My experience occurred when I was anaesthetised for a caesarian section and giving birth to my first child. I remember being in a very peaceful, calm, and dark space and aware that I was 'floating' away from my body. I can only describe it as going away at a 45 degree angle but more like moving into a dimension unlike any in our 3 dimensional world.

After a little while of enjoying the wonderful feelings of peace and calm (and not really being concerned with anything else), a thought occurred to me "what a shame, you have carried this baby for 9 months and you are not going to see it!" It was as though a decision was made, then I felt as though I was falling back and 'slammed' onto the bed (very harsh and uncomfortable) where life/reality here in the world hit me! It was some while later (weeks or even months) that I recalled the details (having remembered them all along, but not really able to put them into words) and I told my husband. He answered "The doctor told me you had 'died' during the operation"! 

Until then I was unaware that had happened. I have subsequently had another baby by caesarian section and 2 hip replacements, all under general anaesthetic, but never experienced anything even similar again.