If your doctor suggests a colonoscopy, maybe talking to him/her about
your sedation ahead of time would help. I woke up during one, and the next time my doctor and I scheduled one, I asked if she could review how much and what meds were given so they would know that they need just a little more than that to keep me asleep the whole time. The one after that went smoothly and I didn't wake up.
Good for you...not waiting until you need to be hospitalized!