You put the animal down. If it were a human being on a respirator, I can understand the moral dilemma, but this is a dog . Dogs are fine creatures, but that doesn't give them the same bargaining leverage as a human being. It would never occur to me to cry over an animal like that. I've felt a sense of loss over some of our pets that died, but never enough to cry about it.
Pets are good, but they're easily replaced.
When Christine was still living in Glenville, her daughter's hamster came down with some kind of tumorous growth. Tom and I agreed that something had to be done to put the animal out of its misery, so we told Christine we'd take care of it and went outside. Tom tried putting it out with car exhaust, which didn't work very well. He wrung its neck instead and we both agreed to tell her that it was quick and painless and leave it at that. It wasn't even her pet, but she cried over that hamster.