Electrical injuries

Background

• Tissue damage occurs via electrical energy (becomes thermal energy once it enters the body) and mechanical injury from trauma
  • Skin, bone, tendon all have very high resistance
  • Muscle, nerves, vasculature have lower resistance, more often damaged
• The primary determinant of injury is the amount of current flowing through the body, which depends on:
  • Voltage
  • Amperage
  • Resistance
  • Type of current (DC or AC)
  • Current pathway
  • Duration of contact

Electrical Injury Types

1. Low-Voltage <1000V
2. High-Voltage >1000V - typically seen in industrial settings or transmission line injuries
   • Associated with electrical burns
3. Lightning Strike
4. Electric Arc
   • Associated with high voltage sources
   • Ionized particles with temperature 3000 °C–20,000 C
   • Can jump 2-3cm per 1000V
   • May radiate enough heat to burn persons 10ft or more away from the arc
   • Blast force may result in trauma

DC vs AC

Direct current (DC) injuries typically due to lightning while alternating current (AC) are household injuries

DC

• Direct current most often demonstrates flow-over phenomenon
• Lightening can reach 1-5 million volts, but current flows over the body and exits to the ground
• May result in little tissue damage and cardiac dysrrhythmias are still of great concern

AC

• Current arcs onto body, envelops surface of body, then arcs to lower electromotive potential (ground)
• With alternative cycle of the current there is contraction and release of muscle preventing full release from source
• Current flows through body tissues

Clinical Features

Immediate Effects

1. Cardiac dysrhythmias
2. Respiratory arrest
3. Seizures

Cardiac Dysrhythmias

1. Fatalities due to asystole or V-fib usually occur prior to arrival
   • Most common dysrrhythmia at presentation is A-fib (V-fib is more common, but patients are dead PTA)
   • Asymptomatic patients with normal ECGs do not develop later dysrhythmias after <1000V injuries

Cardiovascular Injury

1. Contraction band necrosis
2. Medial necrosis of large vessels
   • Aneurysm formation
3. Coagulation necrosis of small vessels
   • Can lead to compartment syndrome

CNS Injury

1. Occurs in 50% of patients with high-voltage injuries
2. Brain injury ranges from transient LOC to CVA to respiratory arrest
3. High voltage injuries involving head are frequently associated with coma and persistent vegetative state

Orthopedic Injury

1. Forceful muscle contractions can cause fracture and joint dislocations (especially shoulder)
   • May occur with voltages as low as 120V
2. Compartment Syndrome
   • Usually associated with high-voltage injuries
   • May occur even with 120V shocks if contact is sustained for longer than few seconds
   • Patient experiences ongoing muscle pain with movement
   • Need for fasciotomy predicted by:
     • Myoglobinuria
     • Burns >20% BSA
     • Full-thickness burn >12% BSA
3. Rhabdomyolysis
   • Associated with:
     • Contact with >1000V
     • Prehospital cardiac arrest
     • Crush injury
     • Compartment syndrome
     • Full-thickness skin burns

Ocular Injury

• Cataract formation has been described weeks to years after electrical injury
  • Document presence or absence of cataracts following all electrical injuries

Auditory Injury

• May be damaged by current or hemorrhage
• Check hearing in all patients

Cutaneous Burns

• Often seen at electrical contact areas
  • Seriously injured patients often have burns on either arm or skull + feet
• Most patients with burns from electrical injury require admission and care by burn specialist

GI Injury

• Suspect in patients with:
  • Electrical burns of abdominal wall
  • History of a fall, nearby explosion, or other mechanical trauma

Pediatric Considerations

• In general, evaluate as for the adult, looking for multi-system involvement
• Perform an ECG in all patients, regardless of voltage
• An oral commissure burn (from chewing on power cord) will create significant edema and necrosis.
  • The child may need Plastic Surgery or Head and Neck Surgery consultation to avoid microstomia.
  • 1-2 weeks after the burn, the eschar may fall off, exposing the labial artery and causing significant hemorrhage
    • Provide clear and thorough precautionary advice including first aid for bleeding (pinch buccal mucosa against outside of cheek until arrival to hospital)

Differential Diagnosis

Burns

• Burn
  • First degree
  • Second degree
  • Third degree
  • Fourth degree
• Smoke inhalation injury (airway compromise)
• Chemical injury
  • Acrolein
  • Hydrochloric acid
  • Tuolene diisocyanate
  • Nitrogen dioxide
• Systemic chemical injury
  • Carbon monoxide toxicity
  • Cyanide toxicity
• Electrical injury

Evaluation

Workup

• 12-lead ECG
• CBC
• CMP
• Lactate
• Troponin
• CK
• Urinalysis and urine myoglobin

Diagnosis

• Typically a clinical diagnosis

Management

• Usual trauma evaluation and resuscitation applies
• Use Parkland formula as starting point for fluid resuscitation
  • Fluids in first 24 hrs = TBSA burned(%) x Wt(kg) x 4ml; Give 1/2 in first 8 hours, then give other 1/2 over next 16 hrs
• Treat rhabdomyolysis and compartment syndrome in usual manner
  • If RBCs and/or myoglobin in UA, urine should be alkalinized at minimum of 2 cc/kg/hr until pigments eliminated
  • Mannitol should be given early to prevent renal tubular damage
  • High voltage injuries to the hand frequently require carpal tunnel decompression as soon as patient is stable for OR

Disposition

Discharge

• Asymptomatic patients with normal ECG on presentation after a low-voltage electrical injury

Admit

• All patients with high-voltage injuries (even if asymptomatic)
• Patients with low-voltage injury if symptomatic (e.g. LOC, severe burns, ECG changes, ↑ CK)
• Abnormal ECG or observed dysrhythmia
• Cardiac biomarkers positive
• Persistent chest pain, paresthesias, or hypoxia
• Cardiac arrest
• Documented LOC
• History of significant cardiac disease or CAD risk factors

See Also

• Lightning Injuries

External Links

• Electrical Injuries: Hertz So Bad - Pediatric Emergency Playbook

References

Authors

Ross Donaldson