My only point regarding
> The average rule is that if heart has not restarted after 6 minutes, brain damage is irreversible
is that it doesn't mean it's worthless to continue CPR. Different people have different preferences about how grievous an injury they would want to survive. Whether to continue comes down to that preference. Have an advanced directive, and make sure your loved ones know what you want to have happen if you are every in an emergency!
My friend was in a coma for 6 weeks and had brain damage because of the lack of oxygen.
On one hand, this was distressing because she lost mathematical ability. This prevented her working in her previous field as a chemistry researcher.
On the other hand, she switched to psychology via a one year Masters degree and is now working on a fascinating project on hacking the mind's compassion responses to activate the parasympathetic nervous system and damp down anxiety (sympathetic nervous system) triggered by cardiac damage.
Just saying that although brain damage sounds terrifying, people can and do cope with it.
I had a teacher in grade school and one day she didn't come back to class, she had had a gigantic stroke. 6 months later she rolled into class in a wheelchair, a changed person, she could not speak or do basic tasks for herself.
Over the next two years she relearned most of her abilities, walking, talking, thinking, speaking, teaching and was back to "normal" again. Then she had another stroke.
She did not give up, and did it all over again.
She was always a cruel teacher in my eyes (I was very young) but seeing her persist throughout what I would assume would permanently put you out to pasture was an amazing experience and I always had enormous respect for her.
She continued teaching and retired ~20 years later.
But future generations will probably laugh at us. Our rule of thumb about deprivation of oxygen and brain damage is based on the idea that brain damage occurs on the "down" side when the brain is deprived. Actually, the damage occurs on the "up" side when a patient is revived under non-ideal circumstances for brain operation. It turns out the brain if you wake it "up" properly can stay "down" as long as other organs. Think kidneys frozen for 24 hours before being successly transplanted. And a proper wake up involves slow extracorporeal rewarming as mentioned in one of the top comments.
If we can accept this down/up inversion as true, then it means that rushing to revive a patient is what does the damage. It means applying CPR in the field as soon as possible does the damage.
If true, it means 20 minutes, or even 2 hours, of not breathing is nothing as long as the cold body is rewarmed slowly.
If true, it means it is better to keep the brain "down", body "frozen", everything cold as possible (but above the temp of ice crystals riping apart blood cells causing permanent limb loss) until --and this is the key part-- a proper wake "up" can be performed.
If true it means the current limits observed with oxygen deprivation exist only because we are still concerned with reviving as soon as possible. Leave that child passed out! (But keep 'em cold.)
If all this is true, it means that saving a loved one is best done buy applying ice over applying CPR.
Future generations will shake their heads in disbelief, at how many people we have needlessly injured and killed with the barbaric practice of rushing to revive. I look forward to the improvement in how we save/restore lives. I look forward to the improvement from the slow but steady diffusion through our collective awareness of of the idea:
Down-and-cold-is-okay/ Prematurely-revived-is-bad.
- this is hacker news I hope people are in it for some sort of rigor, not just for wow effect
I forgot the 66min case, but that brings me to something I heard recently. Some paramedics said they managed to sustain some kid under cardiac arrest for 18 minutes (he had a nice if not full recovery). The average rule is that if heart has not restarted after 6 minutes, brain damage is irreversible. So where does that leave us ? Should we try (say we have many people capable of doing CPM) to pump as long as possible ?
- should we try to lower body temperature as much as possible to slow metabolyc processes ?