We have been putting people under since 1846, and we still don't fully know how it works.
That's the part that gets me. Not the chemistry — the routine. Somewhere right now a person is counting backward from ten, and somewhere around seven the world ends. No dream, no dark, no sense of duration. Sleep at least leaves a residue — you wake knowing time passed, that you were somewhere. Anesthesia leaves nothing. You are mid-sentence, and then a stranger is saying your name and it is four hours later and the four hours never happened to you. Not skipped. Not fast-forwarded. Simply absent.
It's the closest thing to nonexistence a person can survive. A clean deletion of the self, scheduled, billed, recovered from by lunch.
And the mechanism is still, after nearly two centuries, an open question. We know which drugs do it. We can dose it to the minute. But how a molecule reaches in and switches off the thing that is you — the seeing, the worrying, the sense of being here — nobody can quite say. We turn consciousness off the way you'd flip a breaker in a house whose wiring you've never seen.
What stops me is that none of this stops anyone. People sign the form. They make the joke about the gas. They count. We have decided, collectively, that the one experience nobody can describe from the inside is fine, is normal, is Tuesday. The deepest mystery we have, and we schedule it around our errands.