ACEP News
May 2006

By Michael Lutes, MD

Conducted electrical weapons, such as the TASER device, are less-than-lethal weapons that are widely used by military and law enforcement personnel. More than 7,000 law enforcement agencies in the United States have purchased TASERS.

Some police agencies require any subject who has been subjected to TASER discharge to undergo a medical evaluation. In some municipalities, this evaluation may be done by EMS providers; in others, the police may be required to bring the subject to an emergency department. Many states allow civilians to purchase and carry conducted electrical weapons for personal protection.

Familiarity with the TASER device and management of TASER-associated injuries will become increasingly important for the practicing emergency physician as these devices are more frequently employed.

"TASER" is the name brand of a line of devices produced by TASER International. It is the device most widely used by law enforcement.

Unlike the previous generation of "stun guns," the TASER is not intended to enforce compliance with overwhelming pain, but rather to induce incapacitation from involuntary muscle contraction.

Product literature cites a 95% rate of effectiveness. Law enforcement personnel favor the device because of its effectiveness, lower injury rate to subjects compared to other less-than-lethal weapons, fewer officer injuries, and reduced personal and departmental liability.

The TASER uses a compressed nitrogen gas canister to propel two electrode-tipped barbs at a velocity of 170 feet per second.

In comparison, a .22-caliber rifle bullet has a muzzle velocity of about 1,100 feet per second. Paintball guns used for recreational play are metered around 200 feet per second. The barbs are attached to the device by thin wires. The device can project the barbs about 21 feet.

The barb is actually a straight #8 fishhook. The length of the barb is 4 mm; the entire length of the shaft measures 9.5 mm. The barb will frequently attach to clothing and will fail to penetrate the skin. The electrical impulse can be conducted through up to 2 inches of clothing. The device is equipped with a laser for aiming purposes and will typically be aimed at the torso.

Electrical impulses are conducted in a sine wave fashion. About 1.76 joules or 26 watts are delivered per pulse. The device is capable of delivering up to 50,000 volts in rapid pulses during a 5-second period. The device is powered by 8 AA nickel metal hydride batteries.

The average current of the widely used TASER model X26 is 2.1 mAmps. The threshold for ventricular fibrillation is thought to be around 50-100 mAmps. The maximum intensity of a U.S. household current is 240 Amps.¹

Practicing physicians confronted with a subject who has been subdued with a TASER will likely be concerned about that patient's risk for cardiac arrhythmia. It is important to understand that the TASER is a weapon, not a medical device, and hence not subject to FDA regulation. (It is also not regulated by the Consumer Product Safety Commission, having been classified by the Bureau of Alcohol, Tobacco, and Firearms as a firearm and thus not within the CPSC's purview.)

However, several studies have attempted to determine if the device predisposes patients to malignant arrhythmias.

A study of anesthetized pigs (average weight of 60 kg) using an experimental device similar to the TASER failed to induce ventricular fibrillation unless a minimum of 15 times the charge of the TASER device was applied to the pigs.² The study also found that lowerweight animals were more readily induced into ventricular fibrillation. In two studies conducted by the manufacturer, the TASER failed to induce ventricular fibrillation when directly applied to dog hearts.^3,4

The incidence of ventricular fibrillation and death in the human population is more controversial. More than 100,000 individuals have been voluntarily subjected to a TASER discharge. No deaths have been reported in this population. However, there is possibly a "healthy worker" bias in that most volunteers are military or law enforcement personnel, and presumably not under the influence of psychotropic medicines, illicit drugs, or alcohol.⁵

The majority of deaths associated with TASER discharge occur minutes to hours after TASER application. Many experts believe that it is unlikely that ventricular fibrillation would occur in delayed fashion after TASER application, and that these delayed deaths are likely multifactorial or even unrelated to TASER use.

The exact reason why patients die after TASER application remains controversial.

The concept of "excited delirium" appears frequently in literature about the TASER. Excited delirium describes a spectrum of illness that begins with agitation, which leads to tachycardia, hyperthermia, and metabolic acidosis, and can ultimately cause death. Excited delirium may be precipitated by cocaine or PCP use. It is clinically similar to neuroleptic malignant syndrome. Its victims may have an underlying psychiatric disorder. Laboratory findings may include metabolic acidosis, hyperkalemia, and elevated creatine kinase levels.

Patients with excited delirium will often be violent and aggressive. They may be very difficult to subdue and need to be detained for their own safety and the safety of others.

Not surprisingly, this population may run afoul of law enforcement. Police officers understandably would rather subdue these subjects with a TASER device than a physical confrontation, particularly because individuals exhibiting excited delirium may exhibit what some describe as "superhuman strength."

Once detained by law enforcement, these patients may remain extremely agitated and then go on to suffer sudden, unexpected death. The typical scenario involves a violent subject who requires multiple officers to detain him or her. The subject will often continue to struggle while in custody and then "suddenly go quiet," typically due to respiratory arrest.

After these patients are detained, if they are still agitated, they should be brought in for medical evaluation. These patients may be hyperthermic, tachycardic, and volume-depleted, and they may even show signs of metabolic acidosis and rhabdomyolysis. They are not safe to be released to a detention facility without medical care.

Patients exhibiting signs of excited delirium require supportive care.

Sedation should be accomplished with benzodiazepines. Intravenous fluids should be given to correct volume depletion. Rhabdomyolysis and hyperkalemia should be treated. These patients should remain on a cardiac and respiratory monitor while under ED care. Generally, external measures are adequate for cooling. These patients may need to be observed in the emergency department or admitted to a monitored setting.

The management of barb-associated injuries is less controversial.

There is no significant risk to the lungs, heart, or bowel from the TASER device, given the length of the shaft and barb (9.5 mm). There is a theoretical risk to the neck vasculature and genitalia, although there have been no reported cases of significant injury. There is one report of a penetrating eye injury from a TASER barb requiring operative removal and repair.

Barbs embedded in major vascular structures should be discussed with a vascular surgeon. Although there are no case reports of vascular injuries from TASER barbs, barbs embedded in venous structures can likely be removed at the bedside with subsequent direct pressure to the wound, given that the barb is no larger than a needle used to obtain central venous access.

Barbs embedded elsewhere on the body can be removed at the bedside. One hand should be placed on the skin around the barb in order to pull the skin taught. The other hand then grasps the barb and applies steady, inline traction. Given the small size of the barb, there is no need to advance the end of the barb through the skin in order to cut off the tip as is done with other fishhooks.

If the patient cannot tolerate removal as described above, the practitioner can inject a small amount of lidocaine at the site of the wound. The practitioner can even use a small scalpel to cut down to the base of tip of the barb, though this technique will seldom be necessary.

Patients brought in after having a TASER application require a head-to-toe physical examination looking for signs of injury. If the patient was "tasered" while standing, the involuntary muscle contraction caused by the device will invariably lead to a fall. These patients should be evaluated like any other patient who suffers a fall from a standing position.

There is little information on what to do with pregnant women who have been subjected to a TASER device. There is one report of a patient suffering a miscarriage after being subdued with a TASER. However, the miscarriage occurred 7 days after the event, and the patient also had a history of drug abuse.6 There are no clear recommendations on how to handle a pregnant woman who has been "tasered." I would recommend treating such a patient like any other pregnant woman who suffers a fall.

Routine electrocardiograms are likely unnecessary in patients who receive a TASER discharge, provided the patients do not exhibit signs or symptoms of excited delirium.

Product literature reports that the TASER will not damage a cardiac pacemaker. An Ovid database search did not reveal any studies to support this claim. The effect of the TASER device on other medically implanted electrical devices has not been studied.

In summary, the TASER is a less-than-lethal weapon widely used by law enforcement.

Patients brought in after a TASER application who remain agitated and combative should be treated supportively. Barbs embedded in the eyes, major vasculature, or genitalia should be treated in conjunction with the appropriate specialist.

All patients who have been subject to a TASER device require a head-totoe physical examination to exclude any other injuries.

References

1. Koumbourlis, A.C. Electrical Injuries. Crit. Care Med. 2002;30.
2. McDaniel W.C., Stratbucker R.A., Nerheim M., et al. Cardiac safety of neuromuscular incapacitating defensive devices. PACE 2005;28:S284-7.
3. Anonymous. Advanced TASER M26 Less-Lethal EMD weapon. Medical Safety Information. TASER International, 2000.
4. Bleetman A. and Steyn R. The advanced TASER: a medical review.www.taser.com.
5. Sztajnkrycer M.D. Cardiovascular risk and the TASER: a review of the recent literature. ACEP Section of Tactical Emergency Medicine Newsletter 2005;2:2-9.
6. Mehl L.E. Electrical injury from tasering and miscarriage. Acta Obstet. Gynecol. Scand. 1992;71:118-23.

Contributors

Dr. Michael Lutes is an assistant professor in the department of emergency medicine at the Medical College of Wisconsin.

Dr. Robert C. Solomon is a faculty member for the emergency medicine residency at Ohio Valley Medical Center in Wheeling, W.Va., and clinical assistant professor of medicine at West Virginia School of Osteopathic Medicine.

Disclosures

In accordance with the Accreditation Council for Continuing Medical Education (ACCME) Standards and American College of Emergency Physicians policy, contributors and editors must disclose to the program audience the existence of significant financial interests in or relationships with manufacturers of commercial products that might have a direct interest in the subject matter.

Dr. Lutes and Dr. Solomon have disclosed that they have no significant relationships with or financial interests in any commercial companies that pertain to this educational activity.

"Focus On: Management of TASER Injuries" has been planned and implemented in accordance with the Essential Areas and Policies of the Accreditation Council for Continuing Medical Education (ACCME).

ACEP is accredited by the ACCME to provide continuing medical education for physicians. ACEP designates this educational activity for a maximum of one Category 1 credit toward the AMA Physician's Recognition Award.

Each physician should claim only those credits that he or she actually spent in the educational activity.

"Focus On: Management of TASER Injuries" is approved by ACEP for one ACEP Category 1 credit.

Disclaimer

ACEP makes every effort to ensure that contributors to College-sponsored programs are knowledgeable authorities in their fields.

Participants are, nevertheless, advised that the statements and opinions expressed in this article are provided as guidelines and should not be construed as College policy.

The material contained herein is not intended to establish policy, procedure, or a standard of care. The views expressed in this article are those of the contributors and not necessarily the opinion or recommendation of ACEP.

The College disclaims any liability or responsibility for the consequences of any actions taken in reliance on those statements or opinions.

Management of TASER Injuries CME Quiz