SAEM: Shocking Truth: Tasers Safe for the Healthy

CHICAGO, May 18 -- If the human target is healthy, a shock from a Taser X26 causes no lasting ill effects, a researcher reported here.

In healthy volunteers, the Taser shock was painful but did not cause cardiac necrosis, cardiac dysrhythmia, or changes in cardiovascular and blood parameters, Gary Vilke, M.D., of the University of California at San Diego, told the Society for Academic Emergency Medicine meeting.

The devices, used by many police forces across North America, have been controversial. Amnesty International attributes more than 150 deaths to their use.

The new research - in three poster presentations - is "a piece of the big puzzle," Dr. Vilke said in an interview. "We've shown there are no red flags at this point for healthy subjects."

But he said the research doesn't answer the question of what the effects of the devices might be on someone whose heart rhythms are already disturbed, perhaps by drugs or violent exercise.

"I have been Tazed," Dr. Vilke said. "The experience is painful while it's happening but afterward, you only feel sore, like you might after a tough workout."

"Our goal was to find out how, in the absence of alcohol, drugs or other stimulants, humans are affected physiologically."

The Taser has two settings, Dr. Vilke said. There's a distance "probe" mode, in which darts are fired into a target's skin and a five-second electrical pulse causes the muscles to go into spasm. And there's a "drive stun" mode, similar to a cattle prod, which causes a painful stimulus but no muscle spasm.

Dr. Vilke and colleagues conducted three experiments on different populations, most of them peace officers or emergency workers who agreed to get a "probe mode" shock from a Taser X26.

Dr. Vilke said the key experiment measured cardiovascular and metabolic effects in 32 male and female police officers immediately before and for 60 minutes after the Taser shock.

The researchers found that systolic blood pressure, blood acidity, bicarbonate levels, and lactate levels were the only factors that changed significantly (P<0.05).

Systolic blood pressure was slightly elevated (at 139.7 mm Hg) before the shock - possibly in anticipation of the pain, Dr. Vilke said -- and then fell to normal within 60 minutes.

Acidity increased and bicarbonate decreased, but neither change was clinically relevant, he said. For example, baseline pH on average was 7.4, and fell to 7.38 five minutes after the shock.

The lactate changes were consistent with the stress of the shock, he said, and again were not clinically significant.

In a separate experiment, the researchers measured serum troponin I levels -- a marker for damage to heart muscle -- in 66 law enforcement personnel before and after a Taser shock.

Troponin levels were less than 0.2 ng/mL of serum in all volunteers, he said, "suggesting that there was no myocardial necrosis."

Finally, the researchers tested heart rhythms, using a 12-lead electrocardiogram machine on 32 volunteers before and one minute after the Taser shock.

The researchers found a transient increase in heart rate - of 2.4 beats per minute on average - but no clinically significant changes in PR or Qt interval.