Fortunately, anesthetic problems are very, very rare these days, because of the types of anesthesia used and the protocols you can take to monitor them. You know, most vets do some pre-anesthetic blood work to rule out kidney problems or liver problems; the organs that filter your anesthesia through your body. If there's a problem with that, then your pet might not be a good anesthetic candidate and that's how you find those things out.
Even, in the case with Kensie, there's some truth that old dogs need to be monitored more. But old age is not a disease, so you need to still get them proper medical care.
Now sometimes bad breath can be a sign of a medical issue. And one of the big ones you'll see is a lot of times dogs that have kidney disease will have a very bad smelling breath. So you have to know … it’s not just safe to assume that there's some kind of a dental issue. Sometimes it could be something medical, like kidney disease.
Sometimes, they'll get a foreign body lodged in their mouth and you won't know it’s there. But it gets infected, and starts to smell, and your vet may have to help you determine that. So bad breath is usually a sign that you need to see your vet. So that’s generally what I would recommend.