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Electric shock is an injury caused by an electrical current passing through the body.
The source of the current may be atmospheric (lightning) or man-made, as in high and low voltage lines.
Injuries include burns, muscle contractions and seizures, fractures, tissue death, kidney failure and respiratory and heart failure.
Treatment involves separating the victim from the current source, re-establishing vital functions and providing supportive care as required.
Electrical injury can be avoided by education about electricity and its dangers, and correct wiring of appliances and houses, including the use of circuit breakers to prevent short circuits.
Electric shock is injury caused by an electrical current passing through the body. The electricity may be atmospheric (lightning) or man-made (high-voltage transmission and low-voltage lines).
Possible injuries include burns and physiological disturbances, which may range from a minor burn to death in severe cases.
Factors that determine the form and severity of injury include:
the type and magnitude of current,
the resistance of the body at the point of contact – different tissues in the body will offer different electrical resistance,
the current pathway through the body and the
duration of current flow.
AC, particularly of the common 50-60 Hz (cycles/second) variety, is three to five times more dangerous than DC (direct current) of the same voltage and amperage (current strength).
DC tends to cause a convulsive contraction of the muscles, often forcing the victim away from further current exposure.
The effects of AC on the body depend to a great extent on the frequency: low-frequency currents (50 – 60 Hz) are usually more dangerous than high-frequency currents. AC causes muscle spasm, often 'freezing' the hand (the most common part of the body to make contact) to the circuit. The fist clenches around the current source resulting in prolonged exposure with severe burns. Burns from electricity are the result of extremely high temperatures (up to 5000 degrees C) generated at the point of skin contact with the conductor. They usually involve the skin and the tissues beneath and may be of almost any size and depth. Generally the higher the voltage and the amperage, the greater the damage from either type of current.
In general, the amount of injury to the body is directly proportional to the duration of exposure. This is because tissue breakdown occurs with longer exposure, which allows internal current flow.
Heat is produced by current flow through tissues, causing:
severe burns
protein coagulation – the proteins in the cells clump together, destroying the function of the cells
vascular thrombosis – clotting of blood
tissue necrosis (tissue death)
Physiologic changes include:
involuntary muscular contractions and seizures
ventricular fibrillation – a severely disordered rhythm of the heart which is fatal if not corrected
respiratory arrest due to central nervous system injury or muscle paralysis
decreased blood clotting
dehydration
skeletal fractures
Anyone who is either ignorant of the potential dangers of electricity or who doesn’t respect these is at risk.
The effects and clinical signs and symptoms of electrical injuries depend on a complex interaction of the factors discussed above, and may include the following:
An electric shock can startle you and cause you to fall down or be thrown down.
It may cause severe, rigid contractions of the muscles which in turn may result in fractures, dislocations and loss of consciousness.
The respiratory system may be paralysed and the heart may beat irregularly or even stop beating altogether.
Sharply demarcated electrical burns may be present on the skin and extend into deeper tissue.
High voltage may cause death of tissues between the entry and exit point of the current. Massive swelling of the tissues (oedema) may follow as the blood in the veins coagulates and the muscles swell.
Low blood pressure (hypotension), fluid and electrolyte disturbances and the release of myoglobin (an iron-containing protein present in the muscles) into the circulation can cause kidney failure.
Bathtub accident victims, who suffer electric shock while in the water, may show no burns but suffer cardiac arrest.
Lightning rarely leaves entry or exit wounds and seldom causes muscle damage or the release of myoglobin. Coma or other evidence of damage to the nervous system may occur, but usually resolves within hours or days. Death is usually due to failure of both the respiratory and cardiac systems.
Prevention of electrical injuries entails proper design, installation and maintenance of all electrical devices. Education and compliance with instructions as to the use of electric appliances, as well as common sense and respect in dealing with electricity are essential. Any electrical device that touches or may be touched by the body and has life-threatening potential should be properly earthed and incorporated in circuits containing fail-safe equipment. Ground-fault circuit breakers, which trip at current leakage to ground levels of as low as 5mA, are excellent safety devices and are readily available.
Immediate treatment consists of:
separating the victim from the current source,
re-establishing vital functions and
providing supportive care as required.
Breaking contact between the victim and the current source can be done either by shutting off the current or by removing the person from contact with it. Shutting off the current source, if this can be done rapidly, is the best method (e.g. throwing a circuit breaker or switch). Disconnecting the device from its electrical outlet or cutting the wires using insulated tools are other methods.
For low voltage, the rescuer should use an insulating material (cloth, dry wood, rubber, leather belt) to pull the victim free.
Once it has been established that it is safe to touch the victim, a rapid examination for vital functions (pulse, breathing and level of consciousness) should be performed. If spontaneous breathing is not observed, or cardiac arrest has occurred, immediate cardiopulmonary resuscitation (CPR) is required. The victim should also be treated for shock and taken to hospital for further treatment.
A tetanus injection is required for any burn. An ECG, cardiac enzymes, full blood count and a urinalysis are baseline investigations required for all electrical injuries. Other tests may be indicated when necessary.
Any suggestion of damage to the heart, abnormal rhythms or chest pain requires monitoring for at least 24 hours.
Any deterioration in level of consciousness requires a CT scan to rule out bleeding into the brain.
The outcome depends on the severity of the incident.
Progressive damage is usually much more severe than the original lesion would indicate, since the underlying tissues are damaged along the path of the electic shock through the body.
Extensive burns require long-term hospitalisation and often plastic surgery.
In any case of electrical accident where burns or loss of conciousness occur you should seek medical attention as soon as possible.
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