Electrical injuries are not common but can be frightening, devastating, and life changing. They may result in massive tissue destruction, changes in growth patterns, and neurologic injury, including chronic pain syndromes and permanent cognitive deficits, affecting the child's ability to learn and become a productive adult. Children at most risk are exploring toddlers (12–30 months), who suck on extension cords or stick things into electrical outlets, and adventuresome adolescents. The majority of victims are male. Adolescents often use the outdoors fearlessly as a proving ground, incurring injuries from climbing utility poles and trees and trespassing into transformer substations, resulting in high-voltage injuries.1
In developing countries, there are large numbers of deaths in the home, both because families tend to consider household current to be “safe” and because there is little prehospital care available.2–4
The old teaching on electrical injuries involves consideration of voltage, amperage, tissue resistance, duration, current type, and pathway. These terms are still used in the literature, and we will briefly consider them.
Voltage is a measurement of the electrical “pressure” in a system. Injuries are divided into low (<1000 V) and high (>1000 V) voltage. High voltage tends to produce greater tissue destruction.
Amperage is a measure of the rate of flow of electrons. There is a direct relationship between current and heat generated in the material through which current flows given a constant resistance.
Resistance is a measure of the difficulty of electron flow through a given substance. Resistance is measured in ohms
When electricity enters an extremity, it flows readily through all of the tissues, generating more heat in some and more coagulative damage and desiccation in others.
The body is composed of different tissues, which express a different resistance to the flow of electrical current. Thus, body parts exposed to the same intensity and duration of current may show different degrees of heat-generated tissue injury. For a given energy, more severe injuries will occur in smaller cross-sectional areas than the same energy flowing through body parts with larger cross-sectional areas such as a thigh or the trunk. Damage can be especially high at the joints where the low-resistance tissues (muscle) are minimized and higher-resistance tissues (tendons, bone and cartilage) are maximal. Damage to internal organs may be more diffuse and hard to appreciate initially because of the larger cross-sectional diameter of the torso.5 Regardless of overall tissue resistancedifferences, physical factors, which affect skin resistance can be useful in explaining clinical or forensic findings in electrical injury. Skin is the primary resistor to electric current flowing into the body. Its resistance is affected by thickness, age, moisture, and cleanliness. In general, thickly calloused skin will have higher resistance and tends to sustain greater thermal damage at the site of contact but impedes the flow of energy internally. Resistance is tremendously lessened if the skin is wet with sweat or rainwater. Wet skin may show little or no local thermal damage but allows the majority of the energy to flow internally to the heart or other vital structures. This explains why a “bath-tub” injury may show no external signs of injury while causing cardiac arrest.5
Increased duration tends to result in increased damage until such time as the tissue is coagulated, charred, or mummified.5
Current type may be either alternating or direct. Alternating current (AC) is much more dangerous than direct current (DC) at the same voltage.6 Household circuits in the United States (110/220 V) operate at 60 cycles per second (cps) and 50 cps in many foreign countries, frequencies at which neuromuscular function continues indefinitely, leading to tetany. Because the flexors of the hand are stronger than the extensors, the hand gripping an AC electrical source will tend to hold onto the source in a tetanic contraction. Flexion will tend to occur at the wrist, elbow, and shoulder, seeming to pull the victim into the energy source. Tetanic muscle contraction can “freeze” the victim to the current source, prolonging the duration of contact and amount of tissue destruction. The effect of tetanic contraction is also related to the amperage applied—the margin between the household amperage (0.001–0.01 A) that causes a buzz but usually little harm, and that capable of causing respiratory arrest (0.02–0.05 A) and ventricular fibrillation (0.05–0.10 A) is narrow.5
With AC injuries, source and ground are more appropriate terms. It is often impossible to determine where the pathway started from looking at the burn and neither classification matters, as the emergency physician and surgeon care for the outcome, not the mechanism.5
Electric field strength, not listed as one of the factors, is a more useful and accurate concept in explaining and predicting injuries from technical or man-made electricity than the classical Kouwenhoven factors that have traditionally been cited in the medical literature. When 20 kV is applied to a 6-ft man, causing current to ground, an internal electrical field strength of approximately 10 kV/m is generated. When a child chews on an electric cord and suffers a lip burn, the field strength is approximately the same: 110 volts applied to 1 cm of a child's lip generates a field strength of 11 kV/m. While no one would classify the child's injury as “high” voltage, it is a high electrical field strength and produces the same tissue destruction in a small localized area much as would a “high voltage” applied to a 6-ft man (Fig. 138-1).5
It may be the electrical field and presence of AC in low-voltage exposure that causes a greater number of deaths due to low-voltage household accidents in developing countries compared to high-voltage exposure in working areas or on the street.2–4
Not only can electricity cause heating, desiccation, coagulation, and immediate death of tissues due to its thermal effects, it can also cause cellular disruption without immediate death of the cell through the electrical field effect. When an electrical field is applied to a cell, the cell surface can become charged and the cell membrane can be disrupted as water molecules are forced into the bipolar lipid membrane (electroporation).7,8 The pores that are formed allow material and water to flow nearly unhindered across the cell membrane, threatening cellular integrity. As the cell struggles to maintain its intracellular milieu, it can expend tremendous energy and resources, can swell, and eventually become exhausted and die over a more extended period of time.
There are several common mechanisms of injury (Table 138-1). Contact burns are probably the most common and result from direct contact with the electrical source or grounding points. Flash burns occur when the person is close to but not part of an electrical arc or explosion. They vary from very superficial injury with little underlying damage to extensive deep burns accompanied by blunt injury from the concussive force. Arc burns may occur when energy jumps from a source to a nearby person, making them part of the circuit. These injuries typically have deep and extensive tissue damage. Flame burns can occur if clothing or flammable chemicals in the area are secondarily ignited.
TABLE 138-1Mechanisms of Electrical Injury ||Download (.pdf) TABLE 138-1 Mechanisms of Electrical Injury
Concussive injury is not uncommon with electrical injuries, especially higher voltage injuries since there is often an explosion and rapid heating of gases around the electrical source when the victim touches high-voltage cables, transformers, or circuit boxes. Significant secondary blunt injury can accompany the concussive injury if a person is thrown or falls. Fractures or dislocations may occur.
While electrical injuries are often classified under burns, higher-energy injuries may more closely resemble crush injuries caused by muscle destruction, compartment syndromes, and myoglobin production. Some victims of electrical injury may have very little external damage while sustaining serious underlying tissue damage.
Surface burns are found in nearly all nonwater-related electrical injuries.9 However, there may be significant injury even in the absence of burns. The most common areas of injury are the hand, skull, and foot. Subcutaneous tissues, muscle, nerves, and blood vessels also suffer thermal damage. Skeletal muscle damage is produced by heat or electrical breakdown of cell membranes. Tissue that initially appears viable may later die because of electroporation effects, as well as ischemia caused by vascular wall damage, edema, and thrombosis, which may affect either inflow or outflow of blood to tissue.9,10
A common injury for very young children is incurred by sucking on the ends of extension cords resulting in severe orofacial injuries. Burns are often full thickness, involving the lips and oral commissure. These burns are initially bloodless and painless. As the eschar separates in 2–3 weeks, severe bleeding can occur from damage to the labial, facial, or even carotid arteries. There can be mandibular damage, growth retardation, devitalization of teeth, and microstomia from extensive scarring.10
Current passing directly through the heart can induce ventricular tachycardia, ventricular fibrillation, or asystole. A wide variety of arrhythmias can occur, including supraventricular tachycardia, extrasystoles, right bundle branch block, and complete heart block. The most common electrocardiographic (ECG) abnormalities are sinus tachycardia and nonspecific ST-T wave changes. Most rhythm disturbances are temporary.11 Myocardial infarction and ventricular perforation have been reported. Syncope, as a cardiac or neurologic manifestation, occurs in up to 33% of the children affected.12
Vascular injuries include thrombosis, vasculitis with necrosis of large vessels, vasospasm, and late aneurysm formation. Maximal decrease in blood flow will occur in the first 36 hours. Strong peripheral pulses do not guarantee vascular integrity.
Acute renal failure may occur from hypoxia and hypovolemia during resuscitation in combination with myoglobin released by extensively damaged muscle or hemoglobin from hemolysis.13 In rhabdomyolysis, myoglobin becomes concentrated along the renal tubules, a process that is enhanced by volume depletion and renal vasoconstriction mediated by the activation of the renin–angiotensin system, vasopressin, and the sympathetic nervous system. The myoglobin precipitates when it interacts with the Tamm–Horsfall protein, a process favored by acidic urine.14
Kidney damage may also occur from blunt trauma, hypotension, hypoxic ischemic injury, cardiac arrest, and hypovolemia. Oliguria, albuminuria, hemoglobinuria, and renal casts may be seen transiently.
Immediate CNS effects include loss of consciousness, seizure, agitation, amnesia, deafness, seizures, visual disturbance, and sensory complaints. Vascular and blunt injury damage may result in epidural, subdural, or intraventricular hemorrhage. Within several days, the syndrome of inappropriate antidiuretic hormone secretion (SIADH) may lead to cerebral edema and herniation. Peripheral nerve injury from vascular damage, thermal effect, or direct action of current may occur and be progressive. A variety of autonomic disturbances also occur. Late involvement of the spinal cord may produce ascending paralysis, amyotrophic lateral sclerosis, transverse myelitis, or incomplete cord transection. Cataracts can be seen in any electrical injury involving the head or neck.
Passage of current through the abdominal wall can cause Curling's ulcers in the stomach or duodenum. Other injuries described include evisceration, stomach or intestinal perforation, esophageal stricture, and electrocoagulation of the liver or pancreas.
Blunt trauma or tetanic muscle contractions can cause fractures or dislocations. Amputation of an extremity is necessary in 35–60% of survivors of high-energy injury caused by extensive underlying injuries. Infections frequently occur in gangrenous tissue. Prevalent organisms include Staphylococcus, Pseudomonas, and Clostridium.
Victims may suffer depression, flashbacks, attention deficit disorder, sleep problems, and other cognitive difficulties that can affect learning and school performance as well as social function within the family or school.
Extrication is extremely dangerous until the power source is disconnected. Victims should be treated both as burn victims and as blunt trauma patients, with special attention given to spinal immobilization. Except in known low-voltage injuries, aggressive fluid therapy is essential to sustain circulation and begin diluting myoglobin. Transport to a health care facility should not be delayed.15,16
Several reports have shown that most deaths occurred at the scene of the accident due to cardiac arrest with asystole, arrhythmias such as tachycardia or ventricular fibrillation, or secondary to hypoxia from respiratory arrest due to compromise of the respiratory center at the brain stem or oxygenation and ventilation disorder caused by respiratory muscle tetany.2,17–19 These patients may benefit from early cardiopulmonary resuscitation measures either by lay personnel or pre-hospital systems.
Unlike other events with multiple victims, in cases of electrical injuries, the main priority is the critical patient even when vital signs are not shown. Given the common absence of related pathologies and young age, these patients may show good prognosis, even in long resuscitation processes.12
Emergency Department Care
A victim of electrical injury should be approached in the same way as a victim of blunt trauma with a crush injury. The greatest threats to life include cardiac arrhythmias, renal failure from myoglobin and hemoglobin precipitants, and hyperkalemia from massive muscle breakdown in more severe injuries. A thorough search for burns, other wounds, and hidden skeletal injuries is necessary.15,16 Lesser injuries and small burns can be treated conservatively with few or no laboratory tests or x-rays. Referral for appropriate follow-up may be all that is needed.
ECG is not indicated for children exposed to household current (120–240 V) unless there was loss of consciousness, tetany, wet skin, transthoracic current flow, or the event was unwitnessed.11,20 Provided the ECG is normal, observation and cardiac monitoring are not usually required. Different protocols have been conducted determining the safety of the nonobservation and discharge from the emergency service.9,12,21
For more extensive injuries, laboratory tests may include arterial blood gases, complete blood count, serum electrolytes, blood urea nitrogen, creatinine, glucose, blood type and cross-match, and urinalysis for myoglobin. Creatine kinase (CK), although commonly drawn in these patients, is not predictive of the degree of injury. Although CK-MB (muscle brain) isoenzyme elevations can be seen, they may be from damaged skeletal muscle. Radiographs of the cervical spine, chest, and pelvis may be indicated if there is any history of fall, being thrown, loss of consciousness, or pain in these areas.
Other films may be obtained as dictated by physical examination. Electrocardiograms are routinely done in more serious injuries but may not be helpful since they are not very specific, and also most ECG manifestations are transitory and do not represent the severity.11,18 If the ECG is consistent with cardiac injury, further evaluation with echocardiographyor nuclear scanning may be necessary.15,16
For the patient who requires fluid resuscitation and admission, the usual fluid replacement formulas utilized for burn patients often underestimate fluid requirements. Adequate fluids should be given to maintain a urine output of 1–2 mL/kg/h when pigmentation is present and less after it has cleared. Accurate measurement requires Foley catheter placement. A decreasing level of consciousness, unexplained coma, lateralizing signs, or change in mental status necessitates cranial computed tomography (CT) or magnetic resonance imaging (MRI) to rule out intracranial damage.15,16
Extensive muscle damage may necessitate fasciotomy, particularly if the chest wall is involved. Compartment syndromes can occur if venous output is blocked by thrombosis and as tissue edema occurs. Debridement is best left to a burn surgeon and should be conservative for lip burns.15,16
Tetanus prophylaxis should be evaluated and given as needed in the emergency department. Nasogastric intubation may be required and antacids and cimetidine are administered.15,16 Consultations may be required, depending on the severity and type of injury. All children with oral injuries require plastic surgery and dental or orthodontic consults. Neurosurgical, ophthalmologic, and ear–nose–throat consults may also be necessary. Transfer to a burn center may be indicated.15,16
Infection remains the most common cause of death after electrical injury. Despite aggressive debridement and decompression, digit or limb loss may be unavoidable if tissue necrosis is extensive.15,16
Obviously, more severe patients require admission, close observation, and frequent neurovascular checks of the extremities to monitor for compartment syndromes. A multidisciplinary approach, including medical, psychiatric, and social services, is required.15,16
The number of injured due to electricity increases worldwide as humans expose themselves to a greater use of electrically powered devices. In developing countries, where the dangers of low-voltage electricity and household current are often misunderstood or underestimated, injury prevention must involve education and improving the safety measures in homes and rural areas.22,23
Physicians can play an important role in prevention by educating patients and families. The following advice should be given:24
Extension cords should be in good repair and not used to replace or avoid conduit wiring.
Unused outlets should be covered with dummy plugs.
Electrical appliances must be kept away from sinks and bathtubs.
Electrically operated toys should be age appropriate. Use of such toys should be supervised by adults.
Older children and adolescents can benefit from school safety programs that not only address the dangers of power lines and transformer substations, but also the risks of lower-voltage injury.