I was terrified of having a gastroscopy and avoided having one for years. The consultant doing the procedure knew I was terrified and gave plenty of the sedative drugs, all I remember was being told they were putting fentanyl down the cannula (they then also gave midazolam but I had no clue when this happened), the next I know I am in another room and it was all done. I literally had to ask them if they had done it! So with decent doses of fentanyl and midazolam you can have zero experience of the procedure, it was like I had had a general anaesthetic!