# Electrical Injury

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## Description

• Electricity is the flow of electrons through a conductor, across a gradient, from high to low concentration
• Nature and severity of electrical injuries depend on the voltage, current strength and type, resistance to flow, and duration of contact
• Ohm law: Voltage (V) = current (I) × resistance (R):
• Voltage is directly proportional to current and is inversely proportional to resistance
• High-voltage (>600 V) and low-voltage sources:
• Telephone lines: 65 V
• Household general circuit: 110 V
• Electrical range or dryer: 220 V
• Household power lines: 220 V
• Subway third rail: 600 V
• Residential trunk line: 7,620 V
• Industrial electrical power line: 100,000 V
• Household devices can contain a transformer stepping up a seemingly low-voltage source to high-voltage:
• Microwave, television, computer
• Resistance (R) is determined by the current's pathway through the body:
• Nerves, muscles, blood vessels have low resistance and are better electrical conductors than are bone, tendon, fat
• Water and sweat on skin decrease resistance; calloused skin increases resistance
• More resistance means less flow, and more conversion to heat
• Current is measured in amperes (I) and is a measure of the amount of energy flowing through an object:
• “Let go” current is the max current a person can grasp and release before muscle tetany inhibits letting go
• Household general circuit: 15–30 A
• Tingling sensation/perception: 0.2–2 mA
• Pain: 1–4 mA
• Average child “let go” current: 3–5 mA
• Adult “let go” current: 6–9 mA; higher for men than women
• Skeletal muscle tetany current: 16–20 mA
• Respiratory muscle paralysis: 20–50 mA
• Ventricular fibrillation: 50–120 mA
• Alternating current (AC):
• Electron flow rhythmically reverses direction:
• Homes and offices in U.S. use standard 60 Hz
• Can produce continuous tetanic muscle contraction, loss of voluntary control of muscles, prolonged contact
• More dangerous than direct current (DC)
• More likely to result in ventricular fibrillation at household current level:
• Stimulation can continue through T-wave period of cardiac cycle
• Direct current (DC):
• Continuous electron flow in 1 direction
• Defibrillators and pacemakers, industrial sources
• Large, single muscle spasm tends to throw victim from source:
• Increased risk of traumatic blunt injuries
• Shorter duration of exposure
• More likely to result in asystole
• Trimodal distribution of electrical injuries:
• Toddlers (household outlets and cords)
• Teenagers (risk-taking behavior)

## Etiology

Types of electrical injury:
• Direct contact causing tissue destruction:
• Electrothermal burn may cause skin or deep tissue coagulation necrosis
• Minor visible injuries may be misleading for extensive deep tissue injury
• Location of damage is point of contact with source and point of contact with ground
• Flame:
• Burns from burning clothing or other substances
• Electrical arc indirect contact:
• Burns from the heat of a high-voltage arc (a flash burn) that passes electricity through air
• May cause thermal and flame burns
• Flash burns usually result in superficial partial-thickness burns
• Primary electrical phenomena:
• Cardiac arrhythmias
• Muscle contractions and tetany
• Secondary injury from trauma:
• Supraphysiologic muscle contraction
• Fall or being thrown

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## Description

• Electricity is the flow of electrons through a conductor, across a gradient, from high to low concentration
• Nature and severity of electrical injuries depend on the voltage, current strength and type, resistance to flow, and duration of contact
• Ohm law: Voltage (V) = current (I) × resistance (R):
• Voltage is directly proportional to current and is inversely proportional to resistance
• High-voltage (>600 V) and low-voltage sources:
• Telephone lines: 65 V
• Household general circuit: 110 V
• Electrical range or dryer: 220 V
• Household power lines: 220 V
• Subway third rail: 600 V
• Residential trunk line: 7,620 V
• Industrial electrical power line: 100,000 V
• Household devices can contain a transformer stepping up a seemingly low-voltage source to high-voltage:
• Microwave, television, computer
• Resistance (R) is determined by the current's pathway through the body:
• Nerves, muscles, blood vessels have low resistance and are better electrical conductors than are bone, tendon, fat
• Water and sweat on skin decrease resistance; calloused skin increases resistance
• More resistance means less flow, and more conversion to heat
• Current is measured in amperes (I) and is a measure of the amount of energy flowing through an object:
• “Let go” current is the max current a person can grasp and release before muscle tetany inhibits letting go
• Household general circuit: 15–30 A
• Tingling sensation/perception: 0.2–2 mA
• Pain: 1–4 mA
• Average child “let go” current: 3–5 mA
• Adult “let go” current: 6–9 mA; higher for men than women
• Skeletal muscle tetany current: 16–20 mA
• Respiratory muscle paralysis: 20–50 mA
• Ventricular fibrillation: 50–120 mA
• Alternating current (AC):
• Electron flow rhythmically reverses direction:
• Homes and offices in U.S. use standard 60 Hz
• Can produce continuous tetanic muscle contraction, loss of voluntary control of muscles, prolonged contact
• More dangerous than direct current (DC)
• More likely to result in ventricular fibrillation at household current level:
• Stimulation can continue through T-wave period of cardiac cycle
• Direct current (DC):
• Continuous electron flow in 1 direction
• Defibrillators and pacemakers, industrial sources
• Large, single muscle spasm tends to throw victim from source:
• Increased risk of traumatic blunt injuries
• Shorter duration of exposure
• More likely to result in asystole
• Trimodal distribution of electrical injuries:
• Toddlers (household outlets and cords)
• Teenagers (risk-taking behavior)

## Etiology

Types of electrical injury:
• Direct contact causing tissue destruction:
• Electrothermal burn may cause skin or deep tissue coagulation necrosis
• Minor visible injuries may be misleading for extensive deep tissue injury
• Location of damage is point of contact with source and point of contact with ground
• Flame:
• Burns from burning clothing or other substances
• Electrical arc indirect contact:
• Burns from the heat of a high-voltage arc (a flash burn) that passes electricity through air
• May cause thermal and flame burns
• Flash burns usually result in superficial partial-thickness burns
• Primary electrical phenomena:
• Cardiac arrhythmias
• Muscle contractions and tetany
• Secondary injury from trauma:
• Supraphysiologic muscle contraction
• Fall or being thrown

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