Thank you very much, Bruce. Welcome, everybody. And, this is obviously the first section of the anaesthesia portion of the the webinar that online congress.
As mentioned, my name is Kieran, and today I'll be presenting an overview of some of the local anaesthetic techniques, available to us with a particular focus on the the newer developments that we have, encountered over the last few years. Today I'm speaking to you from Singapore, which is highlighted with this. Circle down here and we affectionately call it the little red dot, sitting just below Malaysia and just above Indonesia.
And today's topic is something that I find really fascinating. It's something that's developed rapidly over the last few years, and the use of local anaesthetics to provide anaesthesia, analgesia has really, really, really exploded within both the veterinary anaesthetic and human anaesthetic spheres. So today, what we're hoping to do is to give you a general overview of some of the anaesthetic techniques that are now available to us, and we're going to, as I mentioned, focus on some of the more recent developments.
Many of these techniques are really straightforward, and they're things that you can possibly take away straight away and integrate into your practise immediately. And others are a little bit more technically involved, and they may need you to go away and possibly undertake some more training or even do some more reading and a bit more research into what might work in your particular situation, depending where in the world that you are. So the the objectives of today's talk, hopefully at the end of this, you'll come away with an understanding of why local regional anaesthesia might be advantageous to your patients.
Hopefully you'll be familiar with the different methods of providing local regional anaesthesia to our veterinary patients. You could understand various methods of accurately locating the relevant nerves that we might want to block. And to be aware of any potential adverse effects that may occur and how to mitigate those.
And finally, to be aware of the differences between some of the commonly used local anaesthetics and how we can add various other drugs to our local anaesthetics and improve the quality of our local anaesthetic blocks. OK. So today's talk will cover 4 different sections.
We're going to firstly talk about why we would want to use local regional techniques. We're going to go over a brief pharmacology of local anaesthetic drugs, and, then we're going to cover some of the techniques that are available to administer these drugs to our patients. It's not an exhaustive list, but it will focus on some of the newer things.
And then finally, because any intervention we may make is not without the potential for adverse effects, we're going to look at these and come up with some strategies for how they might be minimised. So onto section one, as I mentioned, these local and regional techniques are rapidly gaining popularity in veterinary medicine as well as human medicine, because they can be quite readily implemented and they really can drastically improve our patient's level of comfort. So to start off on this section, we're going to do a brief review of the pain pathway.
So if we have our, our dog here, and we have a schematic here of the central nervous system, we start down here with our our nose receptor at the end of the nerve, and that can be triggered by various different stimuli. There can be a mechanical stimulus, something that we make a hole in our patient with the scalpel. A chemical stimulus, so something like an acid but pH, that's low, that can cause tissue irritation or a thermal stimulus.
That noxious stimulus is then transduced into an electrical impulse, it's transmitted up to the dorsal horn of the spinal cord. A lot of modulation of this signal occurs here. It's projected up to various areas of the brain, the hindbrain and the forebrain.
There's central processing and descending effects and further modulation, and we may, if it's an acute pain response, have a motor response, or we may have the development of pathological states of chronic pain within that central system. And to to to to sort of take the animal away and look at the pathway, the, the principal advantage of a local anaesthetic agent is that we have our pain stimulus down here. It's transmitted up here and then depending if we have blocked one of our peripheral nerves or the area around the actual painful stimulus, we actually block any of this no susceptive input going up into the central and higher parts of the nervous system.
So we, we, we really blunt that, amount of motorceptive processing and potentials for central sensitization. And I think someone once mentioned that local anaesthetics are really the only true analgesic, and some of our other medications are probably a better term hypoalgesics, because they blunt the response to pain and local anaesthetics can actually stop it. So onto our, our advantages and I think probably the key advantage is the level of analgesia it provides.
I really feel that for my patients, a good local or regional technique provides an excellent level of analgesia. It's a cornerstone of providing multimodal analgesia to our patients, so using a variety of different approaches to minimise the adverse effects of each and to enhance either additively or synergistically, the analgesic effects. We can easily use our local and regional techniques as a technique of preemptive analgesia, so preventing that nooceptive input, getting to the central part of the nervous system and preventing or reducing the incidence of things such as central sensitization.
We can minimise systemic sorry analgesic requirements and we can enhance their effects and reduce their side effects. A similar thing for our anaesthetic agents. If we have a patient who is experiencing a painful stimulus during an anaesthetic, it's really going to make our plane of anaesthesia less regular, less smooth, and we're going to be trying to chase our patient to keep them anaesthetized adequately.
If we have a balanced approach using a local anaesthetic, we can markedly reduce fluctuations in anaesthetic depth and provide a smoother, more stable plane. One of the, the very important things, particularly in some of the regions that I work in, is that these techniques can be incredibly cost-effective. Even some of the more advanced, methods that use some specialised equipment can actually be very, very, cost-competitive in terms of the duration of action and the level of analgesia they provide, as well as reducing the, the number of interventions our patients have to have in order to keep them comfortable.
And finally, probably one of my favourite, other favourite things is that these techniques are really, really flexible. If you can think of a nerve, there is, I guess the potential that you could theoretically block it. Sometimes they're harder to get to than others, and if there's so many other techniques that we're going to cover as well for administration of these drugs.
It really gives you a very, very versatile tool to apply to various different patients. So moving along now to a little bit about the pharmacology of our local anaesthetic drugs. Just a quick review of their mode of action.
So our local anaesthetic drugs are primarily a sodium channel blocker. They prevent nerve depolarization and the conduction of nerve impulses, and they affect these nerves in a predictable order. They will affect all the different types of nerves, not just our sensory nerves, they will potentially affect our autonomic nerves, our motor nerves, and our sensory nerves.
So how do they work? If we look at this diagram here, we have the extracellular fluid here, the intracellular fluid here, a phospholipid membrane here, and some sodium channels here. When we administer our local anaesthetic in an aqueous solution, it's in its ionised state.
In order for it to have its effect, it must become unionised, and that's a pH dependent phenomenon. The unionised local anaesthetic passes through the lipid layer into the intracellular portion, and then primarily we'll come to our sodium channel. And depending on, on the onset of our drug, it will block that sodium channel for a varying period of time.
There is also an effect on the actual lipid membrane itself, and some of them are actually absorbed into the lipid membrane. So, we, by blocking these channels, we block the influx of sodium ions, and we prevent the propagation of an action potential along our nerves. So the local anaesthetic drugs that we use vary because of their affinity for these channels.
They have differences in their onset of action and the duration of action. And there's also a variability in the profile of their potential side effects and toxicity. It's very important to remember that between different countries, particularly as this is an international, talk, that licencing requirements and, availability will vary between countries and it's really important to check your local regulations for, for an appropriate drug selection.
So we have factors such as the pharmacological factors such as the PKA. Of the anaesthetic, and that indicates the degree of solubility and solution and also the degree of ionisation of physiological pH. Protein binding is another very important factor that will determine the duration of action, as will how vasoactive.
The local anaesthetic is, if we have a highly vasoactive substance that causes a degree of vasoconstriction, it's going to prolong our duration of action by reducing the systemic uptake of our local anaesthetic agent and also potentially reduce any toxic effects. And the degree of lipid solubility that we have will also determine the, the potency of how the dose that we need to get a given effect. So just here we have some commonly used local anaesthetic drugs.
This is obviously not in any way, shape, or form an exhaustive list, but to give you an idea of duration of action, we have lidocaine down this end, so with a very short onset of action of a few minutes and a duration of up to 1, 1.5, possibly 2 hours. And in the middle duration of action here, we have bupivacaine and rapivacaine.
The, the, the, the thing to remember with picaine is that it, compared to other agents is potentially slightly more cardiotoxic. It is a rachemic mixture, it has higher protein binding and, a long duration of action, and, other agents such as recubicaine, which is a Single and a tumour, and Levoca. Will have a lower selectivity for cardiac sodium receptors and a lower potential for toxicity.
And then finally over here, something that's very new, very new to me. I have not actually had the opportunity to work with it yet, is a new formulation of liposomal through the cane, where the, the drug is encapsulated in a phospholipid bilayer with an aqueous core, and that will prolong the duration of a of action through a sustained release, I believe, over the period of up to several days. So, as I mentioned previously, there are a number of different drugs we can actually add to our local anaesthetics to enhance the the quality of our block and the quality of our analgesia up to adrenoeponist, so, meatomidine, dexametomidine, some of the others, which are commonly used.
Can prolong the duration of a block and may enhance the intensity of the, the block. This is through binding to the alpha receptors and also through providing a degree of very slight degree of vasoconstriction, so reducing that uptake of our local anaesthetic drug. Opioids as well, particularly when administered spinally or epidurally, will enhance our, our blockade, ayketamine binding to our NMDA receptor.
Adrenaline is something commonly used in human medicine with lidocaine. To, to give us a two-fold effect of causing vasoconstriction, so reducing the uptake of lidocaine and keeping it around the nerve for a longer period of time, and also through binding to a very small amount of the alpha 2 receptors, which may enhance the the mode of action through that mechanism. It's important to remember if you're going to add adrenaline, not to use that in a situation such as distal limb where profound vasoconstriction could actually compromise blood supply to distal structures.
Bicarbonate is also added to lidocaine frequently. This is because it alters the pHF solution, and it will actually, as we need the lidocaine to have a acidic. Solution to maintain its its dissolved state.
It will sting on injection, which is unpleasant, obviously, and also it's more ionised in an acidic solution. So moving our solution to be slightly more basic or alkaline will actually enhance the amount of Or enhance the the availability of that lidocaine to pass into the, the cell wall. Something that's commonly touted as being helpful is using a mixture of different types of local anaesthetics, for example, using lidocaine and picaine together to obtain a solution that will theoretically have a shorter onset of action, but a longer duration of action.
This can be helpful, but it's important to remember that by combining the two, you will actually overall shorten the duration. You won't get as long a duration of action if you're using something like picaine on its own. And I generally tend to allow a little bit more time for my block to work and just use a single, single drug if I want to obtain a duration of action.
So moving on to our next slide, we're going to look at some of the newer techniques that have become available. We'll do a quick review of some of the older ones as well, mainly just going to mention them, not go to them in an awfully large amount of detail. We, We can look at, there we go.
We can look at some of the things like topical preparations. So there is a preparation which you may or may not have come across Elacrine, a mixture of lidocaine and Priloquine. And it will provide desensitisation of the skin, and it's very, very useful as a stress reducing technique for minor superficial procedures such as obtaining vascular access, or veapuncture, particularly in, in, in animals that might be quite adverse to that, and it can definitely reduce distress in our patients, I've found.
Other techniques that we we're probably familiar with, probably all the way back from vet school, are our simple local blocks. So doing a line block along the edges of the incision, a ring block, maybe around a a limb, splash block. So just, instilling some of our local anaesthetic into a surgical wound.
And, some of these are actually very, very useful techniques. So if you're moving, removing something like a small superficial lump, a, a line block or a a simple impultation underneath the area of interest can provide very nice analgesia. Ring blocks can be helpful for working with distal rims and digits.
Flash blocks can be very, very helpful in situations, particularly, such as providing intra-articular analgesia during arthrootomy or arthroscopy. And probably one thing I didn't mention is just a general infiltration block, which is one of the probably one of my favourite blocks is to use that as an intratesticular local anaesthetic for our dissecting through castration, and that provides really nice analgesia, and it's been shown to blunt the response to some of the surgical stimulus that occurs during that procedure. And it's very cheap, very easy to do, and I think certainly gives you a lot of good analgesia and patient comfort for the amount of time and skill invested into it.
And then finally on our older techniques, we have things such as intravenous regional anaesthesia, a beer block where we apply a tourniquet to the limb, inject local anaesthetic, and then during during that window of time before we release the tourniquet, we have analgesic limb that has a number of Potential adverse effects associated with it. We need to be careful with how tightly we apply tourniquet, the duration in which they are applied, and also we need to be careful with potential systemic release of our local anaesthetic after we've finished our block. So some of the newer techniques that I find really useful are things like diffusion or circuit catheters, and what these are is a flexible polyurethane tube with a very small diameter, and it contains multiple holes or pores and allows for even distribution of a local anaesthetic.
Throughout the site there. We can see here that this example, we have the small drops coming off the catheter that they occur between these two markers and we have the pores down here in our catheter and we can Insert this into a surgical wound at closure of the incision, and we can administer a local anaesthetic, either by intermittent injection or as a very slow continuous infusion, and certainly in my experience, and And that of some of my colleagues, it does provide a really nice analgesia for, for large wounds that create large incisions like potentially large mass removals. Again, these catheters are actually fairly inexpensive to purchase, and the local anaesthetics themselves are, again, quite inexpensive, and they really do provide a good level of analgesia, and you can reduce the number of interventions such as repeated injections and some of the side effects for example, for example, from opioids.
Again, with some newer techniques, one thing that has really, really gained a huge amount of popularity, particularly over the last 5 to 10 years or so in the veterinary field, is regional nerve blocks. And what we mean by that is to block a branch of a nerve that supplies a particular region of the of the patient, and we can do that either as a single injection. We can place an indwelling catheter for a continuous perineural infusion of our local anaesthetic, or we can, we could potentially do an intermittent repeat injection, either by repeat stick or by using a dwelling catheter.
Now, the important thing is that we need to know where these nerves are in order to be able to use these techniques. And for us to locate our nerves, there are generally, I guess I break it down into three different ways of doing so. Traditionally, we use our anatomical landmarks, more recently, we can use a thing called a nerve stimulator, which I'll talk a little bit more about in a moment.
And then finally, in addition to all of the above, we can use an ultrasound guided approach, which allows us to accurately identify our nerves. We, we generally, we don't use any of these in isolation, I guess you can there's an increasing. Level of accuracy, we can start with using our anatomy, then move on to adding a nerve stimulator, and you can actually use all three, using the algebra and guided approach to to really increase the the accuracy of placing the block.
So, first of all, we have our, I guess the technique I learned when I was at vet school, palpation of our anatomical landmarks. And we look for bony and soft tissue structures. We need to have a good knowledge of our anatomy, in particular our surface anatomy.
And then we need to be aware of what internal structures are and where they lie in relation to that surface anatomy. Aside from maybe some specialised needles, we don't need any particular equipment to be able to do this. But one thing I find is that it can be less accurate than some of the other techniques that are available.
There's a little bit of guesswork involved and some of the techniques that I find that do work quite well, things like an epidural or a spinal anaesthetic, where there's a distinct bony landmark. And we can use things such as the loss of resistance or hang and drop to confirm placement of our needle in the correct position. However, if you're looking for something like the paraspinal nerves or the brachial plexus, I'm never, certainly in my hands, I'm never really sure how accurately I've placed my block.
I feel like I'm flying blind a little bit. And certainly structures that have defined bony landmarks tend to, in my hands, have a better degree of accuracy. So I like to use these techniques for things such as, as I mentioned, epidural and spinal anaesthesia.
I don't usually feel the need for augmented nerve location, things such as dental nerve blocks, we can usually palpate the rami where the nerves are emerging quite easily, and it's generally very, very easy to Accurately place these blocks. When dealing with the distal limb or the digits, you can often palpate the bony structures and get a good feel for where the nerves are in between those. And also, again in the head, things like the retrovulval block for dealing with ocular surgery, we can certainly place that quite easily.
So what's happened here. There we go. What we can do, after we've we've used our anatomical palpation to locate the general region that we want to place our nerve block is we can use what is called a peripheral nerve stimulator to increase our accuracy.
And what we can do is use a I, A stimulator that will, I'm sorry out of order here. Like, here we go. So we can use an insulated needle.
You can see over here that we have a, a Teflon coated needle with just the very tip, the metal tip exposed, and what we do is using our nerve stimulator here, is administer a low stimulus current at the frequency of around 1 to 2 Hz and We, we use a square wave with the duration of 0.1 to 0.3 milliseconds.
And what we're trying to do is, we're trying to elicit a twitch response, and the, the current use that will elicit that twitch response decreases, the closer to the nerve that we actually are. So by having a, a very small area of current production here, we can accurately gauge how far we are from our nerve, and what we're looking for is motor stimulation. That will vary depending on which particular nerves we are trying to block.
And what we're looking for is to reduce the current of the nerve stimulator down to around about 0.3 to 0.4 mills, giving us a good mode of stimulation, and that will give us a good approximation to the nerve.
If we're going on less than this or a a lower current than this, that possibly means we're too close to the nerve or actually in the nerve, and any any higher current than this means we will probably be a little bit too far away from our desired nerve. So we have here again another schematic, we have our insulated needle. It allows us to locate our nerve quite accurately.
And inject our local anaesthetic around the nerve, and it allows us to use a much lower volume of local anaesthetic, so we can potentially lower the total dose that we administer and reduce some of the, the adverse side effects and potential toxicity that may occur when we give large volumes of local anaesthetic. You can see here, here's a specific needle that we would need to use the insulated needle with depth gauge markings here. Then we have this connector here which is attaching to our stimulator unit, and then we have some tubing here to attach to our syringe of local anaesthetic which is administered in through the needle here.
One of the major disadvantages of this type of technique to locate our nerves is that while it's great for actually telling whether we're near the nerve or not, it doesn't give us a lot of information about the surrounding structures. The, The, the equipment for this is generally quite inexpensive. The nerve locators are generally very affordable, as are the consumables, particularly for the duration of anaesthesia and quality of analgesia that you get.
I certainly think they're worthwhile and probably what I use most frequently in my practise. Take things one step further, we can look at ultrasound guided nerve blocks. And we can get Quite a few advantages from using this type of technique.
We can see in real time exactly what's happening. We can detect other structures that we might want to avoid, like blood vessels. We can improve our accuracy, and we can combine this with a nerve stimulator to, to really get a very accurate, view of where we are in relation to the nerve we want to block.
The downside is that you do need an ultrasound machine, which, if you have one in your practise, that's fantastic. If you don't, they're a very expensive piece of equipment to buy. You also ideally need a specialised probe, which will be a high frequency in the vicinity of 10 to 12 megahertz probe and a linear array probe.
This has limitations in terms of the depth of penetration, but it gives a very nice resolution. And will provide a very good image quality. It can be combined with the use of a nerve stimulator for the best effect, and we have some images here of What you would see with your linear array probe, we can see the hypoechoic areas of our nerves.
You can have a muscle here, and you can see here, you can have the, the, the, the needle that we with which we are trying to locate the nerves and administer our local anaesthetic. And these again are especially designed to be more ecogenic so we can actually visualise them very easily. We can see, here this is a schematic, put a needle shadow generated by the needle, and we try and get nice and close to our nerve here.
So the, I guess the last two techniques, the ultrasound guided technique and the nerve locator technique, are ideal for blocks such as brachial plexus blocks, paravertible blocks, radial ulnar median muscucutaneous blocks of the falling. Femoral and sciatic blocks, which is a nice alternative to an epidural. And blocks of the caudal lumbar plexus, you can actually use an ultrasound probe to help you to locate the epidural space by looking for the shadowing between the bony structures, it's something I'm not particularly confident.
So finally, moving on to preventing complications, we're going to run through what the potential complications are associated with these interventions, and as we go through them, I'll just mention some of the techniques and cautions that we can take in order to minimise the these complications and try and get the best possible outcomes for our patients. So I've divided the potential complications up into 5 different categories. This is how I think of them related to the drug that I'm going to administer, the potential to damage the tissues that I'm injecting into, there's a potential of impeding normal function.
There's always a chance that we have a block failure and our patient may experience pain, and then there's a potential for the introduction of infection. So to start off with our drug-related complications, we, we need to consider which drug that we're using, and we need to choose an appropriate drug for each patient. So for example, intravascular injection is a potential, problem with some of our local anaesthetic drugs, particularly with putrefacine because it's quite cardiotoxic and, inadvertent intravascular injection can actually cause a, cardiac arrest or impediment that's very, very hard to treat, can be treated with administration of .
Intravenous lipid solution, but it's best to avoid that in the first place by making sure that you're confident in your placement of your block, and also before injecting to always draw back and ensure that you're not actually aspirating any blood, that you're not in a, in a vein or artery. And if you are administering a, a large volume of local anaesthetic to make sure that you repeatedly check your placement and that the tip of your needle hasn't migrated and entered into a blood vessel. If we're using large volumes of drugs such as lidocaine, they can be neurotoxic, causing seizures.
So even though the, the dose required is higher and the likelihood is, is, still there causing potential adverse effects. We need to be careful to not actually overdose any of the drugs we administer. So we want to check what our maximum dose for the individual drug is.
So for example, lidocaine, we try to stay under 6 milligrammes per kilogramme total dose, and with bildocaine, usually 1.5 to 2 milligrammes per kilogramme is the total dose. We calculate this for each patient and then if we do only wind up with a very small volume of local anaesthetic, what we can actually do is dilute that to increase the volume that we're able to administer over multiple sites.
Methemoglobinemia is a potential with some drugs such as Usually Prilocaine or benzocaine, so using things like Elacrine, we need to be careful, particularly with cats, that we don't, overdose. There is the potential for, for other drugs, but those two are the most common. And then finally, hypersensitivity reactions, any drug can just at least potentially and .
We treat that as for any other hypersensitivity reaction based on the, whether we're having an anaphylactic reaction or just an allergic reaction. Tissue damage that we can inflict is a multitude of things. We can actually damage the nerve itself on a temporary or permanent basis through laceration of the nerve, or through intraneural injection of our drugs and cause a temporary or permanent damage there.
One of the things that we can do is, is use as many techniques as possible when we are placing our blocks to ensure that we're aware of what structures are where and also being very careful with positioning our needle and being gentle when we're manipulating it within the tissues. The other thing that's very important is to ensure that our patient is adequately restrained either through sedation or anaesthesia because we can't ask them to lie still. Under the same category, it's blood vessel damage, which can cause, lacerations to blood vessels and cause potentially massive haemorrhage or hematoma formation which can affect the tissues surrounding.
And we also need to be aware of other structures that may be in the vicinity of what we are trying to block. So potentially if you're doing a Paris climate or intercostal block, you need to be aware that the, there is potential there to perhaps cause a, a, pneumothorax and, . We need to be cognizant of, of, avoiding that.
One thing we do need to think of very carefully is that when we're blocking a nerve, we're not just blocking the sensory function, we're potentially blocking the motor and autonomic function also. And before you elect to, to do a nerve block, you need to think ahead of what potential blockage of normal function may also occur. So for example, so blocking around the eye, we may actually not be able to adequately protect the eye through blinking or Through operation of the drysis.
So we may need to protect our patient's eye through lubrication and maybe protect them from strong light as well as it can be quite uncomfortable or painful for them. Similarly, if we get an epidural or spinal anaesthetic, we may be blocking some of the sympathetic fibres that come up through the sympathetic trunk, and this may cause a reduction in systemic or vascular resistance and hypertension in our patient. So I think the thing to be aware of is when you're giving a, a, or administering a block is to be aware of what potential complications could occur and plan ahead for, any, any adverse effects either through protecting eyes or limbs, being aware that bladders may not work properly with epidurals, and being aware that limb function may not be optimal if you're using a single limb block and supporting a patient through that until the local anaesthetic wears off.
One of the, the, the most disappointing thing is that our blocks can fail. We may actually miss the mark on where we're actually aiming for. And as an unfortunate consequence of that, our patient may actually be in pain.
So I think to prevent this particular adverse effect, we need to A, make sure that we can be as accurate as possible, be comfortable and familiar with the anatomy of our patient, use as many techniques as possible to ensure that we are placing our block accurately and always, never assume that the block has worked. Always be ready with rescue analgesia or an alternative analgesic plan for your patient should the block fail because it may not be an option to try again. Finally, there is the potential of introducing infection either to the local area or around the nerve or even as a systemic infection, and to counteract that, it's important to maintain an aseptic technique or surgical preparation technique, wear gloves, use surgical prep, and keep the environment around the block clean.
If you're using an end and catheter, ensure that it's covered and is kept clean and away from any faecal material or other sources of infection in the kennel. And check daily for indwelling things or multiple times daily to make sure that there's no signs of infection occurring. OK, so, that is.
The bulk of the presentation, so we're just going to go on to a summary. Again, back to our objectives, hopefully now you can tell why it's it's advantageous to use a local anaesthetic technique in that it is really an excellent analgesic. It provides a great level of patient comfort.
It's inexpensive. The techniques are very, very readily implementable in our daily practise. You've probably got bottles of these drugs sitting on your shelf and some needles, you can get started today or tomorrow, depending on where you are and what time it is.
Hopefully, this will inspire you to go ahead and do some research on different types of local anaesthetic techniques that are available. There are several excellent books on the topic which I'll list at the end. Hopefully this will also give you comfort in trying to locate the nerves accurately and you can maybe utilise some techniques that you have such as your practise ultrasound to start doing.
Different blocks for for limb surgeries or high limb surgeries. You should be aware now that there are potential adverse effects and that there are definite techniques in how to minimise these effects. And then finally, we should be aware that different local anaesthetics have different durations and onsets of actions, different potential for toxicity, and that there are a number of other drugs that we can actually add to enhance the quality of our anaesthetics.
And finally here, I'd just like to bring to your attention some of my favourite additional resources. There are several books published on the topic which are excellent, contain a lot of pictures and very clear instructions on on how to do many of the all all of the the techniques that I have mentioned today, you know, the handbook of small animal regional anaesthesia analgesia, and small regional anaesthesia analgesia textbook. Finally, there is a website called the New York School of Regional anaesthesia or my that is available online.
It's a human website, but it certainly gives some very good in-depth, information on many of the techniques that are available, particularly using a nerve stimulator and also, using ultrasound rider techniques and the pharmacology of local anaesthetics. So thank you very much for your attention and I'll pass back over now. Kieran, thank you so much for that presentation and I think the key take-home message for me here is multimodal.
It's something that we as vets, particularly as, as older vets, we're not necessarily trained in and and made aware of and we sometimes don't really think along those lines. Yes, definitely. It's it's, it's very easy to apply a few different techniques and it's a little bit of opioid, a little bit of a nonsteroidal and provide a regional block and really have very comfortable, alert patients that want to go back to doing what they do best, eating, drinking, playing, all of those things, and recovering more rapidly because of that.
Yeah, you mentioned the local anaesthetic and the testicles. I started doing that probably about a year ago now and especially in cats, I was absolutely amazed at how quickly they come around and they get up and they eat and they, you know, it's like you, you haven't even done surgery. It it it really makes a big difference.
I think in my patients, when we're able to do a successful local technique, they really are comfortable. They really can have a lot lighter plane of anaesthesia, fewer anaesthetic drugs, and they can get back to being themselves, and I think overall that allows them to recover more rapidly and return to as normal function as possible. Yeah, yeah.
One thing that that has always fascinated me, and maybe you can give me the answers on this, in human medicine, they use a lot of intra-articular steroids for chronic joint pain and that which as vets, we don't tend to do. Any, any specific reason for that? I think that, using intra-articular steroids is certainly a good option for our chronic pain patients.
It's, it's not something I do a lot of. We tend I tend to, I guess, use alternative techniques for, because there are potentials for infection and other things, and We do need to anaesthetize potentially our patients in order to give an intra-articular injection, whereas with our our human patients who can do that on an outpatient basis and just ask them to sit still. So I think that, it's more of a, more of an invasive procedure for our vetinary patients and for humans.
It's certainly one thing that deters me from using that, but certainly some and can in selective cases be very, very effective in managing inflammatory pain. Yeah, excellent. Just on us talking about testicle, local in testicles, Hannah asks, and very briefly, cause we're just about out of time, do you put the local into the testicle itself or into the stump after removal of at the castration?
What I ordinarily do is, after the first round of surgical preparation is to stabilise the testicle between two fingers, use an appropriately sized, just a regular hypodermic needle. Place that into the, the long axis of the testicle, obviously draw back and ensure that we're not actually in a blood vessel, and then just inject into the actual testicle until it feels reasonably firm. It obviously vary, the volume that you're going to be able to use is going to vary tremendously between patients and that provides quite good intraoperative and also postoperative analgesia.
Yeah, and it, it really does work very well. Kieran, thank you so much for your time and for your expertise for sharing with us and we look forward to hearing from you again on future webinars, hopefully.