In most cases a preanesthetic injection is given to sedate the patient, then the gas is administered with a mask over the muzzle. Once the pet is sleeping, an endotracheal tube is placed, and the gas anesthesia is ready to be delivered. Many patients control their own level of anesthesia. When they are not deep enough they will breath harder, inhaling more anesthetic and going back to sleep. When the patient is at the correct level, the respiration will decrease and breath less gas.
Safety is the veterinarian's most important concern.
Prior to anesthetic delivery the animal is examined, with particular attention given to heart and lung sounds. The veterinarian should be made aware of any pre-existing medical conditions or medications your animal is taking. The patient under anesthesia is constantly monitored. Observing the color of the gums and the number of respirations per minute are helpful. These instruments add another level of safety to the procedure.