Robin A. Hurley, M.D., L. Anne Hayman, M.D., Katherine H. Taber, Ph.D. Section Editors
Electrical Injury, Part I: Mechanisms
Brandon C. Bryan, Psy.D., Christopher J. Andrews, M.B.B.S., Ph.D., Robin A. Hurley, M.D., Katherine H. Taber, Ph.D.
Cover and Figure 1. Steps in electroporation.1– 4 Left. Cells are enclosed by a lipid bilayer membrane (gold) which separates theextracellular space (blue) from the intracellular space (pink). The trigger that initiates pore formation is an increase in the cell’s transmembrane potential induced by an external electrical ﬁeld (see Figure 2). Right. Pores allow free passage of ions and ﬂuid. Pores will enlarge and new pores will form as long as the electrical ﬁeld is above threshold. Recovery begins as soon as the electricalﬁeld falls below threshold. Closing of pores is a slow process. Once the cell is fully resealed, re-establishment of normal membrane properties and ionic gradients may take a much longer time.
Figure 2. Large cells (Left) are more vulnerable than small cells (Right) because the change in membrane potential (red) induced by an external electrical ﬁeld is much greater.1,4
Figure 3. Electricalinjury is more likely to cause changes in functional than structural neuroimaging. In this case, clear asymmetry is present on images of regional cerebral blood ﬂow (single photon emission computed tomography, SPECT) obtained in the chronic stage. While the appearances are not pathognomic of electrical injury, the asymmetry seen lends support to the existence of functional abnormalities after theinjury. The way in which central abnormality is induced by peripheral shock is still a matter of intense research interest.
J Neuropsychiatry Clin Neurosci 21:3, Summer 2009
BRYAN et al. This report is the ﬁrst of a two-part series on the mechanisms and consequences of electrical injury. Part II, addressing clinical sequelae and symptoms, will appear in theFall 2009 issue of the Journal of Neuropsychiatry and Clinical Neurosciences. n estimated 130,000 emergency room visits are associated with electrical injuries every year, many involving children.5,6 Electrical injuries can occur in the workplace, outside during electrical storms, and in our homes. They may also occur in unpredictable settings. Examples include within an airplane (e.g., coronaldischarge, ball lightning) or when giving cardiopulmonary resuscitation to a person whose internal cardioverter deﬁbrillator is activated.7,8 Occupational exposure to electricity is a very common experience for certain vocations. Ninety-seven percent of electricians in a survey indicated they had suffered an electrical shock; 2.5% reported losing consciousness due to an electrical shock.9Occupations such as utility and construction workers are at greater risk than the general population.1,10 Several hundred people are struck by lightning in the United States every year.11 Persons engaged in outdoor activities (e.g., campers, park rangers, military personnel) are at higher risk than the general population.11,12 While a person suffering a high-voltage electrical injury with severe burns willlikely seek immediate medical care, many victims of lesser shocks may not. A survey of electricians, for example, found that medical care was generally sought only if there was a loss of consciousness, severe burn, or fracture.9 Thus, epidemiological research on electrical injury can only estimate the true extent of the problem. Much like those experiencing sports-related concussions, bothpatients and medical personnel may be unaware of the possible long-term sequelae of even low voltage injuries.
MECHANISMS OF INJURY
Four mechanisms of cellular injury by electricity are presently known. They are the direct effects of the current, thermal burns, mechanical injury due to falls, and electroporation.13 The passage of the current through tissue can cause intense muscle contractions....