Rational for early defibrillation

[*Lifeguard*]

What is the importance and rational for early defibrillation as it relates to the electrical phase verses mechanical phase? [/font:fa756163f9]

[katbemeEMT-B]

Early defibrillation results, hopefully, in restarting the electrical impulses of the heart, which in turn restarts the mechanical contracting of the heart. It is the contracting of the heart chambers which circulates the blood through the circulatory system. With each passing minute the heart is idle (not contracting) the higher the ischemia and dead heart tissue. This results in a heart that does not function as well and sometimes not at all.

[itku2er]

It helps reestablish normal contraction rhythms in a heart that's not beating properly. It does this by delivering an electric shock to the heart, it interrupts the random electrical pulses of ventricular fibrillation and gives the heart a chance to start beating again in a normal rhythm. Hopefully it will "kick start" the heart back into a workable rhythm and out of a lethal one.

Bye mechanical do you mean CPR?

[Richard B the EMT]

Mechanical means the heart acting properly as the "pump" that it is.

[itku2er]

Mechanical means the heart acting properly as the "pump" that it is.

wasnt sure if it was meant to be defib over cpr or defib explained and the mechanical side of cpr or the mechanical side of how the heart works from within explained.

[AZCEP]

Defibrillation does not "kick start" or re-establish "normal" cardiac activity. The act of defibrillation eliminates all electrical activity from the myocardial tissue. The benefit of early defibrillation is in the ability to conserve what energy stores the myocardial tissue has before they are used by the horribly inefficient fibrillatory cycle that presents as VF.

The "electrical" phase of cardiac arrest is the short period of time that the myocardium is best able to respond to a defibrillatory shock. This happens within 4 minutes of arrest, and chances of success are reduced by approximately half for every minute of duration. The "mechanical" phase of cardiac arrest is a period that follows, approximately 4-8 minutes from time of arrest, with complete elimination of any type of contraction, fibrillatory or otherwise. This period is best treated with effective compressions to supplement any blood flow that the heart can generate. Following this is a metabolic phase that is highlighted by the buildup of metabolic waste products that must be eliminated/managed before attempting to manage the presenting problem.

[firedoc5]

The quicker you can defib. the better. Time during an MI causes more damage to the cardiac tissue, which means less quality of electrical conduction. So it's easier to convert a dysrhythmia with earlier defibrillation.

[Novisen]

http://www.ncbi.nlm.nih.gov/sites/entrez?D...Pubmed_RVDocSum

http://www.jolife.com/doc/Maule%20L%20assi...%20and%20Fr.pdf

[Arizonaffcep]

The latest studies by the AHA have found the heart is most receptive to the defibrilation for only a short time after the arresting rythm, due to the inherent hypoxia in the myocardium. This is why the new CPR standards say 2 min of CPR, followed by defib, followed immediately by more CPR. This builds up the "pressure" needed to perfuse the heart.

[firedoc5]

I believe I made a point on another thread that is relevant here, so I'll bring it up. Now this is just for argument sake and not an opinion and food for thought.

Way back when AED's were first being used, actually still in a trial stage, it was argued that with early defibrillation without ALS could be detrimental. If a patient was defibed and did actually convert without ALS to give anti-dysrhythmic meds such as Lidocaine, Bretillium, or Procainamide, they could revert back into fibrilation. In turn they would have to be defibbed again, probably numerous times. It was said that the extra shocks could cause more damage to the cardiac muscle than CPR alone. So, would it be better to do CPR only until ALS arrived or would it be better to defib someone numerous times without ALS hoping they would convert.

Over the years I've heard all kinds of opinions and arguments for both. It's still a sore subject in some systems.

And I know the computers of today are much improved over the first AED's. But still, do you want to fully rely on a computer? I know that there are still a lot of Medics out there that still have the idea in the back of their minds that you can't fully trust a gizmo and leave out the human element. I know there are manual over-rides, but in the hands of civilians or someone who doesn't know anything about ECG interpretation they have no choice but to trust the computer. Sometimes that's scary to me.