What is the role of the circuit type in the pathogenesis of electrical injuries?

Answer

Electrical current can flow in 1 of 2 types of circuits: direct current (DC) or alternating current (AC), in which the flow of electrons changes direction in rhythmic fashion. AC is the most common type of electricity in homes and offices, standardized to a frequency of 60 cycles/sec (Hz).

High-voltage DC often causes a large single muscle contraction that throws the victim away from the source, resulting in a brief duration of contact with the source flow. In contrast, AC of the same voltage is considered to be approximately 3 times more dangerous than DC, because the cyclic flow of electrons causes muscle tetany that prolongs victims' exposure to the source. Muscle tetany occurs when fibers are stimulated at 40-110 Hz; the standard 60 Hz of household current is within that range. If the source contact point is the hand, when tetanic muscle contraction occurs the extremity flexors contract, causing the victim to grasp the current and resulting in prolonged contact with the source.

Table. Physiologic Effects of Different Electrical Currents (Open Table in a new window)

Effect	Current (milliamps)
Tingling sensation/perception	1-4
Let-go current – Children	3-4
Let-go current - Women	6-8
Let-go current – Men	7-9
Skeletal muscle tetany	16-20
Respiratory muscle paralysis	20-50
Ventricular fibrillation	50-120

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Media Gallery

Arcing electrical burns through the shoe around the rubber sole. High-voltage (7600 V) alternating current nominal. Note cratering.
Contact electrical burn. This was the ground of a 120-V alternating current nominal circuit. Note vesicle with surrounding erythema. Note thermal and contact electrical burns cannot be distinguished easily.
Contact electrical burns, 120-V alternating current nominal. The right knee was the energized side, and the left was ground. These are contact burns and are difficult to distinguish from thermal burns. Note entrance and exit are not viable concepts in alternating current.
Electrical burns to the hand.
Electrical burns to the foot.
High-voltage electrical burns to the chest.
Superficial electrical burns to the knees (flash/ferning).
Energized site of low-voltage electrical burn in a 50-year-old electrician.
Grounded sites of high-voltage injury on the chest of a 16-year-old boy who climbed up an electric pole.
Energized site of the high-voltage injury depicted in Media File 9 (16-year-old boy who climbed up an electric pole).
Entrance site of a low-voltage injury.
Grounded sites of a low-voltage injury in a 33-year-old male suicide patient.
Grounded site of a low-voltage injury in the same 33-year-old male patient depicted in Media File 12.
Grounded sites of low-voltage injury on the feet.
A histologic picture of an electrical burn showing elongated pyknotic keratinocyte nuclei with vertical streaming and homogenization of the dermal collagen (40X). Courtesy of Elizabeth Satter, MD.

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Author

Tracy A Cushing, MD, MPH, FACEP, FAWM Associate Professor and Attending Physician, Department of Emergency Medicine, University of Colorado School of Medicine

Tracy A Cushing, MD, MPH, FACEP, FAWM is a member of the following medical societies: Society for Academic Emergency Medicine, Wilderness Medical Society

Disclosure: Nothing to disclose.

Coauthor(s)

Ronald K Wright, JD, MD Associate Professor (Retired), Department of Pathology, University of Miami, Leonard M Miller School of Medicine; Private Practice, Forensic Pathology

Ronald K Wright, JD, MD is a member of the following medical societies: American Academy of Forensic Sciences, American Medical Association, American Society for Clinical Pathology, College of American Pathologists, National Association of Medical Examiners

Disclosure: Received income in an amount equal to or greater than $250 from: Various plaintiff and defense firms involved in electrical injuries and deaths.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Eric L Legome, MD Professor and Chair, Department of Emergency Medicine, Mount Sinai St Lukes and Mount Sinai West; Vice Chair of Academic Affairs, Department of Emergency Medicine, Icahn School of Medicine at Mount Sinai

Eric L Legome, MD is a member of the following medical societies: American College of Emergency Physicians, Eastern Association for the Surgery of Trauma, New York American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Joe Alcock, MD, MS Associate Professor, Department of Emergency Medicine, University of New Mexico Health Sciences Center

Joe Alcock, MD, MS is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Additional Contributors

Jerry R Balentine, DO, FACEP, FACOEP Vice President, Medical Affairs and Global Health, New York Institute of Technology; Professor of Emergency Medicine, New York Institute of Technology College of Osteopathic Medicine

Jerry R Balentine, DO, FACEP, FACOEP is a member of the following medical societies: American College of Emergency Physicians, New York Academy of Medicine, American College of Osteopathic Emergency Physicians, American Association for Physician Leadership, American Osteopathic Association

Disclosure: Nothing to disclose.

What is the role of the circuit type in the pathogenesis of electrical injuries?

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