CPR Whats the point

[Brandon O]

Just my opinion on the matter, but I think it is because whether it works or not is pathology specific.

Without getting into the minute details, if vfib is secondary to an acute MI, "priming the pump" is largely going to be pointless. You won't likely clear coronary artery occlusions with CPR.

I partially disagree.

Obviously, if a total occlusion has caused a large infarct, resulting in massive HF and dysfunction (i.e. cardiogenic shock), the pump is simply broken. The classic presentation here may actually be PEA or asystole, possibly with a last stuttering arrythmia, but as you say, it's not like either pushing on their chest or exiting VF is going to fix the pump. (In an ideal world, we would perhaps be giving these people continuous compressions while we cath them to reopen that artery.)

However, if we imagine a descending pathway from stable baseline to irrecoverable death, many patients who suffer MI follow a gradual downward slope until "falling" off a cliff when their struggling heart drops the ball and enters VF or VT. At that point, the entire heart becomes ischemic, not just the localized area distal to occlusion, but if we can return them to a perfusing rhythm, they might still have many minutes until the actual infarct creates a non-viable myocardium.

In the handful of minutes after this, it's a solely electrical problem, and immediate defibrillation would probably get them back to their prior -- obviously somewhat unstable, but still perfusing -- rhythm. But the longer we wait, the more ischemic the heart becomes globally, and the less likely that it'll have the coordinated automaticity we desire if we electrocute it. So a bit of assisted circulation to refresh ATP and so forth makes sense. (This "three phase" model of arrest -- electrical, hemodynamic, then a metabolic phase involving toxic products and other derangement -- has become popular to explain the need for different therapies at different times.)

So goes the theory, anyway. Again, there's some literature against it now, so it's been downplayed -- although I do think that (as Vene alluded to) with an appropriately discerning eye toward the individual etiologies we might understand why it seems to sometimes work. But part of the idea now is that if you walk in, one person's setting up the defib while the other's doing compressions... it's a parallel, team-based process rather than a serial one, so it's really a false dichotomy.

 

[Veneficus]

I partially disagree.

Obviously, if a total occlusion has caused a large infarct, resulting in massive HF and dysfunction (i.e. cardiogenic shock), the pump is simply broken. The classic presentation here may actually be PEA or asystole, possibly with a last stuttering arrythmia, but as you say, it's not like either pushing on their chest or exiting VF is going to fix the pump. (In an ideal world, we would perhaps be giving these people continuous compressions while we cath them to reopen that artery.)

However, if we imagine a descending pathway from stable baseline to irrecoverable death, many patients who suffer MI follow a gradual downward slope until "falling" off a cliff when their struggling heart drops the ball and enters VF or VT. At that point, the entire heart becomes ischemic, not just the localized area distal to occlusion, but if we can return them to a perfusing rhythm, they might still have many minutes until the actual infarct creates a non-viable myocardium.

In the handful of minutes after this, it's a solely electrical problem, and immediate defibrillation would probably get them back to their prior -- obviously somewhat unstable, but still perfusing -- rhythm. But the longer we wait, the more ischemic the heart becomes globally, and the less likely that it'll have the coordinated automaticity we desire if we electrocute it. So a bit of assisted circulation to refresh ATP and so forth makes sense. (This "three phase" model of arrest -- electrical, hemodynamic, then a metabolic phase involving toxic products and other derangement -- has become popular to explain the need for different therapies at different times.)

So goes the theory, anyway. Again, there's some literature against it now, so it's been downplayed -- although I do think that (as Vene alluded to) with an appropriately discerning eye toward the individual etiologies we might understand why it seems to sometimes work. But part of the idea now is that if you walk in, one person's setting up the defib while the other's doing compressions... it's a parallel, team-based process rather than a serial one, so it's really a false dichotomy.

That sounds very linear.

 

[Brandon O]

That sounds very linear.

Not sure what that means, but I like it.

 

[Veneficus]

Not sure what that means, but I like it.

I do not think the process is a linear progression as you described.

Whether the prevalent thinking or not, the idea that there will be electrical conduction disturbance before metabolic disturbance just doesn't seem logical.

 

[Christopher]

I do not think the process is a linear progression as you described.

Whether the prevalent thinking or not, the idea that there will be electrical conduction disturbance before metabolic disturbance just doesn't seem logical.

Primary VF (i.e. from ischemia) is very amenable to defibrillation, which is why I believe they labeled it the "electrical phase". Cessation of the reentrant wavefronts doesn't equate to cardiac output, but it may improve the situation from VF to PEA; assuming some automatic tissue decides to take over and the zone of ischemia doesn't precipitate VT/VF again. CPR post-defib is the means to improve PEA to "perfusing-EA" if the volume status is too low to support perfusion after VF.

"Priming the pump," I've always understood to mean ensuring some coronary perfusion pressure which in turn means some restoration of the normal flow of O2/glucose/waste products.

I really think we're all talking about the same thing just overloading terms...

 

[OzAmbo]

Devils advocate

If i changed the neame of the thread to "Whats the point of BLS" would you then have a diferent point of view?