veterinary ventilator settings

[stoic]

working on a ventilator-dependant drug delivery model. i'm out my depth here. people fine, whatever; all manner of beasts, i have no idea how to setup a vent.

can anyone recommend a reference book, or a chart, or something?

much thanks.

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[WhtsThFrequency]

Are you near any referral hospitals/vet schools? Probably your best bet would be to contact a veterinary anesthesiologist.

 

[bunnity]

For mechanical ventilation of dogs under anesthesia, we usually do volume dependent ventilation with a tidal volume of 10-15mL/kg, which usually corresponds to a PIP of around 10-15 cmH20. If we do pressure dependent we usually start at at PIP of around 15 (wouldn't really want to go higher than that). It's normally set with 10-15 breaths per minute with an I:E ratio of 1:3 or sometimes 1:2. From there we just monitor end tidal CO2 and adjust as necessary to keep EtC02 about 35-45 (usually increase the tidal volume if needed versus the RR since the RR will also increase dead space ventilation).

Does that help at all? I don't even know where to start with the long-term ICU style vents - way more complicated. And if you're looking at a different species I'm sure it's different from what I posted. I definitely second the suggestion to look up a vet anesthesiologist.

 

[k9emccvet]

There aren't a lot of veterinary-specific guidelines for long-term ICU style ventilation. We just don't have the case numbers that human doctors see, and there are only a couple hundred critical care specialists in the country. I don't think anyone has written a vet ventilator text/reference because the audience is so small. There are chapters in a few critical care books, but not great detail.
In general animals with normal lungs (on the vent from toxicities, neuro dz) are ventilated as bunnity said. For lung-injured pets the settings are extrapolated from the ARDS-Net guidelines; typically higher PEEP/lower FiO2 and much smaller tidal volumes (4-8 mL/Kg for dogs and 4-6 mL/Kg for cats). Most veterinary hospitals get refurbished ICU vents from human hospitals- they are functional machines but often don't have bi-pap or HFOV and very very few vets will have experience with these modalities.
There are some species differences when it comes to the vent, so it's difficult to make general recommendations without knowiing what animals you are working with. Dogs seem to tolerate long-term ventilation much better than cats (they love to get SIRS/MODS and die no matter what you do). I have no experience with ventilating rodents or rabbits-there may be a lab animal vet with more input on these little guys if this what you are working with. Probably your best bet is to find a university or practice with a criticalist or an anesthesiologist.
www.acvecc.org
www.acva.org

 

[stoic]

i'm still getting up to speed, but for sure using a human vent with anything other than a pig is going to be a problem. minimum tidal volumes are too large for any small animal use (with the exception of neonate vents, which we don't have.)

i'm at a uni and we have a vet and staff, but this is new territory for them as well. we have anesthesia machines but i haven't seen one yet with a ventilation system. from what i've read and my past experiences, small animals don't seem to be put into deep enough anesthesia to lose the breathing/swallowing reflex. this is a problem: for several reasons we need to place ET tubes and I'm concerned about vagal activation (particularly in rabbits as their hearts seem to stop for very little reason.)

as a result we are going to need to at least use an induction agent and probably some kind of premedication. i'm leaning towards using an antichiolinergic/opioid mix but am not particularly familiar with some of drugs used in animals. i'm thinking glycopyrolate(sp?)/butorphenol IM for rabbits and scopalimine/fent soaked sugar cubes for pigs. thoughts?

 

[WhtsThFrequency]

I've seen an acepromazine/butorphanol combo used in rabbits before. Glycopyrrolate may be difficult to dose - generally a 0.01mg/kg IV dose. Teeny tiny. Veterinary Anesthesia and Analgesia by McKelvey and Hollingshead has a decent section on small mammal anesthesia with a ton of tables.

 

[stoic]

Thanks for the responses! The information above has been very valuable as we figure this stuff out.

We are leaning towards rabbits - pigs are a bit more than we want to bite off at this time. So rabbits it is.

We need to knock down the breathing reflex for the duration of the drug treatment phase (total vent time will be ~1hr.) I like the glycopyrrolate/butorphanol mix for induction. It guards against vagal stimulation and should be effective at knocking down the reflexes. Additionally, it provides preemptive analgesia for the procedure, which is important because we are going to place trach's instead of ET's. The animals need survive another 24 hours for data collection. Dosed appropriately will the glycopyrrolate/butorphanol and 2% isoflurane maintance produce the desire anesthesia level? WTF, to deal with the glycopyrrolate dosing we will make a dilution stock. Are there any drugs which should be added or changed?

Lots of questions to throw out:
Yombine as a reversal agent? Other reversal choices?
Venous access via central auricular vein? Drip rate of warmed saline 10mL/hour/kg? Recommendations for post-operative analgesia? Our ACU generally uses buprenorphine when post-operative pain is expected. +/- nsaid?

Thanks again for your help, you guys have been awesome.

 

[dyachei]

Thanks for the responses! The information above has been very valuable as we figure this stuff out.

We are leaning towards rabbits - pigs are a bit more than we want to bite off at this time. So rabbits it is.

We need to knock down the breathing reflex for the duration of the drug treatment phase (total vent time will be ~1hr.) I like the glycopyrrolate/butorphanol mix for induction. It guards against vagal stimulation and should be effective at knocking down the reflexes. Additionally, it provides preemptive analgesia for the procedure, which is important because we are going to place trach's instead of ET's. The animals need survive another 24 hours for data collection. Dosed appropriately will the glycopyrrolate/butorphanol and 2% isoflurane maintance produce the desire anesthesia level? WTF, to deal with the glycopyrrolate dosing we will make a dilution stock. Are there any drugs which should be added or changed?

Lots of questions to throw out:
Yombine as a reversal agent? Other reversal choices?
Venous access via central auricular vein? Drip rate of warmed saline 10mL/hour/kg? Recommendations for post-operative analgesia? Our ACU generally uses buprenorphine when post-operative pain is expected. +/- nsaid?

Thanks again for your help, you guys have been awesome.

Typically don't use yohimbine unless you are using xylazine which I didn't see in your post. Are you planning to gas down as part of induction? Otherwise you will likely need something to induce (gassing down is not my favorite)

 

[bunnity]

(gassing down is not my favorite)

Bunnies hate it too!

 

[stoic]

Typically don't use yohimbine unless you are using xylazine which I didn't see in your post. Are you planning to gas down as part of induction? Otherwise you will likely need something to induce (gassing down is not my favorite)

thanks dyachei, i really appreciate the input. what would you suggest instead of yohmbine? epi? also if we need additional vagal inhibition, what drug is preferable in rabbits? i've read they have a active atropine esterase in the blood.

i want to induce before starting the gas. as bunnity says, rabbits hate the smell of iso and especially hate being forced to inhale it. i'm worried about losing rabbits post procedure/drug delivery and looking for ways to keep the physiological stress to what is absolutely unavoidable. there's no point in doing any of this if we can't keep them alive for 24 hours post-surgery.

we are purchasing a veterinary vent to put inline with the anesthesia system, so we won't be able to deliver gas until after the trach is placed. considering this, do you have thoughts on the induction scheme?

 

[bunnity]

thanks dyachei, i really appreciate the input. what would you suggest instead of yohmbine? epi? also if we need additional vagal inhibition, what drug is preferable in rabbits? i've read they have a active atropine esterase in the blood.

i want to induce before starting the gas. as bunnity says, rabbits hate the smell of iso and especially hate being forced to inhale it. i'm worried about losing rabbits post procedure/drug delivery and looking for ways to keep the physiological stress to what is absolutely unavoidable. there's no point in doing any of this if we can't keep them alive for 24 hours post-surgery.

we are purchasing a veterinary vent to put inline with the anesthesia system, so we won't be able to deliver gas until after the trach is placed. considering this, do you have thoughts on the induction scheme?

I think re: the yohimbine -- you only mentioned using torb and glyco and that wouldn't reverse either of those. You really wouldn't be giving epi unless they arrested. I think it would be best to talk to an exotics or lab animal vet about your induction protocol (you have one on your IACUC anyway right?) but torb/glyco definitely isn't going to knock out a rabbit enough to put in a trach.

 

[dyachei]

thanks dyachei, i really appreciate the input. what would you suggest instead of yohmbine? epi? also if we need additional vagal inhibition, what drug is preferable in rabbits? i've read they have a active atropine esterase in the blood.

i want to induce before starting the gas. as bunnity says, rabbits hate the smell of iso and especially hate being forced to inhale it. i'm worried about losing rabbits post procedure/drug delivery and looking for ways to keep the physiological stress to what is absolutely unavoidable. there's no point in doing any of this if we can't keep them alive for 24 hours post-surgery.

we are purchasing a veterinary vent to put inline with the anesthesia system, so we won't be able to deliver gas until after the trach is placed. considering this, do you have thoughts on the induction scheme?

I would have to look up my exotics anesthesia information again - I left it at work and am at home today. You probably are going to want to induce with an injectable anesthetic or something along those lines. I will get back to you tomorrow, if that's ok

 

[stoic]

ughhhh. the more i learn the more my impression becomes "we are accidentally going to kills a lot of rabbits."

premed - acepromazine, bupe, glyco
induction - xylazine, ketamine
maintance - iso

how much bupe q8 (please god, let q8 be ok.... otherwise i'm insisting on someone else doing the middle of the night dosing) will generate a sedative effect sufficient for frequent blood draws in the 24hr window post-procedurally?

 

[dyachei]

ughhhh. the more i learn the more my impression becomes "we are accidentally going to kills a lot of rabbits."

premed - acepromazine, bupe, glyco
induction - xylazine, ketamine
maintance - iso

how much bupe q8 (please god, let q8 be ok.... otherwise i'm insisting on someone else doing the middle of the night dosing) will generate a sedative effect sufficient for frequent blood draws in the 24hr window post-procedurally?

buprenorphine for sedation? its usually q8 but I would worry it may not sedate enough. How sedate do you need them?

 

[stoic]

buprenorphine for sedation? its usually q8 but I would worry it may not sedate enough. How sedate do you need them?

sedate enough to let me draw blood without kicking me in the face. also not dying would be good.

they are going to undergo major anesthesia then be handled for blood draws several times in a 24 hour period.

it's going to be a pain in the ass.

 

[sunshinevet]

ughhhh. the more i learn the more my impression becomes "we are accidentally going to kills a lot of rabbits."

premed - acepromazine, bupe, glyco
induction - xylazine, ketamine
maintance - iso

how much bupe q8 (please god, let q8 be ok.... otherwise i'm insisting on someone else doing the middle of the night dosing) will generate a sedative effect sufficient for frequent blood draws in the 24hr window post-procedurally?

I really think that you need to get in touch with a specialist veterinary anesthetist or exotics specialist and just ask them "what would you do". Just there seems to be a lot of guesswork going into this protocol (and I really don't mean any offense, but there have been some weird drugs put forward by you in your previous protocols) and I don't think this is the best place to try and hash this out.

If you called someone good in exotics/anaesthesia you would have this done in 5 min.

I also think they are more likely to die in the post op 24hr period if you keep them sedated.

 

[WhtsThFrequency]

Too much sedation is no bueno for rabbits.

Why do you need to sedate them that much blood draws? I've never had to. Just wrap them in a towel like an anxious kitty ("bunny burrito") and hit the ear vein (preferably with a touch of local anesthetic, they can be sensitive there but it's the easiest to hit). Unless you guys have some seriously fractious rabbits or need to do a ridiculous amount of draws (the ear vein is sensitive).

Do you guys have a lab animal vet on board? Don't you have to in order to get all the IACUC stuff worked out? That might be the person to ask. And again, I would think that any board certified vet anesthesiologist would be fine helping out via email at least. Or any exotics vet.