I've done it (it's standard in many countries). Honestly, it's a bit horrifying because you are completely at the mercy of someone else but it's bearable. Colonoscopy is definitely easier.

My only experience with global anesthesia was as a child waking up with a massive asthma attack unable to breathe so I try to avoid it.

> Honestly, it's a bit horrifying because you are completely at the mercy of someone else but it's bearable.

Probably not as horrifying as brain surgery or getting your eyes lasered.