I have had multiple colonoscopies and endoscopies done over the years and I have NEVER heard of a physician, group or clinic that performs these procedures with the patient 'remaining awake.' Nearly all practitioners perform these procedures using conscious sedation - what DrOnTV referred to as 'twilight.' Conscious sedation works great. Depending on the physician the drugs used to induce the patient will be the same drugs used for general anesthesia at a lower dose, or a mixture of an anesthetic and a sedative. The purpose of conscious sedation is to induce the patient to a point where relatively no pain is felt, and yet can respond to commands verbally and physically. Additionally depending on the drugs used and the anesthesiologist most patients do not remember the procedure itself, this is because many of the drugs used for general anesthesia have amnesia effects. In either case you will wake up in a light daze, aware of your surrounding but not with-it enough to care, 'recover' for about thirty minutes and then leave with an individual you brought to drive you home. The procedures are safe, nearly painless during the procedures - I cannot remember what went on during any of mine, and very quick. I would recommend this group:
http://connect.inova.com/physician/mddb.practice.pra_view?p_pra_id=5323