Electrical injuries Anastassios C. Koumbourlis, MD, MPH Electrical injury is a relatively infrequent but potentially dev- control system or due to paralysis of the respiratory muscles. astating form of multisystem injury with high morbidity and Presence of severe burns (common in high-voltage electrical mortality. Most electrical injuries in adults occur in the work- injury), myocardial necrosis, the level of central nervous system place, whereas children are exposed primarily at home. In nature, injury, and the secondary multiple system organ failure determine electrical injury occurs due to lightning, which also carries the the subsequent morbidity and long-term prognosis. There is no highest mortality. The severity of the injury depends on the specific therapy for electrical injury, and the management is intensity of the electrical current (determined by the voltage of symptomatic. Although advances in the intensive care unit, and the source and the resistance of the victim), the pathway it especially in burn care, have improved the outcome, prevention follows through the victim’s body, and the duration of the contact remains the best way to minimize the prevalence and severity of with the source of the current. Immediate death may occur either electrical injury. (Crit Care Med 2002; 30[Suppl.]:S424–S430) from current-induced ventricular fibrillation or asystole or from KEY WORDS: high- and low-voltage electrical injury; lightening; respiratory arrest secondary to paralysis of the central respiratory multiple system organ failure lthough electricity is a rela- (2). Electrocutions at home account for suites), where several procedures are per- tively recent invention, hu- Ͼ200 deaths per year, and they are formed utilizing high-voltage energy for mans have always been ex- mostly associated with malfunctioning or diagnostic and therapeutic purposes (e.g., posed to electrical injuries misuse of consumer products (3). Elec- defibrillators, pacemakers, electrosurgi- Acaused by lightning. The devastating cal devices) (5–8). trical injuries are also the cause of con- power of lightning was viewed with awe, siderable morbidity. Electrical burns ac- and understandably, it was attributed to count for approximately 2–3% of all PRINCIPLES OF ELECTRICITY supernatural powers. Zeus, the ruler of burns in children that require emergency Electricity is the flow of electrons (the the ancient Greek gods, was characteris- room care (Ͼ2000 cases per year). The negatively charged outer particles of an tically depicted holding thunderbolts, vast majority of electrical burns in chil- atom) through a conductor. An object which he used as warning or punishment dren take place at home and are associ- that collects electrons becomes nega- against those who disobeyed him. The ated with electrical and extension cords tively charged, and when the electrons discovery and widespread use of electric- (in about 60–70% of the incidents) and ity in the mid-1800s took away (to some flow away from this object through a con- with wall outlets, which account for an- ductor, they create an electric current, extent) the supernatural aura surround- other 10–15% of the cases (3). Lightning ing electrical power but, in return, made which is measured in amperes. The force is responsible for an average of 93 deaths that causes the electrons to flow is the electrical injury a common problem at annually in the United States, whereas work or at home, with the first electrical voltage, and it is measured in volts. Any- the morbidity is estimated to be 5 to 10 thing that impedes the flow of electrons fatality recorded in France in 1879 (1). times higher than that due to other forms Despite significant improvements in through a conductor creates resistance, of electrical injury. (4) which is measured in ohms (1). An elec- product safety, electrical injury is still the Because severe electrical injuries tend cause of many fatalities and of consider- trical injury will occur when a person to occur primarily in the workplace, they comes into contact with the current pro- able morbidity. Electrical injuries (ex- usually involve adults, and therefore, they cluding lightning) are responsible for duced by a source. This source can be a account for only a small percentage of the Ͼ500 deaths per year in the United human-made one (e.g., the power line of overall number of admissions to pediatric States. A little more than half of them a utility company) or a natural one, such intensive care units (ICUs). However, occur in the workplace and constitute the as a lightning. considering that both the home and work fourth leading cause of work-related trau- Electrical power is generated and environments are full of electrically pow- matic death (5–6% of all workers’ deaths) transmitted via a system of three conduc- ered devices, the potential of accidental tors with the same voltage but with wave- injury is ever present, and it is necessary forms that reach their peak at a different for the intensivist to know the character- phase. This three-phase system allows for From the Division of Pediatric Critical Care, College istics and the principles of management of Physicians and Surgeons of Columbia University, a more efficient generation and transmis- Morgan Stanley Children’s Hospital of New York Pres- of this type of injury. Of particular im- sion of power. Power lines used by utility byterian, New York, NY. portance is the possibility of iatrogenic companies are classified according to Copyright © 2002 by Lippincott Williams & Wilkins electrical injury in the ICU (and in the their voltage from phase to phase, and DOI: 10.1097/01.CCM.0000035099.55766.EA operating room and electrophysiology they range from “low” (when they carry S424 Crit Care Med 2002 Vol. 30, No. 11 (Suppl.) Ͻ600 V) to “ultrahigh” (with voltage of ductor in a cyclic fashion. This type of thundercloud and the ground overcomes Ͼ1 million volts). Utility power lines with current is the most commonly used in the insulating properties of the surround- high voltages tend to be located in households and offices, and it is standard- ing air. The current of a lightning strike sparsely populated areas, and therefore, ized to a frequency of 60 cycles/sec (60 rises to a peak in about 2 ␮sec, and it lasts the possibility of an accidental contact Hz). When the current is direct, the elec- for only 1–2 msec. The voltage of a light- with them is relatively limited for the trons flow only in one direction (1, 10). ning strike is in excess of 1,000,000 V and general population (9). This type of current is produced by vari- it can generate currents of Ͼ200,000 A. Through a succession of transformers, ous batteries and is used in certain med- Transformation of the electrical energy to the voltage is gradually reduced, and the ical equipment such as defibrillators, heat can generate temperatures as high power lines that distribute electricity for pacemakers, and electric scalpels. Al- as 50,000°F. However, the extremely homes, buildings, and the general indus- though AC is considered to be a far more short duration of lightning prevents try carry low voltage, defined by the Na- efficient way of generating and distribut- struck objects from melting (11, 12). Ta- tional Electrical Code as Ͻ600 V. Most ing electricity, it is also more dangerous ble 2 presents a comparison between the homes and buildings in the United States than DC (approximately three times) be- major characteristics and effects of light- and Canada have a 120/240 V, single- cause it causes tetanic muscle contrac- ning vs. high- and low-voltage electrical phase system that provides the 240 V for tions that prolong the contact of the vic- currents. the high-power appliances and the 120 V tim with the source (10). This issue of for general use. The latter accounts for safety over efficiency became a dominant DETERMINANTS OF most of the accidental injuries. The one in the early days of electricity when ELECTRICAL INJURY household voltage in most other coun- Thomas Edison (who developed and pop- tries (Europe, Australia, Asia) is usually ularized DC) was fighting against George Electrical injury involves both direct higher (220 V) (9). Table 1 shows the Westinghouse (who developed AC). To il- and indirect mechanisms. The direct different physiologic effects of electrical lustrate the dangerous nature of AC, Edi- damage is caused by the actual effect that currents generated by common house- son convinced the New York State legis- the electric current has on various body hold voltage. lature to use AC for the first death penalty tissues (e.g., the myocardium) or by the Electrical current exists in two forms, by electrocution (coined as “Westing- conversion of electrical to thermal energy the alternating current (AC) and the di- housed”). that is responsible for various types of rect current (DC). In the former, the elec- Lightning is a form of DC that occurs burns. Indirect injuries tend to be pri- trons flow back and forth through a con- when the electrical difference between a marily the result of severe muscle con- tractions caused by electrical injury. In general, the type and extent of an Table 1. Pathophysiologic effects of different intensities of electrical current electrical injury depends on the intensity Current Intensity Probable Effect (amperage) of the electric current (1). According to Ohm’s law, the electric cur- 1 mA Tingling sensation; almost not perceptible rent is proportional to the voltage of the 16 mA Maximum current a person can grasp and “let go” source and inversely proportional to the 7–9mA “Let-go” current for an average man resistance of the conductor: current ϭ 6–8mA “Let-go” current for an average woman 3–5mA “Let-go” current for an average child voltage/resistance (1).