Like Lorraine said, proper anesthetic is important. My vet now uses Sevoflourane which is what's use on humans. The difference between Sevo and Iso is that they wake up quicker with the Sevo...
Here's a great article that compares to two.Maybe print it off and take to your vet to ensure they use one of these gases.
http://www.surgivet.com/smart/archives/Isoflurane%20vs%20Sevoflurane.pdf#search='isoflura ne%20sevoflurane%20anesthetic%20for%20dogs' |