Chapter 43. Electrocution
• Approximately 20% of reported electrocution injuries are fatal
• Generated electricity accounts for over 90% of the deaths, the rest being due to lightning strike
• Children account for 33% of all victims of electrical injury.
The effects of electrical passage are generally worse with alternating current (AC) than with direct current (DC).
The current follows the line of least resistance within the body. Skin has a high resistance when dry, followed by bone, muscle, blood vessel and nerve. The higher the resistance, the greater the damage produced.
The points at which the electrical energy actually enters and leaves the body are marked by burns: the entrance and exit wounds.
Alternating current in the domestic setting produces entrance and exit wounds of approximately the same size.
In an industrial environment, direct current is the most common cause of injury and produces a small entrance wound and a much larger exit wound.
At the time of injury, ventricular fibrillation may have been precipitated by the electric shock.
The greatest threats to life following electrical injury are a consequence of tissue damage, resulting in the release into the circulation of potassium and a product of muscle breakdown, myoglobin. These may cause cardiac arrhythmias and renal failure respectively.
Remember the possibility of secondary blunt injury, which may have resulted from the victim being thrown by the electrical contact. In any unconscious patient, therefore, cervical spine injury must be assumed and closed head injury suspected.
Alternating current is generally more dangerous than direct current at any given voltage because it is more likely to induce ventricular fibrillation.
• Above 10 ma tetanic contractions may make it impossible for the patient to release the electrical source
• Above 50 ma tetanic contraction of the diaphragm and intercostal muscles leads to respiratory arrest
• Above 100 ma primary cardiac arrest may be induced (defibrillators deliver approximately 10 A)
• Above 50 A massive shocks cause prolonged respiratory and cardiac arrest and severe burns.
Suspect secondary injury (including to the cervical spine) in electrocution incidents
At the scene
• When dealing with electrical injury, the first consideration must be personal safety
Safety first!
• Ensure that the current is switched off before attempting to touch the victim or remove the victim from the electrical source
• If the current cannot be switched off, the victim may be separated from the current using a non-conductive object, such as a dry broom handle
• A victim may be unable to release an electrical source. The only course of action will be to interrupt or discontinue the source of electricity, since separation of the victim from the source will be impossible
• In electricity pylon accidents, it will be necessary to telephone the electricity board to prevent them reconnecting an interrupted source, which they will do as a matter of routine after only 20 minutes, since the cause of most temporary interruptions is bird strike, which is generally not investigated
• When a worker on a utility pole is electrocuted, expired air ventilation can often be initiated by rescuers on the pole, with chest compressions if needed as soon as the victim can be lowered to the ground
• Even if there is no loss of consciousness, a victim of high-voltage electrical shock should receive cardiac monitoring and transport to hospital because of the danger of delayed cardiac arrest from life-threatening arrhythmias.
Railway accidents
Many electrical injuries occur on railways, a significant proportion of which are suicide attempts. Railway-related electrocution may be AC or DC; many lines are electrified on the 25 000 Volt AC overhead system, whereas others are electrified on a 750 Volt DC third rail system or the 630 Volt DC fourth rail system, which is used by the London Underground.
The railway is a hazardous environment; it is important not to go onto a rail track unless you have to. One should be aware of warning signs which indicate ‘Reduced Line side Clearance’ or ‘No Refuge’. At all times, one should face oncoming traffic and a high-visibility tabard must be worn.
Telephones are clearly marked at crossings and signals and provide direct communication with Network Rail Control. Permission must be obtained from Network Rail before going on to the track and an official railway lookout should be requested using the trackside phones or through your ambulance control. Overhead line structure numbers, signal numbers or mile-post numbers can be used to identify the exact location.
Using the line side phones, the current isolation procedure and procedure for stopping trains is as follows:
• State:
1. ‘Emergency call’
2. Name
3. Location
4. Why the current needs to be switched off
• Then wait for assistance!
It is important to assume that the electricity supply (whether overhead or a third or fourth rail system) is live until definite assurance that it has been switched off has been received from Network Rail. If it is not possible to switch the current off, expert advice from railway personnel must be followed at all times.
Management
After the safe extrication of the patient at the scene of an injury, immediate management follows basic principles with an evaluation of <C>ABCDE:
• Emergency intervention and resuscitation will occur as for any victim of trauma, to control severe external bleeding, achieve and secure an airway, establish adequate ventilation and provide fluid resuscitation. Accepted conventional algorithms for cardiac resuscitation should be followed in the case of cardiac arrest following electrocution
• Electrical shock victims with no signs of life should receive the most immediate treatment
• In any unconscious patient who has been electrocuted the cervical spine should be immobilized and the patient placed on a spine board
• High flow oxygen should be administered immediately
• Intravenous access should be obtained via a large-bore (14 or 16 gauge) cannula in the antecubital fossa en route to hospital. If there is any suspicion of tissue damage, in the absence of intrathoracic or abdominal bleeding, a fluid bolus of 2 litres of normal saline (20 mL/kg in children) should be given
• If non-compressible haemorrhage is also suspected, IV fluids should be restricted to 250 mL aliquots titrated against the maintenance of a radial pulse
• Cardiac monitoring is essential, as there is a significant incidence of delayed arrhythmias following electrocution
• A brief search should be made for any entrance or exit wounds, which should be covered with a clean, simple dressing during transfer to hospital
• All pregnant electrocution victims should be transferred urgently to a hospital with obstetric facilities, regardless of the type, voltage or ampage of the shock.
Lightning strike
Unlike other forms of electrical injury, lightning strike rarely produces exposure long enough to cause breakdown of the skin, the primary insulator of the body to current flow. The current instead passes over the outside of the body: the ‘flashover’ phenomenon. The majority of the current thus passes outside the body. If the victim is wet, the flow of current may cause secondary burns as the fluid is turned into steam. Because of the flashover phenomenon, true entrance and exit wounds are uncommon.
The almost universal cause of death is respiratory arrest. Lightning acts as a massive DC countershock, sending the heart into asystole that is normally temporary in the otherwise healthy young adults that are most often its victims. Unfortunately, the respiratory arrest that often accompanies cardiac arrest may last significantly longer than the cardiac event and ventilatory support will be required in these patients.
Patients who do not arrest immediately have an excellent chance of recovery: the victim who is moaning and groaning has a degree of stability of the vital signs and recovery is the rule.
For further information, see Ch. 43 in Emergency Care: A Textbook for Paramedics.
