I work in research. Generally, the rule is that you follow whatever is outlined on your protocol. I had a situation where some of my animals were in pain and needed to be euthanized immediately. The communal tools to do this were in use (CO2), and you normally need to sign up for it ahead of time. Because the animals were in pain and this needed to be done immediately, I chose an alternative method of euthanasia that was readily available. This was not approved as a method on our protocol. It sounds pretty serious, but truthfully, even if I had taken the animals to the on site vet, he would have probably suggested the same. For one thing, I worry about this because I 'technically' didn't follow protocol. For another thing, it may raise eyebrows since it involves animal euthanasia
Let me clarify that the alternative method was a method still widely used in research.