My little man was neutered yesterday and I was more upset than he was. We dropped him off at 8 and had the bloodwork done. He also had two baby canines removed. I was VERY worried about the anethesthesia too. They used Isofluorine. The doctor called at 11 and said he was doing great. We picked him up at 3:00 and brought him back home. He was groggy but otherwise seemed ok. He snuggled in bed with us and slept with us the whole night. I would not leave mine overnight. Like the person said before, ask to have the procedure done in the morning even if it means rescheduling so you can watch him overnight. Good luck and let us know how it went.