eMedicine Specialties > Pediatrics: Surgery > General Surgery

Burns, Electrical

Author: Brian E Benson, MD, Staff Physician, Department of Otolaryngology, St Luke's-Roosevelt Hospital Center; Clinical Instructor, Department of Otolaryngology, Hackensack University Medical Center
Coauthor(s): Monika I Sidor, MD, Staff Physician, Department of Surgery, University of Michigan at Ann Arbor; Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School; Franklin Desposito, MD, Professor of Pediatrics and Clinical Director, Center for Human and Molecular Genetics, UMDNJ-New Jersey Medical School; Consulting Staff, Department of Pediatrics, UMDNJ-University Hospital
Contributor Information and Disclosures

Updated: Dec 4, 2008

Introduction

Background

Although frequently grouped together in a single category, electrical injuries are actually a spectrum of injuries. Injuries range from the very mild, as seen with an electrical shock caused by low-voltage household current, to the truly devastating, as seen with high-tension electrical injuries.

Obtaining detailed information regarding the specifics of the injury has a major impact on workup, management, and outcome in patients. Important factors include the amount of current (low-voltage household, 120-440 V; high voltage, 440-1000 V; high-tension voltage, >1000 V), type of current (alternating current [AC] or direct current [DC]), path of current (hand-to-hand, hand-to-foot, foot-to-foot), length of contact (tetany, locked-on phenomenon), and the events associated with the injury (fall, burns, water contact).

Pathophysiology

Simply stated, electricity involves the flow of energy (electrons) along the path of least resistance toward a natural ground. All objects are either resistors or conductors. The skin acts as a natural resistor to flow; dry skin has a resistance of 40,000-100,000 ohms, wet skin has a resistance of approximately 1000 ohms, and calloused skin has a resistance of 2,000,000 ohms. Children's thin skin and high water content results in decreased resistance, compared with adults. The internal resistance of the body is estimated to be between 500-1000 ohms, with bones, tendons, and fat providing the most resistance to electric current. Nerves, blood vessels, mucus membranes, and muscle are the best conductors. With regard to electrical burns, the cross-sectional area is inversely proportional to tissue damage. Therefore, small areas such as joints receive maximal injury.

The current pathway plays an important role in determining injury, with a vertical pathway being more dangerous than a horizontal (hand-to-hand) pathway.

Standard household current in the United States and Canada is 110 V AC with a frequency of 60 Hz. Skeletal muscle is stimulated into tetany by currents with frequencies of 40-110 Hz. Most low- and high-tension electrical current is AC. AC produces tetany and the locked-on phenomenon. Although tetany occurs in all muscles that are stimulated, flexor groups are usually stronger and predominate. As a result, an individual's grasp is uncontrollably locked onto an object, which can increase the length of time the current passes through the body and may result in greater injury. In contrast, DC tends to produce a single large muscular contraction that often throws the patient away from the source. However, at high voltages, both AC and DC produce similar effects.

High-voltage injuries are associated with arc burns and flash burns. Arc temperatures may reach up to 5000°C, and are usually responsible for the severe thermal injuries in high-voltage injuries.

Lightning involves a single massive current impulse that is roughly equivalent to a DC blast of 2000 to 2 billion V of extremely short duration (0.1-1 ms). The peak temperature in the lightning strike channel is 30,000°K. However, the short duration usually precludes serious direct thermal injury. Four modes of lightning injury have been described: direct strike, side flash (discharge from an object near the victim), stride potential (enters one foot and exits via the other), and flash-over (energy passing outside the body with vaporization of surface water and blast effect to clothing).

Lightning may cause full cardiac arrest by inducing either asystole or central apnea. Massive depolarization of the heart leads to asystole. However, the heart's automaticity usually restarts the heart in normal sinus rhythm. Massive depolarization of the brain is believed to stun the respiratory center causing a much longer duration of central apnea. If artificial respiration is provided, many patients can survive.

Electrical injury may cause disruption of the body's normal electrical activities. The neurologic system is affected most commonly. Neurologic dysfunction is present in some form, even if only temporary, in virtually all patients. Transient nerve injuries resulting in temporary numbness and tingling are most common. Mass depolarization of the brain may lead to a loss of consciousness, amnesia, and coma. Spinal cord involvement may result in transverse myelitis. Transverse myelitis may have delayed onset and is associated with poor prognosis for recovery.

Electrical injuries also may affect the heart. As many as 25% of patients with electrical injuries have cardiac dysrhythmia. However, this number probably includes many benign transient entities (eg, sinus tachycardia, premature atrial ventricular contractions, conduction disorders). Sudden death from an AC electrical injury is usually the result of ventricular fibrillation, although asystole and other dysrhythmias are common. Ventricular fibrillation is 3 times more likely to occur if the flow of current is arm-to-arm. True myocardial infarction is rare unless the patient has preexisting cardiac disease.

Another mechanism of injury is related directly to the amount of heat generated by the flow of electrical current through body tissue. At higher voltages, higher temperatures are achieved, resulting in greater direct thermal injury. High-tension voltages cause devastating injuries from huge amounts of internal thermal damage.

Vascular injury occurs as a result of vascular spasm. Heat generated by the injury also can cause coagulation and vascular occlusion. Damage to the vascular wall may produce delayed thrombosis and bleeding. Compartment syndrome may develop as a result of acute ischemic insult to the musculature.

Renal injuries may occur as a result of rhabdomyolysis. Rhabdomyolysis causes myoglobinuria from massive release of myoglobin. Myoglobin crystallization in the kidney tubules may cause acute renal failure.

Electrical burn injuries from surgical instruments have been well documented in the surgical literature but are beyond the scope of this discussion.

Frequency

United States

Electrical injuries account for approximately 20,000 emergency department (ED) visits and 1000 deaths per year. Low-voltage injuries (110-440 V) are most common, accounting for more than 60% of all reported injuries. Children account for 20% of all low-voltage injuries. Electrocution by lightning is not a reportable injury, and accurate statistics are lacking. Estimates range from 300 to several thousand injuries and 100-600 deaths per year.

Mortality/Morbidity

• Lightning has a case-fatality rate of 25-30%. Approximately 75% of individuals who survive a lightning strike have permanent sequelae (eg, cataracts, ruptured tympanic membrane, peripheral nerve damage).
• Low-voltage injuries have very low morbidity and mortality. Both morbidity and mortality increase proportionately as voltage increases.
• Wet skin significantly decreases resistance, allowing an increased exchange of energy and subsequent injury.
• At the same voltage, AC injuries have 3 times the morbidity and mortality rates as DC injuries.
• A pathway of current from hand-to-hand (across the heart) is associated with a mortality rate of 60%, hand-to-foot with 20%, and foot-to-foot with a mortality rate of less than 5%.
• Ventricular fibrillation is 3 times more likely to occur in patients who experienced a hand-to-hand flow of current across the heart.

Sex

Electrical injuries are more common in males.

Age

Low-voltage injuries in toddlers often result from chewing on electrical cords or sticking objects into outlets. In older children and adolescents, electrical injuries may occur as a result of unintentional contact with high-voltage electrical wires during activities such as climbing trees.

Clinical

History

Not all electrical or lightning injuries are the same. A detailed history, including all of the specifics associated with the event, is essential.

• Voltage and type of current
  • Standard household current in the United States and Canada is 110 V AC.
  • Larger household or industrial appliances may involve 440 V AC.
  • Power lines and electrical transformers constitute high-voltage energies and involve over 600 V. By definition, high-tension injuries involve currents of greater than 1000 V.
• Length of exposure and potential transmittance of energy
  • Identify whether the electrical injury was brief or sustained (tetany) and an approximate time of contact.
  • Determine conditions associated with the injury that may have influenced the amount of energy transferred (eg, wet skin, puddle of water, bathtub).
  • If possible, determine the proximity of the energy transfer. Differentiating between direct strike, contact, arc, or side-flash types of injuries is helpful.
• Other patient history
  • Determine symptomatology immediately after the injury (level of consciousness, presence of vital signs, movement of extremities, presence of cyanosis), and provide lifesaving measures.
  • Determine preexisting medical conditions.

Physical

• Airway: Patients unable to maintain their own airway require an artificial airway.
• Breathing: Patients may require artificial ventilation. This is particularly true of patients who were struck by lightning in whom the respiratory center may be temporarily stunned.
• Circulation
  • Circulation can be assessed by determining perfusion to end organs by evaluating the level of consciousness, skin color and temperature, capillary refill, and urinary output.
  • Heart rate should be assessed for appropriate rate and regularity.
• Disability
  • A thorough neurologic evaluation is indicated to determine the presence and level of deficits including global dysfunction (cerebral), localized dysfunction (peripheral nerve), or regional dysfunction (transverse myelitis).
  • Serial examinations are necessary to ascertain progression or resolution of abnormalities.
• Environment-related factors
  • As with most environmental injuries, patients may be at risk for hypothermia, which is associated with increased morbidity and mortality rates. Pay attention to maintaining temperatures within the reference range.
  • Remove wet or burnt clothing, and keep the patient warm and dry.
• Extremities
  • Electrical injuries may be associated with a fall from a height or an explosion, resulting in other associated trauma.
  • Closely inspect all extremities to exclude other related injuries caused by the associated trauma.
  • Even at lower voltages, tetany may cause otherwise unsuspected fractures or dislocations. Isolated swelling, deformity, or pain may indicate a fracture.
• Skin
  • Thoroughly assess the skin for the presence of burns.
  • Flash burns may occur and appear identical to standard thermal burns. Usually associated with higher voltages, flash burns denote an external flash of energy and usually are not associated with a significant internal transmission of energy or injury.
  • Flash burns associated with lightning result from an intense impulse of energy occurring for an extremely brief period of time (lightning side flash) and may cause characteristic distributions of injury. Thermal burns are uncommon in lightning strikes unless clothing catches fire.
  • Linear superficial burns may occur where sweat had accumulated, presumably because of brief intense steam production.
  • Feathering or ferning may occur and is believed to be the result of an electron shower causing transient cutaneous markings. Usually, this is not considered to be a true burn, but it is pathognomonic for lightning injury.
  • Arc burns have a characteristic white center with a rim of congestion or erythema. Arc burns commonly are associated with significant internal transfer of energy and related injury.
• Wound examination
  • Direct energy transmission often results in 2 wounds, an entrance and an exit wound.
  • Classic teaching has been that entrance wounds are smaller and more discrete than the blowout wound associated with exiting; however, this is not always true. A simple description of the location and appearance of the wounds is probably better than attempting to differentiate entrance from exit wounds.

Causes

Major risk factors for electrical injury include improper supervision of children and failure to make a child's environment safe.

• Risks to small children: Young children may experience an electrical injury as the result of chewing on an electrical cord or playing with an electrical outlet.
• Risks to older children and young adults
  • Electrical injury may occur from using an improperly grounded appliance or electrical tool. These types of injuries are less common with the increased use of ground-fault circuit interrupters in kitchens and bathrooms.
  • Electrical injury may occur from inadvertently touching electrical wires while climbing trees.
  • Chest, head, and neck burns; tympanic membrane perforation; and bilateral mandibular fractures have been reported in association with iPod use while exercising outdoors during a thunderstorm.¹
  • Adolescents may exhibit unusual risk-taking behavior or impaired judgment because of mind-altering substances such as drugs or alcohol.

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