I've always been afraid of intravenous sedation (="twilight anesthetic" in other English speaking countries) for the same reason.
The only time I experienced it was for an endoscopy. Because I was a heavy drinker at the time (probably the reason for the symptoms that lead the the endoscopy, ironically) the intravenous sedation had little effect, so I was awake through the whole thing. I didn't find it traumatic, merely unpleasant, but I think other people might have. The local anesthetic at the back of my throat wore off after some time, so I was dry retching every few minutes. At one point they pumped air into my stomach so they could take a sample with a needle (which was in itself painless), and that sensation was also unpleasant.
So while I doubt people undergoing intravenous sedation during routine surgery are in extreme pain, they may be in very uncomfortable situations that most people would rather forget. Also if it had been effective, it would alter your state of mind as well, so that the immediate experience was less bad.
I've had an endoscopy before, to push down some food stuck at the top of my stomach, with no sedation or numbing. Being held down by a couple of nurses and the doctor whilst the procedure was done three times - the first two times I pulled the endoscope out after having panic attacks - was the worst medical-related experienced I've ever had, and it still gives me nightmares. Turns out the doctor was known for being a sadistic bastard who enjoyed seeing his patients squirm; I wish I was making this up.
OTOH I regularly have a colonoscopy under heavy sedation, and never remember a thing.I know there are risks with any kind of sedation or anaesthetic, however anecdotally they've saved me a lot of trauma.
The only time I experienced it was for an endoscopy. Because I was a heavy drinker at the time (probably the reason for the symptoms that lead the the endoscopy, ironically) the intravenous sedation had little effect, so I was awake through the whole thing. I didn't find it traumatic, merely unpleasant, but I think other people might have. The local anesthetic at the back of my throat wore off after some time, so I was dry retching every few minutes. At one point they pumped air into my stomach so they could take a sample with a needle (which was in itself painless), and that sensation was also unpleasant.
So while I doubt people undergoing intravenous sedation during routine surgery are in extreme pain, they may be in very uncomfortable situations that most people would rather forget. Also if it had been effective, it would alter your state of mind as well, so that the immediate experience was less bad.