Make sure this vet cares for her as a senior cat and that means she gets NO preshot!! They should only give her gas and nothing else to put her to sleep!
She will have less stress on her kidneys and wake up faster. Also, be VERY sure the vet does this cleaning and preparing and not a tech. I just had a customer lose her cat to a simple teeth cleaning and I know techs can make mistakes easier than the vet.
Also, ask them to give her a little fluid after surgery to flush her kidneys of any waste from the gas.
IF she needs a antibiotic ask them for clavomox ..not the Baytril or flygle because they are very strong and some cats have been known to go blind from the Baytril if given too much.
She is an old cat so all these precautions should be taken for her.
PS: preshots are made up of a cocktail of hard drugs to put them to sleep fast.