Electrical Injury

Amina Lalani MD, FRCPC

EPIDEMIOLOGY¹,²

Electrical injuries cause over 500 deaths per year in the United States.
Electrical burns account for 2% to 3% of burns assessed in the pediatric emergency department.
Most electrical burns in children occur at home due to:
- Electrical appliances.
- Extension cords.
- Electrical wall outlets.
Deaths are more common in school-aged children.
- More likely due to high-voltage and lightning strikes.
Minor injuries and emergency department visits are more common in younger children.
- Tend to be low-voltage injuries.

DEFINITIONS AND CLASSIFICATION²

Definitions:
- Electricity is the flow of electrons through a conductor.
- Electric current is the flow of electrons away from an object through a conductor.
- Voltage =force causing electrons to flow.
- Resistance =impedance to flow through the conductor.
Electrical injury occurs when contact is made with an electric current that can cause internal and external injuries.
Two types of electric current.
- Alternating current (AC):
  - Most common in home outlets, and more efficient than DC.
  - More dangerous than DC, as it causes tetanic muscle contractions that prolong contact with source.
- Direct current (DC):
  - Used in batteries, defibrillators, and pacemakers.
Electrical injuries can be classified as low voltage, high voltage, or lightning injuries.
- Low voltage: < 600 V
- High voltage: > 1,000 V.
- Lightning injury: > 30 × 10⁶ V.
Contact with electrical current causes injury through muscle contraction, thermal burns, blunt trauma, and depolarization of inducible tissue.
- Direct injury is due to the effect of current on tissues or conversion to thermal energy.
- Indirect injury is due to severe muscle contractions and secondary injury to other systems (e.g., myocardium and tympanic membranes).

FACTORS AFFECTING SEVERITY OF ELECTRICAL INJURY⁴

Intensity of Current

Current is proportional to voltage and inversely proportional to tissue resistance.
Ohm’s law: Voltage =Intensity of current × Resistance.
The effects of current vary depending on the amount (Table 16-1).

TABLE 16-1 Effects of Varying Current Intensity

Current (mA)	Effect
1	Tingling sensation
3-5	“Let-go” current for a child
10-20	Tetanic muscle contractions
20-50	Paralysis of respiratory muscles
50-100	Ventricular fibrillation

Duration of Contact

Resistance of Tissues

Increased resistance decreases current flow forward, and therefore results in increased heat production.
Least resistance: Nerves, blood vessels, mucous membranes, wet skin.
Highest resistance: Fat, bones, tendons.

Pathway of Current

Affects type and severity of injury.
Most dangerous: Vertical pathway along axis of body, as it involves all vital organs.
Hand-to-hand flow may involve heart, respiratory muscles, spinal cord.

Type of Current

Different injury patterns are seen with low versus high voltage.
- Low voltage (< 600 V): Mainly AC, therefore prolonged contact; causes tetanic contractions of respiratory muscles, ventricular fibrillation.
- High voltage (> 1,000 V): DC or AC; causes single muscle contraction that throws victim away from source; causes ventricular fibrillation, indirect trauma.

ASSESSMENT AND EVALUATION

At Scene

Risk to rescuer: Should not attempt to access patient until current has been cut off or victim has been removed from the source with insulated equipment.

Triage