Historically, electrical injury was considered a form of thermal burn injury, singularly mediated by the conver¬sion of energy from electrical to thermal (i.e. Joule Heating). Over the past twenty years, medical research has revealed that electrical shock injury [sometimes mistakenly called electrocution injuries] is more complex than just a burn injury because electrical forces can damage tissue through the direct action of electric forces on tissue structures. Thus, injuries resulting from contact with high-energy electrical energy sources may involve thermal and multiple direct electrical injury mechanisms
If the high-energy electrical source contact involves an arc-fault, then thermo-acoustic blast forces can contribute to the injury. (Capelli-Schellpfeffer et al. 1997). Lightning strike victims experience similar thermos-acoustic blast (ie. “thunder”) forces which contribute to the injury process.
While much of the research attention is focused on complex high-energy electrical shocks, the most common electrical shocks are cause by contact with low energy power sources such as household electrical power circuits. Aside from the small skin burn-puncture contact wounds, the harmful effects of low energy electrical shocks is linked to direct electrical effects on tissues such as interference with normal electrophysiological signaling function of muscles and nerves as well as structural disruption of muscle and nerve cell membranes through a process called electroporation.
Table I contains a very basic list of electrical injury mechanisms. Each of these processes has its charac¬teristic kinetics summarized in Table 1. Molecular alterations in response to direct electrical forces (i.e. electroporation and electroconformational coupling) occur on the time scale of milliseconds. These two damage mechanisms alter structure and compromise functional integrity of the cell plasma membrane. Only with more prolonged contacts on the scale of seconds does thermal damage to deep tissues begin to dominate the injury accumulation pro¬cesses.
Skeletal muscle and peripheral nerve cells are particularly vulnerable to direct electrical force effects because of their relatively large size compared to other tissue cells. Therefore, the magnitude of the electric field required to electroporate skeletal muscle and peripheral nerve cells is typically 100-1000 fold smaller than that required to electroporate other, much smaller, cell types. Engineering models of human high-voltage electrical shock suggest that during the shock the tissue electric field strength can be of sufficient magnitude in the extremities to electroporate skeletal muscle and peripheral nerve cell membranes. They can also cause electroconforma¬tional denaturation of membrane proteins. When cell membranes are disrupted, by any form of trauma, the metabolic energy of the cell will be quickly exhausted leading to metabolic arrest and eventually to lost viability.