Chapter 17
ELECTRICAL POWER and ELECTRICAL INJURIES

Jeffrey R. Jones*

Electrical hazards constitute a narrow but ubiquitous class of occupational physical hazards. Since the first report of death by electrocution in 1879, when a stage carpenter was killed after exposure to a 250  V AC generator, electric current has been responsible for a significant number of accidents that result in severe injury or death. Approximately 1 500 cases of electrocution occur annually in the United States, including about 100 lightning-caused deaths.1–3 Approximately 300–400 of these occur at work, and the vast majority could be prevented if currently mandated safeguards were used and proper procedures followed. Although we now know a great deal about how to prevent electrical injuries, electrical fatalities still account for a significant number of fatalities in the workplace. The majority of injuries and deaths occur while workers are performing duties they normally undertake in the course of their job, suggesting inadequate training or an underestimation of the risks inherent to working around electricity.4 Because lightning injuries differ in significant ways from other electrical injuries, they will be discussed in a separate section in the second part of this chapter. While the focus of this chapter is electrical injuries, it should be recognized that the injured workers might also have exposure to chemical hazards from fires and explosions, including ozone and PCBs.

OCCUPATIONAL SETTING

Electrocution and electric shock

Electrical injury epidemiology

The National Institute for Occupational Safety and Health (NIOSH) examined death certificates over a 13-year period to determine deaths at work from electrical causes (5 348 total deaths, average of 411 deaths per year).1 A subset of those deaths (224 cases) was examined in greater detail to determine actions and risk factors that underlay the electrocutions. Electrocutions accounted for 7% of traumatic fatal injuries each year. Forty percent of the deaths were in construction and 60% occurred in workers less than 35 years old. Ninety-nine percent of the electrocutions were among men; 86% were Caucasian, probably reflecting the demographics of the workforce. Other industries with high rates included transportation/communication/public utilities (16%), manufacturing (12%), and agriculture/forestry/fishing (11%).

When NIOSH examined some of the electrocutions in detail, several trends were noted. Of the total, 33% involved low voltages (less than 600 V) and 66% involved high voltage. Most of the high-voltage deaths involved voltages of 7 200–13 800 (distribution voltages). Most of the low-voltage deaths involved 110–120 V. Utility linemen, who would be expected to have the most safety training, had the highest number of fatalities. In 55% of the deaths evaluated, there had been a failure to use required personal protective equipment (gloves, sleeves, mats, blankets, etc.). The risk greatly increases when repairs are conducted under conditions of widespread damage to electrical transmission and distribution systems, as in the aftermath of a natural disaster such as a hurricane.3 Laborers, who would be expected to have substantially less electrical safety training, had slightly fewer fatalities. In 35% of the incidents, there was no safety program or written safety procedures. When safety procedures did exist, there was a lack of enforcement or supervisory intervention. Supervisors were present at 53% of the incidents, and 17% of the victims were supervisors. Forty-one percent of the victims had been on the job less than a year.

In the construction industry, electrocution is the second leading cause of death. Painters seem to be at particular risk, most likely from working near energized lines using ladders and other potentially conductive equipment.5 The constantly changing nature of the construction work site exposes workers to temporary wiring, which may be substandard, and to harsh or unanticipated conditions that damage tool power cords and temporary power supplies. Portable arc-welding equipment is also responsible for numerous accidents, often as a result of improper grounding.

The greatest number of electrical injuries occurs in white men in the 25–34-year age group. Most injuries occur during the summer months, probably related to increased outdoor activity and the use of electrical equipment and machinery during this time of year. Increased sweating during the warmer months may also increase the severity of the electrical shock.6 Alcohol and drugs have not been consistently found to be significant contributing factors in most work-related cases; however, widespread postaccident testing has not been routinely performed.7,8

Risk factors for electrocution

NIOSH described five scenarios that accounted for the deaths they investigated:1

  1. Direct worker contact with an energized line (28%)
  2. Direct worker contact with energized equipment (21%)
  3. Boomed vehicle contact with an energized power line (18%)
  4. Improperly installed or damaged equipment (17%), typically involving improper grounding
  5. Conductive equipment, such as an aluminum ladder, contacting energized power lines (16%)

Risk factors for injury also include contact with moisture. When electric tools are handled with wet or perspiration-covered hands, resistance to electricity passing through the body is lowered. Risk is also heightened when workers wear clothing inadequate to protect them from electric arc and flash. Working on damp ground or where water is an integral part of a process, such as in irrigation, concrete work, and slaughtering, predisposes the victim to electric shock. Aerial power lines are a well-described hazard in the vicinity of irrigation pipes. In some agricultural regions, irrigation pipes have been the most common source of fatal human contact with electric lines.9

Exposure guidelines

The Occupational Safety and Health Administration (OSHA) has comprehensive standards covering electrical safety in both high and low voltages intended to prevent exposure. The primary required electric safety standards can be found in the following OSHA regulations:

  • Subpart S, 29 CFR 1910.302 through 1910.399, which applies to all electrical installations and related equipment regardless of when they were installed
  • Subpart K, 29 CFR 1926.402 through 1926.408 of the Construction Safety and Health Standards apply to installation of and work on electrical equipment, including equipment to supply power and light to job sites

Other consensus standards, such as National Fire Protection Association (NFPA) Standard 70E, may be incorporated by reference into some state standards.10

Specific sections address the need for lockout/tagout procedures (also covered in a specific lockout/tagout standard, 29 CFR 1910.147—see Chapter 5), proper or assured grounding of equipment, use of protective equipment, work on overhead power lines, and use of portable extension cords and cables. Improper lockout/tagout is one of the most common citations issued by OSHA. Protective equipment, such as rubber gloves and nonconductive sticks, must be adequate for the voltage levels encountered and must meet specific standards established by the American National Standards Institute (ANSI). Insulating gloves and other nonconductive personal protective equipment must be regularly inspected and periodically tested to ensure that they afford adequate protection. OSHA requires the use of nonconductive ladders where the employee or the ladder could contact exposed electrical conductors; it further requires that all metal ladders be prominently marked with a warning label. Clothing must be fire resistant when workers might be exposed to arc or flash, since injuries typically include burns that may be life threatening. NFPA Standard 70E addresses prevention of these injuries.

Pathophysiology of injury

Basic concepts of electrical energy

In order to grasp the consequences of human exposure to electricity, it is important to understand certain basic concepts of electrical energy. The tissue damage produced by electricity is proportional to the intensity of the current that passes through the body, as stated in Ohm’s law:

images

Voltage (tension or potential) is the electromotive force of the system, amperage (intensity) is a measure of current flow per unit time, and an ohm is the unit used to measure the resistance to conduction of electricity.

Two types of current are encountered in the workplace. Voltage is supplied either as a continuous source (direct current or DC), with electron flow moving in one direction, or as a cyclic source (alternating current or AC), with a cyclic reversal of electron flow. Nearly all injuries are the result of contact with the much more common AC. The exception is lightning, which can be thought of as a high-voltage DC shock.

AC is generated by large electromagnetic devices and generating stations, and it is transmitted many miles at very high voltages, typically greater than 100 000 V. Transformers reduce this voltage to 7 620 V, the usual voltage feeding residential and industrial distribution lines. At the local level and at residences, the voltage is again decreased to 110–220 V for domestic use.11 The frequency of most commercial AC current in the United States is 60 cycles per second or hertz (Hz); 50 Hz in much of the rest of the world. Sixty hertz means that the flow of electrons changes direction 60 times per second. The use of a 50–60-Hz frequency has evolved because it is optimal for the transmission and utilization of electricity and because it has advantages in terms of generation.

Pathophysiology of electrical injury

Whether or not death or injury occurs is directly related to the following related factors:12,13

  • Type of current (AC vs. DC)
  • Frequency of current
  • Voltage
  • Amperage
  • Duration of exposure
  • Exposure pathway through the body
  • Area of contact
  • Resistance at points of electrical contact and in tissues

AC is significantly more dangerous than DC at similar voltages. AC can produce tetanic contractions that freeze the victim to the source of the current (an inability to “let go” of energized elements), and it can interfere with the respiratory and cardiovascular centers. Victims do not freeze to DC as with AC, but they can be injured when hurled from the point of electrical contact by the shock or when burned.

The frequency of AC is of importance physiologically. The most critical frequencies are in the range 20–150 Hz. Human muscular tissue responds well to frequencies between 40 and 150 Hz. Sixty-cycle household current lies directly within this range. If the shock spans the vulnerable period of the cardiac cycle, ventricular fibrillation may result. As the frequency increases beyond 150 Hz, human tissue response is decreased, and the current is generally less dangerous.

Although the divisions are somewhat arbitrary, harmful effects from electrical current can be subdivided into the effects of high-voltage current, greater than 600 V, and the effects of low-voltage current, less than 600 V. While most people recognize high voltage as dangerous, such as with overhead power lines, low-voltage current can prove equally deadly. Injury or death can occur with currents of very low voltage; instances of death have been reported with AC of 46 and 60 V. It has been claimed that any current greater than 25 V should be considered potentially lethal, although reports of fatalities from common electrical equipment operating below 50 V are rare.14 Ventricular fibrillation is the most common cause of immediate death in high- and low-voltage injuries. Severe burns are more commonly associated with high-voltage currents.

The amount of current flow, expressed in amperes (A), is the single most important factor in injuries from electricity. Low-power alternating currents may be characterized by the thresholds of perception, “let-go”, and ventricular fibrillation. The threshold of perception is the minimum current that causes any sensation in the human body. The let-go threshold is the maximum level of current flowing through an energized pathway at which a person taking hold of an element of the circuit is still able to release it. Currents greater than the let-go threshold are especially dangerous, because the body receiving the shock is unable to respond to it and break away. The International Electrotechnical Commission (IEC) has derived general values for the thresholds of perception and let-go. The threshold of perception is 0.5 milliamperes (mA), and the let-go threshold is 10 mA for signal frequencies in the range 15–100 Hz.

The threshold for an adverse effect is clearly related to the duration of exposure to the electrical energy. The IEC has derived values for the threshold of ventricular fibrillation by adapting results from animal experiments. For a 50/60-Hz signal, a current of 500 mA may cause fibrillation for a shock duration of 10 ms: likewise, 400 mA for 100 ms, 50 mA for 1 second, and 40 mA for greater than 3 seconds. The likelihood of ventricular fibrillation increases if the shock continues for a complete cardiac cycle.

The pathway of the current is critical to injury. Current passing through the head or chest is more likely to produce immediate death by affecting the central respiratory center, the respiratory muscles, or the heart. Arm-to-arm conduction can pass through the heart, and head-to-foot conduction can affect the central nervous system and the heart. Whereas a small current through the chest can be fatal, a large current passing through a single extremity may have little effect. The above values for the threshold of ventricular fibrillation are for current paths through the whole body, but fibrillation is only triggered by that level of current directly affecting the heart.15 Nonfatal tissue injury is also determined by the current path. However, prediction of injuries from observation of the tissue path can be unreliable. Burn injuries have been shown to be more severe when the electrical energy traverses the long axis of the body.

The effect of electric current on the body depends on the resistance of the tissues involved. Intact dry skin has a relatively high resistance, but resistance falls dramatically where there is moisture, cuts, or abrasions. A callused palm has a resistance of 1 000 000 Ω, dry skin may have 5 000 Ω, and wet skin may have less than 1 000 Ω. The resistance of individual tissues is thought to differ considerably and should play a role in differential injury to tissues. Resistance to current flow occurs in decreasing order through the bone, fat, tendon, skin, muscle, blood vessels, and nerves. However, the theory that electric current always passes through the body along lines of least resistance may not be true; the path may largely depend on the voltage.

Tissue damage in electrical injury is caused by at least two mechanisms. Electrical energy may be converted to thermal energy in tissues and cause damage by heating, including protein denaturation and coagulation. The heat produced is a function of the current strength, duration of contact, and tissue resistance.11,16 The other mechanism is the creation of pores in cell membranes by means of electrical current, known as electroporation.16,17 Electroporation disrupts cell membranes and leads to cell death without significant heating. This occurs when high electrical field strengths are applied.18 It is possible that tissue damage may result from other undescribed electrical effects.11

Health effects

Electric current can cause a spectrum of acute and chronic health effects and often results in multiorgan system manifestations.11,19–21 Injury is most often the result of a direct effect on the heart, nervous system, skin, and deep tissues. Ventricular fibrillation, respiratory arrest, and burns are the most common causes of immediate death. Burns may be minor, requiring minimal debridement, or may cause devastating destruction, requiring aggressive resuscitation and major limb amputation. Other health effects include vascular damage (such as thrombosis, rhabdomyolysis, and subsequent renal failure), fractures due to high temperature or tetanic contractions, cataracts, neuropsychological changes, degenerative neurologic syndromes, and associated trauma (such as from falling off a ladder).

Electrical injury, with the exception of arc flash, resembles a crush injury more than a thermal burn. The extent of internal damage is often more severe than the cutaneous wound makes it appear. Small entry and exit wounds give little useful indication of the extent of underlying tissue damage and may not even be present in brief low-voltage injuries. In addition, there may be a direct electrical effect on the heart, nervous system, and skeletal muscles. Immediate death results from ventricular fibrillation, with or without asphyxia, from paralysis of the respiratory centers, or from prolonged tetany of respiratory muscles. Low-voltage injuries more commonly produce ventricular fibrillation rather than severe burns. Current passing through lower-resistance tissues causes necrosis of muscles, vessels, nerves, and subcutaneous tissues; it can also cause thrombosis and vascular insufficiency.

Cutaneous and deep-tissue effects 

Cutaneous injuries result from induced thermal burns, flame, and arc flash burns. An arc flash occurs when powerful, high-amperage currents travel, or arc, through the air between ungrounded conductors or between ungrounded conductors and grounded conductors.10,22 This results in an instant release of tremendous amounts of energy. Temperatures as high as 36 000 F have been recorded.22 Arc injuries result from current coursing external to the body, jumping from its source to the victim, or arcing between different sites on an extremity. The flexor surface of the forearm is a frequent site of arcing injury. Arcing may cause significant flame burns from ignition of clothing or other materials or from radiant heat. Frequently, an entrance and exit wound can be identified, but there may be severe deep-tissue damage with minimal cutaneous involvement. In severe burns, there may be extensive limb damage, requiring extensive debridement, fasciotomy, and limb amputation.

Arc blast results from the explosive expansion of air and metal in the arc path. When copper turns from a solid to a vapor, it expands 67 000 times.10 This produces high pressures (hundreds to thousands of pounds per square foot), intense sound (exceeding 160 dB), and shrapnel (traveling at speeds >700 mph).10 The pressure can knock workers off ladders, rupture eardrums, and collapse lungs.10

Cardiac effects 

The heart is particularly susceptible to electrical injury. A wide range of abnormalities may be seen, from arrhythmias to structural damage.19 Ventricular fibrillation is a common cause of death in electric shocks. In nonfatal cases, arrhythmias are an important complication. The most common EKG abnormalities noted are sinus tachycardia and nonspecific ST-T wave changes. Ventricular and atrial ectopy, atrial fibrillation, bundle branch blocks, and ventricular tachycardia have all been reported. Generally, these abnormalities do not persist. Patients exposed to low voltages that are asymptomatic and initially have a normal EKG do not typically develop arrhythmias.20

High-voltage injury can cause myocardial necrosis, although the diagnosis can be difficult to make because of the absence of typical chest pain and EKG changes.23 Evaluation of myocardial injury is based on measuring the cardiac fraction of the creatine kinase (CK) enzyme. Recent evidence suggests that a raised creatine kinase MB isoenzyme (CK-MB) level, which is elevated in acute myocardial infarction, is not necessarily indicative of myocardial damage.24 Myocardial infarction has been reported as a rare complication of electrical injury; it may be the result of electrically induced coronary vasospasm.25 Extensive burns and entrance and exit wounds in the upper and lower parts of the body may predict patients at risk of myocardial involvement and thus warrant intensive monitoring.23

Neurologic effects 

Acute central nervous system complications include respiratory center arrest or depression, seizures, mental status changes, coma, localized paresis, and amnesia. In mild cases, the patient may experience headaches, irritability, dizziness, and trouble in concentrating. These symptoms usually resolve in a few days. Peripheral nerve injuries are seen most often with extensive limb burns. Peripheral neuropathy may be seen following exposure to high current loads, even in the absence of extensive burns. Spinal cord damage is the most common permanent neurologic problem. It may cause progressive muscular atrophy or illness simulating amyotrophic lateral sclerosis or transverse myelitis. Symptoms characteristically appear after a latency period, with no (or minimal) neurologic symptoms in the acute stage. Some investigators have described a stereotypical generalized cerebral dysfunction leading to depression, divorce, and unemployment, as well as a high incidence of atypical seizures.26 Complex regional pain syndrome Types I and II (formerly RSD and causalgia, respectively) have been reported following electrical injury.19

Renal effects 

Electrical injuries produce a higher incidence of renal damage than other burns. Factors include shock, direct damage to the kidneys by high-voltage current, and the release of toxic products from the breakdown of damaged muscles. Myoglobinuria is commonly present and is proportional to the amount of muscle injury. In a retrospective case series, myoglobinuria was associated with high-voltage exposure, prehospital cardiac arrest, full-thickness burns, and compartment syndrome.27 Timely administration of fluids and diuretics is important in the prevention of pigment-induced acute renal failure.28 The development of acute renal failure in electrical injury correlates poorly with the extent of surface burns, given that the volume of tissue destroyed is often much greater than observed in a surface burn.29 The therapeutic implication is that the formula for estimating fluid replacement in surface burns may seriously underestimate the fluid required in patients with electrical burns.

Vascular effects 

Vascular complications have included immediate and delayed major vessel hemorrhage, arterial thrombosis, abdominal aortic aneurysms, and deep-vein thrombosis. This large- and small-tissue damage, typically leading to vascular insufficiency, may be responsible for the tissue damage in electrical injury that is not immediately apparent.11

Other organ systems 

Musculoskeletal injuries are often initially overlooked. They may include multiple fractures and dislocations. Shoulder and scapular fractures are frequently reported. Delayed diagnosis of femoral neck fractures has been reported. Injury may result from falls, being hurled from the electrical source, or simply abrupt muscle contraction. Cataracts, conjunctival burns, and corneal burns can occur. Cataracts usually form 2–6 months after the shock, but they can appear immediately or many years later. Intra-abdominal injury should be expected in patients having burns of the abdominal wall. Stress ulcers of the duodenum (Curling’s ulcer) can occur following severe burns.19 Where arcing or burning has occurred, especially in vaults and other enclosed spaces, inhalation injury should be considered, since metals, dielectric fluids, and a variety of other materials may have been vaporized.

Pregnancy

Electric shock during pregnancy may have serious health consequences for the mother and fetus, which may be even more vulnerable. The uterus and amniotic fluid are excellent conductors and fetal skin has a lower resistance to current.30 Reported adverse fetal outcomes include spontaneous abortion, placental abruption, cardiac arrhythmias, fetal burn, and intrauterine fetal death.30,31 When the pregnancy has continued, decreased fetal movements, asphyxia, pathological fetal heart patterns, intrauterine growth retardation, damage to the fetal central nervous system, and oligohydramnios have occurred.30,31

Diagnosis

The diagnosis of electrical injury can usually be made based on history from the patient or witnesses. Even with the available history, an assessment of the extent of trauma, burns, and related complications may be challenging due to related injuries that appear to explain signs and symptoms and other factors.11 Assessment of the patient requires a thorough physical examination, laboratory testing, electrocardiogram (EKG) and cardiac monitoring, and possibly radiology studies. In general, the greater the amount of energy that was absorbed, the greater the underlying tissue damage. Appropriate testing to assess end-organ damage and rhabdomyolysis may include complete blood count (CBC), electrolytes, creatinine, urinalysis, myoglobin, creatine kinase (CK) component levels, and troponin.

Treatment

Treatment in the field involves rapidly and safely removing the victim from the source of the current, immediate and prolonged cardiopulmonary resuscitation (CPR), attention to other life-threatening injuries such as cervical spine injury, and initiation of advanced cardiac life support, if indicated. A rescuer can inadvertently become an electrocution victim. Do not touch victims who could still be in contact with the power source. Before touching the victim, the rescuer should attempt to turn off the electrical source. The victim can be separated from the power by using nonconductive materials such as rubber, a wooden tool handle, a mat, or heavy blankets. If it is not known whether the victim was thrown or fell, a cervical collar should be applied. Efforts should be made to revive victims who appear dead, since there is a good chance that some of them will respond to prolonged resuscitation attempts.11,32

Ideally, fluid resuscitation should begin in the field, especially in high-voltage injuries, which can result in significant volume depletion secondary to exudation and sequestration of fluids in burned and damaged areas. Fluid requirements frequently are much greater than those recommended by formulas that predict fluid needs from the area of cutaneous burns (note: this is not true for lightning injuries). Because deep-tissue damage can occur with limited surface burns, fluid should be administered in sufficient volume to maintain a urine output of 50–100 mL/hour to prevent renal insufficiency from myoglobin deposition. Mannitol may help to ensure an adequate urine flow. Tetanus immunization should be administered if indicated.

There are no clear-cut criteria for the hospital admission of less severely injured patients. Inpatient observation is advisable for patients who show evidence of cardiac dysfunction, symptoms of neurologic impairment, presence of significant surface burns, suspicion of deep-tissue damage, or laboratory evidence of acidosis or myoglobinuria. The evolution of tissue injury and vascular necrosis is usually complete within 8–10 days postexposure. Spies16 has published a comprehensive summary of electrical injuries and proposed treatment approaches. Criteria for cardiac monitoring after electric injury were suggested by Fish20 following a review of the available literature:

  1. Loss of consciousness
  2. Cardiac dysrhythmias
  3. Abnormal 12-lead EKG
  4. Abnormality on mental status or physical examination
  5. Burns or tissue damage that would be expected to cause hemodynamic instability or electrolyte imbalance

Fish20 further summarized factors to be considered in a patient that may have been exposed to significant electricity (Table 17.1)

TABLE 17.1 Factors in the Physical Examination and Work-Up Suggesting a High-Risk Electric Injury.

Source: Fish R. Electric injury Part III: Cardiac monitoring indications, the pregnant patient, and lightning. J Emerg Med 2000; 18(2):186. Reprinted with permission.

  1. Factors suggesting significant effects on the patient
    1. Evidence of inhalation injury
    2. Dysrhythmia
    3. Confusion (do a non-contrast CT scan of the head)
    4. Abnormal physical examination (neurologic, orthopedic, vascular)
    5. Abnormal laboratory examination (Urinalysis, EKG, CK, CK-MB, or troponins)*
    6. Significant burn or other condition requiring treatment
  2. Signs of deep tissue injury, especially in extremities
    1. Edema
    2. Ischemic changes
    3. Sensory or motor loss
    4. Full-thickness skin injury along the path of current without flame burns in the same area
    5. Persistent flexion deformity

* EKG = Electrocardiogram; CK = Creatine kinase; CK-MB = creatine kinase MB isoenzyme.

Arc flash injuries should be treated as trauma following established emergency burn protocols.10,22,33,34

Medical surveillance

No specific medical surveillance is required for workers engaged in electrical work, although they may require surveillance for exposure to other workplace hazards. Injured workers should be evaluated for delayed complications, including cataracts. Injured pregnant workers require ongoing obstetrical monitoring.

Prevention

Occupational electrical injuries are generally preventable. Each electrical injury or fatality should be viewed as a sentinel health event. The incident should prompt an analysis of the work site with the intent of preventing any further injuries. Any injury suggests the need for a job-specific electrical safety analysis and provides an opportunity for preventive intervention in the workplace. The majority of these injuries occur either from lack of education concerning the specific hazards of the work or from failure to follow safe work practices.

Primary prevention of electrical injuries is the ultimate goal. Prevention can be accomplished through the use of engineering and administrative controls, personal protective equipment, and training. Lockout/tagout (disabling machinery or equipment to prevent the release of hazardous energy), the use of appropriate personal protective equipment, and an understanding of the hazards are key to injury prevention. Lockout/tagout and other administrative controls require commitment from management and workers and should be part of a written safety program. Their effectiveness depends on rigorous implementation and enforcement in the workplace. An example of an administrative control would be a scheduled inspection and preventive maintenance program for all power tools and electrical cords.

Training

Persons exposed to electrical risk fall into two general categories: (i) those with training and experience in electrical work as a craft, such as electricians and linemen, and (ii) those not engaged in “electrical work” who nonetheless use or work near equipment with potential electrical hazards. Injury prevention requires both education regarding hazards and attention to safe work practices. Many electrical injuries occur among nonutility/electrical workers, and these employees should be specifically targeted for primary prevention activities. Work site electrical safety education should focus on the recognition of potential electrical hazards and how to avoid exposure to live electrical circuits.28

Proactive safety programs are needed in all occupations that have a high risk of electrical injury. NIOSH and OSHA have produced numerous documents that contain elements of effective safety training, including electrical safety. Some state OSHA programs have stricter and/or more detailed requirements than the federal program. In general, comprehensive safety programs should include written rules and safe work procedures for dealing with electrical hazards.1,35

Workers must be educated about the potential dangers of low voltage, for example, 120 V. They should be instructed to always ground hand tools properly, especially portable powered hand tools. Extension cords used to supply power to portable tools need particular attention, especially at temporary work sites, because grounding can fail. Using battery-powered or double-insulated power tools plugged into ground fault circuit interrupters (GFCIs) can help prevent electrical shock, even under adverse conditions.

Engineering controls

Many options are available to reduce electrical hazards. The single most effective is to de-energize and lock out any active circuit or equipment that could be contacted during the work activity. Failing that, risk can be reduced through measures such as enhancement with visual markers, sleeving to insulate lines in high-risk areas, using ladders made of nonconducting materials, and using procedures to stabilize and prevent equipment from moving into and contacting power lines. “Lookout” workers can help guide aerial equipment. A minimum of l0 ft of clearance is required between operating aerial equipment and a power line.

Many accidents occur during the use of electrically powered machinery or portable powered hand tools. Repairing damaged power cords, maintaining proper grounding, and using GFCIs can prevent the majority of these injuries. GFCI-protected circuits are required at construction sites, but can have much broader application, even at fixed locations. GFCIs represent a simple engineering control that could save dozens of lives each year.

LIGHTNING INJURIES

According to the National Weather Service, 100 000 thunderstorms annually produce approximately 30 million lightning strikes in the United States. These kill, on average, 82 people and injure 1 000–2 000 people per year. It is estimated that 25% of these cases are occupationally related.36,37

Occupational setting

The Centers for Disease Control and Prevention (CDC) summarized lightning-caused deaths from 1980 to 1995.21 During this period, there were 1 318 deaths (82 deaths per year, range 53–100 deaths). Occupationally, many of these accidents occurred in the agricultural and construction industries, but they also occurred in other jobs where people work outdoors, such as wild land firefighting, sailing, and golfing; other activities involving open, exposed situations; and with less frequency, indoors. CDC reported 350 military personnel injured by lightning, with one death, from 1998 to 2001.38 Most victims are injured during the summer months, when thunderstorms are most frequent. The states with the greatest number of deaths were Florida and Texas, but the highest death rates were in New Mexico, Arizona, Arkansas, and Mississippi.

Working (and thus getting paid) may be an incentive to risk exposure. Workers may feel compelled or be forced to continue working when thunderstorms are near for fear of losing their jobs, thus prolonging their potential exposure to lightning. The hazard of lightning is often not realized by those exposed: lightning has struck 10 miles away from the rain of a thunderstorm.

Pathophysiology of injury

Lightning kills 30% of its victims, and 74% of survivors experience a permanent disability.36 Sixty-three percent of deaths occur within an hour of injury. The most common cause of death is immediate cardiopulmonary arrest. Lightning is dangerous due to high voltage, heat generation, and explosive force. Lightning may also injure indirectly by starting forest and house fires, causing explosions, or by felling objects such as trees.

There are significant differences between injuries from electric current and injuries from lightning (Table 17.2).39 The factor that seems to be most important in distinguishing lightning from electric current injuries is the duration of exposure to the current. Exposure to lightning current is nearly instantaneous, so that prolonged contact does not occur. The energy generally travels superficially over the surface of the body. Distinct entry and exit wounds are rare, and deep burns are infrequent. The explosive force of the lightning strike may cause significant blunt trauma if the victim is thrown by a direct strike or by the shock wave created by the flash. Clothing and shoes may be literally blown from the body. Injuries are classified from minor to severe. As with electrical injuries, several organ systems may be affected, and both acute and chronic effects are seen.21

TABLE 17.2 Lightning versus high-voltage electrical injury.39

Factor Lightning injury High-voltage injury
Energy level Very high voltage and amperage Lower
Duration of exposure Brief instantaneous Prolonged
Pathway Flash over Deep, internal
Burns Superficial Deep, major injury
Cardiac Asystole more common Ventricular fibrillation
Renal Rare myoglobinuria Myoglobinuric renal failure common
Fasciotomy and amputation Very rare Common, may be extensive
Blunt trauma Explosive thunder effect Falls, being thrown

Source: Adapted from Cooper M. Lightning injuries. This article was published in: Auerbach PS, Geehr EC, eds. Management of wilderness and environmental emergencies. 2nd ed. St. Louis: Mosby-Year Book, 1989: 171–93. Copyright Elsevier 1989. Printed with permission.

With minor injury, patients experience confusion and temporary amnesia. They rarely have significant burns but may complain of paresthesias and muscular pain. These patients usually recover completely. A ruptured tympanic membrane is a frequent finding, due to the explosive force of the lightning shock wave. With moderate injury, patients may be disoriented, combative, or unconscious. Motor paralysis, more often of the lower extremities, may be seen, along with mottling of the skin and diminished or absent pulses due to arterial spasm and sympathetic instability. Hypotension should be ruled out and, if found, should prompt a search for inapparent blunt trauma and fractures. Victims may have experienced temporary cardiopulmonary arrest at the time of the strike. Respiratory arrest may be prolonged and lead to cardiac arrest from hypoxia. Seizures may also occur. Ruptured tympanic membranes are commonly found, and minor burns may become apparent after a few hours. Patients generally improve, although they may experience chronic symptoms such as sleep disturbances, weakness, paresthesias, and psychomotor abnormalities. As with electrical shock injuries, rare cases of spinal paralysis have been reported.

Severely injured patients may present in cardiac arrest, with either asystole or ventricular fibrillation. In fact, victims are unlikely to die unless cardiopulmonary arrest occurred at the time of the lightning strike.40 Because persons struck by lightning have a better chance of survival than persons suffering cardiopulmonary arrest from other causes, resuscitation should be started immediately.20,36 Resuscitation may not be successful if there was a significant delay in initiating CPR. Direct brain damage may have occurred. Findings of blunt trauma suggest a direct strike. Long-term sequelae in survivors also include visual and hearing deficits, due most often to damaged tympanic membranes and cataracts. Neurological sequelae are described in Table 17.3.

TABLE 17.3 Neurological Sequelae of Lightning Strike.

Source: Fish R. Electric injury Part III: Cardiac monitoring indications, the pregnant patient, and lightning. J Emerg Med 2000; 18(2):185. Reprinted with permission.

  1. Early (and sometimes spontaneously reversible) conditions
    1. Loss of consciousness
    2. Confusion
    3. Abnormalities of motor and sensory function of one or more limbs
    4. Paraplegia, quadriplegia, and focal paralysis, often resolves within hours to days
  2. Conditions that can be persistent
    1. Retrograde amnesia
    2. Late-developing hemiplegia and aphasia
    3. Later-occurring neuritis and painful neuralgia in extremities
    4. Peripheral (e.g., median) neuropathy
    5. Neuropsychiatric disorders with normal brain CT scan and EEG
    6. Coma
    7. Cerebral edema
    8. Inappropriate secretion of antidiuretic hormone (SIADH)
    9. Seizures
    10. Cerebellar ataxia
    11. Painful sensory disturbances

Lightning injury during pregnancy has resulted in fetal death in utero, abortion, stillbirth, and neonatal death.30

Diagnosis

The diagnosis of injury from lightning can usually be made based on history from the patient or witnesses. Since injury can affect many organ systems, an assessment of the extent of trauma, burns, and related complications requires a thorough physical examination and testing. Initial assessment and follow-up should include an evaluation of neurological and neuropsychological symptoms.

Treatment

Initial treatment includes rapid attention to CPR and support, if necessary. In general, fluids should be restricted unless there is evidence of hypotension. Although minor burns may be present, vigorous fluid therapy and mannitol diuresis are not indicated unless myoglobinuria is found. Overhydration with resultant cerebral edema has probably killed more lightning victims than pigment-induced renal failure.39 Fasciotomy is rarely needed in lightning injuries, since most burns are superficial.

Medical Surveillance

No specific medical surveillance is indicated. Follow-up assessment for injured workers should include evaluation of neurological and neuropsychological sequelae.

Prevention

Workers involved in activities in areas where lightning strikes are possible should be familiar with the preventive measures recommended by CDC (Table 17.4).37

TABLE 17.4 Recommendations for preventing injuries from lightning strike.

Source: Adapted from Center for Disease Control. Lightning-caused deaths 1980–1995. MMWR 1998; 47:391.36

  1. During a storm, take shelter inside a home, large building, or vehicle
  2. If outside and unable to reach shelter, do not stand under or near a tall tree or other structure in an open area. Go into a ravine or gully. Assume a squatting posture on the balls of your feet with your head down and your hands over your ears (the lightning crouch) to minimize the chance of exposure to lightning. Do not lie flat
  3. Get out of and away from open water
  4. Get away from metal equipment or objects such as tractors, antennas, drainpipes, and metal stairs
  5. Put down any objects that might conduct electricity (shovels, rakes, ladders, etc.)
  6. In forested areas, seek shelter in a low-lying area under a thick growth of small trees
  7. When indoors, avoid using electrical appliances or telephones

References

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