Which type of electrocution, Alternating Current (AC) or Direct Current (DC), is more dangerous?

Alternating Current (AC) Electrocution Is More Dangerous Than Direct Current (DC)

Alternating current (AC) is more dangerous than direct current (DC) in most electrocution scenarios due to its ability to cause tetanic muscle contractions and increased likelihood of inducing ventricular fibrillation. 1

Mechanisms of Injury in AC vs DC Electrocution

Alternating Current (AC) Dangers

• AC causes tetanic skeletal muscle contractions that can "lock" victims to the electrical source, leading to prolonged exposure and more severe injury 1
• The frequency of AC increases the likelihood of current flowing through the heart during the relative refractory period (the "vulnerable period" of the cardiac cycle), which can precipitate ventricular fibrillation 1
• This mechanism is analogous to the R-on-T phenomenon that occurs in nonsynchronized cardioversion 1
• AC is the type of current commonly present in most North American households and commercial settings, making it a more frequent cause of electrocution 1

Direct Current (DC) Characteristics

• DC electrocution is exceedingly rare, especially in workplace accidents 2
• DC typically requires much higher voltage to cause significant injury and death, and is therefore generally considered safer than AC 2
• Lightning strikes, which are a form of DC, act as an instantaneous, massive direct-current shock that simultaneously depolarizes the entire myocardium 1
• A common misconception is that DC shocks cause asystole instead of ventricular fibrillation, but this is considered a false dogma except in cases of lightning strikes, which can cause substantial neural effects leading to other cardiac arrest rhythms 3

Clinical Consequences of Electrocution

Cardiac Effects

• Cardiopulmonary arrest is the primary cause of immediate death from electrocution 1, 4
• Cardiac arrhythmias including ventricular fibrillation, ventricular asystole, and ventricular tachycardia may result from exposure to both low and high-voltage current 1, 4
• The human heart is exquisitely sensitive to alternating currents, and ventricular fibrillation can be induced with currents of one-eighth that required for mere pacing 3

Other Systemic Effects

• Electrical injuries can vary widely in severity, from an unpleasant tingling sensation to thermal burns, cardiopulmonary arrest, and death 1
• Thermal burns may result from burning clothing or from electric current traversing a portion of the body 1
• Respiratory arrest may result from electric injury to the respiratory center in the brain or from tetanic contractions or paralysis of respiratory muscles 1
• Lightning can produce a wide spectrum of peripheral and central neurological injuries including brain hemorrhages, edema, and small-vessel and neuronal injury 1

Management Considerations

Safety First

• Do not approach an electrocution victim while the power is still on 1
• Turn off the power at its source; at home the switch is usually near the fuse box 1
• For high-voltage electrocutions caused by fallen power lines, immediately notify the appropriate authorities 1
• All materials conduct electricity if the voltage is high enough, so do not enter the area around the victim until the power has been turned off by knowledgeable personnel 1

Medical Management

• Once the power is off, assess the victim, who may need CPR, defibrillation, and treatment for shock and thermal burns 1, 4
• Early intubation should be considered for patients with evidence of extensive burns, particularly those involving the face, mouth, or anterior neck 4
• Rapid IV fluid administration is indicated for victims with significant tissue destruction to counteract shock and facilitate excretion of myoglobin, potassium, and other byproducts of tissue destruction 1, 4
• All victims of electric shock require medical assessment because the extent of injury may not be apparent 1

Important Considerations and Pitfalls

• The extent of electrical injury often does not correlate with visible skin damage, leading to potential underestimation of severity 4
• No electrical burn marks may be present in some fatal cases (5.4% in one study) 5
• Deaths from electrocution are more common in summer months 5
• Most electrocution deaths are work-related and preventable through proper education and safety measures 5
• When multiple victims are struck simultaneously by lightning, rescuers should give the highest priority to patients in respiratory or cardiac arrest 1