Saturday, March 17, 2012

Procainamide - Hipster drug, or too mainstream?

I recently gave procainamide to a patient in the ED. It was a big fuss - we had to send a runner to the pharmacy, the nurse had to blow the dust off the administration protocol. Great fun.

Later on I was describing this to another ED attending, and one of the senior trauma surgeons, overhearing this, exclaimed "You're not old enough to give procainamide!"

He proceded to launch into an Abraham Simpson-esque tale about long-lost antiarrhythmics, and I sort of lost the point of his story...

"... which was the style at the time...
Anyway. The point today is that procainamide is back, and we should be thinking of giving it far more often than we do.

For example, with...

Stable monomorphic ventricular tachycardia
Yet another "chest pressure and palpitations gets rolled into major med. He looks good, no acute distress, joking awkwardly with the techs as the monitor leads are attached. You dutifully punch in the orders for a chest x-ray, troponin, etc., when you notice this on the monitor.

"Is he just shaking real bad?"

Ah. Well, it turns out that his vitals are just fine, and he looks stable enough, but you could use "synchronized cardioversion" to fill out your procedure log. Unfortunately, he just ate a couple burritos on the way over. That's going to make procedural sedation a little dicier, so perhaps you'll try a medication. But which one?

On the one hand, there's amiodarone, which seems reasonable, given how often it's given in the ED. On the other hand, lidocaine is readily at hand.

Dose: Give 1 box.
Well, the AHA thinks that procainamide is likely your best bet here. Just sayin'.

Dose: "It's complicated."
In the 2006 AHA Guidelines for the Management of Ventricular Arrhythmias, makes a few suggestions. First of all, if it's unstable, shock it!

If it's not, the evidence is best (level B) that procainamide converts VT more often than anything else. In one trial procainamide terminated 38/48 episodes of VT - not as good as electricity, but pretty good!

They do recommend amiodarone for the patient who is unstable and has failed cardioversion, and in whom the other drugs aren't working either.  One reference that the guidelines cite in support of using amiodarone describes evidence that "demonstrated a dose-response relation, with at least comparable efficacy to bretylium."

Yes, at least as good as a drug that was taken off the market years ago, and didn't even work for E.T. Sweet.

"Uh, better grab the Glidescope.  I think."

Conversion of atrial fibrillation
You got a 40 year old guy in the ED, who says that he started having strong palpitations about 2 hours ago while at work. No recent drinking, no drugs, but he does quite a bit of running, however.

A healthy patient with a clearly defined time of onset - a great candidate for ED cardioversion! You get the pads, set up the airway gear, and calculate the propofol dose. As you consent him, however, you learn that 30 minutes ago he wolfed down one of these:

Those darn vicious burritos.

Crumb. That's not going to look so great going down his right mainstem. Well, how about drugs?

Well, amiodarone seems to be the default choice. The 2006 AHA guidelines seemed pretty bullish on amio, giving it a Class IIa rating for conversion of AF, relegating procainamide to a measly Class IIb.  The funny thing is, their summary of the utility of amio in AF is not exactly inspiring. They describe trials of amiodarone that show it to be "no more effective than placebo," and "more effective than placebo after 6 to 8 h and at 24 h but not at 1 to 2 h.

They relegate procainamide to the list of drug that are "Less Effective or Incompletely Studied," which has to reflect a little anti-north-of-the-border bias, given that the Canadian cardiologists had already looked over the world's literature, and come to a different conclusion.

When Canadians want to convert AF in the ED, they reach for procainamide. In the 2010 Canadian Cardiovascular Society Atrial Fibrillation Guidelines (also here as a PDF download), our Canadian brethren ranked the best drugs for conversion of recent-onset AF:

"Amio has to be here somewhere..."
One trial was used to cite the effectiveness of procainamide in AF (happened to be a Canadian paper, but published in a U.S. EM journal), showing that it converted about half of the patients. They don't cite other papers, but past results (from 1983 and 1993, for example) could also be used to support the guidelines. One recent trial (done by the same Canadian) showed a 60% cardioversion rate.

Canadian cardiologist, showing their pride with a tattoo on their...  Ok, what body part is that?

Wide complex atrial fibrillation, possible WPW.
So, by this point, you're a wiz at terminating VT, you've mastered the art of atrial fibrillation - there is nothing can triage can do to hurt you.

Fifteen minutes before the end of your shift, they roll in a middle-age women with "palpitations." No problem for a boss like you - you'll have major med tidied up for sign-out in no time.

"Challange Accep... Geez, is that her ECG?"

The tech hands you this ECG:

Her blood pressure is fine, and she doesn't look too symptomatic. She tells you that she has some "extra wires" in her heart, and that she gets spells like this sometimes.

Sooo, irregular wide-complex tachycardia. This could be WPW with atrial fibrillation, so your therapeutic options just narrowed. No metoprolol, no diltiazem. Again, it would be great to cardiovert her, but she doesn't want to consent for that.

Gosh, what medication would work best here?

Well, it ain't amiodarone. That drug has been out of favor, for this situation, for some time. Mel Herbert, of EM:RAP fame, published a review in 2005 entitled "Myth: Intravenous amiodarone is safe in patients with atrial fibrillation and Wolff-Parkinson-White syndrome in the emergency department"
The title pretty much explains the conclusions, but they also concluded that, while amio was the worst of the bunch, electricity was the "only therapeutic modality lacking pro-arrhythmic properties."

Of course, this was old news in some quarters. The 2003 AHA Guidelines for the management of patients with supraventricular arrhythmias was not bullish on amiodarone, and  mentioned only the use of procainamide, ibutilide, or flecainide for chemical conversion of AF with WPW.

So it was not a suprise when the AHA updated the atrial fibrillation guidelines last year, and bumped procainamide up to a Class I recommendation for AF in WPW. Amiodarone is still okay to use, but it is class IIb - weak!

Bottom line
Brush up on your dosing, cuz' this drug is back like horned rim glasses - so old fashioned that it's back in style.

But seriously, review the dosing, because it's a bit more involved than "give 1 vial." Also, it's totally fair "pimping" material!

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