I was sedated when I had my wisdom teeth out. I was maybe 16.
I remember laying back on the reclined dental chair, and the nurse telling me I was going to be given gas. She brought out a rubber mask that fits over the nose only, and fit it around my head. She also put a device on my finger to read my pulse. I remember her telling me that I was going to be given nitrous, and oxygen after the procedure. This made me immediately hard, since I had a fetish for anesthesia and oxygen masks. My pulse must have shot way up, because the nurse was reading my pulse and said to me "try to calm down".
I remember breathing the gas through my nose, and that I had a throbbing erection in my jeans, that I immediately tried to cover with my hand (the one that didn't have the pulse reader on it). The feeling of the gas was kind of similar to the high after smoking marijuana, and (being familiar with weed) I remember thinking "oh shit I'm stoned". I was very self conscious about my erection, but laid back and kept breathing the gas. The nurse or maybe the doctor came in and asked if I was doing okay.
After a minute or so of getting high on the gas, they told me they were going to put me under. The doctor (a guy) had to grab my wrist and gently pull my hand off my erection. I have no doubt that he knew what I was trying to protect. They started an IV in my hand. I remember several attempts to find a vein in the back of my hand, but don't remember the needle actually going in.
The next thing I remember was waking up, and slowly standing and walking out in the waiting room where my dad was waiting to take me home. The sudden change in time was completely disorienting.