I've had several surgeries. Two types of anaesthetic.

First was when I was 4 years old, in the 1980s. Was a gaseous anaesthetic, through a gas mask.

It was a kind of quasi-consciousness, not that I remember having trains of thought or self-actualization, but I remember there being a feeling of the passage of time. I remember seeing colors. No pain during the procedure.

Second type of anaesthetic was for my second and third surgeries (aged 13 and 17), a normal liquid, IV-administered anaesthetic. This one was just a complete knock out blank for me. No cognizance of anything. I was just out in one moment during the backward from 10 countdown, and aware again in the recovery room, in what felt like 3 to 5 seconds later (it was, of course, a couple of hours later).

This second type of anaesthetic had the interesting post-surgery side effect of continuing to knock me out (with no time passage perceived) for hours after the surgery. I would, in my perception, blink, and my visitors would suddenly warp across the room because my eyes hadn't been shut for .1 second like it felt to me, but actually a couple of hours per occurrence, of dreamless, non-time-passing "sleep". Not an experience I'd had before, or since. The last surgery (17) was a bit less disconcerting in regards to this, because I knew in advance about the effect from the previous surgery (13) .