Edit: Basically the vet says that it is extremely important that you are present for the sake of your pet when they are put to sleep so that they will less afraid and comforted by your presence ...…. But because rats need to be given the gas/oxygen mix used for surgery, some vets will not allow pet owners to be present I am vet fortunate because my vet allows me to be present and to hold my rattie during the procedure. I hold and cuddle my rattie in my arms and hold the tube with the gas/oxygen mix near their face. They hate the smell but a few breaths and they start to get sleepy. I am able to hold my unconscious rattie being administer=d the gas/oxygen mix, while they become unconscious to at least a surgical level, while they are injected, and while they remain unconscious until they have passed away.