An electrical injury occurs when a current passes through the body, interfering with the function of an internal organ or sometimes burning tissue.
Electrical injury may result from contact with faulty electrical appliances or machinery or inadvertent contact with household wiring or electrical power lines. Getting shocked from touching an electrical outlet in the home or by a small appliance is rarely serious, but accidental exposure to high voltage causes about 400 deaths each year in the United States. The severity of the injury ranges from minor to fatal and is determined by the following factors:
Intensity of the Current:
The intensity of the current is measured in volts and amperes. Ordinary household current in the United States is 110 to 220 volts. Anything over 500 volts is considered high voltage. High voltage can jump (arc) through the air anywhere from an inch up to several feet, depending on the voltage. Thus, a person may be injured simply by coming too close to a high-voltage line. High voltage causes more severe injuries than low voltage and is more likely to cause internal damage.
Type of Current:
Electrical current is categorized as direct current (DC) or alternating current (AC). Direct current, such as current generated by batteries, flows in the same direction constantly. Alternating current, such as current available through household wall sockets, changes direction 50 to 60 times per second. Alternating current, which is used in most households in the United States and Europe, is more dangerous than direct current. Direct current tends to cause a single muscle contraction often strong enough to force people away from the current's source. Alternating current causes a continuing muscle contraction, often preventing people from releasing their grip on the current's source. As a result, exposure may be prolonged. Even a small amount of alternating current—barely enough to be felt as a mild shock—may cause the grip to freeze. Slightly more alternating current can cause the chest muscles to contract, making breathing impossible. Even more current can cause deadly abnormal heart rhythms (arrhythmias).
Pathway of the Current:
The path that the electricity takes through the body tends to determine which tissues are affected. Because alternating current continually reverses direction, the commonly used terms “entry” and “exit” are inappropriate. The terms “source” and “ground” are more precise. The most common source point for electricity is the hand, and the second most common is the head. The most common ground point is the foot. A current that travels from arm to arm or from arm to leg may go through the heart and is much more dangerous than a current that travels between a leg and the ground. A current that travels through the head may affect the brain.
Duration of Exposure:
In general, the longer the person is exposed to the current, the worse the injury.
Resistance to the Current:
Resistance is the ability to impede the flow of electricity. Most of the body's resistance is concentrated in the skin. The thicker the skin is, the greater its resistance. A thick, callused palm or sole, for example, is much more resistant to electrical current than an area of thin skin, such as an inner arm. The skin's resistance decreases when broken (for example, punctured or scraped) or when wet. If skin resistance is high, more of the damage is local, often causing only skin burns. If skin resistance is low, more of the damage affects the internal organs. Thus, the damage is mostly internal if people who are wet come in contact with electrical current, for example, when a hair dryer falls into a bathtub or people step in a puddle that is in contact with a downed electrical line.
Often, the main symptom of an electrical injury is a skin burn (see Burns), although not all electrical injuries cause external damage. High-voltage injuries may cause massive internal burns. If muscle damage is extensive, a limb may swell so much that its arteries become compressed (compartment syndrome—see Fractures: Compartment Syndrome), cutting off blood supply to the limb. If a current travels close to the eyes, it may lead to cataracts. Cataracts can develop within days of the injury or years later. If large amounts of muscle are damaged (a disorder called rhabdomyolysis), a chemical substance, myoglobin, is released into the blood. The myoglobin can damage the kidneys.
Young children who bite or suck on extension cords can burn their mouth and lips. These burns may cause facial deformities and growth problems of the teeth, jaw, and face. An added danger is that severe bleeding from an artery in the lip may occur when the scab falls off, usually 7 to 10 days after the injury.
A minor shock may cause muscle pain and may trigger mild muscle contractions or startle people, causing a fall. Severe shocks can cause abnormal heart rhythms, ranging from inconsequential to immediately fatal. Severe shocks can also trigger powerful muscle contractions sufficient to throw people to the ground or to cause joint dislocations, bone fractures, and other blunt injuries.
The nerves and brain can be injured in various ways, causing seizures, bleeding (hemorrhage) in the brain, poor short-term memory, personality changes, irritability, or difficulty sleeping. Damage to the nerves in the body or spinal cord may cause weakness, paralysis, numbness, tingling, chronic pain, and erectile dysfunction (impotence).
Doctors check people for burns, fractures, dislocations, and spinal cord or other injuries.
Most people who have no symptoms do not require testing or monitoring. An electrocardiogram (ECG) is done to monitor the heartbeat in some people. For some people, blood and urine tests may be needed. If people are unconscious, imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI) may be needed.
Education about and respect for electricity are essential. Making sure that all electrical devices are properly designed, installed, and maintained helps prevent electrical injuries at home and work. Electrical wiring should be installed and serviced by properly trained people. Outlet guards reduce risk in homes with infants or young children.
Any electrical device that touches or may be touched by the body should be properly grounded. Three-pronged outlets are safest. Cutting off the lower (ground) prong of a power cord with three prongs (so that it will fit older two-pronged plugs) is dangerous and increases the chances of electrical injury. Circuit breakers that interrupt (trip) circuits when current as low as 5 milliamperes leaks are advisable in areas that get wet, such as kitchens and bathrooms and outdoors.
To avoid injury from current that jumps (arcing injury), poles and ladders should not be used near high-voltage power lines.
First the person must be separated from the current's source. The safest way to do so is to shut off the current—for example, by throwing a circuit breaker or switch or by disconnecting the device from an electrical outlet. No one should touch the person until the current has been shut off, particularly if high-voltage lines could be involved.
High-voltage and low-voltage lines are difficult to distinguish, especially outdoors. Shutting off current to high-voltage lines is done by the local power company. Many well-meaning rescuers have been injured by electricity when trying to free a person.
Once the person can be safely touched, the rescuer should check to see if the person is breathing and has a pulse. If the person is not breathing and has no pulse, cardiopulmonary resuscitation (CPR) should be started immediately (see First Aid: First-Aid Treatment). Emergency medical assistance should be called for any person who has more than a minor injury. Because the extent of an electrical burn may be deceptive, medical assistance should be sought if any doubt exists regarding severity.
People with rhabdomyolysis may receive large amounts of fluids given intravenously. A tetanus shot is given if needed.
Skin burns are treated with burn cream (such as silver sulfadiazine, bacitracin, or sterile aloe vera) and sterile dressings. A person with only minor skin burns can usually be treated at home. If the injury is more severe, the person is admitted to the hospital, ideally a burn center. The person is kept in the hospital for 6 to 24 hours if any of the following exists:
Young children who bite or suck on extension cords should be referred to a children's orthodontist, an oral surgeon, or a surgeon who is experienced in the care of these injuries.
Last full review/revision January 2009 by Mary Ann Cooper, MD