I've had several colonoscopies due to colon cancer in the family. I absolutely detest the prep. Absolutely the worst part of the whole thing. 24 hours of supervision is not at all the norm for this test. Why don't you clarify with your doctor ahead of time the reasoning for that? It may be a precaution due to your other health issues, but you won't be feeling sedation for that long. There just isn't that much sedation involved.