Dexdom in rabbits

Re: Dexdom in rabbits

Rajat — Fri, 02 Nov 2012 09:45:12 GMT

[quote user="Michael Woodhouse"]

Wow - some of you guys must charge a lot of money for bunny GAs! Raj - with all due respect dom/ket IM and O2 via mask with iso if needed I bet I can have it castrated and the domitor reversed before you have a sleepy bunny.

[/quote]

You prob could Michael- incidentally for castrates I prefer mild sedation with local IT blocks not full GA most bunnies can be done this way - and is quicker than the faffing with fentanyl and intubation, but for longer ops I think the faffing does reap some rewards. Incidentally the midaz/fentanyl kicks in quicker than a DTK premed. Obv doesn't get them as sleepy but it hits them much faster IME.

and absolutely no offence taken - speed ain't my selling point

Re: Dexdom in rabbits

Rajat — Fri, 02 Nov 2012 09:42:53 GMT

[quote user="David Mills"] Your original argument was against triple combo[/quote]

ahh David, I ain't arguing, just presenting an opinion, an experience... Why is your world view so polarized?

[quote user="David Mills"]The doses aren't 'high' of dom in this instance, just appropriate[/quote]

In triple combo, we are using doses of DTK to bring rabbits to a very heavily sedated/GA state. Some need Iso, some don't while using these doses. Comparatively, these are high doses- in the same way DTK in a dose high enough to cause GA like state in a cat or dog is also a high dose compared to the premed dose. Instead of 0.25mg/kg medetomidine I would use 0.02mg/kg medetomidine as a premed in a bunny. Hence my stating these are 'high'.

[quote user="David Mills"]but I think you need more justification than 'high doses' because its a misnomer. [/quote]

I think I provided that above. If it wasn't broken, I wouldn't fix it. If your protocol works for you then fantastic. My intention as I thought was quite clear, was to share a protocol I found useful.

[quote user="David Mills"] rabbits obviously process the drug differently, or have more receptors or something similar[/quote]

Maybe, maybe not. I take it these are guesses/assumptions?

[quote user="David Mills"]Sometimes we simply over-complicate things or try to re-invent the wheel for no apparent good reason.[/quote]

And sometimes we are satisfied with the status quo and with mediocrity.

Re: Dexdom in rabbits

Michael Woodhouse — Thu, 01 Nov 2012 00:03:06 GMT

Re: Dexdom in rabbits

David Mills — Wed, 31 Oct 2012 23:12:25 GMT

[quote user="Rajat"]

[quote user="David Mills"]Its a fair whack of propofol.[/quote]

Rabbits, in my limited experience, using this protocol require these doses. They will prob require less if you use the usual triple combo doses. In fact I'd bet a tenner they will be lower, by about half.

Just like if you heavily sedated a dog with dom/torb vs acp bupe your propofol induction dose will be much much lower, by around 50%.

2nd point - Propofol is very short acting- leaves the system quickly. So its effects are not present from a few mins after IV induction and hence faster recovery post op cf triple combo (+ in my opinion a safer GA)

And yes I know we reverse the medetomidine and torb/ket wears off - I do find they are much dozier with triple tho - and take longer to come around overall...and I'm not a fan of reversing medetomidine once the animal (dog/cat/rabbit) is under gaseous anaesthesia either..

Hope that makes it clearer

I have no double blinded placebo controlled studies just my limited experience with this approach Not like these drugs have not been used to sedate and induce rabbits before tho.

[/quote]

Not convinced. Your original argument was against triple combo, which can be quite safely used for induction (and maintenance) of GA, just like in cats or dogs if required, on the grounds of 'high doses'. The doses aren't 'high' of dom in this instance, just appropriate; just like d/t/k doses in cats where dom is the same, more or less, as it is for sedation on its own or with torb. You can't label something as 'high' so liberally - rabbits obviously process the drug differently, or have more receptors or something similar. You're at liberty to use what you like, but I think you need more justification than 'high doses' because its a misnomer. In fact, as you say, using propofol inexpertly (too quick induction) is far far more dangerous than a balanced triple combo will ever be for rabbits.

Sometimes we simply over-complicate things or try to re-invent the wheel for no apparent good reason.

Re: Dexdom in rabbits

Rajat — Wed, 31 Oct 2012 20:59:19 GMT

[quote user="David Mills"]Its a fair whack of propofol.[/quote]

Just like if you heavily sedated a dog with dom/torb vs acp bupe your propofol induction dose will be much much lower, by around 50%.

Hope that makes it clearer

I have no double blinded placebo controlled studies just my limited experience with this approach Not like these drugs have not been used to sedate and induce rabbits before tho.

Re: Dexdom in rabbits

David Mills — Wed, 31 Oct 2012 20:49:38 GMT

[quote user="Rajat"]

wasn't happy with triple combo - long recoveries, high doses

[/quote]

[quote user="Rajat"]

Its a fair whack of propofol.

[/quote]

?!?

Re: Dexdom in rabbits

Rajat — Wed, 31 Oct 2012 20:09:39 GMT

Hi Helen

I've played around with rabbit GA drug doses a bit as wasn't happy with triple combo - long recoveries, high doses and GA via injectable drugs wasn't my cup of tea no more. Also found intubating them tricky regardless. I found using a combo of midazolam and fentanyl (0.2-0.4mg/kg M and 2-4ug/kg F) allowed enough sedation and relaxation to insert IV without any stress.

Then I induce with a combo of ketamine 2-4mg/kg IV followed by propofol 4-8mg/kg IV - slow!! They will get apnoeic if given too fast and as hypoxemia is what kills em, its worth taking your time. Some more midaz if needed (rabbit doses are higher in my references about 2-3x that of cats or more, but I haven't gone higher). Its a fair whack of propofol.I always pre oxygenate rabbits for 5 mibns- easiest to do by face mask or flow by while putting in IV. This gives you a buffer of O2 which means you have more time to intubate before rabbit gets into trouble with hypoxemia

Tubing as others described or see here - I like the flecknell, I have them on their back, at the edge of the table, I am crouching on the floor,pull the tongue out to the side, and fail to visualise the larynx. More drugs, try again, see the larynx- spray it with itnraepicaine - assistant is holding the flow by O2 by the nose throughout btw. Dissuade the nurse from holding it to the mouth as obv they are obligate nose breathers and it doesnt work!

Finally, once everything falls into place, using the flecknell and provided tube stiffening metal rod slide the ET tube in (tip - you can bend the wire so that the tube has the right amount of 'curve' for your bunny very gently making sure the metal bit doesnt hit the larynx. As soon as you're in, remove the wire.

You shouldn't get spasm if you spray the larynx with intubeaze first.

This does take time for me - I don't practise enough as we don't see as many bunnies as dogs and cats. I do intend on using hypnorm again cf fentanyl, byt fentanyl also great for periop CRI/intermittent boluses - comfy rabbits= no ileus and quick recoveries!

The easier (but probably more expensive way) is using a laryngeal mask - see here for an excellent website with videos and guides on usage + nice anatomical cross sectional studies.

Bloody costly tho - and far too many sizes - we are prob gonna get one or two and use Ethylene gas to sterilize them when needed.

Just wanted to share a different way of approaching these rabbit GAs. I did discuss these with some anaesthetists too who were interested...they weren't bunny specialists tho so I think the interest was a bit limited!

Cheers

Rajat

Re: Dexdom in rabbits

Helen Wallace — Wed, 31 Oct 2012 18:05:50 GMT

Thank you all so much guys.

Like Martin I'd always been happy with dom/torb ket then blind tubing but I just find with the hypnorm/sevo combo as soon as I get anywhere near the larynx there is spasm. I didn't just want to assume doses on dexdom without checking.

Vetsurgeon is great :)

Re: Dexdom in rabbits

Robin Grimmer — Wed, 31 Oct 2012 17:31:16 GMT

I use 0.1ml/kg domitor and same dose for ketamine, 0.05ml/kg torbugesic all i/m and then nicely asleep to allow intubation. I use an auroscope to visualise the larynx, find this easier with the head pointing upwards and sometimes use an introducer like a dog catheter to go in to the larynx and then slide the e/t tube over that.

Re: Dexdom in rabbits

David Mills — Wed, 31 Oct 2012 16:32:42 GMT

Doses (mls/rabbit) for dexmedetomidine are the same as medetomidine. Medetomidine is a racemic mixture of which only the right ('dex') rotation is active - so half of it is inert (the left-rotation enantiomer). Medetomidine is 1mg/ml, dexmed 0.5mg/ml to account for this - you're getting the same bang for the same mls. Not sure exactly why dexmedetomidine is supposed to be better but I think its because the left-rotation can occupy sites that the dex wants to so therefore onset of action with dex is quicker, along with reversal.

Re: Dexdom in rabbits

Jo Cobbett — Wed, 31 Oct 2012 13:35:54 GMT

Would this be a situation where the V-Gel laryngeal mask would help? I have no experience with it, anyone out there who could offer some advice?

Re: Dexdom in rabbits

Martin Atkinson — Wed, 31 Oct 2012 11:02:22 GMT

[quote user="Helen Wallace"]Martin- do you know what brand your masks are? we also have ones with a rubber diaphragm but I can always smell leakage so if there are better ones out there then I'd be happy to swap. I'd also prefer to have an ET tube in if I can as I do think it's safer for the bunny but I just seem to get so much spasm with the sevo I can't manage it blind... my bad. I'm open to any other suggestions.[/quote] Don't know what brand they are, they just have a rubber diaphragm but there are 3 sizes so that determines the seal. As for laryngeal spasms, I tube rabbits blind by listening for breathing sounds, I sedate with triple comb and attempt to intubate (if they're not deep enough I will mask with isoflurane for a few breaths) if it doesn't go in first time I trickle a bit of xylacaine down the tube, put it on O2 for a minute then attempt to tube again, works 95%of the time. But as Rajat suggests I don't know why we don't use I/V more in rabbits, I guess my method works for me, the bunnies are getting up off the table almost as soon as the last stitch has been put in, so why change?

Re: Dexdom in rabbits

Helen Wallace — Wed, 31 Oct 2012 10:36:57 GMT

@ Rajat- that's a good idea, i/v induction may be the way to go. How do you find laryngeal relaxation is with the propfol?

@ Martin- do you know what brand your masks are? we also have ones with a rubber diaphragm but I can always smell leakage so if there are better ones out there then I'd be happy to swap. I'd also prefer to have an ET tube in if I can as I do think it's safer for the bunny but I just seem to get so much spasm with the sevo I can't manage it blind... my bad. I'm open to any other suggestions.

@ eveyone... I don't want to go into details of someone else's medical history on this forum. I possibly should have posted anon but I didn't think the question really warranted that.

Re: Dexdom in rabbits

Martin Atkinson — Wed, 31 Oct 2012 10:16:42 GMT

[quote user="Helen Wallace"]

Sorry Martin, I didn't make myself clear. I still want to tube the bunnies and get them on a circuit, I just want to avoid having to mask them down to do it if possible.

And yes, right at the moment sevo exposure is an issue for one member of staff.

[/quote] A couple of points spring to mind here: firstly, If the member of staff is for whatever reason (I assume pregnancy) sensitive to even minimal sevo exposure, she is still going to be exposed to some leakage when the rabbit is tubed, unless you're a far better man than I am and can get a cuffed tube down all bunnies. Secondly, we have masks with a diaphragm that forms a very effective seal so there is minimal leakage - certainly no more than a 20 minute op with an un-cuffed tube.

Re: Dexdom in rabbits

Rajat — Wed, 31 Oct 2012 09:51:54 GMT

Helen

I can't help with dexdom dose (as I still use medetomidine) but why not try propofol to induce the bunny?

Re: Dexdom in rabbits

Helen Wallace — Wed, 31 Oct 2012 09:39:36 GMT

Sorry Martin, I didn't make myself clear. I still want to tube the bunnies and get them on a circuit, I just want to avoid having to mask them down to do it if possible.

And yes, right at the moment sevo exposure is an issue for one member of staff.

Re: Dexdom in rabbits

Martin Atkinson — Wed, 31 Oct 2012 09:34:13 GMT

Is the concern of staff exposure to sevo for one bunny GA really so much of a worry that you'd want to lose the advantages of having the rabbit tubed and on an anaesthetic machine?