[AmyChristine]

I just want to add, masking only, is good when there is high risk. However, there is a very fine line between awake and asleep when done like this, the gas has to be even more carefully monitered than when an injection is used first.

Many times when the animal is masked only, they can start to wake and move, even panic while still opened up. When you use the injection to initiate anesthesia and then gas the vet is able to keep them more evenly under anesthesia than with the gas only.