How are doctors so sure a person can’t regain consciousness once their vitals shuts down?

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How are doctors so sure a person can’t regain consciousness once their vitals shuts down?

In: Biology
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They have seen many people’s vital signs shut down. When none of those people can be revived after X minutes, they start to think that nobody can ever be revived after X minutes. Nothing is every 100.0% certain, but they make decisions based on most probably outcomes.

A heart beat circulates blood carrying oxygen around the body, without oxygen cells rapidly start to die and other organs fail, without a heartbeat and lungs breathing all organs including the brain are going to get worse rather than better.

The part of the brain that controls organs is a very basic part of the brain that the earliest organisms used. Higher level of thinking comes with millions of years of advancement. Therefore, certain things shut down in a somewhat predicable order and if *that* part of the brain is deteriorating, then it doesn’t look good for the more advanced parts such as conscious thinking.

I’m going to assume that by “vitals” you mean the two vital organs heart and lungs.

The truth is we don’t know on an individual basis who is going to survive what period of cardiac arrest (which is when the heart stops), but data from group studies enable us to give educated opinions based on systematic experience.

There are a few key facts to consider: the airways and lungs supply oxygen to the blood, and the heart takes that oxygen-filled blood and pumps it around to the body. Together these two organs keep the body well supplied with oxygen, which is crucial for cells to extract energy from the food we eat.

Some cells can survive longer without oxygen by burning the food in an alternative way, but they sacrifice a lot of energy for this. Our brain cells can’t do this because they need maximum energy output 24/7 because they’re working so hard.

Our brain is really what we “are” – it is where our personality, our consciousness and our memories reside, it is what we use to feel love, joy and all other emotions. Therefore, as soon as the brain dies, we are dead, no matter if the heart is beating or not. The heart is nothing more than a special muscle.

This means that if we stop breathing, or our heart stops beating, the single-most important organ for survival *is the same organ that is worst equipped to cope with a lack of oxygen*. The brain burns through oxygen so quickly that if it doesn’t get a constant supply of it, it will start to die within minutes. And, crucially, brain tissue doesn’t regenerate like skin or bone.

That’s why if a heart stops for many minutes, and no one is doing CPR, it is highly likely that even if you can get the heart beating again, the person will never wake up again because too much brain tissue has already died.

There is a lot of data where scientists have looked at the time between when the heart stops, and when the heart started beating again. For every minute with no heart beat (and no CPR) the chance of a successful recovery decreases about 10 percetage points (meaning that after 10 minutes the chances of recovery are practically zero). Experiments with animals and single cells in laboratories show similar results.

**TL;DR: The heart and lungs supply oxygen to the brain. The brain can’t handle oxygen deprivation, which is what happens when “the vitals shut down”. If the brain is dead, there is no chance of regaining consciousness**.