When the brain structures are destroyed and the processes cease, the conscious ceases to exist. This cannot be reversed. Brain death is a complete and irreversible cessation of brain activity. A brain dead individual has no electrical activity and no clinical evidence of brain function on neurologic examination (no response to pain, fixed pupils, no spontaneous respirations, no oculocephalic or corneal reflexes).
Brain electrical activity can stop completely, or apparently completely (a "flat EEG") for some time in deep anaesthesia or during cardiac arrest before being restored: brain death refers only to permanent cessation of electrical activity. In other words, one can be pronounced dead, but not brain dead.
No solid evidence exists which suggests conscious can extend outside our bodies.
Completely irrational.