons which were predominantly the nerve agent, Sarin Sloman and VX, but they also had around 8000 tons of blister agents such as mustard and some phosgene. Um And although Russia had said that they had destroyed all of these, these weapons, these legacy stores, there was an article in the Washington Post in March this year, uh citing uh U S officials who believe that Russia still has on an ongoing research problem. Sorry, an ongoing research program into chemical weapons. Um, and also has the capacity to make large quantities of particular chemical weapons very quickly. Um, chemical weapons have been used extensively around the world in various different places since World War one. Um the key thing about them is that they are not desperately effective against military populations who are protected by having the correct protective equipment such as gas masks or respirators. Um, the mortality rate when gas weapons were used in the first world war was about 10%. So most people affected did not die from them, particularly soldiers, if they were issued gas masks and other PPE they would not be killed, they might get some relatively minor effect, um, use of chemical weapons. And this continued through the Iran Iraq war. Um, the key thing here being that this was predominantly trench warfare. Um, and the Iraqis used chemical weapons to negate the numerical superiority of the Iranians. Um, there were somewhere in the region of 20,000 fatalities during this war from chemical weapons with about 34,000 veterans with chronic ill health effects afterwards, predominantly from masters. And then, of course, um, Saddam Hussein used chemical weapons against his Kurdish population in Halabja in 1988. Um, and this was a combination of several different chemical weapons used against a civilian population with large number of fatalities, somewhere between seven and 10,000 fatalities, um, fairly well documented, um, with the video evidence, etcetera been fairly grim, grim viewing. Um, it's not just states involved in wars that can use chemical weapons because some of them are things that you can make, uh, if you're a terrorist organization and there's a cult in Japan called um she Enrico who released Sarin on the city metro in Tokyo with about I think 12 fatalities, 50 people poison, but several 1000 people presenting to hospital with various symptoms. Um that said it's not that easy to make things like sarin, but you can do it if you've got a lot of money and clearly states that have expertise in this can make things like this reasonably easily. The things to know about the nerve agents such as sarin is that they work by binding Covalin tely to acetylcholinesterase. Um inactivating this enzyme, which is the one that breaks down acetylcholine. Um And then the acetylcholine builds up in the receptors in the CNS and that muscular nicotinic receptors. Um The longer that this is left without an antidote, the more um more permanent bond with the enzyme becomes um the antidotes to nerve agents is an oxen drug like pralidoxime or various other oxygen's. Um We believe that those are effective in military or terrorist poisonings based on animal work and stuff from the Iran Iraq war. Um The toxic drome is very characteristic. Um And those, those of you who have worked in emergency departments will have seen toxic drome. So they kind of particular combination of symptoms and signs from particular poisonings. And this one is very characteristic because the patient's will get a my osis. So they'll get constricted pupils with blurred vision. They tend to be very bradycardic. They get bronco spasm and wheeze profuse respiratory secretions and sweating. Um They also get vomiting, involuntary urination and defecation and then eventually get CNS effects including seizures. So confusion, first of all, hallucinations, seizures, paralysis and then eventually death for respiratory failure. I'm going to show you a veterinary video of a of a nerve agent poisoning. This is a nerve agent sector side. Um and what this shows is a dog who's ingest, it's a nerve agent and what it's got is generalized fasciculation in. So you can see the dogs muscles twitching all over. There are very few good videos of this in humans and I will show you one in a moment. This is very characteristic. I think of nerve agent poisoning. There aren't any other. Um Well, there aren't many conditions where you get generalized for circulation that goes on. This is, this is a video of another nerve agent type insecticide poisoning from the New England Journal of Medicine reproduced with permission from the author and it shows such child who's who's been exposed to a nerve agent type insecticide. Um And you can see he's got tongue for circulation. Um and that's something you don't see in in internal medicine practice. Um He's also got a face for circulation and they're just showing that it got better when he got treated. And then I'm going to show you a video of nerve agent poisoning um from Syria suburb of uh offer Batna uh shows a bearded man convulsing on the ground. This is a quick video clip video. Number eight uh shot outside Mu Adamia outside Damascus appears to show a man frothing at the mouth. Again, the intelligence committee, the senators were told by the intelligence community that these have been verified and they're show the symptoms of a chemical weapons attempt. Video number nine of the 13 shown to members of the senate members of the household. So one of those videos showed was patient's who are having seizures frothing at the mouth, which is is apparently a characteristic feature of these kind of chemical weapons um unconsciousness. Um and I think the child at the end has probably got some broncho spasm and probably incipient respiratory failure. So in terms of management of these conditions, I think the first thing is to recognize that this is what's going on and there are things that you wouldn't particularly expect to see in trauma. So the very small pupils would be unusual in trauma. Patient's. Uh the fasciculation would be extremely unusual. Um Many of our patients are a bit sweaty, but it would be very unusual for them to be bradycardic unless they have exsanguinated under about tell the cardio cardio respiratory arrest. Um So those are the clues, I think particularly things like fasciculation, small pupils, multiple patient's with the same symptoms um would be very suspicious of a nerve agent use. Um The management of nerve agent poisoning. The first thing is to remove the patient's clothing and that will get rid of about 90% of most agents. So for agents like siren, which has a similar consistency to gasoline or petrol, most of that will evaporate if the weather's warm enough and if you remove the patient's close, it will get rid of nearly all of it. Um I'll talk a bit more about decontamination in the moment. So the mainstay of treatment of these patient's is the administration of atropine, which gets rid of the muscular nick effects of the the agent and you give atropine until the heart rate rises above about 90 BPM and the secretions dry up. Um The next thing, the other thing is to say is that the doses of atropine required may be very high. So we potentially talking about 10 to 20 mg of atropine in the 1st 24 hours after exposure. And some patients may need as much as 50 mg of atropine. That's um an order of magnitude more than we would normally give. So for patient's who had a card had a cardiac arrest in a sisterly, then that maximum days of atropine we would usually give would be about 3 mg. So nerve agent patient's are potentially going to need 10 times that um the other thing that the patient needs to get is the antidote, oxy, um antidote. Um And there are auto injectors available, could combine pens that contain atropine, uh nerve agent antidote and some of the combi pencils to have better Diastat peons in them to treat the CNS effects. Um This is something that has to be planned for in advance because the normal atropine vials that you get only have about 400 micrograms in them. If you're going to have to administer tens of milligrams, you need to have special um either multidose vials or vials at a much larger days of atropine in them. Um So the key things for nerve agent poisoning, decontamination, removing the clothing will do most of that. And we'll talk more about wet and dry decontamination in the moment. The anti date which is pralidoxime atropine given um in an escalating does into with the bradycardia and secretions are reversed and then Benzodiazepines are used for sieged as if required. Talk briefly about chlorine. Chlorine was used extensively in the first world War did not cause very many fatalities. But the key thing about chlorine is that it is not a banned chemical under the chemical weapons conventions and it's easily available in many industrial areas. So it can be released by accidental or deliberate artillery strikes on chemical factories. But also people can physically remove uh 500 kg tanks of chlorine, drive them on the back of a lorry to a populated area and explode them. Um They can also make things like barrel bombs which were used in Syria repeatedly against the civilian population. Basically, these would dropped from helicopters and released chlorine predominantly weapon of terror. Uh doesn't necessarily cause a large number of fatalities extremely upsetting um for, for civilian and military populations. The literature on chlorine, there's not a huge amount there from recent years, not much evidence based to, to know how to treat it. Um The key thing about chlorine is that when it's inhaled. So the first thing is that when it hits the mucous membranes and the eyes, the chlorine turns into high um turns into hydrochloric acid and Hipaa Cloris acid. Um It's a very severe irritant. So, patient's get red streaming eyes, nasal congestion, cough, chest pain, and in severe poisonings, they can get pulmonary edema either reasonably quickly or a few hours after exposure. Um there is very little evidence as to what one should do other than supportive treatment. There is some suggestion from animal models that steroids might be helpful in this lung injury. I wouldn't say that there's any certainty about that. Um Chlorine because it's a gas, it doesn't, doesn't need much in the way of decontamination. Uh Most of it should just blow away fairly quickly, but removing the patient's clothing would seem sensible just to make sure there isn't any residual chlorine clinging to their clothing when they get to the hospital. So the supportive care removal from exposure, key thing probably is that that there is there was a lot of mustard agent around in various parts of the world in various legacy stockpiles. Um it has been encountered in the Middle East in old artillery shells that have been repurposed as improvised explosive devices or shells that people have found and moved around without realizing what was in them and then been exposed. The, the effect of mustard exposure is basically um those dependent and dependent on the length of the contact time with it as well. So in mild exposures, people will just get a bit of erythema that develops a few hours after exposure in more severe exposures or more prolonged exposure's where they've had a bigger does, they'll get severe blistering. Um The this this can happen fairly quickly within a couple of hours if they've been exposed to large to those or can be delayed with 12 or 24 hours. It's complicated by the fact that mustard is an alkylating agent. So it has a delayed effect that causes bone marrow suppression. Um So somewhere around 2 to 3 weeks after exposure, the patient's will get significant neutropenia and other parts of the bone marrow will stop working there, potentially going to get any anemia and thrombocytopenia as well. Um Literature from the first World War suggests if someone has more than about 20 to 25% body surface area exposure, then they've got a high chance of dying. I think that might not be true with current treatments um that we use for oncology. Patient's like colony stimulating factors and so on. Um Treatment is generally supportive in very significant burns that it may be necessary to treat this like a thermal burn with debridement and skin grafting and so on. Um Many of these blisters will recover with relatively little scarring and that includes the eye injuries. So patient's kind of very prolonged corneal ulceration, but it's quite rare for patient's to be blinded by this. There's a picture from the first World War of someone who's recovered showing that his skin is actually not too bad, apart from some pigmentation and so on. So mastered, the key thing about mastered decontamination is that the mustard is incorporated into the skin within two or three minutes of exposures. It's quite difficult to decontaminate very quickly. Um predominantly supportive care similar to that of burn. Patient's based on the body surface area affected and deeper deeper mustard burns should be treated as per thermal burns. But with the added complication that two or three weeks after exposure, the patient may get by marrow failure. There's a whole long list of other chemical agents, including things like phosgene that cause severe lung injury, hydrogen cyanide, which is a mitochondrial poison, other vesicants and then a very long list of toxic industrial chemicals. For most of those, the management is supportive with supplemental oxygen, critical care involvement, etcetera as required. There are some specific antidotes to hydrogen cyanide um where you can use um sodium Thiosulfate and hydroxocobalamin. Uh and there are antidotes against lewisite. Um with stuff called British anti lewisite, which has got another name as a chelating agent. Um, so the key thing about these other chemical agents that is that usually certainly most parts of Europe, the regional fire service will have the technology to identify what the agent is. If it's an industrial site that's been bombed accidentally or on purpose, there should be, um, local, local authorities should have a list of which chemicals were stored there. Um You should be able to work it out, but the key thing is going to be supportive care. Um There's a whole load of other stuff that we practice and hope never to have to use like exercising the major incident, training in your local hospital, fire service, emergency services and so on thinking about decontamination, preparing for things like nerve agent that do have specific antidotes and making sure that those antidotes are available in your regional health services. Um And I'll talk a wee bit about decontamination. So the main thing about decontamination is it's fairly simple to do 90% of most contaminants we will be removed by removing the patient's clothing. Um This reduces the risk of introducing a chemical agent into your hospital and contaminating your emergency department in the in the UK and many other parts of Europe, we use wet decontamination with the fire service who have some pop up tents and showers essentially that can be done very simply just using by the fire service using a hose and just hosing people down. The problem with that. Of course, is that for most of the year in many parts of Europe, the patient's will then get hypothermic as soon as you make them wet, um, dr decontamination. So what, that's a military wet decontamination facility which has a conveyor belt for injured patient's with people in chemical warfare suits, um, carrying out the decontamination, cutting the patient's out of their clothes, giving them any immediately life saving treatment that they need. So tourniquets, um antidotes and so on and then passing them through to a medical facility. Once they've been decontaminated, dry, decontamination is very similar to the patient's clothes are removed and then they're decontaminated using Fuller's earth, which is a kind of powdered clay that is very absorbent of, of the chemical agents will remove them. There's more information available from a supplement to critical care medicine which was published about nearly nearly 20 years ago, but it's still very relevant. And then the Centers for Disease Control in the U S published online free information on dealing with most chemical agents, biological agents. I'm not going to talk a lot about this because I don't think it is particularly relevant. The key thing is that if you have outbreaks of things that are meant to not be around anymore like smallpox virus, um It raises the question of whether this is a, is a deliberate release and we know that in the past various countries including Russia had active bioweapons programs that involved things like smallpox, um tularemia, etcetera, etcetera. The other thing to think about is if you, if you start to get outbreaks of unusual pneumonias or things like that, that turn out to be resistant to antibiotics, that would raise the question of whether this is a deliberate release of a biological agent, there's biological toxins as well. There's a big long list of them including things like rice in various staphylococcal toxins and so on. And these I think are somewhat difficult to deliver on a large scale to um you know, if you're in an attack on a military population or a civilian population. But these are available in theory, at least most of them supportive management, they tend to cause severe problems with the acute lung injury or rising, for example, would cause a sepsis like serves like syndrome with protein synthesis failure, diarrhea, renal failure, multi organ failure, and so on. And there are some specific antidotes available to some of these agents. I wasn't really going to talk very much about nuclear explosions. Other than to say that if, if someone sets off a tactical nuclear weapon in your city, you would expect 100,000 deaths immediately and 100,000 injured patient's um at which point, the provision of advanced medical care becomes more or less an afterthought and most doctors will be involved in managing large numbers of refugees and preventing cholera outbreaks and things like that rather than having the capacity to treat patient's. The other thing of course is that the infrastructure, wherever the nuclear explosions happened tends to get destroyed. Um what was expected to get destroyed. So there won't be any functioning hospitals anywhere near the, wherever the bomb has gone off, there's a useful resource available which is the National Health Service, um emergency preparedness and response guide. So if you Google NHS E P R R, it will bring up this document which is freely available and it has eight memoirs on various different kinds of injuries of warfare. So it's got things like chemical weapons and so on. And it and also for hospitals that are in areas that haven't been affected previously. This may be helpful just to familiarize people with the kind of injuries they might see. The key thing about it is it's an aide memoire. So it's got one side of one side of paper that will tell you the things you need to do when the patient is in front of you.