Anesthesia, being knocked out, unconsciousness...what does the Buddha have to say about it? This is something that I have trouble coming to grips with. If the mind can be aware without a body or brain then how is it possible that one can experience things like the Bardo when we know that without certain conditions the mind becomes unaware? Anesthesiologists can purposely put people into this state. One second you are going under for surgery and the next second you are laying in a hospital bed without any awareness of the lapse of time. If one were to extinguish ever becoming or going doesn't that mean an unconscious state? Does Buddha ever explain this phenomenon?
The mind is always reacting to sensation on the body what every any state you are in, including but not limited to anesthetized, knocked out, unconsciousness, etc. Only time you do not sense any sensation is when you are in Pala Samapathi. So you are always have some level of awareness of the body through sensations at the deepest level of the mind or subconscious mind. At the surface level (conscious mind) you might not be aware of it.

Also see: From the Deepest Coma, New Brain Activity Found