Dogs and Anesthesia

I have 2 questions. Do you know of any problem with the manufacture etc. of isoflourane or other anesthesia? My dog is scheduled for minor surgery and I am concerned. Two animals were lost on the table at my vets in the last few months due to reaction to anesthesia. Do you have any recommendations concerning a friends 3 year old collie that was adopted recently and spayed 7 days ago. She whined for 4 days after the surgery, is not active or interactive as she was, and seems depressed. To make matters worse, she has hardly eaten since the spay.