I was cathed several times a couple of years ago. They used this IV stuff that they called "milk of amnesia" for conscious sedation. Apparently it knocks the patient down, but they can still ask you to do things (like cough, for example). But I don't remember a thing.
The second procedure was fairly long - ended up taking 7 hours or so. Afterwards I was told that at one point my blood pressure had dropped, so they reduced my level of sedation a bit and I partly woke up and decided to get off the bed. Apparently it took several people to hold me down.
I don't remember it at all, but I wonder if it didn't invoke some memories for me (on occasion I wake up suddenly from bad dreams, jumping out of bed) My cardiologist seemed a bit uncomfortable to talk about my waking up, so I wonder if I said anything. I'm a bit proud of myself - I imagine that I had a flashback and protected myself well, since it took that many people to hold me down! That helped to improve my body image, which is often that of a skinny 12 year old, not of a 6'2", 210 lbs man.
Other than that, the procedure went well - pretty routine.
Good luck to you!