OK, welcome everybody. Thank you very much to the webinar vet, Anthony and Dawn and all the team for inviting me to do another webinar for them. Getting used to this now during lockdown, one day we'll all be meeting again, I'm sure, but for now, we're doing more, content online.

So, welcome again, and today we're gonna be talking about sedation and anaesthesia techniques for equine dentistry. So we gonna kick right off. And I'm gonna start by saying that, you know, good, good dentistry requires good anaesthesia, and the two are intricately linked, and we use some form of anaesthesia for all of, all of our dentistry.

We don't do any dentistry without some form of anaesthesia. So anaesthesia technically includes sedation, local and regional anaesthesia, and it does also include general anaesthesia, but. We haven't done a general anaesthetic now for any dental or referral case for, I think.

9 years now, perhaps 10 years. So it's been a long time, not saying that we won't ever do one again, but it does seem to be extremely unlikely or extremely unusual to require general aesthetic, with modern techniques and modern local and regional techniques that we have. And here's Nicky just doing some routine rasping.

I'm gonna turn the sound off. But you'll see Nikki here rasping, and the horse is lightly sedated. Everything, everything's going really well, Nicky's sat down, very comfortable.

You can work like this all day long, and so, you know, we don't do any dentistry without some form of, of sedation or anaesthesia. And you can see this horse only lightly sedated. We're gonna, we're gonna talk about sedation in detail in a moment.

But I think it, you know, for good veterinary dentistry in the way that we want to approach, the horse's mouth, and we want to examine, and we want to grasp and, you know, maintain that horse's mouth to the absolute optimum, we're going to need to do sedation to examine properly and to treat everything that needs treating. And there's no doubt, you know, good anaesthesia means that you can perform better dentistry, and, you know, the, the modern techniques that we're doing now, here we're doing an endodontic procedure on a 110. And for, for all sorts of reasons, you know, unless the anaesthesia, the sedation and the local anaesthesia and everything else is really good, you, you really won't have a chance of even beginning to try and do procedures like this.

I just play that video again and you'll. Not that the tongue is not moving at all. And sometimes when we post these videos online, people say, oh, is that, is that a cadaver?

And we say, no, no, no, no, it's it's just a sedated horse and there should be no tongue movement. And I'm going to talk in a minute about how you reach that point, or how you, how you achieve that, so that you can sedate your horses to the point where the tongue isn't moving, but they don't fall over, which is always good. So we've got to get into this level, and you know, the techniques and the instrumentation that we're using nowadays is, is so advanced, here we're using a reciprocating, flexible file, to perform an endedontic procedure.

And, you know, we, we're gonna need, we, for all of these things, we need good sedation, we need good local and regional anaesthesia, especially when we're dealing with, with the pulp and painful areas. And here's another example of a good balanced anaesthesia. We're doing a sinus sinus flap.

We've already extracted a tooth, and now flushing some solid in specsated pus from the rustral and ventralcoal sinuses. And you can see the horse's ears moving again, this is not a cadaver. This is just a well sedated and well anaesthetized horse, so very good local and regional anaesthesia, and the horse really not feeling anything.

You get the occasional twitch just to demonstrate that it is actually alive, but beyond that, the horse is very comfortable indeed, and it, it still amazes me that the range of procedures that we can do on the horses under local and regional anaesthesia, and I really don't think there's any. Need for doing general anaesthesia in any cases like this, and there's so many advantages to doing these cases standing. OK, so let's talk about sedative choices.

I don't really need to go into great detail about what sedatives are available. I'm sure you're all very aware about alpha 2s and all sorts of things, and some medics out there probably know a lot more than I do about them. But I, you know, this is, this is the mainstay, noticed abroad, it's called Dorma Eden.

I've always wondered why abroad they call it Dorm and not Dom. And, we of course got lots of different makes over here. We use Diomidine more than any other, to be perfectly honest, but for 7 years, or for 10 years, when I started doing referrals from sort of 2006 to, well, 1st 8 years anyway, I used, remiphidine, Sedibet, and I was really happy with it, and, and for various reasons.

Mostly I got a better deal when I started my own business on, some Diomidine, so I, I switched to Diomidine and . Got used to it, so I think it's really what you get used to, and I, I think that's a real take home message is, you know, if you go to a conference and someone says, oh well I use this combination, just be careful about going back and trying that on the next difficult case that you have. I, I think you're much better to just get really used to one particular technique and have the others available, but the more you use one specific technique or method or combination.

The more you will learn to read the signs of the horses, and know, where you are, with that sedation. So we know about alpha 2s, they have this ceiling of effects. So, you get, you do eventually get to a point where you can increase the dose, but actually you don't really increase the depth of sedation much more.

And we do recommend a a continuous rate infusion for anything that's gonna be prolonged for about half an hour. We're actually starting to do a little study on this, . But at the moment, we pretty much do continuous rate infusions to anything, that goes over 30 minutes there thereabouts.

I put the doses on there, you can, you can pause the presentation and, and look at the dosages. So there's some more dosages there, for you. I'm not gonna go through those, just a bit of a waste of time.

And then most of us will be aware that we're gonna be combining those with an opioid. And of course, most of the time we'll use good old Borphenol. But there are, of course, others.

Morphine and buprenorphine would be the most common other ones that have been used. But, there's been some interesting, studies on buprenorphine. Although it, it looks very good on paper, it has been shown to have significant psychomotor effects post-procedure.

It's been a, it was a nice study. I'm sorry, I haven't got the link. But, there was a nice presentation as well that we saw a few years ago at one of the conferences showing the, aftereffects and this sort of box walking and, and, and really quite stressed horses in the postoperative period.

So, I must admit, 95% of the time we would use Borphenol. And once again, I think that whatever you use, it's fine. If your preference is morphine, that's fine, but I think you really want to try and stick to the same combination and get used to it.

A little word on aromazine, I used to use a lot of ACP, use it, I must admit, very, very little these days, but we do use it occasionally on horses which arrive at the clinic very excited, if owners say that it's a particularly stressy horse or something that's got very sweated up in the box. Sometimes we'll just pop the horse in the stable, a small dose of of aromazine. And I think that that can really help to calm them down.

So I think that's a really important thing when you're starting any advanced procedure, or really any procedure, is to have the horse in a nice calm state before you start. So there's absolutely nothing wrong. Pop it in the box, even get the horse in the night before, and get it used to its surroundings and get it settled.

There's, there's really nothing worse than having a horse jump off the back of a lorry with its eyes on stalks and then expect it to just bring it straight in and start a difficult process. Procedure, you're sort of starting with without all the odds stacked in your favour and that's, you know, critical for any of these dental procedures. There are some drawbacks with ACP of course, and everybody would be aware of this sort of chronic or long, long-lasting parahimosis, penile prolapse.

And I'll just draw your attention to this very wide ranging huge study that was done some years ago now. That demonstrated that actually there's no increased risk in stallions over geldings, so the risk is in any male horse. It's very low risk, and they had 3 out of 8000, anaesthetic or 500 of those that had received ACP.

And they had irreversible parahimosis and required surgery. And of course, for gelding, that's not too much of a disaster, but for a breeding stin, it would not be great. So this does put some people off, but it is incredibly, incredibly low risk.

And I wouldn't hesitate to use it, in, in cases where I felt there was a benefit if the horse was very excited, but I must admit we do not use it routinely. So we use a good old alpha 2 + opioid and I have to admit we just use domidine and brophenol for 95 to 98% of our procedures. This is a little, sorry about all the wordy slides, but this is a little bit of text about the supposed or proposed.

Excitatory effects with the opioid, and a lot of people will blame the sort of twitching that you get during sedation on the opioid. Well, I don't know for definite whether it's the opioid or not. All I can tell you is that.

This twitching seems to be particularly bad with older horses and with some individual patients, but for the most part, for the vast majority of horses, it will settle down once the dosage of sedation increases. And there have been a couple of studies showing that actually it happens just with alpha 2s and alpha-twos with the opioid, and there was no difference in this particular study in 2012. There's no, no difference in the trembling and twitching, with the combination or with just the alpha 2 on its own.

ACP does seem to reduce it a little bit, but do be very careful in the older horses because the hemodynamic effects can result in the horse becoming very attaxic or even sort of lying down. I wouldn't call it falling over as such, but they just tend to just, become really unstable with, with the ACP as well. OK, so I'm just gonna talk about actual dosages now and again, you can just pause this, if you're watching us back and just write this down, but I'm gonna, I'm gonna move on to some really simple ways of doing it.

This is kind of a sort of textbook thing, good to Tomaine first. And then pop in your IV catheter, prep for regional anaesthesia, whatever you need to do, and then 10 minutes later, give the morphine or butterphenol, give your non-steroidal anti-inflammatory, do your nerve block, set up your CRI and get that running, . That's fine.

We, we'll pretty much mix domidine or alpha 2 plus the, opioid in the same syringe. I don't see a problem with that. I must admit, if we're using morphine, we do often wait 10 minutes and give the morphine 10 minutes, after the alpha 2.

But with Borphenol, we do just always mix the two in the same syringe, and haven't seemed to notice really any problem with that at all. But I would recommend, give the Alpha 2 a chance to work before you start stimulating the horse. So, I would, I would advise against just injecting your Alpha 2 combination and then immediately popping on the gag and opening up and fiddling around.

I think you really want to give the horse some good time to, to relax and settle down. Always remember the very first I went, time I went to visit, Thorbjorn Lundstrom, who, of course, does a lot of endodontics. He, he, he was really particular about this, and he would give his, he, he would give one.

10 milligrammes of ditomidine, and then just go and sit down in the other room and read the paper, and, look out the window for a bit, for 10 minutes or 15 minutes. It wouldn't touch the horse, wouldn't even be in the same room as it. And it would just settle down really nicely.

So, that's a good tip to give it some time to work. Always sedate your horse before it comes into the stocks I can't stress this enough. So this is Jess, and she's just waiting outside.

I've already injected this horse, and we would start, we always give the same dose of dittoidine as buorphenol, alpha 2, and opioid here. It just, it keeps it easy. It makes, it, it avoids any sort of difficulties of calculating doses.

So we very often start for an average sized horse, we'll nearly always start with 0.7, 0.7, given IV.

And then we'll just leave the horse standing outside the clinic for a few minutes and just until the head starts to go down, we can have a little chat to the owner. If the owner's there at the moment, we're all distancing and we don't have owners in the clinic. So, Jess is just there waiting for it to come in.

And the number of practises I go to doing referrals, and, They, you know, nothing wrong. The practise want to do the sedation, that's totally fine. But the number of times they bring the horse into the stocks or they have difficulty getting it in through the door, and there's someone bashing it with a broom and, and pushing it up the backside, and they can't get it in, and eventually, by the time it gets in, it hits the bar at the front and runs back out, bangs its head on the roof.

And now you have a stressed horse, and you can completely avoid that by. Always sedating your horse initially before it comes into the room, and, and, and, and it's such a simple tip, and it, it makes everything so much easier. I always question why people don't do that.

And then we would just top up to effect of dosages of about 0.2 to 0.3, not 3 mil, sorry, a little mistake there in the text.

Top up to effect using 0.2 to 0.3, of each.

To effect, sort of, you know, minimum of sort of 5, 10 minutes in between dosages. And once you feel the horses at the right level, then you begin your continuous rate infusion. So actually what you're doing is you're kind of giving bonuses.

As you would for general anaesthesia, so if you imagine general anaesthesia, you give a big bolus. In order for the horse to go to sleep, and once you're happy with the depth of the anaesthesia, then you start on the gaseous anaesthesia to maintain it. And that's exactly how I view a continuous rate infusion.

The bonuses are to get the horse to sleep, and the CRI is to keep the horse asleep. In some very fractious horses with conditions such as this really nasty mandibular abscess here from a a fractured lower 10, 310, this degree of pain, even with a nerve block and and good sedation, you do sometimes find that they just still seem to be sensitive. And in these cases, I think that they can become difficult to sedate, they become very fractious.

I think they're already on a, on a, a sort of a, a knife edge, before they start. And there's even some cases where we see a kind of a wind-up syndrome where the sedation just doesn't seem to work. In those cases, you're better off just to pop the horse back in the stable, let it calm down, perhaps try again the following day using some aceromazine.

Make sure a nerve block is working, that's absolutely key. I think a lot of cases have failed extractions where people say the horse was impossible. I think a lot of those are that the nerve block probably didn't work, and, and I'll often do those procedures and we'll pop the nerve block in, and that everything's fine.

And if it happens to me, my nurses are very good at saying, oh, Chris, would you like to repeat the nerve block? And they'll just lay everything out for me to do the nerve block again, because they know if the horse is moving its head when I'm touching things. And it's uncomfortable, it's probably that the nerve block hasn't worked.

But you do get the odd really fractious source, and I think in those cases you can consider an alternative alpha 2, so just switch to remiphidine, for example, or switch todomidine if you've used ramiphidine, or even use combinations, add some xylazine into the mix. Add some ramiphidine, and I, I, I've sat in some presentations recently where clinicians routinely use all three, you know, xylazine, remiphidine and domidine in the same CRI in the in the same mixture. I don't do that, but I, I think that there's, you know, there's no reason that you shouldn't try this, especially in horses where for some reason the sedative combination you're using doesn't seem to be working.

OK, so what I've got here, just check how we're doing on time, I don't want to run over. What I've got here is I've got a little chart now, just bear with me a little bit, again, apologies for the text. .

Now, on the right we have a graph, and on the X axis we have time, and on the Y axis, I want you to imagine this is the depth of sedation. Ignore the numbers, it's they're just arbitrary figures. The depth of sedation is on the Y axis and time is on the x axis, and as we progress along to the right, the depth of sedation increases if you've given a bolus.

So let's say we've given a bolus down here, 0, it's 0.7.7.

Then 5 minutes later we've topped up again, maybe we noticed a little bit of twitching of the ears and the level wasn't quite deep enough. And then we get to here and the initial dose is starting to wear off and we might give another dose to sort of supplement it and then and and then we go on. And you want to try, and then we're gonna try and keep the horse roughly at the same level as things progress.

So we may start the CRI for example, at this point here, and then we may adjust it up and down and our depth of sedation will, will sort of go up and down, but we want to try and keep the level of sedation at approximately the right level by running that CRI at. The required effect. And that's a little bit of a, you know, you, you learn, those of you who've been doing a lot of dentistry will know how this works, but you'll notice the tongue starting to move, or the ears beginning to twitch, or the horse looking around, or maybe a bit more movement.

And they come to movement in that in a minute. And we're gonna try and, so we're gonna try and keep the sedation roughly, and here in the arbitrary figures sort of in between the 8 and the 12. So I've put here a green line, this is our working level.

And when I say working level, once the sedation is above this line. The tongue movement stops. It just stops, and the horse relaxes and everything is, everything is great.

As soon as the sedation drops below that level, so in this little area here, you will notice the tongue starts to move, maybe the horse starts to chew a little bit on the gag. The ears, it might even vocalise, the ears might twitch or the ears are sort of looking around as it were. You'll notice something that signifies that you'll no longer have the sedation at the required level.

So it's got to stay above this line and you're gonna have to work out for each different patient what that depth is. But you will notice a specific point, and it is a depth of sedation, that's all it is, there's no magic to stopping the tongue moving. It is just a depth of sedation.

Once you get beyond that, the tongue will just stop moving. I think what happens is a lot of people never get to that point because they're very worried that the horse is going to go beyond this profound excessive sedation zone where actually a lot of patients will become excessively attaxic and lean very hard onto the corner of the stocks, for example. So it's this kind of, it's kind of keeping the horse in this working zone that I think people find difficult.

And I think one of the problems with that, is, is, is young horse, old horse, painful horse, etc. Nerve block not worked, all the rest of it. All of these things will influence how narrow or how wide that zone is.

So this zone between the green line and the red line will become wider if you have a young horse and some, for example, cold blooded breeds. So if you have a young, big boned warm blood, for example, you will find that this working zone is much wider and that you reach it at a much earlier level. Unfortunately, if we have a very old horse.

If we have any anything beyond sort of 1819, 20, especially sort of thoroughbreds, for example, you find that this working zone is very narrow, and you may find that, as we have on this graph here, we may not even properly get into that zone, you have to get the the dosage a lot higher. But you risk, getting into this sort of profound sedation zone, and the owner starts getting very nervous, and the horse might start sinking back down onto its hocks as these older ones do sometimes, and it can all become a bit more difficult because that zone becomes very narrow. And the tongue movement just doesn't seem to stop.

And as, as you get to a 30 year old horse, as you'll know, it becomes almost impossible because they just don't seem to, have that same working zone. I think another thing that causes some problems and confusions is the ataxia, and the trembling, and the jerky head movements that we see at the beginning of sedation. And I liken this to a kind of induction phase, and I think it's a little bit like stages of anaesthesia.

You know, we've all taught at university that one of the first stages of anaesthesia is actually sort of movement and trembling and vocalisation. It's just that when you give a bolus of anaesthetic. The animal goes through those phases very quickly.

You've all seen animals coming around from anaesthesia, where they go back through the phases very slowly, so they will vocalise, they'll tremble, they'll shake, and that is the process of the very light phase of anaesthesia. And it's the same with sedation while horses are going to sleep during the sort of induction phase, if you like, they will do a lot of ataxia, trembling, move the legs around, can't quite find the position, and twitching of the head is, is very common during this phase, and you must not mistake that with the horse being too sleepy. I think that is something I've noticed that people are a little bit less experienced with sedation.

Will fall into this trap of thinking that actually the horse is too, too, too fast asleep or too deep under sedation, and therefore they reduce the dose or do not top up at the required time, and therefore they never actually get the horse into the working zone. But this ataxic phase will last for about 10 to 15 minutes. Sometimes longer, and then you will reach this blue line here and you'll suddenly get your eureka moment.

The horse is relaxed, the horse is quiet, the tongue stops moving, you're in this working zone. Everything's great, your CRI's running, your nerve block's working. Now you can perform your procedure.

As long as you keep the horse within this zone, you can get your procedure done in in quick, sharp time because if you're doing an extraction of a cheek tooth, for example, and the horse can't feel it and you're in this working zone, it is just like operating on a cadaver, and I always say that if you get everything right, it should be just like operating on a cadaver. And as I say, there's no magic secret, it's just finding this working zone and getting your. Other methods of anaesthesia, right.

For young horses, it said that zone is a lot wider, so it's a lot easier, but you will still have this initial phase of ataxia. With the older horses or with really painful cases, unfortunately the sort of ataxic phase can last a lot longer in the sort of induction phase, and you're going to have to get the sedation a lot deeper. So for all of this phase here, the sedation's not deep enough.

We're not into the working zone, so the horse will still really be twitching. As it gets higher, you may find you come out of it, but you will go back into it once the sedation drops. So.

I must admit they are particularly challenging, and I often say to clients, if I'm dealing, for example, with a painful condition, severe diastoata and periodontal disease in a in an old horse, I will say to the client, look, I'm I'm going to get the sedation really quite deep, and I'm going to work as quickly as I can. I'm not going to be talking to you very much during the procedure. I'm not going to be showing you all the ins and outs on the oroscope.

I'm just gonna get the procedure done super fast, and then I'll talk you through it at the end. So that's my approach for those ones. If you just can't inject a horse at all, get near it, etc.

Then I'm gonna put, I've put this up. This is the Liverpool University Maggi Mix formula, and I have to say it's, it's brilliant. The original one was ACP alpha 2, and opiate, and the original one that I always used was ACP.

Diomidine and morphine mixed in a syringe and given intramuscularly. You can use domidine buttrophenol and ACP. Yeah, I mean, of course, you can just use din buorphennil, I am, that's no problem.

But that original combination with the morphine, I have to say, does work extremely well. Remember, if you use remiphidine, I don't know about Xylazine, actually, I've never done it with Xylazine. I think they mix OK.

But remiphidine definitely does not mix with ACP. It forms a precipitate, and you would not want to inject that intramuscularly. OK, so now we're gonna move on to local anaesthesia, and really whatever procedure you're gonna be doing, for horses, you want to be thinking about some form of local or regional anaesthesia.

This is absolutely key. The only way we can get these advanced procedures done in the standing horse is, is to supplement our sedation with . A regional or local anaesthesia.

And I, I, I can remember going to a practise not that long ago, actually, which is, quite a big practise, and they were really struggling with the cheek tooth extraction. I happened to be in the room, so I went through to help. And I said, Oh, you know, how long ago did you put the nerve block in?

Because the horse is really feeling the, the tooth. And, and they sort of looked at me and said, Well, isn't that really dangerous to do a maxillary block? You know, we, we, we, we don't tend to do that.

We just rely on sedation. And that's the problem. You can't just rely on sedation.

You really have to add the, regional anaesthesia, and, and, and the risk of the regional anaesthesia is always lower than the risk of general anaesthesia, and all the complications and things involved with that. So don't be afraid. The risks are minimal, and the more you do, the better you get it, the more confident you'll become.

OK, so, different types of local anaesthesia that we have, we've got topical, which we'll mention, we've got intraligamentary or the ligamentous block or periodontal block, periodontal ligament block. Then we've got just papillary, so the papillary is just this, region of the gingiv that sort of comes up in between the teeth. So we call that a gingerival block and just local diffusion.

Actually, that's what they do a lot in humans, especially for maxillary teeth, they'll just inject into your. Palate or gingiva and allow the local anaesthetic to diffuse through the spongy bone, across to your tooth. And it works very well in humans, but obviously it doesn't work so well for big teeth in young horses, in, in horses, so we have to do better than that.

For procedures such as this one, we'll often use intrapulpal. If there is any remnants of vital pulp in here, for example, we can do intrapulp injections of local anaesthesia, and there have been human techniques reported where you do intraosseous or intralesional, and I've done that occasionally, and I'll show you an example in a moment. Topical local anaesthetics, use these all the time.

I think they're really useful. Simple, simple things, lidocaine spray, which is ylocaine, the feline intubation spray that you see here on the right. This can be really effective, for example, if you're, if you're changing a, a, a socket or flushing a dental socket, and it, and the horse is really painful, which they often are, a couple of sprays with this into the socket.

And just wait for 5 minutes or a few minutes and you'll find that the whole procedure is a lot easier. I really, really like using topical anaesthetics. Diastoma, periodontal disease, we use a lot of this oroquix, which is a periodontal gel here at the bottom.

This is ridocaine and lidocaine mixed in a thermosetting matrix. So it starts off being very liquid, but it becomes a lot more viscous once it warms up to body temperature. So it kind of runs down into the peridontium, and it warms up and then it sits there and it has a local effect.

And I find that a real benefit for. For diastoma management. And here we are just using it.

It comes with its own gun, or you can use a normal pressure syringe, which I'll show you in a moment. So I'm just clicking a little bit of this down one side, and just letting it run down there, and then also down it, put that down the other side as well. And just, just reduce the whole sensation, and it just seems to make the whole thing a lot more pleasant.

If you haven't got a dental anaesthetic pressure syringe, and the sealed cartridges of anaesthetic, then you really need to get one if you're doing, any amount of dentistry beyond grasping. Even for wolf teeth extraction, these are just brilliant. So we have a 2.2 for UK or 1.8 mil for Europe, sealed cartridge.

And a small metal, usually they're metal, a pressure syringe and very small needles. These are 27 gauge inch and a half needles, and with these, you can inject really well into gingiva. I remember lecturing many years ago, and I was told by a number of people on the day on this particular course that there's no way you can inject into Gingiva.

And everyone was using sort of 2 mL and 5 mil syringes with a giving set and a butterfly, and it just didn't really work. This is the way to do it, this is the way the humans do it, human dentists do it, and it works brilliantly. And this is how we do a ligamentous block.

So we'll inject, is this a video? No, it's not a video, this is a video. So here's a ligamentous block, and we're just passing the.

Anaesthetic or passing the needle, just bent the needle and and inserting it up into the periodontal ligament and then just injecting 1 to 2 mLs. In humans, when they do this, the anaesthetic works within 15 to 20 seconds. And I can vouch for the fact that this is extremely fast acting when I had to do some a little bit of surgery on an ingrained toenail.

Sorry about that, if that's conjured up a bad image for you. But I had to cut off a little growth that had come out and cut off part of the nail. So I injected a little bit of this and it was numb instantly and I could cut it off and everything.

Please do not repeat that, do not do that at home, because a dentist friend told me that was extremely dangerous because of the adrenaline that's present within a lot of these mixes. So do not do that at home. So, I have given you a warning now.

Here's another example of a ligamentous block. Sometimes you'll find the needles just bend so that, because they're so bendy and friable, but here we go, just that one's bending a little bit, but now I've put it in. Interestingly, you'll see that it's bulging up here, so it may not have quite, I think that's gone subgingival and not up the ligament.

But, you'll find sometimes it just slides up beautifully up the ligament, and you inject, and it, it really, really augments the block very, very well. I've heard some people saying that they don't do nerve blocks anymore since they've started using this technique. I think for any horse, certainly under 15 years of age and, and maybe over than that, I think this is an augmenting technique to your nerve block.

I would not just rely on this. Anything over 15, certainly over 20s, if you're out in the c if you're out of the clinic on the yard and you've got a loose cheek tooth to extract in an older. Horse, then it's brilliant.

Of course, you don't need to do a nerve block in those situations, but I think if you're doing a serious, size tooth extraction in a slightly younger horse, then this is a brilliant technique to augment your block and means that you can start working a lot more quickly, but I would always supplement this with a proper traditional nerve block as well. Here I am doing an intra-alveolar or intraosseous block. This, maxillary, facial swelling from this abscess of the 20107, was quite soft, and actually I was very easily able to inject the needle into this and just deposit some local anaesthetic all around the root region.

And I can't see any reason why you, why you couldn't do things like that, if, if you wanted. OK, we're gonna talk about nerve blocks now. So the big subject, how we do these nerve blocks.

I'm just gonna spend the next 20 minutes, the final part of the presentation, telling you how to do these blocks. So you all know that we're blocking the trigeminal nerve. I've put the facial nerve on there as well.

Actually, I think this is one of Henry Tremain's images from one of his, presentations from previously. So, thank you, Henry for that. But there we go, we're blocking the trigeminal nerve.

And the branches of it and we're mostly gonna be interested in these four locations. So we've got the mental nerve block, where the nerve is exiting the mental foramen. Similarly, the infraorbital foramen, so the maxillary nerve is exiting the infraorbital foramen here.

And it enters the terrigo palatine fossa, so it enters the infraorbital canal here, after it emerges at the base of the ear and traverses across the palatine bone to enter the terrigo-alatine fossa here deep to the eye. This is the scary one that everybody worries about, so I'm gonna show you a technique that I use for that, which I'm really, really happy with. And then we'll talk about the inferior alveolar block or the mandibular block where the nerve enters the mandibular foramen and passes through the mandibular canal supplying the mandibular cheek teeth and exits, of course, at the mental foramen.

So there's the nerves are gonna be blocking. So first of all, nice and simple, infraorbital and mental block. OK, when I say nice and simple, when you look at these in a skull, they're huge great holes, but of course, when you do it in practise, and they're covered in fascia and, strips of muscle, it can be a lot more challenging to find these.

Sometimes you'll find them absolutely easy as anything, straight away. Other times you're palpating away and really pushing hard, and you seem not to be able to feel them. Always good to have a skull nearby, just to double check your landmarks, and, yeah, just gonna talk you through those now.

So infraorbital block. So the classic technique for doing this. I'm gonna move on to the next image, is to use one hand and to spread out your fingers, and you place the, your index finger on the caudal extremity of the nasal incisive notch.

Then you place your ring or 4th finger on the roster extent of the facial crest, and your middle finger will fall on the levator labi superoris muscle, which you deflect dorsally and you will feel the crescent shape of the caudal edge of the infraorbital foramen with your finger. You do have to push fairly hard in a sort of caudal direction, but you will feel that classic semi-circular ridge of bone. Now, .

I was doing this with one of our residents the other day, Johanna, and she said that ah she she really finds this block difficult, so I had to demonstrate how to do it and, and I, I was expecting it to be the one horse that sort of jumped and twitched and wouldn't let me, but I was able to inject two. Cartridges using the 27 gauge needle into the infraorbital foramen absolutely easy as anything, and the animal didn't move at all. Notice here Katrina's cheating a little bit.

She's holding the nose with her, with her hand. I've actually only just noticed that I've been using this slide for for at least 10 years. I've only just noticed that she's got a little bit of a twitch going on there with her hands, so that's clever nursing for you.

And it doesn't look that sedated, this pony, actually, this is a really old image from, from, as I say, 10 years ago, but I think, you know, have your horse really, really well sedated for this. You can do what we call an exit block, which is where we just first of all deposit a little bit in the region of the nerve, just as it exits the foramen, without actually passing the needle in. And that can really help.

The only problem is it creates a little bit of edoema and can make the landmark more difficult to palpate if you've left that for a few minutes to work. So I often do just try to very, very gently advance the needle, and I do inject a little bit as I go. So I'll inject a tiny bit, advance it, inject a tiny bit.

It does seem to work extraordinarily quickly, and I do find that it's an advantage for doing that, but that's not a. That's not a a a a sort of a, a clinical trial, that's just my anecdotal experience. Mental framing is probably one of the most difficult actually of all the blocks, to a palpate the foramen and then to pass your needle into the foramen.

And you do have to get your needle well in the foramen, and I've put here advance the canal up the canal 5 millimetres in this direction. That's actually not correct, and that is not how I do it now. I apologise for that.

So this technique has been updated. And what we're doing now is we passed the needle a lot more in a ventual direction of either you can do it slightly cordially or slightly rosterally, but you have to get the anaesthetic at the bottom of this canal. And the reason for that is that the, the nerve that supplies the incisors is not the one that exits the nerve, it's the one that's still in the canal.

So you need to get beyond this one that's supplying the lips and the musculature. You need to get deep to the one that's supplying the incisors, assuming you're doing a procedure on the incisors or the canine. So you do need to get deep into that, this is from .

This is from, from the States, and showing a, a study. It's not, it's not Saunders. I, I, I apologise for that.

it's Jen Rawlinson, and she, she's done a paper on this, demonstrating the depth that you have to inject. So it's like 10 mil at least into that foramen to be able to get that. There is also a technique demonstrating how to do this intra-orally.

I have never even tried this because I'm comfortable and happy doing it the other way, so, just draw your attention to that paper, I have heard some colleagues doing that. Apparently you can get trauma. This is again one of Henry's images.

I have not experienced this myself, but, do, do be aware that it has been reported that some horses, as they come around from the anaesthesia, can rub themselves, and we think it may be just that it feels a little bit strange as the sensation returns. So perhaps a good reason for keeping horses in after these procedures for 24 hours or so. So now I'm going to move to the maxillary block, which is one that everybody worries about, and probably for good reason.

When you see this image of all these needles, passing into the Terrago-Pallatine fossa in attempt to show you where and all the different kinds of approaches you can to, inject this, nerve. Now for me, I would absolutely use none of the approaches in either of these two images because. It's not only the maxillary nerve that passes into this foramen, there's also, of course, the descending palatine artery.

It's also passing through this foramen, or very close to it. And if you poke your needles in that direction, you will almost certainly, or you'd certainly be very high risk of puncturing the descending palatine artery. Which, is, is what you want to avoid.

So I would say the last place you want to start poking your needles is in this direction here. You're just asking for trouble. And I think in, in, in times gone by when, when more people had complications with these, that's, I think what we were probably doing.

We were probably aiming for the foramen, rather than aiming for the nerve, and I think that caused us some problems. So, I'm gonna sort of cut to the chase here, and, not read through all this text, but, there's, there's a traditional technique which has been described by originally Dave Bardel. I did a good paper on it, who was an aesthetist at Liverpool for, for a good while, published a nice paper showing two different methods for blocking this was, this was actually for head shaking investigations.

And there was the angle technique where you directed the needle very much towards or trying to get it actually sort of down the terrigopalaine fossa. And then on the right there's the perpendicular method where you went underneath the, underneath the zygomatic bone. Just under the lateral campus and injected the needle in a perpendicular plane until it touched the palatine bone, and the PBI means that that was the palatine bone insertion technique.

And this is what many of us did for a long time, and it was well studied, and it was shown that really actually neither technique was completely risk free, and this was the problem. Here's the, descending pallattine artery being punctured in this case. In this cadaver specimen and you can see the nerve, just ventral to it in this, in this particular image.

This is the, the flat surface of the bone just back here. And then another very nice study came out from Carsten Staik and Astrid and and the gang from Germany, a very nice paper showing MRI images of the potential risks of doing palatine bone insertion techniques. So the recommendation following this paper was to, and you'll see the image on the right here, the furthest image on the right shows the needle in the perpendicular plane contacting the palatine bone.

And the, and the, risk, in doing this is that you are close to the artery and therefore you're more likely to cause trauma or a rupture, and a big hematoma. Here on the left, . The writing's upside down because the horse was an anaesthetized, I think, upside down.

Here on the left, the needle has been passed a little bit short of the palatine bone. It stops about 10 to 15 mil short of the palatine bone and injects into this body here, which is the periorbiter or the periorbital fat body. You're actually injecting into the fat body rather than injecting deep, closer to where the nerve is, and the idea is that the anaesthetic diffuses to the maxillary nerve, having been deposited in a safe location, and it reduces the risk theoretically.

I did this for about 3 years and then gave up on it because for me, I found that it was taking a long time to work. I still got the occasional haemorrhage, and it just, yeah, I just, I just wanted to find another technique. So if you're comfortable with that technique, if you want to use that technique, perfect.

I'm just gonna show you now, seeing as it's my lecture, I'm gonna show you what I do. And Nicole here does pretty much exactly the same, and she's kind of come to it, we've come to it both in, in, in sort of different directions, but we've ended up at the same thing. So I've got some really simple landmarks for you for this presentation.

Firstly, imagine a line following the line of the facial crest extending cordially. Second, Find a site which follows this angle of the eyelid. I'm just gonna flick to my next couple of slides.

So there's your first line, and then your second line follows this margin of the eyelid. Now, Do be careful because of course all horses have got slightly different shaped eyes, but in general there seems to be this. The angle of the eyelid here, it doesn't seem to be a semic circle like the ventral eyelid.

There does seem to be this downward and straight line. And if you find the intersection of those two, that will pretty much give you exactly a point which seems to be about the ideal location to inject. And from here, I will inject in a perpendicular plane.

I used to angle it at a Bit forwards towards the opposite medial cancers, do not do that now. Absolutely perpendicular straight in. So it's pretty much exactly the same as the perpendicular method, the PBI palatine bone insertion method, but you're just starting point is a little bit further cordially.

And I think the benefit from that is then the needle point is located further caudal to the palatine bone. And of course the structures radiate away and diverge as they extend cordially from that structure. So the risk of puncturing is less.

We're much more likely to hit flat bone. And not, a location where the artery is. And I have to say, we've done hundreds and hundreds of these, and I shouldn't say this, and I'm touching wood, but I just cannot remember the last time, A, it didn't work, or B, we had any kind of complication, haemorrhage or anything like that.

We do see some pupillary dilation, and we have had 2 cases in the last 5 years of corneal ulceration. And there has been a nice study performed now, I think from Germany, from Gershausen, which demonstrated using Shermatier tests that there is a, a lack of tier production or a reduction in tear production following a maxillary block. And so therefore, you're very well advised to add some artificial tears during and after the procedure, and we do that routinely now.

So here's a video of performing this block. I'm gonna start the video and you just see this is quite an old video now. So I've put a tiny blab of local anaesthetic and the location of this nerve, I think this is probably 76 or 7 years ago, and I was directing it slightly rotally at this point.

I do not do that now. Keep it out straight. This is a 22 gauge needle.

And it's it's a 90 mil, needle, spinal needle, withdrawal, and then connect and then inject. One adaptation you can do to this is is using an extension set so that if the horse does move, it doesn't waggle the needle around. But I tend to just use this.

We're using 10 mil in this instance and now use between 5 and 10, depending on the size of the horse. And quite a lot of horses are using about 6 or 7 mil, and it seems to be just as, just as good. Withdrawing a little bit through back to the needle as we go, and then injecting the full amount and then withdrawing the needle.

You'll find that the location for the entry of the needle is very often exactly where the transverse facial artery is. So you will have to decide whether to go dorsal or ventral. There's my little blab where I made, and you'll see that it's pretty much exactly on this angle.

So if we find the angle of the extension of the facial crest. And the angle of the eyelid, brings us to an intersection pretty much exactly here. And that, I've discovered is the landmark for me.

So here we go again. Now, if you're absolutely bang on with your technique, and if you are, if you go in exactly in the right place, then theoretically you could actually hit the nerve. So you do need a very well sedated horse just in case.

There should have had the sound on. It's a lot more impressive with the sound on. So this was, this is at practise, Jason Till's practise, and he, he got a bit of a shock when the horse jumped like this.

But again, it's very well sedated. Everything's fine. The horse comes back and relaxes, and we can carry on with the procedure.

Just withdraw the needle a couple of millimetres and carry on with the injection. Everything's fine. So do be aware that the horse could potentially twitcher fairly violently if you touch that nerve, and it's a very good reason for having the horse really well sedated.

Jennifer Rawlinson, who I mentioned earlier, who's a dental specialist from America, says that she does not place a lab of local anaesthetic at the injection site. And I asked her why not, and she said that if the horse feels the needle going through the skin, then it's not sedated enough for the procedure. I do place a lab of local anaesthetic, at the injection site, but I think she's got a very good point.

The horse does need to be very well sedated before you do this, and don't forget horses will sometimes look like they're quite sleepy if you've given them one dose of sedation and they're resting on a headstand and they're not having any stimulation. And the first bit of stimulation you give them is putting this needle in, you could be in trouble, so I would always do a little top up a couple of minutes before you start this nerve block and make sure the horse is properly asleep. We mentioned complications, I'm not gonna go through these in great detail.

We can get some, in the old days, this is an old slide, and I got a few cases of really marked, Horner's syndrome, ptosis of the upper lid, severe sweating. One case I had it all the way down the right flank. And when I think back to those times, I was using 15 to 20 mL of local anaesthetic for my maxillary blocks, as was described in the paper of the day.

And I think that's the reason, it's just that the anaesthetic is diffusing to other sympathetic nervous things that I don't really understand about anymore. But I think that's the reason you're blocking the sympathetic chain or something. So, less volume is good and accurate placement is good.

Complications, I think, as I said, a lot is excessive volume. Paralysis of the extraocular muscles, eyelid prolapse, corneal abrasion, well, I think that's actually the ulceration that I mentioned earlier, and an infection, you know, an abscess and a hematoma. Yeah, don't wanna get one of those.

I should also have mentioned the ultrasound technique, and I should have given you the link for that. The reason I haven't is because I've never in my life done it. We do so many of these blocks, doing almost one, do, do sometimes 3 a day or whatever.

But, the number that we have prob well, as I said, I can't remember the last time we had a problem, so, but I think if you're, if you are worried about it, and if you're good at ultrasound scanning. And you're good at doing ultrasound guided needle injection techniques, and you really know your anatomy inside out of this area, then, I think read that paper, and, and, and, and do that, . But yeah, it's, I have to be honest, it's, that's, that's not for me because I'm so comfortable with this technique.

So now we'll just move on to the mandibular block just before we finish, the inferior alveolar block, and this is a lot more simple and straightforward, and it's a really nice block, and I find this really, really, really effective, and I can't recommend this enough. Even, even though you're using a long needle, it does seem to be a very successful block. There are a number of different ways of performing this block.

The most important thing to note is that when you're injecting your needle along the medial border or axial border of the mandible, the attachments of the of the . The terragoid muscles, mean that you, will be injecting your passing your needle through muscle, and that can give you the sensation that you don't really know where the needle is. So my recommendation is to use a 2 gauge needle, spinal needle, and allow it to or direct it in along and let the end of the needle run along the border of the mandible, so you can feel it, and you know that you're in contact with the bone.

If you can't feel contact with the bone, when you get. It's the required depth, you will not be sure of the location of the needle and it could have, could have moved off further median and you could be blocking all sorts of things. So make sure that as you pass the needle through, that it does keep contact with the bone, and I'll just quickly show you how you do that.

So the location, you probably will know how to find the location. You follow the occlusal line of the cheek teeth, and then you do a line perpendage so that just according to the lateral canthus of the eye, and X marks the spot. That will be the position of the mandibular foramen on the, of course, on the axial side.

We use 20 gauge 6 inch, spinal needle, and as I say, advance this needle, I do put a little block in, do always do, I should have said, we do always surgical scrub for all these blocks, especially for the maxillary block, do surgical scrub and everything surgical, clean. Now what you can do with this block is you can use the bevel of the needle to advance, up. Have I got a video of it?

No, I haven't got a video of it, apologies for that. I did have a video before. This concept of using the bevel of the needle, so, what you're gonna do is you're gonna insert this needle with the bevel facing towards you.

OK, so the point of the needle and the flat bit is closest to you and the bevel is kind of angled towards you. And as you then inject that, or pass that needle along the inside of the mandible and you direct it towards you, you will find that at some point it touches bone. And then you might find that you can't advance it, so then you rotate the needle 180 degrees, and now the bevel will be facing the bone and it will slide along.

If you're not sure if you're still in contact, rotate it back again, 180 degrees, and you'll find it digs in again to the periosteum. And then you can keep doing that until you're at the required depth, which you've measured from the outside. And then you inject between 10 and 20 mL of local anaesthetic.

And again, I would be using 10 mL now, intraepicaine for all of these blocks, . And 10 mL it seems to be absolutely fine. There is a potential complication of lingual trauma, not so much in this location, but, more, further caudally, where the cheek teeth are, because, a very nice study from Lynn Caldwell and Jack Easley showed that the lingual nerve is positioned very close to the mandibular nerve, and this, of course, supplies sensation to the tongue.

And if you are a little bit too deep or you lose too much volume, or it just happens anyway. You can block the tongue, and then the horse can't feel it, and therefore it chews its tongue when it's come round. Happens much more so if you do this bilaterally, and there's been some really nasty cases of lingual trauma documented from bilateral mandibular blocks.

So we tend to avoid doing bilateral lower cheek tooth extractions for two reasons. One is for this reason, the second is that we had a couple of horses that have been really quite uncomfortable and not eating brilliantly after that. If you do have to do it, and have done it quite a number of times successfully as well, then I would do the most difficult and challenging side, using the nerve block.

And on the other side where you perceive the extraction to be easier, always a tricky one, that, because the easier side will always end up being more difficult in practise. But you can do that using a ligamentous block and other methods and higher sedation, and you'll often succeed. In, in, by using that, especially if it's a slightly older horse, I'm not sure I'd recommend that in a 4 year old.

I would do that in two different procedures with a 4 to 6 week interval. There is an intraoral technique described, this is the reference to the paper by Travis Henry and Frank Frank Vtrata and the team there, similar to the human and the small animal method. I tried this a few times, wasn't brilliantly happy with it, don't think I was reaching the nerve, but, do feel free to have a look at this and, and, and, and work that out for yourself if you, if you feel the need.

The other thing I should mention as we're closing, is that postoperative analgesia should always form part of your sort of, anaesthesia and analgesia plan. And I think, you know, if you're doing procedures which are taking a long time, we generally don't go over 2 hours now for pretty much anything. But if you're going, for longer than that, do consider, you know, do consider perhaps even repeating the nerve block or using it, using buprenorphine, and, sorry, yeah, buprenorphine, .

Instead of sort of buppivacaine, I apologise, bupivvicaine instead of mepivacaine for your block, which is gonna last a lot longer. Some people would do that anyway. I must admit, we stick to, mepivacaine, have very good results.

But do think about this the day after. I think, you know, when I, I've had one tooth out a couple of years ago, and this was really sore for me, for, for, for 5 days after the procedure, so. At least phenylbutazone, probably some Flunexine the the following morning, perhaps some Flunexine to go home with for the first day or two.

Others have used paracetamol, for pain relief, and there's also. References to using swabs soaked in local anaesthetic, placed in the socket to provide, postoperative analgesia. So there's all sorts of methods you can use.

So if the horse seems dull, if it doesn't seem to be wanting to attack its hay net later, then do consider that there's, that there's some post-operative pain. OK, so that's time up. I hope that's been useful.

If you have any questions or queries, then you can direct those, either through the webinar vets or you can direct those to me, either through the Facebook page or through the email address which is on here or any other way that you have. And contact me. So thank you all very much and thank you again to Dawn and to Anthony from the webinar vet for inviting me to present this webinar.

Thank you.