Monday, July 31, 2006

Stun Guns and the Heart

Although there have been incidental reports regarding "neuromuscular incapacitating devices (NID)" or "stun guns" causing rare instances of death, the frequency and of cardiac stimulation by these devices and the circumstances required to cause cardiac stimulation were previously unknown. A new study in pigs to test the incidence of cardiac stimulation was recently described Canadian researchers in this week's on-line version of the Journal of the American College of Cardiology.

They studied 150 discharges of two different manufacturers' stun guns in 6 anesthetised pigs. Nearly half (74) of these discharges stimulated the pigs' hearts. Stimulation was documented by intracardiac electrodes that were shielded from outside electrical interference. All cardiac stimulations occurred when the barbs from the device were attached to the pigs' thorax - none occurred when the barbs were off the pigs thorax.

The researchers were able to fibrillate (i.e., cause cardiac arrest) one pig when adrenaline (epinephrine) was administered before the application of the "stun."

What was most interesting, was that the rate of stimulation was different for the two models of stun guns tested: The X26 Advanced Taser (with its 6 Watts of power delivering 0.36 Joules of energy per pulse, that delivers a big first pulse of 1.5 microseconds, followed by a longer wave of 50 microseconds causing 195 mV of stimulation) was more likely to cause cardiac stimulation than the M26 Taser (with its 26 Watts of power 1.76 Joules of energy with each pulse, but delievers it in a single short impulse causing 77 mV of stimulation).

Deaths from perpetrators subdued with stun guns are rare: one study they cited reported 3 deaths in 218 subjects (1.4%). Seeing as 5000 law enforcement agencies in North America have these among some 130,000 officers, there are several implications:

1) Police forces should review the model of device they have, and
2) They might want to aim low (guys, beware!), and
2) Further research in humans might be warranted, but use of guns to subdue victims still seems more dangerous than stun guns.


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