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Friday, March 6, 2015

Update: Cyanokit for cardiac arrest in fire victims

I had written about this topic last year, but a recent EM:RAP segment and ensuing Twitter discussion prompted me to revisit the issue. Sadly, there is no new evidence to add to the discussion.  Nonetheless, let's revisit the question: 

If a pulseless patient is pulled from a smoky, burning building, will giving Cyanokit during CPR help?
Step 1

1. There is no known “50% ROSC rate” because of Cyanokit.

The four studies looking at this issue are, by design, unable to support any such conclusion. They were case-series, with no controls whatsoever. They gave Cyanokit to a number of people, and some of them lived. However, we have no idea if the “save rate” was better or worse than usual care. These studies show that EMS can administer Cyanokit, but they can’t speak to its effectiveness at all.  As a result, even toxicologists don’t make much of these studies.

Furthermore, most of the “saves” in one study had ROSC before they received the Cyanokit. It isn’t clear in the other studies when the patients received the antidote, and the amount of missing data makes it hard to interpret.

Go read the original studies; the links are at my post Does Cyanokit save lives in cardiac arrest

Step 2

2. Meds, in general, don’t increase save rates in cardiac arrest.

Although the AHA teaches a “reversible cause” approach to arrest, this isn’t helpful most of the time. For example, although heroin OD and severe hypoglycemia may cause cardiac arrest, there is no AHA recommendation to give naloxone or dextrose in cardiac arrest. In fact, naloxone use is discouraged.

Same with tPA. An AMI or a PE commonly triggers cardiac arrest, and tPA could theoretically “treat the cause.” But the evidence showed that, overall, it didn’t work during cardiac arrest. True, many of us have tried it once or twice, but not routinely

Step 3

3. I’m no EBM diehard, but we have to do better than this!

The evidence for Cyanokit is sort of like the evidence that supported Digibind (for digoxin OD) or fomepizole/Antizol (for methanol/ethylene glycol OD). Neither one of those drugs had a supporting RCT, or even a strong case-control trial. Indeed, the important studies showing their benefit were open-label, and uncontrolled. (E.g. Brent 1999 “Fomepizole for the Treatment of Ethylene Glycol Poisoning,” and Antman 1990 “Treatment of 150 cases of life-threatening digitalis intoxication with digoxin-specific Fab antibody fragments.”). 

However, the low rate of adverse effects, and the strong mechanistic and animal data, along with the difficulty of conducting a true RCT, argued strongly in favor of using these drugs, despite active discussion regarding the costs. So it’s appealing to use a similar argument to support using Cyanokit.

This argument, however, also suggests that recommendations for the routine administration of Cyanokit are very premature. The studies of Digibind and Antizol were of far higher quality than the 3 French and 1 Texas Cyanokit studies. 

For example, both Brent 1999 and Antman 1990 used prospective collection of data (rather than chart review), and both used clear, quantitative criteria for the use of the antidotes. That approach generated high quality data, which could be used to make valid comparisons with historical cohorts. By contrast, the Cyanokit studies are of very low-quality, based on chart reviews with unclear methods, and have plenty of missing data. 

Step 4

4.  Cardiac arrest at fire scene, especially in a firefighter?

It’s probably an MI, and the key issue isn’t getting a miracle drug started, but getting access to the patient to start high-quality CPR, and defibrillating as early as possible. Getting the gear off a “downed” firefighter requires a coordinated team effort, with plenty of practice beforehand.

Step 5
"Pit crew" style CPR has been proven to save lives. Firefighters have been shown to have high rates of cardiac disease, and high rates of on-duty arrests. It's a fact that it's hard to do CPR on someone wearing bunker gear and a SCBA. If your FD isn't drilling for this scenario, an expensive drug isn't going to help. 

The good news about saving a firefighter's life is that it's free and proven - but you have to put in some effort. Check out the Firefighter Down- CPR website for the specifics on how to improve your response. Here's the vid: