ABSTRACT
CONTENTS 10.1 Introduction ..................................................................................................................... 333 10.2 Electrical Transport within Tissues ............................................................................. 334 10.3 Physicochemistry of Tissue Injury............................................................................... 336
10.3.1 Low-Frequency Electric Shocks...................................................................... 336 10.3.1.1 Direct Electric Force Damage......................................................... 336 10.3.1.2 Thermal ‘‘Burn’’ Injury ................................................................... 339 10.3.1.3 Electro-Conformational Denaturation of Transmembrane
Proteins .............................................................................................. 341 10.3.2 Radio Frequency and Microwave Burns ...................................................... 342 10.3.3 Lightning Injury ................................................................................................ 342 10.3.4 Diagnostic Imaging of Electrical Injury......................................................... 343
10.4 Summary and Conclusions ........................................................................................... 343 Acknowledgment....................................................................................................................... 345 References ................................................................................................................................... 345
No engineering achievement has had a greater impact on human culture than electrical power. As electric power gains its significance and vital importance in today’s modern society, it poses equal threat to human society in terms of safety. Most citizens have experienced an electric shock at least once in their lifetime. The fear reflex generated by the bad experience of pain usually prevents us from further tampering with electricity. However, no matter how careful we are, accidents do and will occur, especially among electrical workers who have to handle commercial electrical power lines everyday. Recently, use of electrical power has made it into the mainstream of law enforcement. Nonlethal electrical weapons now provide a new intermediate force option for the police. The purpose of this chapter is to provide a basic overview of harmful effects of electrical force from both the engineering and the medical perspectives. Basically, the range of clinical manifestations of electrical shock is not well documented.
Many survivors of accidental electrical shock never seek medical attention. The data that exists is from those who do seek attention or from few case studies of electrical workers.
Furthermore, there is considerable variation in how electrical injury and safety is managed across various countries and cultures. In industrializing countries safety practices are often not the top priority, resulting in high rates of injury. A study of burn injuries by Nursal et al. [1] during a 1 y (2000-2001) period indicated that 21% of burn subjects were victims of electrical injury . In highly industrialized nations, electrical shock rates are on the decline. In the United States, workplace electrocution remains the fifth leading cause of fatal occupational injury with an estimated economic impact of more than $1 billion annually [2]. The rates of injury may be the highest among electrical workers, mostly caused by working on ‘‘live’’ electrical equipment, wiring, light fixtures, and overhead power lines [3]. A study in Virginia suggested that public utilities have the highest rate of fatal electrical injuries among all industrial sectors. More than 90% of these injuries occur in men, mostly between the ages of 20 and 34, with 4 to 8 y of experience on the job [4]. Another source [5] suggests that the average age of victims was 37.5 y and the average years of experience amounted to 11.3 y. In one of the author’s own (German) study, the incidence in a 9 y period was 8.3%, 96% of victims were male, and the mean age was 32.7 y [6]. For survivors, the injury pattern is very complex, with a high disability rate due to accompanying neurologic damages and loss of limbs. Away from the workplace, most electrical injuries are due to either indoor household
low-voltage (<1000V) electrical contact or outdoor lightning strikes [7]. Domestic household 60-Hz electrical shocks are common and usually result in minor peripheral neurological symptoms or occasionally in skin surface burns. However, more complex injuries may result depending on the current path, particularly following oral contact with household appliance cord disclosures or outlets in small children [8]. Compared to a high-voltage shock that usually is mediated by an arc, low-voltage shocks are more likely to produce a prolonged, ‘‘no-let-go’’ contact with the power source. This ‘‘no-let-go’’ phenomenon is caused by an involuntary, current-induced, muscle spasm [9]. For 60Hz electrical current the ‘‘no-let-go’’ threshold for axial current passage through the forearm is 16 mA for males and 11 mA for females [10,11]. There are roughly 200 human deaths annually in the United States due to lightning
strikes and there are three times those many who survive. The range of lightning injury extent is quite broad, depending upon the magnitude of exposure and the condition of the victim. Usually lightning hits result in surface burns, complex neurological damage similar to blunt head trauma, peripheral neurologic injury, and cardiac damage [12]. Radio frequency (RF) and microwave injuries are less common. Nonetheless, they represent an important medical problem to understand. In short, electrical trauma may produce a very complex pattern of injury because of the multiple modes of frequency-dependent tissue-current interactions, the variation in current density along its pathway through the body, as well as variations in body size, body position, and use of protective gear. No two cases are the same.
