My girl was spayed at age six and she is liver compromised (at least slightly). I know it is scary and I'm going to to downplay that. It can be risky to do it, but it can be risky not to do it. With the right testing before and the right anesthesia though, it will very likely be just fine. Just remember, old age is not a disease.
Besides the preop bloodwork, you could add a bile acids test, chest xray, EKG, and U/A on. That's a really good way to go if the $$$ is available.
Also, do you mean you are using propofol is the induction drug or to maintain? What is the plan to maintain? Iso?
BTW, Ellie did fantasic (had liver biopsy at same time which increased the risk). She came home that night and was well on her way to recovery within a day or two. No regrets about it.