Anaesthesia Procedures In Dogs

[Erny]

This should probably go in the health forum, but because it is a spin off another thread that began in this forum http://www.dolforums.com.au/index.php?showtopic=217517, thought I'd continue on here.

My question relates to anaesthesia procedures and I am obviously quite confused/unknowledgeable about how it all works. I don't think I need to know technicalities so much (otherwise I might as well go to Uni and do the years worth of study our many talented Vets do) but I'd like to understand the basics of it a bit more than I do.

So, my boy had a teeth cleaning procedure recently.

He had a pre-med which (in the other thread) we've deduced is "Ace". This of course is what makes my dog initially sleepy and less aware of surroundings/goings on.

I'm informed by another (obviously more knowledgeable than I) DOLer that he then would have had an IV induction agent and then onto gas.

Ok - so what does an IV induction agent do?

It was also suggested that the pre-med would have most likely been an Ace/meth combo. What is the difference between Act and Meth and why would they be used in combination with each other?

I'd like to be able to get my head around these things and I'd appreciate your help

Edited March 25, 2011 by Erny

[Rappie]

Acepromazine is a sedative drug used (in basic terms) to help the animal relax. It can help to reduce anxiety and awareness of surroundings, although technically it does not have an anxiolytic (anxiety reducing) effect. At higher doses it can cause quite a bit of 'grogginess' - although in Australia we tend to use lower doses than in the USA. Methadone is an opiod drug, used primarily to provide pre-emptive pain relief but it also has some sedative effects. By giving pain relief before the pain receptors are stimulated, we reduce the amount of reaction from stimulation during a procedure and can better control pain afterwards (much easier to prevent and treat, than try to 'rescue' it later).

Together the two agents reduce the amount of anaesthetic agent required to induce and maintain anaesthesia. The induction agent is the one that is given to cause initial anaesthesia, they generally only have quite a short duration of action - the newer drugs only about 5-10 minutes, thiopentone a bit longer. This is long enough to place a tube into the trachea and start the animal on inhaled gas - or the maintenance agent, which is used to keep the patient asleep. The advantage of using gas over continued IV administration of a drug, or a longer acting injection is that we have much better, and more rapid control over the anaesthesia itself. If the patient is too light, we can deepen the plane of anaesthesia. Too deep and we can lighten it. Once the gas is turned off, the recovery is usually fairly rapid. In most routine surgeries, the premedication drugs last longer than the procedure, so the patients wake up nice and quietly from their 'snooze'.

If no premed is given, a lot more induction is required to make the transition from awake, to asleep and it can be referred to as a 'crash' induction (although this often refers to a gas only induction). The recovery can be equally violent - much thrashing and incoordinated movement. There is a middle phase known as 'excitement' between conciousness and unconciousness - premedication allows us to basically skip this step.

Why do we want to use more drugs? When we use them in combination, we can use lower doses of each drug and get greater effect. Each of the drug have their own side effects, so by combining them we get a better anaesthesia with less side effects, which then gives us a smoother result and better control over what is going on.

That's a very quick run down, but I'd be happy to answer more questions. Let me know if it doesn't make sense and I will explain further.

Edit for spelling/grammar. It's late, lol

Edited March 25, 2011 by Rappie

[Flick_Mac]

We are just doing anaesthetics at uni at the moment... learning about all the drugs and the anaesthetic machines.

In fact, today, in another prac we had dogs under purely by IV drugs (not sure what they were using... we weren't monitoring the dogs) and they had to be very closely watched and topped up with IV anaesthetic agent every 20 mins or so. I definitely prefer using gas!

[Sayly]

We are just doing anaesthetics at uni at the moment... learning about all the drugs and the anaesthetic machines.

Same with us Flick, I think we've only had about 4 lectures so far though and pracs are later in the semester for my group, but I'm finding this thread and the other one very interesting!

[Rappie]

IV maintenance certainly has it's place but it's not generally used for long term maintenance for surgery. It's great for some situations where a light plane of anaesthesia is needed and it can be used as a constant rate infusion - good for situation with constant seizuring like snail baits or status epilepticus, or if for some reason you can't use an anaesthetic machine (like in an MRI). Sometime we might only use an IV agent if we want a very quick anaesthesia, like to pull a toe nail or remove a bone lodged in the mouth etc - but these cases would still get a premed.

For interest, providing local anaesthesia is another way to reduce the amount of anaesthetic agent used. We use lignocaine blocks a lot for tooth extractions, it means we can have all the benefits of a lighter plane of anaesthesia like less hypotension but without having a dog react to stimulation from instruments in the mouth etc.

Edited March 25, 2011 by Rappie

[Erny]

Rappie :

This is long enough to place a tube into the trachea and start the animal on inhaled gas - or the maintenance agent, which is used to keep the patient asleep.

Thanks Rappie. That clears the order of some things, for me .... .

In relation to the above - I don't know if I am mis-reading it or not. So you start the animal on inhaled gas OR the maintenance agent ... . What other "maintenance agent" would there be? IV drugs?

I'm still a bit confused because I know there are different ways of doing things, for different reasons and for different dogs. But this does help me to some extent .

ETA: I think your post above answers my question here. We were typing at the same time .

Edited March 25, 2011 by Erny

[Rappie]

Gas is generally the maintenance agent but it can be something else (IV infusion).

Gas can also be the induction agent, but I generally treat this as a last resort option. It does all sorts of undesirable things to blood pressure, respiration and oxygen levels, is stressful to animal and personnel, and if nothing else means all the humans get a whiff of gas which is an OH&S issue.

It can get confusing but the naming mainly refers to which stage of the anaesthetic process you're at - induction, maintenance, recovery etc.

Edit to add: The important thing is that there is no ONE way to do things. As Stormie said in the other thread, the safest anaesthesia in a particular situation is one that you are comfortable with. There are lots of drugs that do lots of things and many can be used to achieve the same purpose. It is up to us (vets / anaesthetists) to choose drugs that are appropriate for our patient and the procedure, so that we can plan a safe anaesthetic.

I know I bang on about 'planning' anaesthesia - it means taking into account 'expected' unexpected occurences and putting in place measures to prevent or counteract their effects. If we do an eye surgery, we know that meddling with the optic nerve can cause increased vagal tone which can slow (or stop, in extreme cases) the heart rhythm - so we might either include atropine in our premed, or have it drawn up ready. If I have an anaesthetic to do on a dog with heart disease, I will change my induction protocol, use local blocks where possible and have a written list for my nurse of emergency drugs and the doses specific for that patient. It also includes post operative pain relief etc. Although the great majority of cases are going to be 'same old', we must treat EVERY patient as an individual.

Edited March 25, 2011 by Rappie

[Erny]

Lol .... I think you must have read my mind, with your explanation in the 2nd para of your post. I did wonder about it but also thought that it would be particularly awkward for procedures where treatment to the dog's mouth (as in for teeth cleaning) is required.

Your last sentence clears it up quite nicely, and you're right ..... I was getting confused with thinking the procedural phase names also dictated the meds being used.

Thanks Rappie - I can't think of any more questions, although I'm sure that's only because I don't know enough about it to ask.

ETA: Appreciate your edit too, Rappie. It is all helping to make more sense of something I found quite confusing.

Edited March 25, 2011 by Erny

[Flick_Mac]

That's awesome Rappie - we're just getting into the juicy pracs... we have an anaesthetic one where we're knocking dogs out, putting them on iso then waking them up again. I know a few people who've already gone had dogs wake up on them and were quite happy, because now they're comfortable if it was to happen in a real patient scenario.

[Erny]

putting them on iso

What's "ISO" ?

Should I know this? (Erny heads back to re-read in case it has been written or that there may be clues in prior posts )

[Rappie]

Good luck with it all Flick Mac! Anaesthesia was one of my favourite subjects are uni, but we were lucky enough to have 3 fantastic tutors/ lecturers to challenge us. I know it seems overwhelming and some of the physiology gets boring, but it's really fascinating in practice Of course, there's the possibility that I'm just reminiscing all the fun times - I'm a mentor for one of our veterinary nurses doing her Cert IV and we've just had a final year vet student with us for a month.

[Rappie]

putting them on iso

What's "ISO" ?

Isoflurane = inhalant gas. It's predecessor was halothane (halo!). There is also sevoflurane (sevo) which is not used much in private practice.

[Flick_Mac]

Rappie - I thought I'd HATE anaesthesia, but I actually quite like it. We have a bit of a dragon as our main lecturer, but she won't let you get away with 'I don't know', which is good too! And all of our tutors are pretty damn good too which makes things so much better. Oh, and we're down to very small groups which helps a tonne!

I got to induce a dog with Alfaxan at uni the other week, then other people had a go attaching monitors etc. 4th year is WAY better than 3rd.... it feels so much more relevant! I really feel like a 'baby vet' which is what we keep being referred to as!

(Sorry for abbreviations Erny, and going OT!)

Edited March 25, 2011 by Flick_Mac

[Staranais]

I got to induce a dog with Alfaxan at uni the other week, then other people had a go attaching monitors etc. 4th year is WAY better than 3rd.... it feels so much more relevant! I really feel like a 'baby vet' which is what we keep being referred to as!

(Sorry for abbreviations Erny, and going OT!)

Just wait - 5th year is even better!

[jrm88]

I love anaesthesia. I don't think people realise that while it is the vets inducing the animals and dose rates, it is the nurses actually doing the anaesthesia and monitoring the animal while they are under. That is why I get a bit narky when people always go the cheapest route with surgeries. Some practices may not have a dedicated nurse to monitor/do the anaesthesia which puts the animal at a much bigger risk and also may not have all the monitoring equipment. (e.g. alot of practices do not monitor blood pressure but will give a NSAID during surgery even if they do not know if the animal is hypotensive!)

When I am doing an anaesthesia my eyes are on the animal, not running off to answer the phone or attend to a client at the front. We monitor heartrate, respiration rate, blood pressure, Co2, oxygen saturation, temp, ecg and the depth of anaesthesia.

I think we do need to educate clients about the anaesthetic process so they understand what we are doing and why we are doing it (its the best for their pet!)

[Staranais]

(e.g. alot of practices do not monitor blood pressure but will give a NSAID during surgery even if they do not know if the animal is hypotensive!)

I have seen that in several practices too, and I hate it. It's just so risky. I get that some practices don't have a capnograph or even a pulse-ox, but they should all have a doppler, & really, how much effort is it to set it up and then take BP every 5 or 10 minutes to make sure everything is getting adequately perfused?

You're right, more client education is needed as to why it is good practice to do these things, and why they are charged for.

[Kiramon78]

(e.g. alot of practices do not monitor blood pressure but will give a NSAID during surgery even if they do not know if the animal is hypotensive!)

I have seen that in several practices too, and I hate it. It's just so risky. I get that some practices don't have a capnograph or even a pulse-ox, but they should all have a doppler, & really, how much effort is it to set it up and then take BP every 5 or 10 minutes to make sure everything is getting adequately perfused?

You're right, more client education is needed as to why it is good practice to do these things, and why they are charged for.

It's the cheap dodgy ones that are giving all practices a bad name. All our animals are given fluid therapy, iv cath etc.... I've been to some places that have one nurse doing reception & surg at the same time, hell I've worked in some and wasn't happy. I've also seen some done on cold benches with no iv access. It's definitely a 'you get what you pay for' world out there.

[Staranais]

It's the cheap dodgy ones that are giving all practices a bad name. All our animals are given fluid therapy, iv cath etc.... I've been to some places that have one nurse doing reception & surg at the same time, hell I've worked in some and wasn't happy. I've also seen some done on cold benches with no iv access. It's definitely a 'you get what you pay for' world out there.

Yes and no. The more expensive ones probably also need to step up and educate clients as to why they feel it's important to give fluids & do more intensive monitoring, otherwise clients just assume you're a rip off when you charge more for "the same" surgery.

Trouble is, it's hard to do that without knocking other vets & other practices, which goes against the code of professional conduct that vets are expected to adhere to.

[Kiramon78]

It's the cheap dodgy ones that are giving all practices a bad name. All our animals are given fluid therapy, iv cath etc.... I've been to some places that have one nurse doing reception & surg at the same time, hell I've worked in some and wasn't happy. I've also seen some done on cold benches with no iv access. It's definitely a 'you get what you pay for' world out there.

Yes and no. The more expensive ones probably also need to step up and educate clients as to why they feel it's important to give fluids & do more intensive monitoring, otherwise clients just assume you're a rip off when you charge more for "the same" surgery.

Trouble is, it's hard to do that without knocking other vets & other practices, which goes against the code of professional conduct that vets are expected to adhere to.

I very much agree. We recently had another vet (they went a got a second quote on a surgery) make the owner question why we did a GA on a small dog with a fractured leg to do x-rays and why we didn't just use sedation. (picture small bitey scared puppy with nasty femur fracture). Yes they did under quote us and yes the owner went there, but we know we did the right thing.