Acidosis, lactate, electrolytes, muscle enzymes, and other factors in the blood of Sus scrofa following repeated TASER^® exposures

Abstract

Repeated exposure to electro-muscular incapacitating devices could result in repetitive, sustained muscle contraction, with little or no muscle recovery period. Therefore, rhabdomyolysis and other physiological responses, including acidosis, hyperkalaemia, and altered levels of muscle enzymes in the blood, would be likely to occur. Experiments were performed to investigate effects of repeated exposures of TASER^® International's Advanced TASER^® X26 on muscle contraction and resultant changes in blood factors in an anaesthetized swine model. A total of 10 animals were used. Six swine were exposed for 5 s, followed by a 5-s period of no exposure, repeatedly for 3 min. (In five of the animals, after a 1-h delay, a second 3-min exposure period was added.) The remaining four animals were used for an additional pilot study.

All four limbs of each animal exhibited contraction even though the electrodes were positioned in areas at some distances from the limbs. The degree of muscle contraction generated during the second exposure period was significantly lower than that in the first exposure series. This finding was consistent with previous studies showing that prolonged activity in skeletal muscle will eventually result in a decline of force production.

There were some similarities in blood sample changes in the current experiments with previous studies of muscular exercise. Thus problems concerning biological effects of repeated TASER exposures may be related, not directly to the “electric output” per se, but rather to the resulting contraction of muscles (and related interruption of respiration) and subsequent sequelae. Transient increases in hematocrit, potassium, and sodium were consistent with previous reports in the literature dealing with studies of muscle stimulation or exercise. It is doubtful that these short-term elevations would have any serious health consequences in a healthy individual. Blood pH was significantly decreased for 1 h following exposure, but subsequently returned toward a normal level. Leg muscle contractions and decreases in respiration each appeared to contribute to the acidosis. Lactate was highly elevated, with a slow return (time course greater than 1 h) to baseline.

Other investigators have reported profound metabolic acidosis during restraint-associated cardiac arrest. Since restraint often occurs immediately after TASER exposure, this issue should be considered in further development of deployment concepts. On the basis of the results of the current studies, the repeated use of electro-muscular incapacitating devices in a short period of time is, at least, feasible, with the caveat that some medical monitoring of subjects may be required (to observe factors such as lactate and acidosis).

Introduction

There is a need in both military forces and civilian law-enforcement agencies for non-lethal weapons that can quickly and effectively incapacitate hostile adversaries without causing permanent injury. TASER^® (Thomas A. Swift's Electronic Rifle) is the registered trademark of a battery-powered device that generates electric pulses designed to accomplish such a mission. A number of deaths after exposure to such weapons have recently been reported in the popular media, with much interest in these events generated within the forensic science community. (For comprehensive review of TASER effects, see Bleetman et al. [1].) Disagreements have occurred among forensic pathologists [2] regarding the potential lethality of exposure to the TASER.

Several reports of TASER use by law-enforcement personnel have involved repeated shots to a single individual in a short period of time. Effects of the TASER could result either (a) directly from the electrical properties of the applied stimulus or (b) from the resultant muscle contraction. Although such contraction is not synonymous with conventional muscular exercise, there may be some similarities. Rhabdomyolysis (breakdown of muscle tissue to the extent that contents are liberated into the circulation) may be caused by either excessive muscular activity [3] or electrical injury [4]. One may expect any possible electrical injury due to TASER exposure, however, to be quite different from conventional electrical injury (due to, e.g., 60 Hz alternating current) since electrical properties (most importantly, current flow) of the two modalities are dissimilar.

Repeated exposure to electro-muscular incapacitating devices, such as the TASER, could result in repeated, sustained muscle contraction, with little or no muscle recovery period. Therefore, rhabdomyolysis and other physiological responses, including acidosis, hyperkalaemia, and altered levels of muscle enzymes in the blood, would be likely to occur.

The current study was not intended to fully address the suitability of employment of electro-muscular incapacitating devices, but rather to obtain initial data on effectiveness and any immediate health effects. These experiments were performed to investigate effects of repeated exposures of TASER International's Advanced TASER X26 on muscle contraction and resultant changes in blood factors in an anaesthetized swine model. This was, to our knowledge, the first study of such factors after any type of TASER exposure.