Straight talking anaesthesia for beginners | Veterinary Videos & Podcasts

Hello and welcome to this Webinar. Straight talking anaesthesia for beginners. My name is Valley Walters, and I've been a registered veterinary nurse now for 25 years.

And for six of those years, I worked in the teaching hospital, at the Royal Dick School of Veterinary Studies for the University of Edinburgh and only did anaesthesia. I was a service dedicated anaesthesia nurse. And that was all I did back to back anaesthetics day in, day out.

I've lots to get through in this webinar. So we're gonna jump straight into it. These are your learning objectives.

Pause on this page if you want to read specifically what you're going to learn. But now we're gonna launch straight in. First of all, when you're Anaesthetizing a patient, you will need to perform a pre-op check.

And this is also known as the check to see if the patient will survive the general anaesthetic. I appreciate it is ultimately the vet's responsibility, but nurses ought to know how to perform one, too. And I just really want to stress that we need to consider patient welfare when we're performing a pre op check.

So do these super sympathetically and calmly. This is a normal day at work for you, but for animals being admitted and without their owner nearby, it's well outside their realm of what is normal. And the more worried and scared an animal gets, the more likely it is that they are going to escalate to threat, repelling or aggressive behaviour.

And then we have to use more aversive handling techniques to restrain them. That's horrible for everybody. And we'll also have to use higher doses of premeds and induction agents, which comes with side effects, obviously.

So everything we're gonna do with our patients is gonna be done really calmly, and in a nice, calm, quiet environment as well. OK, when we're doing the pre op check three things that we're gonna be looking at. And it's central nervous system, cardiovascular system and the respiratory system.

Central nervous system. So a patient with normal mentation so behaviour and level of consciousness will be described as bright, alert and responsive, or BAR, which hopefully I am coming across as or quiet alert and responsive or QAR, and that a patient that's got abnormal mentation may be described as depressed or dull or slow to react, groggy or even comatose. We also want to be looking at that animal's, central nervous system and looking for any signs of depression.

So for any signs of drowsiness or sluggishness or incoordination from that patient, then we're gonna look at the cardiovascular system, and we can start by doing something called blanching, which is where we, lift up the lip and we press on the gums until the gums turn white. And those, capillary refills that have been blanched should, refill with blood in under two seconds. That's what we're looking for.

And we're also looking for the colour of those mucus membranes. They should be a nice, healthy pink colour. And this lets us know, that the animal's blood pressure is good and that blood is circulating and oxygenating everywhere that it should be.

We should be looking at, taking peripheral pulses and not just femoral pulses if we can feel the pulse on those peripheral arteries. So, looking at the meta dorsal metatarsal artery on the bottom left picture and the carpal artery on the bottom right picture. If we can feel those generally, that means that blood pressure is good, and it's really good to practise taking these when the animal is conscious so that when they become un unconscious under anaesthetic, we know what those pulses have already felt like.

When you're taking a pulse rate, you wanna count for 15 seconds and then just times by four, this will give you your minute pulse, pulse rate, or you can count for 30 seconds and times by two. Or if it's been a really long day, you can't do maths anymore. Just count for the full 60 seconds.

We're also gonna have a listen to the heart and check that that sounds OK. As I said, this is ultimately the vet's responsibility to do this. But nurses ought to be able to perform a pre op check, too.

Finally, we're gonna look at the animal's, respiratory system and observe the animal breathing in the cage. We're looking at the respiratory rate and the respiratory pattern. Count for a minute for these so that you have a more accurate, number for what the respiratory rate is.

You want to also look that, then check that the breathing looks normal. So, for example, that that the the breathing is not laboured and that it's not abdominally breathing. Healthy dogs should have normal rhythmic breathing, and their chest and abdomen should move in and out together.

If the abdomen is pushing out as the animal breathes out, known as abdominal breathing, it could mean that they're having trouble removing air from their lungs. And so this is often seen in patients who have congestive heart failure or who have a pneumothorax, which is air around the lungs or are suffering from pleural effusion, which is fluid around the lungs. Or they have bronchitis.

So have a look out for that, and then look out for signs of, yeah, respiratory effort. And then we're gonna have a listen to the chest, and listen for any detection of, abnormal lung sounds that could indicate respiratory disease. These are your normal heart rates and respiratory rates for cats and dogs.

And generally the rule to remember is the bigger the animal, the lower the heart rate and the lower the respiratory rate premedication. So giving the good drugs to calm them down. Now that you've done your pre G a check your pre anaesthetic check.

It's pre-med time, and I do advocate for giving a pre-med before placing the IV cannula because it makes it much easier to place that IV cannula. And it's so much nicer for the patient as well, to to be pre-med to have those good drugs on board something quite painful is happening to them. If you've ever had an IV placed yourself, it's not a very pleasant experience.

And if you're in the clinic without your owner, all these people and other animals around you and then something painful happens to you, es behaviour can escalate towards aggression. So let's just pre-med them first. Don't fight with these animals to get the IVS in very often as the animals, struggling.

They've blown one vein. Second vein gets blown, and then someone says, Let's pre-med it, and I just think, Why didn't we do that in the first place? Fighting with an animal is really awful for the animal, and, often we have that mentality where we think we need to win and we don't.

We need to make everything as calm as possible for the animal, So a good pre-med first premeds also reduce stress for the animal during induction and anaesthesia, so it's less stressful for the patient, less stressful for staff as well. If everything goes nice and smoothly, a good pre-med will reduce the dose of anaesthetic drugs required to induce anaesthesia and will also reduce the amount of maintenance anaesthesia that you have to give as well. So it's a really good idea to make sure your pre-med is, tailored for that specific animal.

How worried and nervous they were and any accompanying health conditions they have. So a good pre-med is really the the start of a good anaesthetic. It will obviously provide analgesia, and I'll talk a little bit later about pre-emptive analgesia.

So we wanna have that on board before we start all the cutting. And it will also help with recovery so you'll have a smoother recovery from the anaesthetic. And that's through some residual sedation from the pre-med and also because we've got that lovely pain relief on board as well.

Use the lumbar, axial or or the neck muscle when you're giving your pre-med. Traditionally, we've often used the quadriceps or the hamstring, but anecdotally, this is more painful for the animal, and also you're in danger of hitting the sciatic nerve when you use that leg muscle. So use the lumbar, or or the neck, muscles there.

If you're worried about hitting the spine or hitting the kidneys, don't worry, you won't hit the kidneys, But if you're worried about hitting the spine with your needle, when you are doing a lumbar or a a neck IM injection and you simply make an L shape, put your long finger on the spine feel for the the vertebrae of your patient. Make that L shape and then you're going in into your L there, and you'll be safe if you do that. Also, you've probably been taught to go straight in at a 90 degree angle, but lots of experience.

anaesthetists and vets and nurses will go in at a 45 degree angle, providing the animal is not O obese. And this seems to be less painful for them. So in the in the picture there, with the dog being injected, you can see it's more of a 45 degree angle.

Try it. You often see less reaction from the patient when you're doing it. Jet nine Slowly When you've had a vaccine yourself in the muscle, it's that separating of cells as the fluid goes in.

As the vaccine goes in, that really hurts. And then don't rub afterwards because the pressure of the fluid separating those cells is what is what's painful. And then when you rub it, it just hurts even more, and so we don't wanna hurt them even more.

And also, we don't wanna get any of that rub on our fingers synergistic effects. So giving drugs from different classes have a better effect on the animal. So if you're using a sedative, like meat toine or Dex meat toid, also known as sedor or DOMA, plus an opioid.

So opioids are methadone Comtan, Simon or, drugs like buprenorphine, also known as BUPA Tesic or beta. Combining those together, you might want to put in some acepromazine as well. If that animal is super anxious, you're gonna have more a better effect than can be achieved just when you use them together than using them all individually.

That's what synergy means. And because these drugs are from different classes they can be safely used together, and by combining drugs together to make a beautiful cocktail for your premedication, you can use smaller, which leads to less side effects. So you might have less respiratory depression or less cardiovascular depression by using a few drugs together.

So it's absolutely ideal to, decide what you're gonna use for each individual patient, rather than having a one size fits all recipe in your practise, it should be tailored to that individual animal pre-emptive analgesia. As I mentioned a couple of slides ago, is giving the pain relief before you do the painful thing to the animal. And, it reduces sensitization, so I will just read this out to you.

Transmission of pain signals evoked by tissue damage both scalpels and cutting leads sensitization. So sensitization is when there is a physical change in the neurons or the nerve cells, and the patient's nervous system is persistently in a high activity state, so the transmission of pain signals evoked by tissue damage leads to sensitization of the peripheral and central pain pathways. Pre-emptive analgesia is a treatment that is initiated before the surgical procedure.

In order to reduce this sensitization And owing to this pro protective effect on the Noso Acceptive system, the Noso Acceptive system is a system that processes noxious stimuli such as surgery. The effect on the noso acceptive system pre-emptive analgesia has the potential to be more effective than a similar analgesic treatment initiated after to surgery or what we call rescue analgesia so immediate post-operative pain may be reduced and the development of chronic pain may be prevented. Now it's less well studied in veterinary medicine.

But in human medicine, we know that inadequate, inadequately treated pain at the time of surgery can lead to chronic pain in the future. So we really want to make sure that we're treating acute pain, and pain before the pain is inflicted so that we don't lead to those chronic pain states later, later on in life. And if you think about yourself, if you have, the twinge of a headache coming and you take your paracetamol and your ibuprofen, that headache completely disappears, doesn't it?

But if you wait for that headache to to grow into a full blown pounding headache and then take your paracetamol and ibuprofen, headache never really goes away and you still can feel a dull throb in the background. So drugs and, analgesics on board nice and early. Prevent.

Worse post op pain placing an IV cannula. So once your patient is nicely, nicely, pre-med, you are gonna place your IV cannula. But first of all, once you've given that your IM injection, you're gonna place them in a in a quiet place.

And you're not going to cover the cage up? You're just going to observe them As the pre-med starts to work, don't stand in prep with them. Still chatting to everybody, which, we can sometimes be tempted to do put them somewhere nice and quiet.

Keep an eye on them if you cover the cage. You cannot see what's happening as they as they start to relax into that. Pre-med, and dreadful things can happen when they're left alone.

And I've seen a couple of patients in the span of 25 years go down in the corner of the cage with their head down, and their necks bent over and they've suffocated, and they they've died and they're in for routine surgery, and that is absolutely awful. So make sure that you're observing them as they go down with their premeds. When you're placing your IV cannula, So yeah, give them 10 to 30 minutes.

For that pre-med to work, and then when you're placing that IV cannula top tip is to keep a hold of the pore. And don't, constantly let go, to to get what you need and then re hold animals sort of don't enjoy that constant release and hold release and hold because they're not really used to having their legs held. So have make sure you've got everything open and ready, and you can do, hold the pole with one hand and then do everything with your other hand.

Make sure that you flush your IV cannula rather than pull back to check that you are in. So once you've popped it in and you've bandaged it really comfortably in place, what taped it in place, Then get a little bit of saline, two mills of saline and the syringe and then just flush into the cannula. Hopefully you've got a bung on the end, or a T connector.

Put your fingers like in the bottom right hand picture on the top of the vein and short, sharp blasts, and you'll feel the saline whooh through that vein. And it's really important that that you feel that so that you definitely know your IV cannula is in place because, too often I've seen animals with IVS that are supposed to be in place, and then you go to inject the propofol and that vein blows and propofol stings as well, so it can sting in some animals. So, you want to be in, definitely sure that you are in the vein and that the, induction agent isn't gonna go, subcutaneously.

Also, I've seen it at euthanasia, and that's just horrendous. When a vein starts blowing, just as the owner is is saying goodbye. So always be flushing through rather than pulling back to check that you've got blood there if bandaging comfortably as well.

You won't see animals interfere with their IV lines. Usually try not to bandage over joints because that causes the animal to, often interfere with their bandage as well. Cats need to knuckle their paws in, over like that.

So we want to make sure that they are staying as comfortably as possible. And why place an IV cannula? I do know practises that don't don't place IV cannulas in, a lot of their G a.

So for something quick, like, a cat cast rate or perhaps something that's had a quad anaesthetic. They might not get IV cannulas placed, but things can go wrong. And it's R really hard to place to flip up a leg and place an IV cannula when your adrenaline's flowing because that animal has crashed so things can go wrong.

We want to have that IV access to give any extra anaesthetic agents that we often need to do under an anaesthetic. We need it there for emergency drugs cos they are gonna go intravenously, and also it provides fluid therapy. And again, all your G A patients should be on fluids.

I hate that it's an optional extra for patients. It should be a built in cost into the anaesthetic. I understand that it isn't, and I understand why it isn't for a lot of practises, but it really should be because giving fluids helps to provide obviously normal fluid maintenance requirements.

It helps maintain adequate blood pressure. And, fluid losses, which might occur during surgery through blood loss and evaporation, but also dehydration. Is an extremely unpleasant feeling, and those animals might not add water for many hours by the time the anaesthetic is over, and dehydration can also lead to hypotension so low blood pressure impaired cardiac function, inadequate tissue perfusion, infection and kidney failure.

And we're challenging the body a lot when we give it an anaesthetic. So we really want to be helping maintain those fluid balances the anaesthetic machine. So the anatomy anatomy of an anaesthetic machine can always be divided into six main parts.

Anaesthetic machines come in all shapes and sizes, but all of them will have a back bar. They'll all have an oxygen supply. Whether that's attached to the machine or or comes from a an a source outside of the practise, they'll all have a flow metre.

An emergency oxygen flush, a vaporizer, either iso fluorine or sever fluorine and a common gas outlet. And no matter what machine you're using or what practise you're working in, you should be able to identify these six main parts and you should be doing this before you induce anaesthesia, obviously, so that you are familiar with the machine. You should check your anaesthetic machine so that you know it's definitely going to work once that patient has been induced.

So first of all, most importantly, alongside oxygen, you need to check that there is adequate, volatile agent, and you simply do this by looking at the level on the viewing window or the site glass on the vaporizer. Too often I've seen patients induced, and then they go to turn the vaporizer on and there's nothing in the vaporizer, and then you have to feel it really quickly, and it just makes for a really stressful anaesthetic. You wanna check that the filling port is closed by, twisting the knob clockwise if this is has been left open because someone has just filled it and they've not tightened it properly when you turn on your oxygen that the ISO fluorine can start bubbling out of there, and then that's a health and safety problem.

And if you've ever breathed in spilled iso fluorine, it's really not good for you. It gives you the worst headache, so make sure that that knob is fully closed. Check that the vaporizer dial does move freely through its entire range by twisting it again.

I've seen patients induced. They've gone to turn on the vaporizer and it's stuck and they cannot move it. And that's all very stressful and disastrous.

So just nice anaesthetic machine. Check checking your oxygen. Now you're gonna open the oxygen cylinder, losing the using the oxygen cylinder key Lefty, loosey righty tighty.

And then you're gonna look at the pressure gauge to see how much how much, oxygen is left in the cylinder, you're gonna turn on the oxygen flow metre up and down through the entire range. If you've got, a bobbin in there, you should make sure that the bobbin is spinning. Because it's designed to spin.

If it didn't spin, it just sat there. Then we might not actually know if the if the oxygen is flowing or if the bobbin is just stuck there, then make sure that it is spinning and you read from the, top of the bobbin when you're when you're reading how much oxygen is going through in the middle of the ball. If it's the little ball that you've got in your flow metres and you're gonna turn off the oxygen flow metre.

And you're gonna check that the emergency oxygen flush works by pressing it. Obviously, you should hear a sh of oxygen. As you press it, and then it should stop.

Once you've stopped pressing the button once you've released it just as a side note, never use the emergency oxygen flush When a patient is connected to the anaesthetic machine via a an anaesthetic circuit, it comes out way too fast and it can damage their lungs about 20 to 30 litres per minute. It will come out so it comes out extremely quickly. It can damage their lungs.

And also, if you're doing an IP PV and you're trying to fill up your bag more quickly, the emergency oxygen flush actually bypasses the vaporizer anyway, so it doesn't collect any iso fluorine or sever fluorine before it comes to the patient. Unlike if it goes through the flow metre. So if you're trying to keep that patient anaesthetized and you're I, you're bagging it.

You're not actually going to be giving any a a anaesthetic agent to the patient. I passes the vaporizer, so just keep your hands off the emergency oxygen flush when a patient is connected. Now we want to calculate the amount of oxygen left in a cylinder.

So we want to know a K A also known as will this cylinder last me for the whole general anaesthetic. So oxygen cylinders are typically filled to a pressure of 13,700 kop pascals, which often reads as 100 and 37 on the pressure gauge. So this pressure gauge that you can see here is full to the very brim that is a full cylinder, and E cylinders, which we commonly use on mobile anaesthetic machines, will contain 608 80 litres of oxygen.

But you can see on the table here what size, how much oxygen the other size cylinders will hold? It doesn't matter the size of the cylinder, it will still be filled to 13,700 kop pascals. And as the oxygen drops, the pressure drops at the, at the same.

So it's it drops linearly. So as oxygen goes down, the pressure goes down at the same rate. But this is gonna help us know how much oxygen is left in a cylinder.

So if you look at this cylinder here, this is an E cylinder. So F to 680 litres. This looks about half full, maybe a little bit under.

But all you have to do for this is divide 680 litres by two. And that gives us 340. So we know that this cylinder has got about 340 litres of ox has been in it.

This one looks about a quarter full. So we divide that by four, and that will tell us that we've got roughly 100 and 70 litres of oxygen. This cylinder looks about three quarters full, so you divide your 680.

If it's a new cylinder by four and then you multiply it by three, dividing it by four will give us the quarter amount. That's left times Doing it by three will give us the three quarters amount that's left. So this cylinder has got roughly 510 litres of oxygen in it.

Anaesthetic circuits or the posh names. Breathing systems is something I'm just gonna touch on quite quickly. And these are used to deliver anaesthetic gas from an anaesthetic machine and into a patient's lungs via the endotracheal tube.

Inhalational anaesthesia is so efficient, and it's a really controlled method of ensuring that patients stay adequately anaesthetized during surgery and also reduces the risk of light, anaesthesia and therefore the animal's ability to feel to move during a surgical procedure. But it also prevents us from delivering too much. And so having deep anaesthesia or accidental overdoses, which can happen when we're using Tver.

So total intravenous anaesthesia. I'm not gonna talk about the advantages and the disadvantages of each of anaesthetic circuit. I could cos I'm quite passionate about it, but it is beyond the scope of this lecture to cover all of that.

And I don't have time cos I've so much to go through it, that really is a whole other lecture. This table here is just to show you which circuits are appropriate for which size animal. And then in the next slide, I'm gonna tell you how to, calculate how much oxygen to deliver per minute, depending on which circuit you're using.

And the weight of your animal. Now some people find remembering how to calculate, your fresh gas flow, how much oxygen you're gonna deliver find it quite difficult to remember the circuit factor and the mass that they need to do. And there is a little rhyme.

And if you can remember these top four the a ST piece, the ba the lack and the, and the mil la then you're OK because the circle is something separate. So if you just try and remember the a ST piece and the vein that's that's gonna set you up for, being quite successful. So if you think of them as their letters A and B and you can see there that the circuit factor, which is the amount you have to multiply the minute volume by to work out the fresh gas float.

Talk about this in a sec is 2 to 3. And I've also written that it's good for IP PV. So if you're needing to bag a patient or do intermittent positive pressure ventilation your airs T piece in your brain, your A and your B are gonna be your circuit of choice.

So you sing a little song which is a B 2 to 3 good or IP PV. And if you can remember that if you remember that your airs in your air in your brain your ST piece in your brain is 2 to 3 for the circuit factor, for the circuit factor, Then you can usually remember that the lack, the parallel lack and the Mini Lac is just 1 to 1.5 that just you can just remember that cos that's easier.

But yeah, a B 2 to 3. Good for IP PV If you get that in your head, if you know you're gonna have a patient as well, that's gonna need IP PV for whatever reason, those will be your anaesthetic, circuits of choice. And you can remember that little rhyme to help you so calculating fresh gas flows.

First of all, you want to calculate the patient's tidal volume. Now, this is the amount of oxygen that a patient breathes in and out in one breath. So imagine it like the tide, the amount of oxygen they breathe in and out in one breath.

And for cats and small dogs, they need 15 mils of oxygen for every kilo of body weight. And for medium and large dogs, it's 10 mils per kilo. So all we have to do to work out the tidal volume is to 10 to 15 mils times by their body weight.

That will give you the tidal volume. Then we have to calculate the patient's minute volume. And this is how much oxygen they're gonna breathe in and out in one minute.

And all you have to do this is multiply the tidal volume that you've just calculated by the respiratory rate. So how many breaths they take in one minute? Multiply that by the tidal volume at one breath in and out, and that will give you your minute volume.

Note this down. So then, to work out your fresh gas flow, you multiply the minute volume by the circuit factor and that will give you a fresh gas flow rate. And this is what the amount This is what you're gonna set your oxygen flow metre to.

OK, so I hope that makes complete sense. So yeah, the circuit factor is the amount you must multiply the minute volume by to prevent Reb breathing. So when you're using an a ST piece, a vein or a lack or a McGill, if you've still got a McGill in practise, you need to have fairly high fresh gas gas flows to prevent that animal from simply reb breathing.

It's exhaled breath, which is full of carbon dioxide. That's why we have such high fresh gas flows when we're using non rereading systems, which, which is your T piece. Your pain, your lack and your McGill circle is, a different type of anaesthetic circuit that is a rebreather circuit, so we'll talk about that one in just a minute.

But let's just double check that the the mass is clear. So if we've got a three kilogramme cat on an a ST piece, we want to calculate how much its fresh gas flow is gonna be, what we're gonna set that flow metre to. So, first of all, you are going to, work out the tidal volume, which, for a cat is 15 mils of oxygen for every kilogramme.

So 15 times three is 45 mils, and we're gonna multiply that by its respiratory rate. So let's say it's 20 breaths a minute that gives us then, a minute volume. So 45 times by T 20 gives us a minute volume of 900 mils.

That's how much oxygen that cat needs in one minute. But we still need to multiply it by the circuit factor to prevent that animal from rereading in its exhaled breath and the circuit factor for the T piece. Remember a B 2 to 3 good or IP PV.

So the circuit factor for the T piece is 2 to 3 Do both calculations, so you can check. So, between 1000, 800 mils per minute and 2700 mils per minute. Divide that by 1000 and that gives you your litres.

So for a cat three, a small three kilogramme cat, you're gonna need 1.82 0.7 litres of oxygen per minute.

Now, if you're doing a 14 kg dog G A and you're gonna use the parallel lac, you refer back to the table. You'll see 14 kg. You'd probably be using a lack or a bin on this patient.

But let's do the Lac today. That's a 10 mil per kilogramme. Oxygen.

Delivery it will need for its tidal volume. So 10 times 14 it's 100 and 40 mils times it by the spirit rate. But let's say it was 15 breaths a minute that we counted in our pre op check.

So that's 2100 mils it needs. That's its minute volume. How much it will need in one minute.

Multiply that by the circuit factor, which we remember is 1 to 1.5. So divide that by 1000.

This dog needs a fresh gas flow of 2.1 to 3.2 litres per minute.

And this is why we do not just set patients to two and 2 2% iso fluoride, two litres of oxygen generally not going to be sufficient, though I do obviously know, and I did it myself in the past. A lot of people would just go two and two not, very accurate, realistic issues with large dogs. Now, if you're working in a practise that doesn't have a circle, or people aren't comfortable using the circle cos it is a bit more complicated, then it might be that you use the lack or the bin.

But there are realistic issues with large dogs going on lacks and bins. So let's just say that you know, you're gonna be doing IP PV and you've chosen the bane and you've got 35 kg dog. You're gonna run into problems so 10 times 35 to get your tidal volume.

35 3 makes 350 mils for your tidal volume. Then you times that by your respiratory rate. So let's imagine as well.

So now you've got a minute volume of 4.2 litres a minute with not even multiplied by the circuit factor. We know that the bin maybe 2 to 3 the bin as a circuit factor of 2 to 3.

So look how high this fresh gas flow is gonna have to be between 8.4 and 12.6 litres.

So that's a disaster, cos flow metres often don't even go up past 10 litres per minute. So this is when we really want to be considering using your circle. So the circle is a rereading system that has got soda lime, within a canister within it.

And that absorbs the exhaled CO2. And because that's absorbing your exhaled CO2, you don't need such high fresh gas flows to wash that exhaled breath away before the animal breathes. And again, there's unidirectional valves or one way valves on the circle, which means the animal cannot possibly physically breathe in its exhaled breath of carbon dioxide.

So the circle is super economical and can be used on patients 15 kg or over. Just some considerations to be aware of when the patient is first anaesthetized and placed on the circle system. High levels of nitrogen are exhaled by the patient because room hair room air, which the animal has been breathing, has a high nitrogen content.

If this nitrogen is allowed to build up in the system, then the gas that the animal is breathing will will become, Hy hypoxic. mixture. So therefore, a higher fresh gas flow just initially needs to be used for the 1st 15 to 20 minutes to avoid this.

So usually that's 100 mils per kilo per minute. So stuff for 35 kg dog that's still only 3.5 litres a minute, and you would run this with your valve open or semi open.

And then, after you've done your 15 to 20 minutes, you can drop them to a litre a minute and have that valve semi open, and it's really economical. The less oxygen you use, the less volatile agent you will use as well. So it's better, for, financially, it's better.

There's advantages to using the circle like it's nice and warm. It keeps the patient warm. You're gonna be changing that oxygen cylinder less frequently as well.

It leaves you free to check on your patients more. So the circle is a is a great breathing system to use. You can even use lower fresh gas flows if you're monitoring tidal CO2 on your patients.

So if you've got, capnograph and you know how to use it, have this attached and you can drop below one litre if you need to. A little bit daunting to start with to have such a big animal on such a low fresh gas flow, but you can do it, but don't drop below half a litre per minute of oxygen because the vaporizer is not accurate after you drop below half a litre of oxygen. And please don't forget to keep an eye on the soda line because it does become exhausted.

So with the soda line, you need to be looking for, colour change. Once it's once it's exhausted, it won't be absorbing CO2 anymore. So when you see a colour change, so often it goes from white to, Violet.

If you're using the white stuff or pink to white. So obviously remember which way round it is, if it's no longer producing heat because these are hot when you feel them, or if the animal is rereading and you'll see that if you can if I'm not touching on typography today. But if you understand typography, you see that the the line is not going down to base to the baseline, and that means the animal is rereading or if the animal is hypercapnic.

So if you're using capnograph and you can see that it's, Nidal CO2 has gone above 45 milligrammes, of Mercury. Then, that could be a sign that your soda line is exhausted. If there's when when you've got over 50% colour change, that is really when you should be changing your soda line.

But remember that these can change back to their normal colour overnight. So when you see that colour change 50% or more, make sure you change it there and then you can also record how long you've been using that particular circle breathing system for, and once you get to eight hours, then you should be changing it. Regardless.

It's quite a crude way of doing it, and it re requires really a, accurate record keeping. But you will see it on some cylinders. People will write down how long it's been used for.

It does rely on everybody doing it. But then after eight hours, then you change it, but basically keep an eye on the colour using the correct size bag. So is the bag size gonna be OK?

This is very simple maths. All you have to do is multiply the animal's tidal volume by 3 to 6, and that will tell you if the bag size is correct. So, for example, if you have a 22 kilogramme dog, to work out its tidal volume, remember you times by 10.

So the Tide's going in and out that one. How much oxygen they're gonna need in one breath. So a 22 kg dog will need 220 mils.

We multiply it by three. That's, 0. 0.66 of a litre.

We multiply it by six. It's 1.32 of a litre, so we could potentially have a dog, on a 1 to 2 li on a one litre bag or a two litre bag.

Go bigger just to be on the safe side if you can't do the maths. If you're racing around too much, you can't do the maths you can. It's crude, but you can just get the the bag light on the dog's chest.

If that looks about the size of the lungs and it fits that size dog's chest, then you can use that bag, but basically want to make sure that if that dog takes a really big breath that there is enough room in that, bag. When the animal exhales, OK, calculating the total amount of oxygen needed for the procedure so that you will know if you've actually got enough oxygen in your cylinder, so Now that you know how to calculate how much fresh gas flow you're using, you're gonna be using. Now you want to check.

You have got enough of the length of surgery that you're going to be doing. So calculate what your fresh gas flow will be. Discuss with the vet how long the procedure should take, and then you simply multiply your ga your fresh gas flow length, your your fresh gas flow and then times that by the length of the procedure in minutes.

So your fresh gas flow times by the length of procedure in minutes, and then you look at the oxygen cylinder and you gauge if you've got enough oxygen there or not. So if you've got your 14 kg dog, say it's gonna be a bit spacey. We calculate it on the parallel lack.

It would need 2.1 to 3.2 litres of oxygen.

Let's say a bit spa is gonna take 60 minutes, so times are 3.2 by 60. That gives us 100 and 92 litres of oxygen that we're going to need.

OK, And that's, not being very generous because, as we know bit sprays can go on for longer than that. But if you're doing a 60 minute procedure, 14 kg dog on a bit spray, 100 and 92 is the minimum amount of oxygen you're gonna need. So this cylinder looks about a quarter full.

It's an E cylinder. So remember we've done 680 divided by four, and that gives us 100 and 70 litres in this cylinder. So I would be making sure I have a another cylinder on standby ready to swap over.

Or I'd get a different anaesthetic machine with a fuller cylinder just if you've got the luxury of swapping anaesthetic machines and then give this to someone who's got a much shorter procedure coming up to get it used up. But just be aware that you can easily calculate if there's enough oxygen left for the procedure you're doing in a cylinder Leak testing. Now we should be leak testing our anaesthetic circuits, because we don't want to be breathing in an anaesthetic gas, too, and also we want to make sure that all the anaesthetic gas we're delivering does go to the patient.

So it does say it does say adequately anaesthetized. I remember I did a shift once, and I leak tested, before doing it, as I automatically always do. And I got told I was posh for doing this.

And it's not posh. It's just being safe. So the way you do this is you attach the anaesthetic circuit to the common gas outlet, and you close the A PL valve.

And then using usually the palm of your hand, you cl the patient end of the anaesthetic circuit. If you're ever in any doubt, which is the patient end, if you just there's loads of tubes everywhere. It's always the end that's got, a ring, a ring within a ring.

And that's obviously the bit that will connect to the ET tube. If you look at all the tubes on your anaesthetic machine, the one that's got an outer an outer circle and then an inner circle always gonna be your patient end. And in an emergency, that can be really helpful if you're so you're not just connecting loads of different tubes.

OK, so include the patient end with the palm of your hands. So you're like that and then using the emergency oxygen flush. Fill the reservoir bag full capacity.

Once it's really full. You can give it a squeeze, and the bag should maintain its pressure. You should not hear any hissing or any leaking.

And you certainly shouldn't see the bag deflating once you know that your bag is, that your whole circuit is not leaking. You can then reopen the a PL valve. And it's really important that you remember to reopen the a PL valve.

Because the high fresh gas flow, that is coming in to the patient. If you haven't opened that a PL valve, the animal will be able to expire. It won't be able to exhale, and it will be stuck in inspiration.

And then that pressure that's on that high thoracic pressure prevents venous return to the heart, and therefore, it, reduces cardiac output so the animal will die very, very quickly. So just remember to always reopen your a PL valve after leak testing. Now, now you've done this.

So you've been doing all of this stuff in the morning leading up to the anaesthetic. Now you want to be choosing your en, your endotracheal tube size. So a lot of time over time you'll become very experienced at choosing which, size tube.

You're going to collect, and lay out before your anaesthetic. Some people like to measure the end of the nasal, the endotracheal tube between the, the the septum width to help decide what size tube you're gonna use. This can certainly be useful in the in the early days.

You also want to make sure that your length is correct as well, so you can hold it up against the patients. As seen in this picture, the connector end. The end that's gonna connect to your anaesthetic circuit should be flush with the incisors and the tip of the ET tube that goes down into the lungs.

That shouldn't go past further the point than further than the point of the front of the shoulder. If it's longer than this, you could accidentally injure debate one lung, and if it's longer than that coming out of the mouth, then that is a lot of dead space between the animals. Where it's actually gonna have the 02 exchange going on, and then where it connects to the anaesthetic circuit.

That's a lot of dead space. And then we could see reb breathing, which is an issue when you're collecting your tubes off the rack. You wanna choose the, the size you think you want the size above and the size below, and then lay it out in a hair free area.

If you're doing a brachy a brachycephalic anaesthetic, just grab all the tubes. You're gonna you're not gonna know what you need. Just grab them all.

Make sure you grab really tiny ones as well. Cos what you think you need, it's probably gonna be a lot, lot smaller and inflate your cuffs before you, use them on the patient. You want to make sure that these cuffs on the tubes aren't leaking and you simply do that by filling the balloon of the ET tube with a S, a syringe of room air and then leaving them sitting on the side for 10 minutes and make sure that they don't go down.

Fill them to full capacity again before you induce anaesthesia. Make sure you've de deflated your, cough because you should have everything ready to go and not be panicking on inflating coughs before you, place them. Okey dokey.

And then you want to prepare all your equipment. You just wanna make sure you've got everything you need. I'll just let you have a look at this picture.

Just bed and heat source on table. That goes without saying there should always be a bed on the table. If you've got heat mats.

That's brilliant. Use those as well. Your anaesthetic machine has been fully checked.

Your circuit's been fully checked by yourself. Your a PL valve is open. Ready to go.

You've got your induction agent. So you're on fax alone or your propofol that's drawn up. Hopefully you've got extra in there as well.

You should have saline flush because when that patient comes through, should flush that ca cannula again. Before you try and put in your propofol or or or Alfa alone, your ET tubes should be all laid out lubed, if that's what the vet prefers, a bandage tie to tie it in place in your P is ready. If it's a cat.

A laryngoscope laid out. There are no points in the veterinary world being able to intubate a cat or a dog without a laryngoscope. So if you've got one in your practise, absolutely use it.

It makes for better intubation some people that like using them because they think it makes them look weak. Just use it. It's fine.

You want your syringe for inflating your cuff. Your eye lube should be nearby. Your monitoring equipment plugged in, set up everything untangled, ready to be attached to your patient.

If you've got the luxury of monitoring equipment, your general anaesthetic chart and your pen should be nearby, not scratching around. Have you got a pen I can borrow, and then your emergency drug should also be nearby. And you should have calculated the amount that you're going to need should something go wrong with that patient.

So you're not panicking in a moment of of something, bad happening, OK, we're gonna induce anaesthesia now, so Oh, my goodness. Here we go. It might be out with your control, but try and get the vet to inject really slowly.

And, don't They don't have to give that full bolus. Whack it in to the patient. You want to just be giving little incremental amounts and then checking to if the patient is beginning to become unconscious.

If you whack it in way too quickly, then often you get apnea and it, which is a cessation of breathing, and that can last a while. And that's really an annoying when they stop breathing, Cos. Then when you attach them to the anaesthetic machine, they're not getting any oxygen or iso fluorine or se of fluorine.

So nice and slowly, slower you go, the more likely it will be that you don't experience. The patient doesn't experience apnea whilst they're being induced. You are continuously monitoring the respiratory rate and the pulse rate once they have finished injecting.

Don't immediately discard of the propofol or the Alfa alone, because you might need a bit more of this for an emergency top up later. So keep hold of it. But everything now is nice and calm.

Shouldn't be anybody else really in the room? Just you and the vet, with comfy area for the patient in, inducing into an IV cannula. Once the animal is unconscious and you know it's unconscious because it will have a relaxed jaw tone, its eyes will have will be starting to rotate vent.

Its blink reflex should be reduced. Swallowing should have ceased. Once all of this is happening, then you can start thinking about placing an endotracheal tube.

Let's have a drink, and the nicest way of placing an ET tube is to place a bandage behind the upper canines. Hold the head up, fingers behind the ears and push. Extend that neck so you've got a really lovely straight line.

See some people scruff, for intubation, and all that does is that. Then just tighten the larynx, and it makes it a lot harder for the person intubating to be able to place the endotracheal tube. So as these pictures show, it's a really nice straight neck that we've got there.

If the vet is struggling a little bit or the nurse to get an ET tube in, then you can pinch the skin over the neck and pull out, and that can help widen the larynx. And they're all often very appreciative of that. So that's, a top tip for you.

If it's a cat, you want to apply the inch. Bees, obviously prior to intubation cats can, have very sensitive larynx and it can go into spasms. So we we apply a little bit of local anaesthetic in the form of usually in bees to the cat's larynx before, and you wanna give that 30 seconds to work.

So try and not let them spray and then intubate it. Just be time to be absorbed through mucous membranes. Then you're going to place the endotracheal tube, and you're gonna secure it in place by tying around the ET tube and then behind the ears.

And this is better than tying around the muzzle. If you tie around the muzzle, we can accidentally tighten it too much. And this causes an ischemia or a restricted blood flow, to the muscle, which can cause problems.

As I said, the connector end should not extend past the incisors. If you yourself are intubating the animal, which, truthfully you are, you're working in a practise that lets you do this. My top tip is to make sure the tongue is really pulled out as far as you can got your laryngoscope and stay as ventral as you can.

You don't accidentally pop it into the oesophagus. Stay nice and ventral, and you should get that tube in. If you, if you can't, then potentially the person who's holding the the head up and extending the neck.

Maybe they could just hold it up a bit higher and a bit straighter. Remember that nobody can intubate the trachea of an animal that is still swallowing. So give more induction agent.

You'll see in both these photos that the induction agent is still in the bung of the IV cannula so that more can just be trickled in. Once you've trickled it in, you have to wait another 30 odd seconds to let it work. And if you've got someone who's who's injected a bit more and then trying to intubate, just put your bandage down.

Stop extending the head for them it so that the the induction agent has got time to work and then and then extend again for them. Don't let them keep poking cos it's keeping keeping them stimulated. We want everything whilst we're waiting for anaesthetic agents to work everything to just be calm.

And then, yeah, as I say, use the laryngoscope. There are there are no points of being able to intubate without a laryngoscope. So if you've got it, use it.

It's better for you and it's better for the patient. OK, now we want to ensure that the endotracheal tube is in and we do this not by pushing on the chest, not by ripping some hair out of the poor dog's body, putting in front of the endotracheal tube and then pushing on the chest and seeing if the hair blows. It's quite old fashioned.

So please don't do this. It also pushes out the last remaining, molecules of oxygen in that body. You've probably had an apnea, so it's not gonna be taking a fresh breath any time soon.

And you've just squished all those alveoli together. So what we would like you to do is connect the ET tube to the anaesthetic circuit and set it to the prec calculated fresh gas flow. Do not turn your iso fluorine or your Sebo fluorine on just yet.

We just want oxygen going in whilst we do these last little bits. OK, you have got time. Propofol lasts for 5 to 10 minutes and you've got your pre-med on board.

So this animal is probably going to stay nicely anaesthetized. Whilst you do this, it doesn't quickly need iso fluorine or ceva. Fluorine Plus, your propofol should still be in the bung or your Alfa should still be in the bung of the IV cannula.

If you need to, you can just give it a little bit more that way. We don't want to be putting in isofl or sever fluorine before we know that the tube is in the right place. And before we know there is a good seal around that ET tube.

So we wanna check. It's definitely in the trachea. And we do this by closing the a PL valve.

Squeeze the reservoir bag and you look at the chest of the animal. If the chest rises, then the tube is in the correct place. And don't forget to open the a PL valve.

Once you have done this cos we need that animal to be able to exhale, you've K. If you've kept that valve closed, the animal can't exhale. Pressure builds up, in the lungs squashes the heart and they die.

So if your tube is not in the place, then you need to extubate and you need to reintubate and try again and then go through this procedure again. Close the a P ulcer. Squeeze the bag.

Don't over squeeze the bag. So that you're blowing up the lungs just to a normal chest height. If it's in brilliant, here's a little video to help you visualise this.

So a PL valve fully closed bag squeezed whilst you're squeezing, you're looking at the chest. There's the chest rising and down again and back to open the a PL valve. The second biggest cause of anaesthetic.

Death in humans is leaving the a PL valve closed. So please, please remember to open it. Now, How much air should we put in?

I've seen and I've done it myself over many years. Just put in some arbitrary amount and then I give the balloon a little squeeze. And I think, yeah, that feels about right.

There are special puffer uppers that will measure the amount that you need, but if you haven't got this and there's a really, really easy and accurate way of doing it, and again you need to close the a PL valve. So to check for leaking around the ET tube, close the a PL valve someone squeezes the reservoir bag and you're listening for any noise around the ET tube, and the noise usually sounds like this. As the valve is closed and the bag is being squeezed.

You're having a list with the to the ET tube. And if you hear that means that the ET tube is not a tight fit and gas can leak around the ET tube. It's called breathing around the tube.

So what you want to do is inflate the cuff of the ET tube with a syringe, as as someone else is squeezing the bag until you can't hear that noise anymore. Once you stop hearing that noise, you know you've got a tight seal around, around the in the animal's track. Here, you know you've got a good seal, and you can reopen that a VA PL valve.

Also, the reservoir bag will have resistance, so the person who's squeezing can also tell you they'll say, I can't squeeze anymore. And then you know you've got a good seal and you'll say, Yeah, I can't hear anything And then you're both in agreement that you've got a really good seal, and it's really important for health and safety reasons, especially if you've got pregnant members of staff that you're not breathing in, anaesthetic gas day in, day out, open that a PL valve. You will kill your patient if you don't right.

Here's a little video demonstrating just that this is a child house. So do not worry about the colour of that tongue in case someone's squeezing for her. Ideally, she should be looking at the chest as well.

Just in a perfect world, it would have been good if she was looking at the chest and listening at the same time. There we go. So she's had to do a couple of goes.

And now she's happy that there is a good seal. And we're not gonna be breathing in gas. OK, valve is now reopened.

Now you can start, thinking about setting the vaporizer, so make sure that your oxygen is still being delivered at the pre calculated fresh gas flow rate that you that you've already calculated. Now you can turn your vaporizer on if you're using ISO fluorine, it's typically set to 1.5 to 2%.

And if it's CO 3 to 3.5. But don't whack it up to these big amounts if your patient, if your pre-med was, was really good, or if you think that you've sent your patient too deep a little bit too deep with with your ISO fluorine, so just play it by ear.

But typically these are the settings that we're going to be using. There are several factors that influence the vaporizer setting. So, as I said, if you've had an animal that's super heavily premedicated, then you will need less ISO fluorine or se fluorine.

If you are delivering nitrous oxide as well, it's not as popular these days, but if you are giving nitrous oxide again, it will be less on the vapour. You'll need less vaporizer. A le a lower vapour setting.

If the animal is hypothermic, cold animals need less iso fluorine. They also take longer to recover, so it's not a good idea to let them be cold to save money on ISO fluorine. Severe hypertension.

So if they have got very low blood pre pressure, they need less anaesthetic as well. And obviously we don't want them to be hypertensive. Too much inhalation inhalation agent can reduce their blood pressure further.

And then that reduces, renal blood flow, for example. So not good. Especially if you're gonna be using nonsteroidals and then those young animals so neonates and and older animals, geriatrics.

They also require less inhalational agent pregnant animals, too, will need less. So it's not. It's really not a case of two and two for every single patient.

Be aware of vasodilation. This can occur when you've got an anaesthetized animal. So, B, when an animal vasodilates the diameter of the veins increases the pressure in those veins drops, and also you get more blood flow coming to the skin.

So, and this will cool the patient down quite quickly. So you need to provide heating agents. So if you've got bear hug it brilliant heat mats use those.

That's brilliant. But also blankets and just and hot hands. If you need to have gloves filled with hot water, make sure you're not burning and cooking the patient.

You'll be taking the temperature very regularly, but we don't want these patients to become cold. It's It's quite disastrous for an anaesthetic when they become really cold. And obviously you should have your fluids running as well.

So we've got really good blood pressure going on for these patients. OK, checking pulses. This is so important.

There is no point continuing surgery on a dead animal, So keep on checking those pulses, but your dorsal metatarsal in the left hand picture your carpal artery in the right, and I'm so sorry I didn't have a picture of a lingual artery, but it's basically the, underside. It's got the lingual artery, and it's near the midline on the on the ventral, the underside of the surface of the tongue, and you can just pull out the tongue and put your fingers underneath in the midline. And if you can't feel it, straight away, then sometimes put a bit of KY on your fingers or or on the tongue.

Can really help you feel that pulse, and it's a It's a brilliant one to be able to use cos you're normally at the head end anyway, so just have that tongue out and have your fingers on that pulse. As I say, peripheral pulses are better than checking a femoral pulse if you can feel a peripheral pulse. It generally means your blood pressure is good.

And if your blood pressure is good, then your animal is circulating nicely and oxygen is being delivered everywhere it needs to be delivered to. Now. We need to monitor the depth now that the patient is anaesthetized.

We've checked. It's still alive. We've connected everything checked.

It's still alive. We've done all our, vaporizer settings. We've also checked.

It's still alive. It's now time to start monitoring the depth of the patient. You should not be monitoring and prepping for surgery.

At the same time. I appreciate in many practises that they might have the luxury two nurses, one monitoring and one prepping, clipping and prepping. But if you can divide this job up because anaesthetic deaths when they occur, more likely to occur at the beginning of anaesthetic.

And at the end of an anaesthetic, it's a bit like flying a plane. Takeoff and landing, are the most stressful but exciting times, depending on how you view it. And so we This is when we need to be monitoring the absolute closest.

What actually happens in real life in practise is most of the monitoring takes place, during the middle of the anaesthetic. So we want to make sure we've got two members of staff and then in a busy room like this who is monitoring this anaesthetic? It's this person here, which is me feel for those peripheral pulses.

Blood pressure is good. If it has one, you're gonna be looking at the chest, seeing that rise and fall, you're gonna be checking the colour, of the patient and the capillary refill time. So we're gonna be doing that blanching on the gums, gonna check eye position, muscle tone, and then you're gonna look at responses.

You are the best bit of monitoring equipment. Monitoring equipment is great, but you must never, ever solely rely on it. You, your eyes, your fingers, even your nose for its smelling ISO fluorine are the best bits of monitoring equipment.

This is a great example of why we shouldn't rely on our monitoring equipment solely. This is a pulse oximeter. You can see this patient here is saturating at 98% and, and it has a pulse rate of 71 beats per minute, and it's an elf on the shelf OK, this This is not evidence that they are alive.

This is evidence that your monitoring equipment can lie to you. And I'm sure plenty of you have worked with vets who have left the monitoring equipment on when they've when you've done it on the table euthanasia and you'll see that the pulse ox keeps reading and the ECG keeps reading. So just remember your fingers on the pulse and observing that patient looking at the bag.

And looking at the chest are are the most reliable ways of monitoring. OK, I'm gonna move on now. These are your normal parameters.

You can pause on the screen, but this for a patient under anaesthetic, these are your normal parameters that you should be, looking for central nervous system responses is what we're going to be looking at so that we know that the depth of our anaesthetic is going to be OK. And central nervous system. Depression is what happens when an animal is anaesthetized.

So when how the dog can go from sitting upright like and looking very worried, to just being literally a puddle of jelly on the table is because all the central nervous system. Responses are are diminished. They've all gone.

And that's what we want for, an an anaesthetized patient in a good depth of anaesthetic. So if you've got a patient that's light, you're going to see these, in your different these responses in your different parameters before a patient can be classed as light anaesthetic. I just want to mention there's a stage before that, before you reach light anaesthesia and it's called involuntary excitement comes just before light anaesthesia.

So you might have noticed. When you're inducing anaesthesia, you're holding the patient. The vet's injecting and you might see the patient stop swinging its head from side to side.

Or it might stop paddling. This is called involuntary excitement. There's nothing A patient cannot help but do this.

You might have the most placid of patient start paddling and start struggling if they get stuck in this involuntary exci excitement stage. It's a bit of a disaster if you've only used a needle to induce anaesthesia. This is why an IV cannula is so important when they start paddling.

It can be hard to get a needle back into the vein, but with an IV cannula. You just keep injecting. Keep putting your Prolio off axone into the vein and inject past that phase of involuntary excitement.

And then once they're past the phase of involuntary excitement, obviously we don't want to do it too much so that we don't fully completely depress and kill the animal. So we're doing we're titrate to effect. Then you move into the phase of light anaesthesia.

OK, so eye position with light anaesthesia, it's still gonna be central, But you're going to see that the pupil, is still a little bit responsive to light, so you might still see that the pupil is quite small. Palpal the blink reflex is present. Jaw tone is still there.

So you need to be careful when you're checking jaw tone that you don't get bitten. I do know people have been bitten by animals. During light anaesthesia, little bit of movement may Still, the cornea will still be moist, and we normally see an increase in heart rate and respiratory rate in this moment.

And then as the anaesthetic becomes, we progress through the anaesthetic, we should, arrive at adequate or surgical plane of anaesthesia. And with these patients, this is what we want to see throughout the whole of surgery. The eye position rotated vent.

So it's down, or ventral medially. Our pupils should be absent or D sluggish. No, no jaw tone, no movement or near is still moist Heart rate.

Respiration usually decrease. So this is the eye, that we should be, the eye position that we should be seeing with no pulpy people. And when you're checking the palpil, it is just a gentle stroke on the medial pans.

Not a big path like that, OK, just a gentle stroke to check the response. If we have given too much anaesthetic and we've gone into deep anaesthesia, what we'll see then is the eye coming back into a central position and the pupil will be dilated. Look how dry that cornea is as well.

It's got a real fishy eye stare going on here. Obviously we we have the others. The jaw tone is absent, movement is absent, heart rate and resp respiratory are even more decreased now.

So your eye is your best friend during anaesthetic and your monitoring that a note on checking jaw toone don't just pull at the bottom of the jaw to check jaw tone. You're not actually measuring against anything if that's how you're checking jaw tone. The vet in this video is just gonna show you how to measure your tone.

He, this was an attract you to return programme anaesthetic machines available. So this is Teva anaesthesia. Total intravenous anaesthesia.

But you can still see that the patient is still intubated. Still got an IV cannula. There's an esophageal stethoscope in there as well.

So all the monitoring that goes on is the same, even though it's not connected to an anaesthetic machine. So you've got one finger or a thumb on the upper canine, and then you push away, I'll just show it again. Yeah, so usually your middle finger on the lower canine and then use your thumb to raise the lower jaw at lower Canine.

And then this muscle here in your hand starts becoming very sensitive to how much tone is in that muscle. How much you've had to, how much effort you've had to put in to open the jaw. So that is the correct way of checking jaw tone.

Now we'll just do a quick bit of troubleshooting. So, bradycardia, why is the heart rate slow? Well, drugs can certainly slow the heart rate and heart rate.

A low heart rate means the cardiac output might be insufficient to maintain adequate blood pressure. Drugs can cause this problem. Giving too much of the inhalational agent can also cause a bradycardia and also something called vagal stimulation.

So this is activity of the vagus nerve, which is responsible for regulating the heart rate and vagus Excuse me, stimulation might be caused by laryngeal stimulation. So when you're intubating the patient handling or pulling traction of the viscera during surgery, ocular manipulation, or ocular pressure surgery, and periosteal stimulation. So we need to just be aware that bradycardia could be caused by that, but but very often it's caused by drugs or or a deep anaesthetic.

So what can you do to correct that slow heart rate where you can reduce your anaesthetic depth by turning down the vaporizer? You can ask the surgeon to stop stimulating the vagus nerve if they can possibly and you can administer drugs such as atropine or glycopyrrolate if necessary. But don't give it if you've given meat toid so sedor or doma cos this coadministration can result in, arrhythmias and then a significant hypertension.

So really high blood pressure if you give atropine and glycoprep blood pressure. So that is how you can, treat bradycardia. And then we've got reasons for the opposite.

So tachycardia again drugs can affect that. Atropine. Epinephrine.

Adrenaline. Tucky cards, Yeah, can decrease cardiac output because there is less time for the ventricles to fill. So then the workload on the heart is increased.

And this, Myo myocardial oxygen con consumption can lead to a myocardial hypoxia. So we do need to be careful with this, and then prolonged tachycardia can predispose the heart to ventricular arrhythmias. And this is when the heart rhythm, is abnormal, and then the lower chambers of the heart might twitch instead of bump.

And then this can limit or even stop the heart from supplying the body with blood. So we really don't want to be seeing prolonged tachycardia, so we want to be correcting it straight away, but drugs can cause it in an adequate depth of anaesthetic when you've got them too light that can, cause a tachycardia. Pain can cause tachycardia.

We need to be so tuned in to what we're doing in the surgery. And it might be something super painful, that we're very aware of, like pulling on the ovaries or, drilling through bone. But it also might be the position of the patient that's causing them to be tachycardic.

So if you've got a very arthritic animal and you put them in a super unnatural, uncomfortable position, then they might respond with a tachycardia and then hypertension. So low blood pressure, will cause the heart to beat faster as it tries to correct its blood pressure. And then a low blood circulating volume will also cause the heart to in increase and get the blood around the body.

So how can we treat it? We can increase the depth of anaesthetic. Obviously, we need to identify the underlying cause of this tachycardia.

But we can increase the anaesthetic depth by turning down the vaporizer. We can increase, our analgesia if we think it's a pain response and the way to know if it's a pain response rather than an inadequate depth is to look at your depth of anaesthetic. So if you've got eyes rotated ventrally, you've got no palpable reflex.

You've got no jaw toone, muscle tone movement, vocalisation, and you see a tachycardia, Then that animal needs more analgesia. But if you see a tachycardia when you've got blinking and the eyes have come back up in a bit of movement, then that animal needs more anaesthetic. And when you're thinking about analgesia, it might be that you can do something fancy like on the left picture and do a constant rate infusion of an analgesic drug.

Ketamine. Or it might be that you can, add in some more methadone If you've given methadone in the premeds, there's always quite a lot of wiggle room with methadone, so you can give a top up of methadone. If you have got a dog on the table and it's acting a bit painful, then paracetamol could be given IV.

But also you could offer the vet some local anaesthetic, and they could inject that into the area that they operating on so that, the the the signals of pain are completely blocked to the brain by giving a local anaesthetic. So there's always something you can be doing to make things better for your patient. You can reposition them if it's an arthritic patient, and you put them in a really awful position, hold out their hips.

Maybe too much might be that you need to pad underneath them and make them more comfortable to reduce that tachycardia. And if they're hypertensive, then obviously you can be administering fluids at a rapid rate. Try and get that blood pressure back up hyperventilation or or tachypnea or tachypnea, however you want to pronounce it, but this is defined as an increase in the minute volume.

So remember the volume of air that the animal, breathes in and out in one minute. And it's normally, due to an increase in respiratory rate so pain can cause this inadequate depth of anaesthetic can cause this. And remember, pain doesn't have to be in really common, uncommon procedures like or procedures.

If you're working in first opinion, it could be something that's routine, like dental pain as well. When you're extracting a tooth, so think about that is a really painful procedure. But because we're doing dentals every day.

We often don't think too much about how painful it is. Pyrexia. So an infection and hypothermia can also cause, can also cause tachypnea.

And this is due to an increased heart rate as the body tries to cool itself. And then you've got, like, increased oxygen. Need treatment of hyperventilation or Ayia Well, you can increase the anaesthetic depth, obviously, by turning up the vaporizer, or administering more anaesthetic drug intravenously.

If it's looking like the animal is gonna get way too light, you can give more analgesia if it's pain that's caused it, and you can actively call them if they hypothermic. So this is a cat here. That was, tip Nick, whilst having a tooth extracted.

And this is local being injected. If it's a sterile surgery and the vet wants to inject local anaesthetic, then you can give them a sterile needle and syringe, and then they can and you hold the bottle for them and they can draw it up themselves. Lots of ways around it.

Reasons for hypoventilation. So that's defined as a reduced minute volume due to a reduction in respiratory rate and a reduced respiratory rate, so hyperventilation that can lead to hypercapnia, which is increased levels of CO2 in the blood. And it's important that we treat hyperventilation because hypercapnia can cause central nervous system depression, and we definitely don't want that to happen.

And hypothermia, which can also happen, can, lead to respiratory arrest. So if if they're hypothermic, then we'd really need to be treating these cold patients. But hyperventilation can also be caused by an overdose of anaesthetic, and accidentally intubating one lung, which is why our ET tube needs to be the correct length.

Treatment for hyperventilation is quite straightforward. Reduce your anaesthetic depth. Consider IP PV.

So that's close the valve. Give a breath. Open the valve, aiming for about four or five breaths a minute, or we can actively warming them actively warm them.

We obviously have to identify the reasons for hyperventilation, but these are some of your treatments. OK, what should you be monitoring? This is an anaesthetic chart that you can record on every five minutes, and we should be noting down the animal's pulse rate, respiratory rate, their eye position, colour of the mucus membranes, the capillary refill time and their jaw tone and their temperature.

And we should be noting this every five minutes. If you've got monitoring equipment, then, yeah, note down the blood pressure, the oxygen saturation and your tidal CO2 as well. If you haven't got much monitoring equipment, don't worry.

As I said, nothing can replace a well trained nurse when it comes to monitoring. And as as you've noted, machines shouldn't be relied upon, too much. Make sure that you are letting the vet know how the patient is doing under anaesthetic, and you can make suggestions to the vet about what you think the patient might need, whether it needs more or less iso fluorine or more analgesia, or the fluids increased or more heat sources if you feel confident enough to do that, or you can ask the vet what they would like you to do in response to your findings, so it depends what level of confidence you're at.

But it might be that you're confident enough to say his respiratory rate has dropped and his eyes look to becoming safe with pupils dilated. Would you like me to turn down the vaporizer? Very reasonable suggestion.

Or you might be happy to say the eyes are ventral. There's no jaw tone or palpable reflex, so depth is good, but there's been an increase in heart rate and respiratory rate. Would you like me to give more analgesia?

And the vet then can make an informed decision about what should be done with that anaesthetic. But in time and with, an experienced, RVN guiding you, you'll hopefully be able to gain confidence to be able to problem solve on your own. But you should always be checking in with the vet first.

You don't want to be breaking the law because we should be under veterinary direction. Anaesthetic charts must be filled, and they are a legal document, and they should read like a story so that when you look at an anaesthetic, chart it. You can see how you responded to any, changes in depth or any changes in parameters.

So, for example, the heart rate increases due to pulling on the ovaries. You should have noted that you gave, for example, 0.1 mix the kick of methadone slow IV that it it does read like a story or, you should be giving an explanation for an increased respiratory rate.

And then the provision of IP PV. And it might be that patient you might have written Patient moved from ventral dorsal recumbency to sternal cos that can stimulate an increase of heart rate and respiratory rate. But we should be noting down what was happening as each of these differences, or abnormalities occurred during the anaesthetic.

OK, we are almost done. And I want to finish with Nolan PAK a your analgesia arsenal when we're thinking of analgesia, we need to try and remember this acron acronym so that we can make sure that we've thought about every analgesic that we can give to a patient. So no, and P stands for your nonsteroidals.

O is for opioids. L is for local or lidocaine. A, a is for your alpha two agonous your medicidin.

So a lot of people don't think that that's got analgesia in it, but it has. N is for N MD a antagonists. That's Caine.

So that is a great drug to have on board because it potentiates other analgesics as well. And then your last one dogs only is paracetamol. So when you're thinking of analgesia, think Noel and P have we exhausted everything in our arsenal for this painful animal.

When to extubate. When the animal when the animal is fully conscious, is when we're gonna extubate. But just before we extubate, I just want to say something about turning the vaporizer down slowly whilst the vet's putting in the final sutures, animals should not be in a limbo state of anaesthesia.

They should either be anaesthetized or they should be recovering. Nothing in between turning the vaporizer down as you come to the end of the surgery. So whilst you're suturing is a hangover from the days that we used an, an inha inhalation agent called Halothane Halothane it did take them along Time to recover, wake up, recover from.

And so we did used to turn it down slowly. If you are still using halothane, then keep on doing this. But with iso fluorine, certainly with super fluorine, it's very short acting so on or off.

Nothing in between. Placing sutures is really painful and you do not want to be become unconscious as sutures are being placed. Once you have turned off the Anna off the, the vaporizer.

Keep the patient attached to the anaesthetic anaesthetic circuit with oxygen still flowing for a few minutes. This isn't to flush the patient out. Its own lungs will flush out the ISO fluorine, but it is to ensure that all those exhaled breaths that will still contain iso fluorine for several minutes of going into the scavenge and not into room air, you might have walked into, up, theatre after a surgery sometimes or into kennels of recovering patients and gone Stinks of ISO in here.

So with those with all patients, they should be kept attached to the anaesthetic machine so that their exhaled breast can go into the SCA scavenging system and not into room air. Make sure the kennel is warm and cosy. Hypothermic animals really suffer in research in humans.

It's shown that actually being cold is what they've reported as being the worst thing about their time in hospital. And that's even over the the procedure, the surgery itself. So don't let them be hypothermic.

Also, do not overstimulate them to hasten the return of the re reflexes before extubation. We're all busy we've all got big opsal list. But when you artificially stimulate them, when you pump their legs and when you tickle their ears, if you clap in their ears, you are artificially rising their depth of anaesthetic, and then they'll swallow and you remove the tube.

You now no longer have a protected airway, but because the tube's out, many people think they can just leave the patient safely because it can't bite through the tube now and choke. But what you've done is remove your protected airway artificially stimulated that patient, and now it's gonna sink back down into the depth it actually was. So stroking is fine.

Using their name is fine. Their name is familiar to them, so please do that. But don't artificially overstimulate them.

If you've ever had an N aesthetic yourself, it is a very strange and worrying experience, So please, please treat them super calmly. When anaesthetic does occur, 40% of them occur in the recovery period, so be patient. Sit with them, try not to hurry them.

Dogs can be extubated when swallowing. If they're racy, keep it in for as long as you possibly can. They are loving having that tube in cats can be extubated when they're blinking, and the blinking will be seen before swallowing.

So you do E, extubate cats earlier than you would a dog. And this is because of the sensitivity of their larynx. So we want them still to be a little bit anaesthetized.

When we take out that tube and irritate their larynx, keep monitoring them until they are sternal. That is when we know that they can hold their own head up, heads up and usually, breathe quite happily themselves. So recovery, as I said, use their name to reassure them.

It's the only thing to them that is familiar about their day. T PR temperature pulse respiration regularly. If the patient is warm and the thermometer is bothering them and consider the patient's welfare do you need to keep taking the the temperature You do still need to keep temp, taking a te, pulse and respiration, but you might need to lay off on the thermometer, bothering a bit pain.

Score them one hour post extubation. Please. Please don't forget to do this.

Use the Glasgow composite measure pain scale. I cannot stress enough. I don't have enough time to talk about this.

I've gone over, but please be pain scoring them after you've ex an hour after extubation and then regularly after that. No animal in this day and age should be painful after surgery. Surgery is 100% predictably, predictably painful, but suffering is optional, so please pain, score them and report to the vet.

All your findings offer meal and water when they are fully conscious, but make sure that you're observing them. Make sure that cats have got a litter tray, and that dogs are taken out to the toilet. It's a really unpleasant feeling, needing the toilet and not being able to go.

It's very stressful for them, and it reflects very poorly on the practise. If they go home and we in their carrier, they're cocking their legs as soon as they get out of the practise, so make sure that they've had the opportunity to toilet continue with fluids. Some places like to take out the cannula as soon as the anaesthetic is over, But number one you don't know if you'll need to give emergency drugs, and two, they should be on fluids and still getting fluids.

And then you remove the cannula about 30 minutes before going home. Very often that cannula is left in till the last second. The owner turns up panicking, ripping out the cannula.

You have to put a pressure bandage on patient go ho goes home with a pressure bandage on, and the owner might forget to take it off, and then it swollen, poor, and it's all just awful. So everything nice and calm and done in a good process. I hope that was helpful.

Thank you so much for listening. I'm sorry I went over. I was gonna finish with a a picture of me with a patient that I loved.

But I just wanted to use this last second to promote the cenas vein for IV cannulas. Don't keep bashing away the cephalic. If they're They're all tattered and gnarled and have been used lots and lots of times.

Treat yourself to a fresh the Penis vein. Lateral or medial. They are beautiful.

They're springy. You usually get them first time. They're away from the head end so often it's less stressful for the patients.

Thank you very much.

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