I’ve read enough medical threads that I firmly believe that TV is wrong and that doctors don’t shock patients that have flatlined in order to revive them. My question is, why doesn’t it work? I know that when doctors perform heart surgery, as in my dad’s bypass, they stop the heart, put him on a bypass machine and then restart the heart with an electric shock. Obviously, the paddles are quite different, but in theory, what’s the difference?
Well, why should it work? If your computer doesn’t boot, do you jolt it with a pair of jumper cables and expect that to fix it? The heart is a piece of precision electronics, too.
I’m an engineer, not a doctor, but here’s my understanding of it.
Your heart has a built-in pacemaker. The way your heart works, this pacemaker (called the SA node) fires off regularly, and in a normal working heart, this causes a chain of events through the heart that creates its overall pumping action.
When the heart is in fibrillation, instead of a nice, normal beat, things fire off chaotically without being properly led by the SA node, and instead of a proper pump, the heart muscles just shake. The heart is no longer pumping blood, and you die.
A shock under these circumstances will cause all of the heart muscles to clamp, and when the electrical shock is removed, the heart will often go back into a normal rhythm with the SA node again setting the pace.
If you are flatlined, the SA node is no longer working. It doesn’t matter what you do at that point. The heart’s natural pacemaker is kaput. There’s nothing operating to generate the heartbeats. Shocking the heart will make the muscles clamp, but with nothing working to initiate the heart’s beating sequence, the heart’s muscles just relax and do nothing once the electricity is removed.
I don’t really know how they stop and start a heart for surgery, but I suspect that they are really just throwing the heart into fibrillation and cooling it so that is chaotic beating is just some mild shaking that doesn’t interfere with their surgery. Then they warm it up when they are done and shock it back into a normal rhythm. Even though the heart isn’t beating during surgery, I suspect that it’s nowhere near flatlined electrically.
“shocking” is done when you have e.g. fibrillation, where the heart’s “pacemaker” is generating electrical activity but has lost the normal rhythm and the heart muscles are just fluttering or twitching. the defibrillator attempts to get your heart to “re-set” into a normal rhythm.
if you’re flatlined, your heart isn’t generating any electrical activity period.
How does it work with jump-starting a transplanted heart, which is usually not beating at transplant time.
Apparently a healthy heart, which a transplanted heart is, starts working on its own as soon as it is full of blood-- in other, words, when the arteries are unclamped-- and occasionally even goes into a normal rhythm, but most go into a poor rhythm and need defibrillating.
I assume the same thing can happen with a heart on bypass. When there’s nothing to pump, it stops pumping, and then when there is blood to pump again, it starts up again.
According to Johns Hopkins, paddles are used to start the heart beating once again.
From here.
Counterintuitively, the purpose of a defibrillator is actually to stop the heart, not to start it. When it works the way it’s supposed to, the heart does the re-starting part all on its own. But stopping the heart won’t work very well if it’s already stopped.
This would imply that the paddles mentioned in the above link are “fibrillators” instead of defibrillators. I suppose that’s possible.
Delivering a shock to someone who is in asystole (flatlining) is like trying to reboot your computer when your power goes out.
mmm
I hope not. Ventricular fibrillation is bad for you.
A malfunctioning device that delivered an electric shock could probably fibrillate you.
He looks too fibrillated. If only there was some way to unfibrillate him. (major SNF nerd points to who knows this quote)
I just watched a video of someone having a heart valve repaired. To do this they bypassed the heart through a machine and then used (I think) potassium to slow and eventually stop the heart altogether. The surgeon did the repair (amazing) and then, after testing it with water, allowed the heart to restart (no paddles etc). A few hours later the patient was sitting up and talking, and was discharged after two weeks with a highly optimistic prognosis.
Maybe worth mentioning that this was done at the taxpayer’s expense and neither the patient or her relatives had to concern themselves with the cost.
Although there’s an intrinsic pacemaking system designed to cause each muscle cell to contract in unison, individual heart cells will contract on their own, in say, a nutrient bath. In fibrillation, each cell is depolarizing randomly and no pumping contractions occurs. A defibrillator shock causes every cell to immediately depolarize regardless of where it was in it’s own depolarizing/repolarizing cycle, and, maybe, if we’ve reoxygenated the tissue enough, or fixed one of the other things, a perfusing rythym will ensue.
If the cells aren’t depolarizing anymore, you’re just wasting time and juice. I’m skeptical that John Hopkins quote isn’t misleading.
It doesn’t sound misleading according to this cardiothoracic surgeon although he does mention that the heart often restarts itself. Youtube.
Bolding mine.
Makes for a more relaxed patient, hence a better prognosis.
Any hints?
It’s an animated series.
Well, I work in the ER, so this is not my area of expertise, but I suspect he means sometimes it starts in an organized rhythm on its own, and sometimes they have to nudge it from a disorganized one into an organized one, so that it ‘starts’ actually pumping.
It would not be surprising if the cardioplegic solution wears off inconsistently enough that initial movement is disorganized and maybe it settles down on its own, but not always.
He also says they use the paddles ‘just like on television,’ so I think either that’s misleading and they’re using some kind of intervention I’m not familiar with, or ‘starts’ is short for starts an organized, perfusing rhythm rather than starts from a standstill.
How about we let heart surgeons interrupt and start the heart as they will ,
Except for heart surgery, the cause of flatlining would be lack of oxgynated blood in the coronary arteries. Shocking the heart won’t create the flow of oxygenated blood… it won’t undo the the problem causing the flatline either.
start CPR, and then do something about the blood clot or anurism or blood glucose etc levels