Don't t-a-a-a-a-a-a-aze me bro!

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A report in Popular Science (authored by Jeremy Hsu) points to a recent paper published in Academic Emergency Medicine. In this, Dawes and colleagues report on an investigation on the effects of TASER on sheep intoxicated with methamphetamine (MA). I was alerted to this by Damn Good Technician who wanted a little bit of context for what would seem to be a WTF? kind of study.
The study was conducted in Dorset sheep who were anesthetized, and administered 0, 0.5, 1.0 or 1.5 mg/kg of methamphetamine HCl (curiously from dissolved Desoxyn, the approved pharmaceutical product) in an IV infusion. The drug treatment was a between subjects factor (N=4 per group) and animals were monitored for “continuous blood pressure, heart rhythm (one-lead), pulse oximetry, and capnography… Arterial blood sampling was performed at baseline, 30 minutes after the administration of the methamphetamine, and after each exposure from a TASER X26”.
To answer the question of why?, and for appropriate background on the science try a PubMed search for “cardiac TASER“. I note a study in which 5 sec of TASER didn’t cause cardiac damage or symptoms in law enforcement trainees and another showing minimal cardiac effects on law enforcement volunteers after vigorous exercise. Also of interest are the case studies of atrial fibrillation in a previously healthy adolescent and recovery of a teen in TASER induced asystole. These, a mini-review by the Dawes group and other searched papers should give you some context and support from the feeling you might have from half-remembered MSM reports over the years that TASER is suspected of being somewhat less than “safe”.
What I’m not finding right away is very much about the drug intoxicated suspect who might be TASER’d by law enforcement. Remember this guy? My best estimate was that he was acutely intoxicated with 3,4-methylenedioxymethamphetamine (MDMA, “Ecstasy”) although that might be one of my blog interests talking. You might also wish to consider some papers found by searching PubMed for “methamphetamine cardiac toxicity“, “methamphetamine vetricular fibrillation” and “methamphetamine heart attack“.
Together this background would seem to identify a situation crying out for additional study.

It is worth noting right off the bat, given the comments following the Popular Science Article, that these studies were conducted (in the US) by research scientists under Institutional Animal Care and Use Committee approval and the usual Federal regulatory, and other, oversight mechanisms¹.
Methodologically, the study examined four different TASER shock durations starting with a 5 sec continuous shock that seems to be the standard in human investigations. This study included 15, 30 and 40 sec intermittent shocks in which the longest continuous duration was 20 sec. If you watch the end of the Cochella video, these might seem to be more realistic conditions to test over the published studies in law enforcement volunteers I mentioned above. This consideration ties back into why we need to resort to animal models instead of just using law enforcement volunteers. The case reports identify some cases of serious harm to the TASee and the research literature reports essentially no (consistent?) harm. To cross this bridge we need to set up experimental conditions that seem more likely to get us closer to ones that will cause harm. That changes the ethical calculus for human subjects’ research versus animal research. Also, the combined effect of a stimulant drug and TASER might be presumed to be additive- again, problematic for human subjects research.
The MA doses were physiologically significant in this model, even though subjects were under anesthesia.

All animals given methamphetamine demonstrated signs of methamphetamine toxicity with tachycardia, hypertension, and atrial and ventricular ectopy … One smaller animal (animal 8, 30 kg, at 1.0 mg⁄ kg methamphetamine) had a supraventricular tachycardia (SVT) shortly (7 minutes) after methamphetamine administration requiring cardioversion. One animal (animal 11, 78 kg, at 1.5 mg⁄ kg methamphetamine) had
apparent seizure-like activity shortly (4 minutes) after methamphetamine administration that resolved spontaneously.

Effects of the ECD (Electronic control device, i.e.TASER) stimulus:

Smaller animals (n = 8, ≤ 32 kg, mean = 29.4 kg) had supraventricular dysrhythmias immediately after the
ECD exposures (including SVTs and frequent premature atrial contractions). Larger animals (n = 8, > 68 kg, mean = 72.4 kg) had only sinus tachycardia after the ECD exposures.

Note the bimodal size distribution, the authors accidentally ordered too-small animals in their first cohort but decided to go ahead with the study. This ended up being fortuitous as it identified possible age-related differences (interestingly the authors just focus on the size question, I’d like to know more about sheep development and whether these smaller animals were juveniles, adolescents, young adults or whatever). Unfortunately, however, that pushes the study right into trying to make something out of individual differences². And that really compromises the ability to conclude much of anything definitive from a study.

One of the smaller animals had frequent episodes of ventricular ectopy after two ECD exposures, including runs of delayed-onset (2-5 minutes after the exposure), nonsustained, six- to eight-beat unifocal and multifocal ventricular tachycardias that spontaneously resolved. This animal had significant ventricular ectopy after the methamphetamine administration and prior to the exposures as well.

Now tachycardia (elevated heart rate) and hypertension (increased blood pressure) I more or less grasp but not being a cardiac physiologist I had to resort to the Googles for a couple of these.
Ventricular ectopy:

Ventricular ectopy leading to ventricular tachycardia (VT), which, in turn, can degenerate into ventricular fibrillation, is one of the common mechanisms for sudden cardiac death.

Supraventricular tachycardia:

..the heart rate is sped up by an abnormal electrical impulse starting in the atria.
-The heart beats so fast that the heart muscle cannot relax between contractions.
-When the chambers don’t relax, they cannot contract strongly or fill with enough blood to satisfy the body’s needs.
-Because of the ineffective contractions of the heart, the brain does not receive enough blood and oxygen. You can become light-headed, dizzy, or feel like fainting (syncope).

Sinus Tachycardia:

..is a heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min in an average adult.

cardioversion:

..is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs.

For some reason the authors don’t make much of a stab at inferential statistics to deal with the main quantitative measures of heart rate, blood pressure, etc. The MA group (N=4) means are presented for each of the doses and stimulus-duration conditions, as are the stats for a nonparametric comparison with the control no-drug group. The didn’t even specify any correction for multiple comparisons. I would have like to have seen some analysis of the main effects for drug dose and the duration of the TASER stimulus to see if heart rate and blood pressure increases depended on either factor or an interaction of the two. Doing a very rough scan of the table it doesn’t look like there are systematic effects of the drug dose or the duration of the shock on either measure. This latter would seem to be a particularly important analysis. As I mentioned, it seems to me that the human studies use just the single 5 sec shock…it would be nice to provide evidence to address concern over administration of a longer shock duration or multiple closely spaced shocks.
Nevertheless, as the authors conclude, there was no obvious smoking gun here.

Methamphetamine intoxication was associated with both supraventricular and ventricular irritability. In small sheep, electronic control device exposures did exacerbate this irritability, but this did not occur in the larger sheep. There was no ventricular fibrillation after electronic control device exposure.

This is just an initial study (as far as I can find) of the interaction between a stimulant drug and shock such as would be produced by a TASER. It appears to be essentially negative in that there were no consistent effects in the life-threatening line followingTASER stimulus. It did point to a possible age- or size- related difference that might be interesting to follow up on.
The major caveat to this study is the fact that they used an anesthetized preparation. Some physiologists seem to think the brain is a huge confounder of your study and it is okay to get it out of the experiment. I disagree. In a body of literature that I talk about all the time on the blog, if you anesthetize laboratory animals you prevent thermoregulatory, locomotor and cardiac effects of MDMA that are seemingly most relevant to studying the causes of medical emergency and death in the human user. The present study is presumably directed at the suspect who dies after being TASER’d by law enforcement so….hmm. An experimental model in which the animal was awake and allowed to express normal behavior, more or less, would have been much superior.
As one final caveat the researchers acknowledge that the study was supported (research funding and consulting agreements) by TASER International. (This blogger is not, btw). Thus an additional consideration for my readers is the usual Conflict of Interest one where it comes to research conducted by academics with funding from a private, for-profit company. My uninformed view would be that these present findings would be viewed as positive by the company. One wonders how they would feel if the study showed that TASER stimulus that was safe in the undrugged individual caused increased risk if the individual was intoxicated with methamphetamine.
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¹See the Speaking of Research page on research oversight for additional details.
²This is not necessarily a bad thing. If a drug interaction with TASER was a consistent thing, presumably we’d have more evidence from human arrests. Since TASER is considered to be generally safe and suspects are not dropping like flies, we might conclude that what we are most interested in would be relatively rare circumstances. I.e., individual differences in susceptibility to develop cardiac complications of a TASER shock when on methamphetamine (or other drug).
Dawes DM, Ho JD, Cole JB, Reardon RF, Lundin EJ, Terwey KS, Falvey DG, & Miner JR (2010). Effect of an electronic control device exposure on a methamphetamine-intoxicated animal model. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine, 17 (4), 436-43 PMID: 20370784