Low flow anaesthesia - is it worth it?

RE: Low flow anaesthesia - is it worth it?

Arlo Guthrie — Thu, 19 Feb 2026 13:51:49 GMT

DanB Thanks, that's very interesting.

[quote userid="50456" url="~/f/clinical-discussions/32641/low-flow-anaesthesia---is-it-worth-it/179229#179229"]There's a very easy, almost comforting cynicism to be found in the small scale of our own efforts: fewer than 100 companies produce over 70% of all global emissions, so why are we recycling at home, or cyling to work, or lowering the fresh gas flow rates used for patients under anaesthesia? It's more a question of perspective at that point, and I personally don't think being unable to stop entire nations burning coal completely frees us from any duty of care to the environment we all have to live in.[/quote]

I agree up to a point! I mean clearly something is not worth doing if it has little impact. But impact might be measured in other ways than JUST emission reduction. For example, the more people who adopt low carbon behaviour, the more that people in positions of power are likely to, too.

But it does seem to me that the emissions from veterinary anaesthesia are a very, very, very small part of the equation, so to my mind, the question of whether it is worth upgrading equipment on the grounds of sustainability comes down to cost. Vet profession is already under fire about the costs, and the increasing unaffordability of veterinary care, so then one has to weigh up the sustainability benefits vs animal welfare.

[quote userid="50456" url="~/f/clinical-discussions/32641/low-flow-anaesthesia---is-it-worth-it/179229#179229"]Another issue with greenhouse emissions specific to anaesthesia is they have a disproportionate effect on warming the environment relative to their actual emission level, because of how effectively they absorb infrared radiation (the worst example was desflurane, which fell out of use for this exact reason). A study in 2019 compared anaesthesia hours at MAC level to driving a car, and found using isoflurane at 1.3% at 1L/min of oxygen is equivalent to driving 12 miles, so 2L/min is 24 miles and so on...[/quote]

Yes ... the figures i used to compare veterinary anaesthesia emissions with coal-fired power stations was CO2e (equivalent) which takes that into account.

[quote userid="50456" url="~/f/clinical-discussions/32641/low-flow-anaesthesia---is-it-worth-it/179229#179229"]Re: patient benefit - is it worth it? Yes, but in some ways that likely aren't immediately apparent. There isn't data on improved recovery times specific to low flow as far as I know (although hypothermia from high rates of fresh gas delivery is an issue, and hypothermia is a proven contributor to perioperative mortality generally). Higher flow rates ultimately deliver more volatile agent, whether the patient needs it or not, and there you have all the usual implications for cardiovascular depression, hypotension and tissue injury. If the patient isn't metabolising the volatile then they exhale it, quite possibly in the recovery kennel into the face of the staff member monitoring them if there wasn't sufficient time between turning off the vapouriser and disconnecting the patient from the circuit, so there's a human health argument as well.[/quote]

To my mind, THIS is really the most important factor.

I think that the profession has, over the last 20-30 years, advanced at a phenomenal rate, driven largely by the fact that vets and nurses are driven PRIMARILY by the desire to do the very best for the patient in front of them, and less by money.

The problem is that 'the best' has now become very expensive, and some might argue out of proportion to the species being treated.

So I come at this very much from the perspective of challenging the cost/benefit equation.

To me, its not enough to say simply say that something is clinically better. I think there needs to be evidence. And the evidence needs to show a benefit that justifies the cost.

in simple terms, you might say that capnography is a "good thing", and I would say: "erm, yes, but how many patients dying before capnography, and how many after, and does the cost justfy the benefit".

I am not saying I know either way ... you know far more than me!

Just arguing that as the cost of veterinary care has increased, I think everyone needs to be less driven by the idea of offering the very best that science can offer, and more by whether it is affordable and proportionate.

Am I being unreasonable??!!

RE: Low flow anaesthesia - is it worth it?

DanB — Thu, 12 Feb 2026 17:19:49 GMT

I think these are really 2 different questions, possibly 3 if you include the effort to reduce overhead costs. Coming from a referral anaesthesia background and having taught low-flow techniques to various levels of practice, it's not completely cut and dry.

Re: sustainability - is it worth it? Yes, in the sense that where we have some ability to minimise our impact on the environment we have an ethical responsibility to exercise it, and not being in charge of the operation of coal-fired power stations, we can find other ways to reduce our contribution to climate change.

There's a very easy, almost comforting cynicism to be found in the small scale of our own efforts: fewer than 100 companies produce over 70% of all global emissions, so why are we recycling at home, or cyling to work, or lowering the fresh gas flow rates used for patients under anaesthesia? It's more a question of perspective at that point, and I personally don't think being unable to stop entire nations burning coal completely frees us from any duty of care to the environment we all have to live in.

Another issue with greenhouse emissions specific to anaesthesia is they have a disproportionate effect on warming the environment relative to their actual emission level, because of how effectively they absorb infrared radiation (the worst example was desflurane, which fell out of use for this exact reason). A study in 2019 compared anaesthesia hours at MAC level to driving a car, and found using isoflurane at 1.3% at 1L/min of oxygen is equivalent to driving 12 miles, so 2L/min is 24 miles and so on...

Re: costs to practice - is it worth it? Maybe, in that volatile agents and oxygen are expensive. Isoflurane at 2% using 2L/min of oxygen costs about 25p/hr, but sevoflurane at 2% and 2L/min costs over £4/hr (human hospitals get sevo far cheaper, but that's a separate issue!) so multiply to some of the standardised O2 rates used in practice, with the old excessive circuit factors, especially for non-rebreathing circuits, and it soon adds up. Does it offset the cost in training or purchasing equipment like capnography? It's possible it doesn't when things are all added up.

Re: patient benefit - is it worth it? Yes, but in some ways that likely aren't immediately apparent. There isn't data on improved recovery times specific to low flow as far as I know (although hypothermia from high rates of fresh gas delivery is an issue, and hypothermia is a proven contributor to perioperative mortality generally). Higher flow rates ultimately deliver more volatile agent, whether the patient needs it or not, and there you have all the usual implications for cardiovascular depression, hypotension and tissue injury. If the patient isn't metabolising the volatile then they exhale it, quite possibly in the recovery kennel into the face of the staff member monitoring them if there wasn't sufficient time between turning off the vapouriser and disconnecting the patient from the circuit, so there's a human health argument as well.

I'd also argue there's an indirect patient benefit in that low flow can't (safely) be done without capnography, and if it takes a corporate sustainability campaign to get capnography into practices that didn't have it before, then anaesthesia safety overall will only improve.

So it might depend on how you look at it. I think there are more benefits than drawbacks, whether it ultimately saves the planet or not.

RE: Low flow anaesthesia - is it worth it?

Arlo Guthrie — Wed, 11 Feb 2026 19:51:17 GMT

Selena Carnell - interesting. I presume you've done a fair amount of monitoring in your time, interested to know what opportunity you've had to compare. Also, for a layman idiot like me, what does this mean:

[quote userid="2368" url="~/f/clinical-discussions/32641/low-flow-anaesthesia---is-it-worth-it/179227#179227"]but most of the nurses i work with tend to whack up the oxygen.[/quote]

I know you mean that they turn up the 02, but why and what is the consequence of that?

RE: Low flow anaesthesia - is it worth it?

Selena Carnell — Tue, 10 Feb 2026 21:28:31 GMT

Personally i haven't seen any benefit in low flow towards quicker recovery times.

It does reduce the amount of Isoflurane used, but most of the nurses i work with tend to whack up the oxygen.