Victims of electrical injuries present either in extremis or as the seeming well patient with insidious, developing disease.
A targeted history usually gets you the information you need.
 

 
Four main things to find out:
1. Household or Industrial electricity?
Household electricity uses alternating current, or AC.  Voltages across the world range anywhere from 100 to 240 V.  Here in North America, most outlets and appliances use 120 volts, which is the measure of electrical tension, or the potential difference in electrical charge.
Cut-off between low voltage and high voltage is 1000 V.
Industrial energy may be AC or direct current, DC.  DC current propels the victim -- think of this as a blast injury.  The same voltage in AC is three times as damaging as that voltage at DC, because AC causes muscle tetany, and prolonged contact time.
2. What was the likely pathway that current took?
Did the current pass through the thorax?  -- Think dysrhythmias.  Through the head or neck?  -- Think damage to the CNS and risk for later central respiratory arrest; acoustic nerve damage; cataract formation.  Did the current pass along an extremity? -- Think compartment syndrome and rhabdomyolysis.
3. What was the contact time?
The electrical charge meets resistance and converts to thermal energy, which causes tissue necrosis, increasing with the contact time.  Was your patient extricated?  Was there tetany?  Was he found in a pool of water or liquid?  Longer contact time correlates with extensive injuries that may only be apparent hours later.
4. Are there any associated injuries?
Think of electrical injury as a trauma – major trauma rarely occurs in isolation.   Was the patient flung after contact?  Did he have a syncopal episode? -- Think precipitated dysrhythmia and fall.   Was there any chest pain?   -- Consider stress-induced ischemia.
 
Pearl: Patients may be confused initially or unable to localize symptoms because of CNS disruption.  Get collateral information, re-interview, and re-examine as needed.
 

 Case 1: Toddler with an oral commissure burn
An electrical burn to the angle of the mouth cauterizes superficial bleeding vessels, and hours later the wound becomes covered with a white layer of fibrin, surrounded by erythema.  Edema and thrombosis will continue, and at 24 hours there is typically a significant margin of tissue necrosis.  Most patients do well, and the burn heals by secondary intention.  The eschar will slough off in 1 to 2 weeks.  The labial artery is just deep to the burn, and as the eschar sloughs off, it can be exposed.  It’s a high-flow artery to the face, and if disrupted, the child may have significant bleeding and possibly hemorrhagic shock.
These children need close wound care follow-up, and potentially outpatient coordination with Head and Neck Surgery and/or Plastic Surgery consultants.
Precautionary advice:  take the moment to talk to parents about the risk, and show them how to apply pressure to the wound, pinching the inner and outer cheek together with the thumb and index finger until the child arrives to the hospital.

Case 2: School-age child with knife versus electrical outlet
A a “kissing burn” occurs when the electrical charge creates an arc and jumps to a more proximal portion of the extremity.
The kissing burn typically occurs at flexor creases such as the wrist or the antecubital fossa.  There is often extensive underlying tissue damage even under the skin where it doesn’t appear to be involved.  Compartment syndrome and subsequent rhabdomyolysis and renal failure are the highest-risk complications.

Case 3: Adolescent after a taser exposure
Nitrogen capsules propel two barbs into the dermis, which deliver short bursts of energy; most patients have no harm from the electricity delivered.
How to remove a dart:  The darts are typically 9 mm long, but the small barb is typically not buried very deep in the skin.  Hold the skin taught, use a hemostat to grasp the end as close to the skin as possible,