At our clinic where I work, we usually give an injectable anesthetic
(Telazol) before the IV euthanasia solution in cats and ferrets.  The
injectable goes into the thigh muscle usually, and is quick acting and
relatively painless and stress-free for the patient.  They just quietly
and gradually go to sleep, making it a lot easier for the vet to administer
the IV euthanasia solution, you don't have to be poking around for a vein
(especially when the pet's blood pressure is usually low and veins
difficult to find), trying to restrain the pet, just a more peaceful time
all around and the owner can hold their pet while they drift to sleep from
the injectable anesthetic.
 
Hope I've helped answer some questions!
 
Tracey
[Posted in FML issue 3305]