Irreversible brain damage occurs after how many minutes of anoxic brain injury?

• A. 4-6 minutes
• B. 6-8 minutes
• C. 12-15 minutes
• D. 8-10 minutes

Answer: (D)

When oxygen stops reaching the brain, its cells quickly run out of the energy they need to stay alive. ATP depletion causes failure of the ion-pumping machinery, a dangerous influx of calcium, and a cascade of processes (including excitotoxicity and free radical damage) that lead to neuronal death. Some brain tissue can recover if blood flow and oxygen return quickly, but once a sustained period of anoxia stretches to about eight to ten minutes, the damage becomes irreversible in most cases. Temperature, individual health, and brain region can shift the threshold a bit, but eight to ten minutes is the standard window used in EMS training to indicate likely irreversible injury.