4
$\begingroup$

We mostly can defibrillate the heart before 1 min of ventricular fibrillation by electroshock.Then we often can't do defibrillate it with electroshock.

What's the reason and What's the best way to defibrillate heart within 1 min after ventricular fibrillation?

$\endgroup$
  • 3
    $\begingroup$ This edit changes your original question a bit. The best way to defibrillate a heart within one minute of VFib onset is with electric shock. In fact, short of certain drugs in certain instances, it's the only way to defibrillate Vfib, regardless of the amount of time that has passed. I don't want to edit your question because it has the appearance of impropriety. But the truth is, the heart can be defibrillated with shock alone after one minute. After 4 minutes, the brain is negatively affected, therefore CPR is recommended before then. $\endgroup$ – anongoodnurse Jan 15 '15 at 9:34
  • $\begingroup$ down voter! Can you explain it for a down vote for below answer. $\endgroup$ – user12874 Feb 14 '15 at 15:57
7
$\begingroup$

To say that there is a cutoff of one minute at which time shocking becomes ineffective is incorrect. The best way to defibrillate a heart within one minute of VFib onset is with electric shock. In fact, short of certain drugs in certain instances, it's the only way to defibrillate Vfib, regardless of the amount of time that has passed.

If the one minute cut-off were true, survival rates of out-of-hospital arrests would be more dismal than they are. Even with the availability of automated external defibrillators (AEDs) to treat out-of-hospital arrest, the collapse to response time is well over a minute. Someone has to notice a collapse, feel for a pulse, and call for a defibrillator (or get it themselves), expose the chest, apply the paddles, wait for the monitor to display the rhythm, clear the area and shock. If you were told that this usually occurs in under a minute, you were misinformed.

Seattle is the best city in the US (probably the world) in which to have a heart attack.[1] The population has a high rate of training in CPR, a highly trained corps of paramedics and EMTs, and a quick response time. So it's logical to do studies about factors affecting survival of out-of-hospital arrests in Seattle. A study published in 1999 found that CPR did not have any effect on outcomes of out-of-hospital arrests unless the interval time (from arrest to defibrillation) was greater than 4 minutes.[2] (In other words, shocking without CPR was no different in outcome than shocking preceded by CPR; both resulted in cardioversion to a stable rhythm and a return of of spontaneous circulation in the same percentage of patients.)

However, that is not to say that CPR (chest compressions +/- respirations) are unimportant. A 2003 study found an unacceptable level of CPR was performed when AED paddles were connected (i.e. there was an over-reliance on shocking).[3]

The new Advanced Cardiac Life Support guidelines call for CPR to be initiated immediately, regardless of witnessed or unwitnessed arrest (i.e. down time).[4] It needs to be noted, though, that this recommendation does not rest on defibrillation with the aim of return of spontaneous circulation(ROSC), but on improved neurological outcomes.[5] This, not ROSC, is what the new ACLS recommendations are based on, because ACLS is not considered highly successful if the patient leaves the hospital only to be hospitalized elsewhere in a persistent vegetative state.

[1] King County may be the best place to have a heart attack
[2] Influence of Cardiopulmonary Resuscitation Prior to Defibrillation in Patients With Out-of-Hospital Ventricular Fibrillation
[3] Interruption of cardiopulmonary resuscitation with the use of the automated external defibrillator in out-of-hospital cardiac arrest
[4] VF/Pulseless VT
[5] Delaying Defibrillation to Give Basic Cardiopulmonary Resuscitation to Patients With Out-of-Hospital Ventricular Fibrillation A Randomized Trial

$\endgroup$
  • $\begingroup$ according to below answer, We absloutely need to have electroshock after pumping the heart by hand. $\endgroup$ – user13018 Jan 15 '15 at 8:54
  • 2
    $\begingroup$ @Thirdkidney - if you like that answer, up vote it. But please don't compare one answer to the other like that. If you have a question, ask it. Be clear. In physiological studies, dogs could be shocked out of VFib successfully for 7 minutes without CPR. Look at the studies, not just the answer if you need evidence. $\endgroup$ – anongoodnurse Jan 15 '15 at 8:57
  • 1
    $\begingroup$ @Thirdkidney - I answered it well, with references, and am completely fine with it, thank you. $\endgroup$ – anongoodnurse Jan 15 '15 at 9:02
  • 1
    $\begingroup$ @Thirdkidney I am surprised you accepted the other answer. It makes a lot of claims with absolutely no evidence to back it up. It is, essentially, the opinion of some random internet user. I'm not saying it is wrong (I don't know and cannot judge), just that there is no reason to think it is correct. This answer, on the other hand is supporting its claims with references so if the two answers disagree, I would believe this one. Incidentally, I also happen to know that Medica is a practicing physician, yet another reason to rethink your acceptance. $\endgroup$ – terdon Jan 15 '15 at 16:25
  • 1
    $\begingroup$ Oh, bugger. Sorry! Anon, good nurse then. $\endgroup$ – terdon Jan 15 '15 at 17:09
4
$\begingroup$

Unless defibrillated within 1 minute after fibrillation begins, the heart is usually too weak to be revived by defibrillation because of the lack of nutrition from coronary blood flow. However, it is still possible to revive the heart by preliminarily pumping the heart by hand (intermittent hand squeezing) and then defibrillating the heart later. In this way, small quantities of blood are delivered into the aorta and a renewed coronary blood supply develops. Then, after a few minutes of hand pumping, electrical defibrillation often becomes possible. Indeed, fibrillating hearts have been pumped by hand for as long as 90 minutes followed by successful defibrillation.

A technique for pumping the heart without opening the chest consists of intermittent thrusts of pressure on the chest wall along with artificial respiration. This, plus defibrillation, is called cardiopulmonary resuscitation, or CPR.

Lack of blood flow to the brain for more than 5 to 8 minutes usually causes permanent mental impairment or even destruction of brain tissue. Even if the heart is revived, the person may die from the effects of brain damage or may live with permanent mental impairment.

$\endgroup$
  • 1
    $\begingroup$ I thought a few minutes (say 2-3 instead of 5-8 min) was already pretty devastating to the brain? $\endgroup$ – AliceD Jan 15 '15 at 5:08
  • 2
    $\begingroup$ This answer would be greatly improved if you could add references supporting your claims. $\endgroup$ – terdon Jan 15 '15 at 16:27
  • $\begingroup$ Some references are some physiology books,for instance guyton and hall physiology and bern and levy physiology book which I read these books before. $\endgroup$ – user12874 Jan 15 '15 at 17:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy