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Friday, May 4, 2012

Taser Voltage Enough to Kill

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A shock to the chest from a stun gun can cause sudden cardiac arrest and death, a small study suggested.
In eight cases of stun-gun induced loss of consciousness, the first recorded rhythms were ventricular tachycardia/fibrillation in six and asystole (after about 30 minutes of nonresponsiveness) in one, according to the first clinical study of taser effects published in a peer reviewed journal.
An external defibrillator reported a shockable rhythm in one case, but no recording was made, Douglas P. Zipes, MD, from Indiana University School of Medicine in Indianapolis, reported online in Circulation: Journal of the American Heart Association.
Given the animal and clinical data, Zipes concluded that shocks from stun guns can cause ventricular fibrillation, which can lead to death.
Stun guns, also known as tasers, are classified as nonlethal weapons. They are not considered firearms and, therefore, are not regulated by the Bureau of Alcohol, Tobacco, Firearms, and Explosives, Zipes noted.
However, they are capable of delivering an initial shock of 50,000 volts, followed by shorter 1,200-volt shocks that the user can stop, repeat, or sustain longer.
The safety of stun guns has been questioned, particularly by Amnesty International, which reported more than 500 deaths in the U.S. following shocks from stun guns since 2001.
Of the cases studied, about 60 deaths have been directly linked to the stun gun, either as a cause or contributing factor, according to Amnesty International.
Zipes traced the first documented case of stun-gun death in the literature to 2005. Animal studies, as well as a few human studies, have shown that shocking the chest with the TASER X26 (the model preferred by law enforcement) or a new prototype causes cardiac electrical capture, which is the ability of the electrical impulse to initiate a cardiac response. Some animal studies have shown that the shock could provoke rapid ventricular fibrillation.
In fact, the "concept of cardiac capture by transthoracic electrical impulses in humans ... is now a standard part of resuscitative equipment," Zipes wrote. He added that the threshold for automated external defibrillators is the output of the TASER X26.
With this as background, Zipes said he wanted to determine whether tasers can cause an electrical response and whether that could lead to an arrhythmia and subsequent death.
He analyzed eight cases that were part of litigation associated with taser shock (one from 2006, four from 2008, and three from 2009). In each case, the device used was the TASER X26. All but one individual died.
When such information was available, Zipes used records from police, hospitals, and emergency response teams; as well as data from stun guns, automated external defibrillators, ECG strips, depositions, and autopsy results.
All eight men had previously been clinically healthy, he noted. All received shocks in the anterior chest near or over the heart. And all lost consciousness during or immediately after the shock.
One of the potential mechanisms of ventricular fibrillation from a taser shock could come from a sudden loss of blood pressure from an initial shock-induced increase in heart rate, which is exacerbated by repeated shocks, potentially causing ischemia and provoking ventricular fibrillation, Zipes wrote.
He admitted that not all deaths following taser shocks can be linked to the shock itself. However, when loss of consciousness happens during or immediately after the shock "and the subsequent rhythm is VT/VF ... it becomes difficult to exonerate the effects of the shock," he wrote.
Zipes stressed that the report is not intended to condemn the use of stun guns by trained professionals.
In that vein, he offered several suggestions:
  • Avoid chest shocks if possible
  • Monitor the person following a shock
  • Suspect the possibility of an arrhythmia in those who lose consciousness
  • Be prepared to resuscitate, including the use of an automated external defibrillator
The study is limited by not having an ECG recording during the application of the shock, Zipes said.
The study was funded by the Krannert Institute of Cardiology Charitable Trust.
Zipes reported that he has served (and in the future may serve) as a paid plaintiff expert witness in electrical control device-related sudden cardiac arrest/death cases.

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