This actually happened to me: You're about to be put under, prior to your seven year colonoscopy, and the attending nurse says to you, in a low, soothing voice: "You may feel an intense, momentary burning sensation at the site of the IV needle."
Gee, thank you so, effing, much! I mean, those could have been the last words I ever heard, this time around. I remembered them when I came to, and I really wanted to yell at that woman, but I wanted to get home, more, so we left.
It was just stupid, maybe even sadistic, on her part. The anesthesia works lightning fast. Even if I felt an intense burn for a millisecond, I would have gone under near-instantaneously, so screw that warning! All it did, in reality, was make me think, "Why are you telling me this, now?" right before I was out. Not cool, one bit.
If they want a patient to know about a burning sensation, which I never felt, then give that patient the warning well before you wheel him/her into the procedure room.
Bummer, indeed!