The only thing I'm really worried about Is going under. The last time, when I had surgery on my hands after the dog attacked me, my heart stopped while I was under and they had to resuscitate me. When I came to the dr told you I need to tell you. I cut him and told him I saw everything, cause I did. Won't get into all the details, but it was pretty cool.
Never had it done myself but I have heard that some use a drug called "Versed" which doesn't put you out and you can function just like normal but you will remember nothing. That stuff is freaky as hell because you can carry on a conversation with your Dr. or anyone else but you won't have any idea that you did. They used that on me for my heart catheter and I have no recollection of what they did or what I did for a couple of hours afterward, then memory was sketchy for another couple of hours. My wife had no idea what the drug would do and had no idea that I couldn't remember any of the Drs. instructions even though I was talking to him like everything was normal.
