[Sudden cardiac arrest].

Circulating blood that contains oxygen is required to keep tissues in the body alive and functioning. The brain may sustain damage after blood flow has been stopped for about 4 minutes. There is irreversible damage to the brain after blood flow has stopped for 7 minutes. To be successful, CPR should be started within 6 minutes of a person having a sudden cardiac arrest. Low body temperatures (hypothermia), seen in near-drownings and exposure to the cold, prolong the time that the brain can survive.