Thankfully, I "work with" (i.e. work together on treating my ferrets) an
excellent vet who has an extraordinary amount of experience with ferrets.
My ferrets have undergone quite a few surgeries and have, thus far, come
out with flying colors -- not that this would keep me from worrying the
next time...
 
Anyway, from what I can recall from discussions with my vet, there are
a number of factors that can prevent a ferret from coming through a
surgery: health, type of anesthesia, length of time under anesthesia,
amount of oxygen (i.e. breathing), and body temperature to name a few.
My vet has an actual respirator that he hooks ferrets to to ensure that
they receive ample oxygen because they have a tendency to not breathe
properly under anesthesia.  He also has a heated surgical table and
heated oxygen tank to ensure they have enough oxygen and stable body
temperature.  He also uses Iso.
 
Just wanted people to note that there's more to it than just the type of
anesthetic used.
 
Suzanna Donahue and the fuzzilicious fuzznosticators
[Posted in FML issue 4294]