Automated external defibrillators and survival after in-hospital cardiac arrest

Also posted over at Rogue Medic (now at EMS Blogs).

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Yesterday I described the problems with the recent article claiming that corruption was the reason the AHA (American Heart Association) recommended AEDs (Automated External Defibrillators) be placed in non-acute care parts of hospitals.^[1] Today I will look at the study that seems to have inspired the article, even though it came out a year ago.

Does the research claim that there is any suspicion of corruption in the recommendation?

No. The corruption claims appear to be entirely due to the ideological bias of this conspiracy theory site.

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Image credit.

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Although some studies have shown that AEDs improve survival for out-of-hospital cardiac arrests occurring in certain public locations in which 45% to 71% of cases are treatable with defibrillation,^5​,6,7​ these devices may be less effective or potentially harmful when used in hospitals where only 1 in 5 hospitalized patients have initial cardiac arrest rhythms that respond to defibrillation.^{8 [2]}

Is it wrong to look at the research and recommend that the AEDs be used in settings where a manual difibrillator is not available?

No.

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Image credit.

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The difference between a manual defibrillator and an AED is that the AED will interpret the heart rhythm itself. The nurses and doctors do not need to be able to do this. This makes AEDs ideal for public places where non-medical people can use them to shock a patient out of a fatal heart rhythm. In those settings, AEDs probably save thousands of lives each year.

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Image credit.

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With a manual defibrillator, there is much greater cost for equipment and for training to be able to identify shockable rhythms. In the hands of someone familiar with resuscitation a manual defibrillator can be used to deliver a shock with only a few seconds of interruption in compressions, while the AED requires almost a minute of interruption. The greatest problem with resuscitation may be interruptions in compressions.^[3], ^[4]

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Image credit.

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What were the results of the study?

Click on the images to make them larger.

The big benefit from an AED would be when a shockable rhythm is the cause of a cardiac arrest in a less than acute care setting. The nurses are not likely to be certified in ACLS (Advanced Cardiac Life Support). The doctors probably have not treated a cardiac arrest since their last ACLS class. There are no manual defibrillators in that part of the hospital.

While the use of AEDs would require longer interruptions of CPR for the AED to analyze the rhythm, one expectation would be that there would be a significant increase in successful resuscitations of patients with shockable rhythms. According to the data above, only about 1/5 of patients who had the AED applied actually had shockable rhythms ventricular fibrillation of pulseless ventricular tachycardia.

The patients were very well matched for everything that might predispose toward a survival advantage in either group.

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Even worse is that the anticipated significant increase in resuscitation of patients with shockable rhythms did not happen.

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The good news is that hospitals seem to be doing a great job of defibrillating patients quickly without the AEDs.

The median time to shock is 2 minutes. That is recognizing a pulseless, apneic, unresponsive patient, calling a code, beginning CPR, and getting the defibrillator to the patient, turning it on, and delivering shocks to appropriate patients.

The message from this study appears to be that the hospitals are not experiencing significant delays in delivering shocks without AEDs, so there is not likely to be any benefit from adding AEDs. The possible worsening of outcomes is probably due to complicating the response to resuscitation.

Hospitals are big buildings with a lot of people. Many of these people will experience cardiac arrest. Those are two of the things that suggest that AEDs would improve outcomes.

There is an important difference between hospitals and casinos, airports, and other buildings that showed dramatic increases in survival from cardiac arrest after the addition of AEDs and the training of staff in the use of AEDs.

I started out by asking, Is it wrong to look at the research and recommend that the AEDs be used in settings where a manual difibrillator is not available?

Hospitals already have plenty of manual defibrillators and staff trained to use the defibrillators. While there may be many ways to improve the responses in hospitals, the addition of AEDs does not appear to improve responses to cardiac arrest.

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Should the AHA have made this recommendation? The AHA too often goes from no recommendation to permanent part of the treatment guidelines without any transitional phases for assessment of benefits. Their reasoning is understandable. What if this is a treatment that will save thousands, or tens of thousands, of lives? Do we want to delay such a wonderful treatment. Part of me still expects to see the ACLS guidelines printed by Acme.

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As with second marriages, the AHA seems to continually expect optimism to triumph over experience. The AHA needs to be more cautious.

It is too easy to implement a plan and too difficult to reverse course. How many of the AHA guidelines worked out as planned? Are we really going to miss out on the next multi-thousand patient life saver? If we don’t play the lottery, are we giving up on a shot at millions? We need to put less emphasis on unproven interventions.

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In light of our data, national organizations and hospitals may need to reconsider the use of AEDs in general hospital ward units or develop different strategies for using them.^[2]

Maybe hospitals should donate/sell their AEDs to places/organizations that are more likely to benefit from AEDs. Large buildings, EMS agencies, fire departments, police departments, et cetera.

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Footnotes:

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^[1] Bad Shock – Automated Devices for Jolting Hearts May Save Fewer Lives in Hospitals
Rogue Medic
Article

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^[2] Automated external defibrillators and survival after in-hospital cardiac arrest.
Chan PS, Krumholz HM, Spertus JA, Jones PG, Cram P, Berg RA, Peberdy MA, Nadkarni V, Mancini ME, Nallamothu BK; American Heart Association National Registry of Cardiopulmonary Resuscitation (NRCPR) Investigators.
JAMA. 2010 Nov 17;304(19):2129-36. Epub 2010 Nov 15.
PMID: 21078809 [PubMed - indexed for MEDLINE]

Free Full Text from JAMA with links to Full Text PDF Download

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^[3] 60 Year Old Male CC: Sudden Cardiac Arrest
EMS 12 Lead
Article

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^[4] Charging the Defibrillator While Continuing Chest Compressions – Part I
Rogue Medic
Article

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