TIVA

RE: TIVA

Rob Loxley — Fri, 14 Dec 2018 20:07:57 GMT

[quote user="David Mills"]Has there been any work done looking at how accurate they are[/quote]

There are a few papers looking at injecting blue dye into a cadaver then dissecting out to see where it ended up

RE: TIVA

Kate Richardson — Fri, 14 Dec 2018 14:49:03 GMT

[quote user="Evelyn Barbour-Hill"]

[quote user="David Mills"]John Robinson a number of years ago said nerve blocks are not benign, you're blindly injecting into a neuro or neurovascular bundle with an acidic substance. [/quote]

John Robinson sayeth sooth. If you are going to do a nerve block, you should aim to deposit the fluid near the nerve, not into it (obviously) nor into a narrow bony canal in which it runs: the increased pressure can do serious damage. For the infra-orbital nerve, for instance, deposit at the opening of the canal, not inside the canal as is often suggested.

I think this is why I had this case as mentioned in another post which I suspect has some neuritis; I have been oober careful not to advance needle into the canal since.

[quote user="David Mills"]Has there been any work done looking at how accurate they are, and the learning curve required?[/quote]

Seriously objective work? Not that I know of. But I'm not a reference buff.

I don't think I was very accurate until I went on some practical CPD and got shown with a skull exactly where I was meant to be depositing the local, then practiced on cadavers, and now feel very confident I am accurate and doing it as safely as I can. Visualising it on the skull made it click for me. Learning curve wise, not that steep, just need to do a lot initially and then it becomes second nature. I can only go on my own experience, but I do feel they are effective. I'm always reviewing my techniques, and happy to try new things/change my ways. I even tried doing a dental procedure without a tie on the et tube a few times, didn't like it though

[/quote]

RE: TIVA

Anthony Dennison — Fri, 14 Dec 2018 13:04:03 GMT

[quote user="David Mills"]Has there been any work done looking at how accurate they are, and the learning curve required?[/quote]

Not quite the same, but one of the equine residents at Bristol when I was there was doing a study into the accuracy of nerve blocks for head-shakers.

I've just asked my sister, who is a dentist. Humans get local blocks under GA.

RE: TIVA

Nicola Cole — Fri, 14 Dec 2018 12:02:18 GMT

[quote user="Gillian Mostyn"]

[quote user="David Mills"]It's one of the drugs of choice for pregnant women during labour [/quote]

Yes, that has always made me smile too!

I will use some drugs, such as NSAIDS, with the owners consent. But when the data sheets say 'do not use', even with no reason why not, that is difficult to ignore.

[/quote]

It is but I believe it can’t be given too close to actual delivery (not sure what cut off is but at 10cms dilated I don’t think they’d give it)-presumably because it affects fetal respiration.

RE: TIVA

Anthony Todd — Fri, 14 Dec 2018 09:15:58 GMT

What I can't reconcile is the total absence of any reference

Thanks, I'll tell Google...

RE: TIVA

Evelyn Barbour-Hill — Thu, 13 Dec 2018 23:53:15 GMT

[quote user="David Mills"]John Robinson a number of years ago said nerve blocks are not benign, you're blindly injecting into a neuro or neurovascular bundle with an acidic substance. [/quote]

[quote user="David Mills"]Has there been any work done looking at how accurate they are, and the learning curve required?[/quote]

Seriously objective work? Not that I know of. But I'm not a reference buff.

RE: TIVA

Gillian Mostyn — Thu, 13 Dec 2018 23:50:29 GMT

[quote user="David Mills"]It's one of the drugs of choice for pregnant women during labour [/quote]

Yes, that has always made me smile too!

I will use some drugs, such as NSAIDS, with the owners consent. But when the data sheets say 'do not use', even with no reason why not, that is difficult to ignore.

RE: TIVA

David Mills — Thu, 13 Dec 2018 23:31:35 GMT

[quote user="Beats"]Do not use in pregnant animals."[/quote]

It's one of the drugs of choice for pregnant women during labour

RE: TIVA

David Mills — Thu, 13 Dec 2018 23:29:11 GMT

[quote user="Kate Richardson"]I use bupivicaine (Marcain), 0.2mls per nerve block for dentistry[/quote]

I was speaking to my dentist and they apparently no longer use bupivicaine in human dentistry as it has a relatively unpredictable onset and magnitude of action.

John Robinson a number of years ago said nerve blocks are not benign, you're blindly injecting into a neuro or neurovascular bundle with an acidic substance.

Has there been any work done looking at how accurate they are, and the learning curve required? I must admit to being cynical about nerve blocks in general in terms of accuracy and efficacy, apart from in large animals where the efficacy is obvious.

RE: TIVA

Gillian Mostyn — Thu, 13 Dec 2018 22:54:33 GMT

As has been said, it can probably be given peri or post op, just not preop

RE: TIVA

vetbl.locum — Thu, 13 Dec 2018 22:54:04 GMT

[quote user="Beats"]

[quote user="vetbl.locum"] pethidine Do you have link?[/quote]

https://www.vmd.defra.gov.uk/ProductInformationDatabase/SPC_Documents/SPC_110168.DOC

"4.7 Use during pregnancy, lactation or lay

Do not use in pregnant animals."

it's not pregnant once the pups have been removed though?

[/quote]

Thanks

RE: TIVA

Gillian Mostyn — Thu, 13 Dec 2018 22:46:38 GMT

Weirdly, it is on my NOAH app but not the NOAH website.

I found it on the VMD product database. Everything is on there... The NOAH one is just a selection.

https://www.vmd.defra.gov.uk/ProductInformationDatabase/Default.aspx

RE: TIVA

Beats — Thu, 13 Dec 2018 22:37:12 GMT

[quote user="vetbl.locum"] pethidine Do you have link?[/quote]

https://www.vmd.defra.gov.uk/ProductInformationDatabase/SPC_Documents/SPC_110168.DOC

"4.7 Use during pregnancy, lactation or lay

Do not use in pregnant animals."

it's not pregnant once the pups have been removed though?

RE: TIVA

vetbl.locum — Thu, 13 Dec 2018 22:28:25 GMT

[quote user="Gillian Mostyn"]

Regardless on whether you can find papers, pethidine is specifically contraindicated ... the UK data sheets say clearly 'do not use in pregnant animals'. Make sure you get informed consent if you are working in the UK!!!

[/quote]

I cannot find a datasheet on NOAH for pethidine Do you have link?

Vetergesic says do not use but Comfortan says not recommended

Thanks

RE: TIVA

Gillian Mostyn — Thu, 13 Dec 2018 21:56:29 GMT

[quote user="vetbl.locum"]and give pethidine pre op to C-sections (I cannot find any papers regarding the risk to pup mortality rates)[/quote]

RE: TIVA

Beats — Thu, 13 Dec 2018 20:10:31 GMT

[quote user="Anthony Todd"]What I can't reconcile is the total absence of any reference to this fundamental concept in human anaesthesiain that a "general anaesthetic" seems to rely only on a premed andanaesthetic agent with no mention of the advantages of pre-anaesthetic analgesia based on the belief or concept that an anaesthetic is just that, the removal of feeling??[/quote]

"Regional anesthesia has become an integral and common component of both intraoperative anesthesia and postoperative analgesia in infants and children. Advantages of regional blockade include the reduction of general anesthetic dose requirements, effective blunting of hemodynamic and autonomic responses, and excellent postoperative analgesia with decreased requirement of systemic analgesics and their concomitant side effects."

from the 2019 book: 'A Practice of of Anesthesia for Infants and Children', 6th edition, p.941 in chapter 42 'Regional Anaesthesia'

[quote user="Anthony Todd"]In paediatric dentistry AFAIK there are no nerve blocks, just a GA???[/quote]

"It is thought that giving LA injections during dental treatment under GA will result in numbness and therefore pain not being felt for a couple of hours, after which time painkillers can control the pain."

from the recent Cochrane Review (as per all Cochrane Reviews it simply concludes that there is a lack of direct evidence of benefit to the practise, but nonetheless I suspect it is fairly standard practise hence the Cochrane Review in the first place?) https://www.cochrane.org/CD009742/ORAL_does-a-local-anaesthetic-injection-in-children-and-young-people-having-dental-treatment-under-general-anaesthetic-reduce-pain-after-treatment

Further quote from abstract to Chapter 42 cited above in case of further interest:

"However, the risks of local anaesthetic toxicity may be magnified in infants and children because of their size and immaturity, and great care and precision must be used when choosing volume and concentration. Because the vast majority of regional blocks in children are performed with patients under general anesthesia, early signs of toxicity are usually obscured. The emergence of lipid emulsion therapy for local anesthetic systemic toxicity has dramatically altered our approach and the successful outcome to these events and should be administered promptly. Large-scale prospective data from multicenter collaborative studies have documented that regional anesthetics in children have a high degree of safety, and prospective data have confirmed that administering blocks to children under general anesthesia confers no increased risk of injury. While one must have specific technical skills, as well as an understanding of the differences in pediatric physiology, anatomy, and pharmacology, to use regional blockade in infants and children, the benefits of these techniques are great."

RE: TIVA

Anthony Todd — Thu, 13 Dec 2018 19:17:23 GMT

[quote user="vetbl.locum"]Are you kidding me? GA only holds you/animal still, most GA drugs do not provide any analgesia, they only stop outward signs of pain such as screaming or biting you!'[/quote]

What I can't reconcile is the total absence of any reference to this fundamental concept in human anaesthesiain that a "general anaesthetic" seems to rely only on a premed andanaesthetic agent with no mention of the advantages of pre-anaesthetic analgesia based on the belief or concept that an anaesthetic is just that, the removal of feeling??

[sorry site seems to have gone wonky, or my computer has]

eg2 In paediatric dentistry AFAIK there are no nerve blocks, just a GA???

RE: TIVA

Kate Richardson — Thu, 13 Dec 2018 14:45:03 GMT

[quote user="Beats"]

[quote user="Kate Richardson"]I use bupivicaine (Marcain), 0.2mls per nerve block for dentistry[/quote]

What concentration? 0.5%, 0.25%, less?

Do you not find that bupivicaine takes too long to take effect to be MAC sparing during GA? (But I appreciate can provide post-operative analgesia).

toxic dose of bupivicaine in cat lower than lidocaine I reckon.

4 x 0.2ml (0.5% bupivicaine) injections in a 2.5kg cat would = 1.6mg/kg bupivicaine in addition to whatever lidocaine was sprayed at time of intubation.

Above what mg/kg dose of bupivicaine would you get concerned re toxicity risks?

Accidental intravenous administration potentially of more concern with bupivicaine also re its cardiotoxicity?

[/quote]

0.25%, Marcain polyamps. So I have no concerns about toxicity if I have to do all 4. Always draw back before injecting, so also in practice I am not concerned about iv administration, but its a theoretical risk.

I don't find the speed of onset an issue. If there is an obvious extraction needed, I will do that nerve block fairly soon after anaesthetising, then proceed to xray and assess the full mouth and block the rest accordingly if needed, then by the time I start extracting the first tooth, the block is effective. And by the time I get to any other extractions in other quadrants, those blocks iare also effective. My feeling is that it actually becomes effective quicker than the 20-30 minutes the books state.

RE: TIVA

Beats — Thu, 13 Dec 2018 13:12:16 GMT

[quote user="Kate Richardson"]I use bupivicaine (Marcain), 0.2mls per nerve block for dentistry[/quote]

What concentration? 0.5%, 0.25%, less?

Do you not find that bupivicaine takes too long to take effect to be MAC sparing during GA? (But I appreciate can provide post-operative analgesia).

toxic dose of bupivicaine in cat lower than lidocaine I reckon.

4 x 0.2ml (0.5% bupivicaine) injections in a 2.5kg cat would = 1.6mg/kg bupivicaine in addition to whatever lidocaine was sprayed at time of intubation.

Above what mg/kg dose of bupivicaine would you get concerned re toxicity risks?

Accidental intravenous administration potentially of more concern with bupivicaine also re its cardiotoxicity?

RE: TIVA

vetbl.locum — Thu, 13 Dec 2018 13:09:08 GMT

So:

'Are you kidding me? GA only holds you/animal still, most GA drugs do not provide any analgesia, they only stop outward signs of pain such as screaming or biting you!'

If i understand correctly we use nerve blocks on dentals which are a relative minor procedure and yet we delay morphine for C sections on bitches.

I find veterinary practice confusing these days............

Rgds

PS I do use nerve blocks both pre & post and give pethidine pre op to C-sections (I cannot find any papers regarding the risk to pup mortality rates)

Why we abandoning preemptive analgesia and balanced GA?

RE: TIVA

Kate Richardson — Thu, 13 Dec 2018 11:16:49 GMT

[quote user="Richard Carter"]

so what volumes local in cats (presume we talking lidocaine) as my understanding was toxic dose was fairly quickly reached in a 3kg cat

[/quote]

I use bupivicaine (Marcain), 0.2mls per nerve block for dentistry

RE: TIVA

Richard Carter — Thu, 13 Dec 2018 11:06:16 GMT

so what volumes local in cats (presume we talking lidocaine) as my understanding was toxic dose was fairly quickly reached in a 3kg cat

RE: TIVA

Kate Richardson — Thu, 13 Dec 2018 10:25:27 GMT

[quote user="Beats"]

[quote user="Laurence Webb"]To put it another way, if you can do it, why not?[/quote]

In relation to dental nerve blocks:

One why not may be that if the patient still can't feel it's tongue after waking up it may proceed to self-harm it through biting?

Another might be that in cats damage may be done to neurovascular structures in performing the blocks?

[/quote]

I perform nerve blocks regularly, as I perform on average 3-4 dental procedures in cats every week. Hugely beneficial in reducing the amount of inhaled anaesthetic and for us that is the biggest factor in maintaining blood pressure. On average, cats on 1-1.5% isoflurane with nerve blocks in place so surgical extractions, including cats that have had full outh extractions. Occasionally they don't seem to have worked, but I would say 95% of the time very effective. I have personally never had self induced tongue trauma (and hope I'm now not tempting fate). I have had the occasional cat seem distressed/uncomfortable 3-4 hours post surgery which I have put down to the nerve block wearing off and discomfort becoming apparent or just simply that tingling feeling as sensation returns, usually Burmese/oriental types so suspect breed disposition and varies from mild to one case which had quite severe 'pain', however, this resolved with time and additional analgesia.

I have one case where I suspect iatrogenic damage to the infraorbital nerve as cat still has intermittent facial discomfort post dental treatment and all teeth were extracted cleanly on that side; I suspect I inserted the needle a tiny bit too far into the canal, so have been even more careful since then to not insert it too far.

But on the whole, feel they are of great value as potential to prevent the pain in the first place, which leads to less wind up, and 95% of cats are back to eating normally within 24hours, often within 4-6 hours post surgery.

RE: TIVA

Evelyn Barbour-Hill — Thu, 13 Dec 2018 01:28:36 GMT

[quote user="Sarah Keir"]Are you kidding me? GA only holds you/animal still, most GA drugs do not provide any analgesia, they only stop outward signs of pain such as screaming or biting you![/quote]

Er, no. General anaesthesia implies analgesia. "Balanced anaesthesia": a balance of all three components, viz. unconsciousness, relaxation and analgesia.

If there is no analgesia, it's not a general anaesthetic.

RE: TIVA

Laurence Webb — Wed, 12 Dec 2018 22:23:14 GMT

Yes. These are possible problems although not ones that I have seen (I'm a GP, not a dentist) but I only use two blocks - the maxillary nerve and the interior alveolar nerve blocks.

[quote user="Beats"]One why not may be that if the patient still can't feel it's tongue after waking up it may proceed to self-harm it through biting?[/quote] If you are take care that you direct the needle along the inside if the mandible you should avoid affecting the lingual nerve so the tongue innervation is inaffected

[quote user="Beats"]Another might be that in cats damage may be done to neurovascular structures in performing the blocks?[/quote]The technique that I was shown just instills local close to the area of the nerves, not directly into the nerve bundles and it then diffuses in to numb the nerves. Slightly different to putting a needle into the infraorbital canal or mental foramen which may be more effective but also more likely to cause iatrogenic damage.