that is really too bad about your dog. I've got one that is 18yrs old and she's on all sort arthritis medication, but still failing over time. Its like I told the other people in my family about her'. You exhaust ever feasible option you have but in the end its just best to let go. Again, I'm really sorry to hear about your dog, but if he's led a good life then let him die with the dignity that he deserves as part of your family. best of luck.