A number of vet practices have been reporting problems in the last few days in getting hold of the anaesthetic gas isoflurane, due to supply problems from the manufacturers. However, instead of lasting a few days and then coming back on stream, the shortage sounds like it might last a while, with the Veterinary Medicines Directorate (VMD) reporting that 2 of the main suppliers have restock dates as late as February or even March next year. In this blog, we’re going to look at how this might affect vets and pets across the UK in the next few months.
Is it anything to do with Britain leaving the EU?
No – it seems to be a routine manufacturing shortage. These actually happen all the time with all sorts of drugs as the demand for them varies. Fortunately, not everything in this world revolves around Brexit!
What is isoflurane?
Isoflurane (commonly abbreviated to “iso”) is the standard anaesthetic used for most surgical procedures in small animals (and humans, for that matter). A “standard” anaesthetic protocol for a dog or a cat would typically involve an injectable “premed” (a combination of drugs to help them relax and a painkiller) followed by an injectable induction agent (a drug that makes the animal go to sleep, usually propofol or alfaxalone, although sometimes ketamine might be used). However, while they kick in fast, these drugs wear off quickly, so once asleep the patient is kept that way by mixing a small amount of anaesthetic gas into the pure oxygen they’ll be breathing. This maintains what we call “surgical anaesthesia”, so they stay asleep until the operation is finished. You can read more about the procedure on this blog.
Aren’t there other anaesthetic gases?
Yes there are – in veterinary practice, another drug called sevoflurane (“sevo”) is fairly widely used and has similar properties but works much faster. However, it’s also much, much more expensive (partly because it’s more complicated to make, and partly because we need to give slightly more of it per breath), and so it tends to be reserved for critical cases. There are also older agents such as halothane; however, these are rather outdated and less safe in some situations, and so while they have a few advantages they are rarely used nowadays.
However, even if a practice has access to halothane or sevoflurane, they can’t just change over from iso to one of these because the anaesthetic systems aren’t compatible. These drugs come as a liquid, and are put into a special device called a vaporiser. This allows a small amount of the liquid to evaporate, and then mixes with the oxygen the patient will be breathing in. The vaporiser has a dial that allows the veterinary team to adjust how much gas is mixing into the oxygen, and thus how deeply asleep the patient is. If they go too deep it is very dangerous and can result in toxicity or even death (although this is very, very rare nowadays).
The problem is that each of the anaesthetic gases has different physical properties, meaning that a vaporiser designed for one can only be used with that particular gas. So, adding sevo to an iso vaporiser (for example) could result in a lethal overdose – or the patient waking up at the wrong moment.
Are there any other alternatives?
Well, there are several options for affected practices. Firstly, they could invest in a sevo vaporiser, and move over to that gas – however, in that case all anaesthetic prices would have to rise somewhat to cover the increased costs, so it seems unlikely that many practices will go down that route (although referring patients to a practice that uses sevo might be an option in a few cases).
Instead, most practices are attempting to source human-licensed isoflurane, or import stocks from elsewhere in the EU. Both of these are perfectly legal, as long as the vets have made reasonable efforts to get hold of the veterinary form, and in the case of the imports, that they obtain a proper import license from the VMD. However, these are also likely to be more expensive, and if this shortage is very prolonged, it might be that overseas suppliers – or even human hospitals – may run short of supplies.
So either way, it costs me more money?
Possibly. However, there are some further alternatives. For many short procedures, anaesthetic gas may not be required – for example, cat castrates often don’t take long enough to move them onto gas. As a result, many vets will probably explore the idea of “TIVA” – Total Intravenous Anaesthesia – using a mixture of injectable drugs such as ketamine to keep the patient asleep. Similar techniques are widely used in large animals, and on feral cats, so it isn’t something new, just something that could be extended safely to a wider range of cases.
Another possibility would be the use of “anaesthetic sparing” drug combinations. For example, practices that use more powerful painkillers (like methadone) instead of weak or medium strength ones (such as butorphanol or buprenorphine) find that their patients need less anaesthetic gas during surgery. Some practices might also start to use nitrous oxide (the gas in “gas and air”) which can also dramatically reduce iso requirements in surgery. So, we might see more and more practices using these potent painkillers for routine surgery (which is probably a good thing!), and therefore eking out their supply of isoflurane.
Another possibility is that some practices might postpone routine, or elective, procedures until new supplies become available. While this may not be convenient, it would allow the limited stocks to be reserved for critically ill animals.
The bottom line…
This is a temporary solution, so don’t panic! Even if your practice completely runs out of veterinary isoflurane, there are lots of other options available so procedures can still go ahead. If you are at all concerned, though, talk to your vet – most of us are very happy to talk about our anaesthetic protocols if you’re interested! And remember, if you are asked to postpone, it’ll be because the vets are trying to save the supplies for the patients who need them in an emergency.