There's been some debate about
whether a nurse (or a even a GI) should administer propofol at all. Many nurses would prefer that an anesthesiologist administer it. The dosage is tricky, and there is a fine line between enough and too much. Once too much has been administered, there is no reversal. Advanced measures must be taken to maintain an airway until the effects wear off. All these safeguards are limited at a basic outpatient center.
A lot of people think a puncture will be the end of the scope coming through the colon, like a needle through cloth. That's not the case. When the scope gets "stuck," it needs to be reduced (unkinked), and sometimes the pressure of the side of the scope puts too much pressure on the side of the colon, like a curve in a curve. Effectively and safely reducing the cope takes times.
At some outpatient centers, propofol is used to speed up the scope so that as many scopes as possible can be performed in a day. The more sedated a patient, the less feedback, and the more likely that reducing the scope will lead to a puncture.
The general population should seriously reconsider surveillance scopes after a certain age. Without any extra risk factors, sedation is more likely to cause death than colon cancer. There are safer methods of screening colon cancer and more on the way.