An NDE involves your soul/spirit leaving your body before death, but as the silver cord,(pure energy) hasn't severed due to the fact that there is hope and your body is able to survive, IMO it has everything to do with Spiritualism.(Just my thought's).
A blackout where you don't remember anything before you come around again is simply your soul remaining in your body due to the fact the injury(or whatever) isn't sufficient for you die.This is why(thanks to modern medicine people are being bought back from death), more NDE's have been reported recently.