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Hidden realities of electrical injuries

McCollum, Kyle BS; Gowrishankar, T.R. PhD; Lee, Raphael C. MD, ScD

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doi: 10.1097/01.NURSE.0000827148.34185.26
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Since the advent of electrical energy generation and transmission, the modern world has become increasingly dependent on electrical power. From a simple light bulb to a life-saving defibrillator, electricity is involved in nearly every aspect of industrial society. Alongside its critical role, the widespread use of electricity has also introduced a public health concern. While electrical shock rarely causes any lasting consequences, it can, under adverse circumstances, result in permanent damage spanning from minor trauma to death.

According to the Electrical Safety Foundation International, electrical injuries are one of the leading causes of workplace injury and lost work time. Between 2003 and 2019, electrical shock was the seventh leading cause of workplace fatality.1 In 2019, only 8.7% of the 1,900 occupational electrical injury cases reported in the US were fatal.2 Roughly 9% of all workplace fatalities are caused by electrical shock, with the majority occurring in large-scale construction, power line repairs, or maintenance activities.3,4 The vast majority of electrical injuries are nonfatal.

Survivors of electrical injury present with a broad range of clinical manifestations that can be challenging to understand without a detailed analysis of the electrical power source, the anatomical path of the current through the body, and the duration of the electrical contact. Complex multiorgan system injury may exist in a patient with innocuous skin contact burns. Local tissue destruction is usually the most obvious diagnosis for electrical injury survivors, in which case they are sent to burn clinics for acute care. However, even survivors of very brief electrical shock with no evident burn injury can manifest neurologic, cardiac, and neuromuscular complications.

The voltage of the power source is often the only parameter known at the time of treatment and is the standard measure used to determine the clinical approach to patient care. However, the severity of electrical shocks is far more complicated than a simple “low versus high” voltage classification. Several factors influence the severity of electrical injury including shock voltage, shock duration, the path of the electrical current, and affected tissues (see Key definitions).5 The contact voltage is usually defined as the voltage of the electrical power source contacted by the shocked individual. A more meaningful clinical definition would be the difference in electrical potentials between skin contact points. However, this information is rarely known and only the voltage rating of the power source is available. If the electrical potential at one point of contact is greater than the electrical potential at the other point of contact, then current will flow between the two points in what is known as an electrical shock. Additional parameters to consider include variations in body size and the presence of protective gear.5

The estimated maximum electrical field strength—how fast the voltage is decreasing from one place to the other inside the body—in the subcutaneous tissue for an adult male contacting a 20,000-volt (V) power line with one hand and touching a ground metal object with the other is roughly similar to that of a 120-V appliance cord in a child's mouth. Despite having drastically different contact voltages, the injury biophysics of these injuries is nearly identical. The volume of tissue damage and the affected organs differ, but the degree of injury is likely to be the same. The severity of a patient's electrical injury depends not only on the contact voltage but also on the distance between the electrical contact points on the body. This variability in the clinical presentation makes electrical injuries one of the most challenging injuries to triage in acute care settings. The clinical presentation of each instance depends on the electrical field lines. When the points of contact are in the hands, the heart is in the path of the electrical field lines and the patient could experience cardiac arrest. There is often no time for a complete engineering evaluation; the acute care clinicians must depend on their clinical experience to determine the extent of workup and treatment. Clinical monitoring is important to reduce the risk of missing life-threatening injuries.5 To that end, this article discusses some fundamental concepts and misunderstandings that surround electrical injuries.

The physics of electricity

Electrical current is defined as the passage of electrical charges. Current will pass when the voltage in one location within a conducting material is different than in another. How much the voltage changes from one place to another determines the electrical field strength in that location. Direct current (DC) travels in only one direction, whereas an alternating current (AC) flows back and forth due to alternating voltage drops across the conductor. In most countries, a victim of electrical shock has experienced a commercial 50-60 cycle AC electrical current that alternates direction twice per cycle.5 At this frequency, the current passing through the body changes direction 100-120 times per second, thereby rendering the commonly used terms “entrance wound” and “exit wound” misleading; the current goes in and out of all contact points repeatedly, so these wounds can be more accurately described as “contact wounds.” If the skin is wet, internal electrical injuries may occur without clinically obvious skin contact wounds. In part, because the epidermis is the greatest resistive barrier to current flow, the most severe heating and electrical forces initially occur at skin contact points until the epidermal resistive barrier breaks down. However, wetting the skin causes the epidermal resistance to dramatically decrease, thus resulting in less burning at the contact sites.

Mechanism of injury

While the magnitude of the voltage can provide insight into the circumstances of the injury and the amount of tissue likely to be injured, it does not provide sufficient information to understand the mechanism(s) of tissue damage.4-7 For example, on a dry day, the static electrical shock generated by touching a doorknob typically involves much more than 1,000 V; typical “taser-like” stun guns deliver low-power high-voltage shocks in the range of 15,000 to 30,000 V. This would be classified as a high-voltage shock and, per common protocol, would warrant an ECG and cardiac monitoring.8 This protocol is confusing because high-voltage taser shocks directly to the chest area do not directly cause cardiac injury. The confusion exists because it takes a considerable current to produce strong electrical fields in the body. Thus, both contact current and voltage are needed to assess risk of cardiac injury. Taser-like stun guns have very limited current capacity.

Human tissue is susceptible to both thermal and nonthermal mechanisms of injury, including electrical and mechanical (acoustic blast) mechanisms.9 Thermal injury occurs from the heat generated by the passage of the current. Heating tissue to supraphysiologic temperatures results in alterations in protein structure, including protein denaturation and subsequent necrosis. At the point of contact, this is translated into changes in the appearance of tissue, commonly referred to as burns. While burns will be most severe wherever the current passes across the skin since resistance increases when heated, heating will occur everywhere along the current's path through the body.10 The most severely affected locations will be the cross-sectional area where the current path is smallest, such as the wrist or elbow.

Muscles and nerves are most susceptible to electrical injury because these tissues are specifically designed to be very sensitive to electrical signals that they use to communicate. When a strong electrical field from an electrical shock occurs, the membranes of nerves and muscles can be ruptured by electroporation. Membrane rupture is a lethal injury to the cells that causes nerve damage, muscle lysis such as rhabdomyolysis, and necrosis.11

The commercial power frequency is 60 Hertz (Hz); the threshold for human perception of a current passed from hand to hand is approximately 1.0 milliampere (mA).12 One mA is the minimum current sensed at 60 Hz frequency, which is the frequency encountered in household electrical injury. As the current reaches 16 mA, the muscles in the arm develop involuntary spasms. Within 10 to 100 milliseconds, the muscles located in the current's path will contract. If the hand is holding the conductor when this excitation-contraction response occurs, the strong forearm flexor muscles will contract, causing the victim to tighten their grip on the conductor and thereby maintain uncontrollable contact with the source of current. Alternatively, if the victim is close to but not touching the conductor at the time of current passage, the strong muscle contractions generally propel them away from the contact.13

Lightning injuries

Lightning is one source of high-power energy that can inflict injury through electrical arcing; the current passes around the body, rather than through it. The thermoacoustic blast forces generated by lightning can reach temperatures and pressures high enough to result in instant death. Peak lightning currents reach into the 30,000-50,000 ampere (A) range for a duration of 5-10 microseconds.14

Direct lightning strikes also cause a brief shock pulse that can arrest all electrophysiologic processes. When indicated, CPR should be initiated; delayed resuscitation is the most common cause of death as bystanders are often afraid to touch the person.12,15 There is no residual electrical charge on the body after several milliseconds, which is not clinically significant for harm to a rescuer.

Superficial markings and burns on the skin's surface represent the path of the current. Muscle and nerve necrosis is rare. Late neurologic and ophthalmologic sequelae are known to be potential complications.10

Patient presentation

While some electrical shocks result in cardiac arrest or other myocardial damage, most patients with electrical injuries will present with what appear to be relatively minor injuries. Yet such injuries can often be more complex than they appear and understanding the different modes of tissue injury that occur in electrical injury is important for proper triage.10

Physical findings may include thermal burns, muscle edema, muscle rigor and paralysis, fractures, dislocations, cardiac dysrhythmias, and impaired central nervous system (CNS) function. Muscle injury results in the release of cellular contents into the bloodstream including creatine kinase (CK), lactate dehydrogenase (LDH), and myoglobin.16 Despite these potential signs of injury, the clinical presentation of a patient does not correlate with the full extent of the injury. Electrical damage to peripheral nerves and skeletal muscle tissues is not usually detectable by physical exam.

There is no correlation between the extent of visible burns and the severity of the injury. Assuming that there is a correlation can severely compromise care as life-threatening cardiac, brain, and other organ damage may be present. Very brief electrical shocks may cause cardiac arrest or seizures without a noticeable thermal burn, especially if the skin is wet at the time of impact. Nonthermal injury to nerves and muscles can develop in milliseconds, whereas thermal burns take several seconds to occur. Prolonged contact with the electrical source can result in tetanic contractions induced by skeletal muscle excitation and can be strong enough to cause orthopedic trauma, rhabdomyolysis, and muscle necrosis.15

Evaluation and management

In the event of an electrical shock, the first step is to stop the injury process. When electrical power circuits are involved, the circuit must be de-energized by a professional before tending to the victim.17,18 There have been numerous reports of injuries sustained by individuals who were trying to rescue the initial shock victim from contact with a high-energy power line. Burning clothing must be extinguished and removed unless melted into the skin. In this case, cut away clothing that is not adhered to the skin. Fabrics with high plastic content, such as polyester, are more likely to melt. It is safe to touch the person only after they are no longer in contact with the power source. This is true for lightning strike victims as well.

The next step is to follow the ABC guidelines for trauma resuscitation. Airway, breathing, and circulation are assessed and supported as needed before implementing the appropriate treatment.19 CPR is initiated or continued, as needed, and Advanced Trauma Life Support procedures and protocols are performed. For patients who sustained injuries from a lightning strike, life support efforts may be successful even if there are no CNS responses, as it often takes time for the CNS to recover from high-field pulse like in keraunoparalysis or keraunoparesis, which is the state of muscular stunning that can result in skeletal muscle paralysis or paresis.

The next priority is to contact the police or fire department for help with an injured patient.

Patients thought to have life-threatening injuries, large-bore peripheral I.V. access and an indwelling urinary catheter for monitoring urine output should be established. Spinal, skeletal, and organ injuries can result if a patient has either fallen or been thrown by the force of the electrical current. Radiographic imaging, including computed tomography (CT) scans are needed to identify unstable spinal, skeletal, and organ injuries. Radiographic imaging of the extremities involved are also important to evaluate for skeletal fractures or joint dislocations. Appropriate immobilization and splinting should be initiated. If there is a history of a loss of consciousness, a head CT is indicated.

A thorough exam must be performed after initial interventions and diagnostics are performed. Nonviable skeletal muscle and nerves are often found beneath undamaged skin. Although uncommon, burn wounds in abdominal viscera and other organs have been reported. Blood oxygen-carrying capacity chemistries should be immediately evaluated and monitored. Metabolic acidosis and elevated serum potassium levels may begin to develop during resuscitation because of skeletal muscle injury. Elevated muscle proteins such as serum CK and LDH will rise over the first 48 hours with muscle damage from the electrical shock or a subsequent fall occurred. Care should be taken to prevent rapid loss of body heat through open wounds. Tetanus prophylaxis should be administered as established by the World Health Organization guidelines.20 Depending on the degree of injury, a patient with an electrical injury should be admitted or transferred to a burn center for additional care as clinically indicated.10

Once beyond the emergency care phase, the patient may face limb- and life-threatening sequelae from internal tissue destruction, compartment syndrome, and organ system dysfunction (see Acute compartment syndrome). This requires multidisciplinary intensive care at a burn center or an ICU. The distribution of the damaged tissues and organs depends on the current path through the body. Corneal burns or abrasions and tympanic membrane rupture may exist and should be treated if diagnosed. Large burn wounds often result from super-hot arc-blast contacts and clothing ignition.

Muscle compartment pressures should be measured where edema is present. If available, MRI can rapidly localize tissue edema. If MRI is not available, then the muscle compartments within the current's path between contact points should be monitored. Elevated compartment pressures may result from tissue damage caused by the electrical injury as well as fluid volumes administered during resuscitation. Muscle compartment pressures of greater than 30 cm of water is an indication for muscle decompression by fasciotomy. It may be necessary to check the pressures at specified intervals over several days.

Rehabilitation

Discharge from the hospital does not mark the end of a patients' rehabilitation journey. While there are many reports about the acute management of these injuries, there is little information about postacute management.14,15,21 The effects of an electrical injury can persist long after the initial injury occurs. New and recurring symptoms can manifest months or even years after injury; therefore, survivors should seek routine follow-up medical care.

Common late complications of electrical injuries include paresis, paralysis, scarring, posttraumatic neuropsychological disorders, and altered coordination and balance. Loss of synchronized body movements can lead to painful myofascial neuromas called trigger points. These neuromuscular complications often reduce job performance and lead to loss of employment. Chronic pain can lead to mental health disorders.21 These problems can require therapeutic intervention by experienced rehabilitation specialists and physiatrists to minimize the impact on survivors' lives. Those who have lost muscle may need surgical reconstruction.

Delayed-onset neurocognitive and neuropsychological abnormalities that often arise following electrical trauma require treatment by experts, including a neurologist and a neuropsychologist. Signs and symptoms can range from focal deficits to global cerebral dysfunction. Other potential disorders include hearing loss, headache, memory changes, neurocognitive decline, behavioral changes, emotional volatility, anxiety, posttraumatic stress disorder, and depression.22-24

Some clinical manifestations of electrical injuries are associated with progressive decline and can be delayed or prevented. The consequences of an electrical injury can persist throughout a survivor's life but can improve with proper medical management. Workforce reentry helps to mitigate the consequences of lost self-esteem. This should be guided by consultation with the employer, patient, coworkers, and an experienced occupational medicine and rehabilitation team.

Particularly in instances where electrical shock does not result in obvious large burn wounds, nurses need to be aware of the other internal injuries that may exist. By understanding the internal consequences of electrical shock, nurses can best support the need for a thorough evaluation for nerve muscle, and organ injury even with minimal signs of thermal burn injury. In addition, nurses can advocate that patients with postshock neuropsychological complications receive timely evaluation and treatment. Additionally, nurses can serve as an important community resource as they educate people about the prevention and treatment of electrical injuries.

Key definitions

  • Contact voltage – usually defined as the voltage of the electrical power source contacted by the shocked individual
  • Power source voltage – the voltage rating of the source of electrical shock and often the standard measure used to determine the clinical approach to patient care
  • Shock voltage – the voltage difference between contacts points of the electrical shock
  • Shock duration – the duration of tissue contact with an energized power source
  • Electrical shock – electrical discharge through the human body
  • Electroporation – the process in which electrical pulses create transient openings in the plasma membrane of the cell
  • Thermal injury – occurs from the heat generated by the passage of the current. Heating tissue to supraphysiological temperatures results in alterations in protein structure, including protein denaturation and subsequent necrosis.

Acute compartment syndrome

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Figure

Dorsal aspect of the left hand of a food service worker 4 hours after touching 220 V. Tissue edema begins to form because of increased vascular permeability and the release of intracellular contents into the extravascular space causing edema in the muscles. Fasciotomy to fully decompress all involved compartments is the definitive treatment for acute compartment syndrome.

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    Keywords:

    burns; electrical injury; electroporation; thermal injury

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