How long does it take for a person's cells to all die after clinical death?

Clinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain human and many other organisms' lives.

It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest.

Brain injuries start to accumulate almost immediately after Clinical Death.

Full recovery of the brain after more than 3 minutes of clinical death at normal body temperature is rare.

Usually brain damage or later brain death results after longer intervals of clinical death even if the heart is restarted and blood circulation is successfully restored.
Although loss of function is almost immediate, there is no specific duration of clinical death at which the non-functioning brain clearly dies.

The most vulnerable cells in the brain, CA1 neurons of the hippocampus, are fatally injured by as little as 10 minutes without oxygen.

However, the injured cells do not actually die until hours after resuscitation.

Brain failure after clinical death is now known to be due to a complex series of processes called Reperfusion Iinjury that occur after blood circulation has been restored, especially processes that interfere with blood circulation during the recovery period.

Hope this helps!!!
~Alkka♥