How long does brain activity last after cardiac arrest?
How long does brain activity last after cardiac arrest?A reader asks: A friend told me that when you have a cardiac arrest, within 20 seconds all brain activity is lost due to lack of blood flow and it doesn’t start again until the heart starts beating. Is this true?Answer: Close, but not exactly. The common medical understanding is that cardiac arrest victims become unconscious within 20 seconds of the loss of blood flow (heart stops). That’s not quite the same thing as losing “all brain activity.” It just means the brain is incapable of keeping you awake. All brain activity is thought to be over by about 3-4 minutes from the moment the heart stops, which is one reason why we want to start CPR as quickly as possible. It’s also why
