On TV it appears that every time a heartbeat monitor flat-lines they pull out the paddles of a manual external defibrillator (MED) and give a few shocks, often explicitly cranking up the output when an initial charge doesn't restore a heartbeat.
My technical understanding of this is that a MED is only indicated when the cause of the heart "stopping" is some form of fibrillation or arrhythmia. Granted, maybe "off-screen" is an electrocardiograph the EMT is referencing. But if not, would an EMT ever use a MED if the only thing he knew was that a person had no pulse?
Or, is it the case that a heart will only stop due to either fibrillation or arrhythmias that a MED can reverse?
What if a subject does have a steady heartbeat: Can a MED stop a beating heart?
I suppose that if a subject has no pulse one might argue that the MED can't hurt. But is a MED a substitute for CPR? E.g., if you had a MED and no better information on the patient would you apply both MED shocks and CPR, or what is the current best practice?
Back to TV depictions: They almost always show the subject of MED arching his back for roughly a full second when the charge is applied. I've never seen a real MED application, but my understanding is the pulse is only supposed to last 12ms. Also, since it is applied across the chest, the skeletal muscles most prone to contract would presumably be the chest and upper abdominals, which would (if anything) cause the exact opposite contraction, and only for an instant.