Using a 1 litre bag with a circle

RE: Using a 1 litre bag with a circle

Courtney Scales — Mon, 24 Aug 2020 08:54:09 GMT

Hi Tanya - the reseviour bag needs to hold around 2-5 x the tidal volume which is ok up to around a 20-50kg dog! Don't forget the circle system is massive in itself and has about 5-10 litres of tubing and canisters anyway. Leave the APL valve open with a flow rate of around 0.5-1L/min after 10 minutes of a higher FGF initially.

RE: Using a 1 litre bag with a circle

James Colver Cert. Ed, RVN — Fri, 14 Aug 2020 05:32:00 GMT

Great explanation of low flow from Susanna Taylor here
https://www.vetnurse.co.uk/001/veterinary-nurse-clinical/small-animal/anaesthesia/f/discussions/31424/how-to-save-isoflurane-upcoming-supply-problems

RE: Using a 1 litre bag with a circle

Cyonica — Thu, 13 Aug 2020 09:25:21 GMT

No worries :) I've never actually tried it, I've only ever used it as partially open. I think the issue is you still have to provide their metabolic O2 requirement, so there will surely always be a build up of gas that you have to keep letting out? If the valve's partially open then the flow rate should be the same I'd think, as it's only their metabolic requirement anyway, and then you don't need to worry about barotrauma. I'm speculating now though, I really don't know much about using them closed!

RE: Using a 1 litre bag with a circle

uzi — Thu, 13 Aug 2020 05:20:35 GMT

thank you for the input katherine - i managed it on a really big dog initially as completely closed - then when i had a cat i really struggled. thanks for that

RE: Using a 1 litre bag with a circle

Cyonica — Wed, 12 Aug 2020 20:16:25 GMT

[quote userid="23986" url="~/001/veterinary-nurse-clinical/small-animal/anaesthesia/f/discussions/32032/using-a-1-litre-bag-with-a-circle"]We've recently had this debate in my practice as me and few other nurses do use a 1 litre bag on a circle circuit when the patient is between 10kg and 15kg. Is this ok to do with a circle?[/quote]

The reservoir bag should be 3 - 6 times the patient's tidal volume, irrespective of the circuit being used. I'm not aware of any reason why the size of bag would affect the way a circuit works.

[quote userid="23654" url="~/001/veterinary-nurse-clinical/small-animal/anaesthesia/f/discussions/32032/using-a-1-litre-bag-with-a-circle/176337#176337"]when you are using a circle should the APL be closed off completely or partially[/quote]

Only ever partially, it's really hard to use it as a closed system so not worth trying to do. I don't know of anyone who does or who recommends it. Do you have a capnograph? The flow rate for a rebreathing system is 10ml/kg/min, but most vapourisers are inaccurate below about 0.5L/min so for the circle I have all patients on 1L, and on the ADE I try to keep them all on 500ml up to 50kg, but I also use the capnograph to adjust flow rates according to the patient.

RE: Using a 1 litre bag with a circle

uzi — Wed, 12 Aug 2020 05:20:35 GMT

I am new with using the circle at my practice, we have the new stinger anaesthesia machine it has a small circle canister that allows 2kg animals to be put on a circle circuit.

my question is - when you are using a circle should the APL be closed off completely or partially. if i leave it closed off its ok for a while then it starts to get very full even if i lower the flow rate. if i leave it partially open the resps go up and does seem to be working as well - so kind of confused.

any help advice about the APL valve postion would be greatly appreciated - thanks

RE: Using a 1 litre bag with a circle

James Colver Cert. Ed, RVN — Wed, 12 Aug 2020 00:56:53 GMT

As Apache says, no problem. As long as the bag isn't becoming distended due to too much pressure, or going flaccid with negative pressure, it's fine.

RE: Using a 1 litre bag with a circle

apache — Wed, 12 Aug 2020 00:29:14 GMT

As long as you exceed tidal volume there is no issue