Signs and Symptoms of Electrical Injury
– Burns caused by resistance heating, leading to extensive and deep burns
– Involuntary muscle contractions and the no-let-go phenomenon
– Internal burns due to high voltage levels
– Tissue damage through heating and/or electroporation injury
– Joule heating in deeper tissues causing damaging temperatures
Effects of Electrical Shock on the Body
– Ventricular fibrillation
– Domestic power supply voltage can induce ventricular fibrillation
– Direct current requires higher currents for fibrillation compared to alternating current
– Direct pathway to the heart can cause fibrillation with lower currents
– Ventricular fibrillation can lead to cardiac arrest if not immediately treated
– Tetanic muscle contractions at high currents can prevent fibrillation
– Neurological effects
– Interference with nervous control, especially over the heart and lungs
– Electric shock can cause neuropathy at the entry site
– Neurologic symptoms can occur immediately or be delayed
– Delayed neurologic consequences have a worse prognosis
– Ventricular fibrillation can cause cerebral hypoxia and neurologic consequences
– Mental health
– Psychiatric effects can occur as a result of electrical injuries
– Behavioral changes can occur even if the current didn’t pass through the head
– Symptoms may include depression, anxiety disorders, moodiness, memory loss
– Feelings of low self-esteem and guilt can be present
– Lower threshold for frustration and difficulty learning
Arc-Flash Hazards
– Thermal burns due to arcing faults are common in electrical injuries
– Arc flash produces light radiation similar to electric welders
– Severe burns can occur due to the heat produced
– Protective gear such as face shields and heavy leather gloves are necessary
– OSHA found that up to 80% of electrical injuries involve thermal burns from arcing faults
Pathophysiology of Electric Shock
– The minimum current a human can feel depends on the current type (AC or DC) and frequency.
– A person can sense electric current as low as 1mA for 60Hz AC and as low as 5mA for DC.
– AC current passing through the arm of a 68-kilogram human can cause powerful muscle contractions at around 10mA.
– High enough current can cause tissue damage or fibrillation, leading to cardiac arrest.
– AC currents of more than 30mA (rms, 60Hz) or DC currents of 300-500mA at high voltage can cause fibrillation.
– Skin impedance is the main contributor to the body’s impedance in the case of a macroshock.
– Dielectric breakdown of the skin occurs at voltages above 450-600V.
– Wet or broken skin can significantly lower the body’s resistance to electrical current.
– Bypassing the skin and establishing an electrical circuit through the body increases the potential lethality, especially if the circuit goes through the heart.
– The voltage-current characteristic of human skin is non-linear and depends on various factors.
– Skin impedance exhibits asymmetric and time-varying properties.
– Resistance measurements using a standard ohmmeter do not accurately represent skin impedance.
– Skin voltage-current characteristic is quasilinear for sinusoidal electrical stimulation below 10 volts.
– Skin conductance can increase by several orders of magnitude in milliseconds, but this should not be confused with dielectric breakdown.
– Macroshock occurs when current passes through intact skin and through the body.
– Current passing from arm to arm or between an arm and a foot is more dangerous as it is likely to traverse the heart.
– Microshock involves a very small current source directly connected to the heart tissue.
– Microshock is largely theoretical as modern devices used in these situations have protections against such currents.
– The lethality of an electric shock depends on current, duration, pathway, and voltage.
– High current and longer shock duration increase the likelihood of lethality.
– Current flow through vital organs, like the heart muscle, is more likely to be lethal.
– High voltage can cause dielectric breakdown at the skin, allowing increased current flow.
– Medical implants, pre-existing medical conditions, age, body mass, and health status can also affect lethality.
Dangers and Prevention of Electrical Injuries
– Alternating current is about twice as dangerous as direct current per unit of current flow or applied voltage.
– Human lethality is most common with alternating current at 100-250 volts, but death has occurred below this range.
– Shocks above 2,700 volts are often fatal, with those above 11,000 volts usually being fatal.
– Exceptional cases of survival from high-voltage shocks have been reported.
– Severity and lethality of electric shock depend on time, frequency, and duration of the current flow.
– National electrical codes emphasize the prevention of electrical injuries in buildings.
– Extra-low voltage electrical systems reduce the risk of dangerous current exposure.
– Isolated power systems are used in sensitive areas like operating rooms.
– Residual current devices and ground fault circuit interrupters provide protection from current leakage.
– Electrical devices have non-conductive insulation or conductive metal enclosures for user safety. Source: https://en.wikipedia.org/wiki/Electric_shock
An electrical injury, (electric injury) or electrical shock (electric shock) is damage sustained to the skin or internal organs on direct contact with an electric current.
| Electrical injury | |
|---|---|
| Other names | Electrical shock |
 | |
| Lightning injury caused by a nearby lightning strike. The slight branching redness (sometimes called a Lichtenberg figure) travelling up the leg was caused by the effects of current. | |
| Specialty | Emergency medicine |
| Complications | Burns, rhabdomyolysis, cardiac arrest, bone fractures |
| Frequency | >30,000 per year (USA) |
| Deaths | ~1,000 per year (USA) |
The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or only produce a light tingling sensation. However, a shock caused by low and otherwise harmless current could startle an individual and cause injury due to jerking away or falling. A strong electric shock can often cause painful muscle spasms severe enough to dislocate joints or even to break bones. The loss of muscle control is the reason that a person may be unable to release themselves from the electrical source; if this happens at a height as on a power line they can be thrown off. Larger currents can result in tissue damage and may trigger ventricular fibrillation or cardiac arrest. If death results from an electric shock the cause of death is generally referred to as electrocution.
Electric injury occurs upon contact of a body part with electricity that causes a sufficient current to pass through the person's tissues. Contact with energized wiring or devices is the most common cause. In cases of exposure to high voltages, such as on a power transmission tower, direct contact may not be necessary as the voltage may "jump" the air gap to the electrical device.
Following an electrical injury from household current, if a person has no symptoms, no underlying heart problems, and is not pregnant further testing is not required. Otherwise an electrocardiogram, blood work to check the heart, and urine testing for signs of muscle breakdown may be performed.
Management may involve resuscitation, pain medications, wound management, and heart rhythm monitoring. Electrical injuries affect more than 30,000 people a year in the United States and result in about 1,000 deaths.
