This article in New Scientist (I don’t know anything about this publication) suggests that people who arrived at the hospital technically dead by any standard definition have been chilled to very cold temperatures for a couple hours, operated on, and resuscitated. This is not too surprising because you do occasionally here of people who drown in very cold water and get resuscitated after longer periods of time than you would think. Also, if bears, chipmunks, and frogs can do it with basically the same organs as us, why not us? But still, this is something new that could change the traditional definition of death and maybe lead toward the idea of hibernation present in every space travel story ever.