I had one with sedation, but it don't think it worked, as I remember it all! Only thing I didn't remember was afterwards, I was about to ring my other half to say I was ready and I couldn't remember how to use my phone! Very odd, but that only lasted a minute or two.
I was terrified, but it was OK, not the most pleasant experience. Going in and seeing the table/bed and the nurses around it was daunting. They couldn't find a vein either, which didn't help.
I had throat spray, then the injected me, but it don't think it went in, wonder if they couldn't get a vein at all, but didn't tell me after three goes.
I lay on my side and they put a mouth guard in and fed a tube down, it made me gag a bit, but trying to take deep breaths in my nose helped. I gagged several times and my eyes were watering, but it wasn't painful as such, just unpleasant. It lasted about 10 minutes.
Afterwards they let me lie on a bed in recovery for half an hour before I went home. I has no ill effects after, or sleepiness.