https://biostasis.su...r-a-few-minutes
“Cryonics can’t work. Dead is dead! Besides, everyone knows that the brain dies after three to five minutes without oxygen.” We hear that often. Sometimes “everyone knows” means genuine established facts as in “everyone knows the Earth orbits the sun.” But often this means something completely different: It can mean that the speaker has heard the assertion a few times, assumed it to be a fact, and has not investigated further.
Even a quick look at the actual evidence shows this assertion to be incorrect or – to be charitable – correct only in specific circumstances.
In the first hour or so with no circulation most of the problem is not with lack of oxygen but the damage caused when circulation is restarted. If brain death results, the cause would be better understood as restarting circulation without preventing damaging side effects. Damage done by getting things flowing again is called reperfusion injury or, sometimes, ischemia-reperfusion injury (IRI) or reoxygenation injury. Reperfusion injury is referred to as “paradoxical injury” because the act of restoring normal blood flow, meant as a therapeutic measure, actually induces damage.
