Hi X,
I recommend Iso or even better Sevo for ferret anesthesia.  Can ketamine/
valium be used?  Yes, but the ferret does not wake up as fast after the
surgery.  A ferret neuter is similiar to a small dog neuter (some will do
them just like a cat neuter) and only takes 10 minutes or so.  With Iso or
Sevo they are up and moving around 10- 20 minutes after the surgery.  With
ketamine/valium the recovery time can be a lot longer (1-2 hours).  Thus I
would just go with the gas anesthesia and avoid the injectables such as
ketamine/valium or ketamine/ace, etc.
 
Hopefully your vet will use Iso or Sevo.
Jerry Murray, DVM
[Posted in FML issue 3680]