Electrical Injury

Electrocution causes a variety of injury patterns depending on the:

• Current size
  Determined by:
  • Current source
    • AC
      Maximal risk at ~50-60Hz.
      • Low-voltage
        Typically at homes or offices.
        • May cause loss of consciousness
      • High-voltage
        Typically industrial.
        • Extensive thermal burns
        • Violent muscle contraction may cause further injury
    • DC
      
      • Violent muscle contraction may cause further injury
      • Much less likely to cause VF than AC current
    • Conducted electrical weapons
      Typically tasers, and similar devices.
      • Injuries due to consequences of the shock
        e.g. Falls.
    • Lightning strike
      Very high voltage, short duration static electrical discharge.
  • Tissue resistance
    Significant determinant of injury.
    • Wet skin has 1000 times less resistance than dry skin
    • Medical devices that breach skin (e.g. IV lines) significantly ↑ susceptibility
    • Classified into two types based on ability to induce VF:
      • Microshock
        Induce VF when applied directly to myocardium; typically ~1ma.
      • Macroshock
        Induce VF on surface contact; typically ~100mA.
• Current duration
  Function of current source.

Let-go Current Threshold: mA vs. Frequency

Causes of microshock include:

• Pacing wires
• Pulmonary artery catheters
• Central lines
• Arterial lines
• IV lines
• Static shock from staff

Epidemiology and Risk Factors

Risks:

• Majority occur in:
  • Workplace
    60%.
  • Home
    50%.
    • Children <6 at highest risk
• Powerlines
• Electrified railway tracks

Pathophysiology

Aetiology

Effects of Electrocution by Source

Current (A)	Source	Effects
10-100μA	Earth leakage current	Microshock (VF)
300-400μA	Equipment fault	Tingling
>1mA	Equipment fault	Pain
>10mA	Equipment fault	Tetany
>100mA	Equipment fault	Macroshock (VF)
>1A	Equipment fault	Burns
>5A	Equipment fault	Sustained asystole
>1000A	High-tension powerline	Severe burns Amputation
>12,000A	Lightning	Coma Burns Amputation

Leakage currents are low-amperage currents that flow to earth due to imperfect insulation or coupling between electrical and magnetic fields around an AC source.

They are generally harmless, but have capacity to cause microshock.

Clinical Features

Injuries can occur due to:

• Depolarisation of muscle cells
  
  • Cardiac
    • VF
    • Asystole
  • Skeletal muscle
    • Violent movement
    • Tetanic contraction
      • Prevents letting go
      • May prevent respiration due to tetanic diaphragmatic or intercostal contraction
• Vascular injury
  • Thrombosis
    ↑ Risk of small vessel injury.
• Neurological injury
  Due to:
  • Cardiorespiratory arrest
  • Direct injury
    Current passing through brain.
  • Secondary trauma
• Burns
  May be extensive and include:
  • External electrical burns from arcs
  • Internal burns due to tissue heating
  • Thermal burns from heated jewelery or flammable clothes
  • Flash burns

Defibrillators rely on asystole occurring at sustained currents >5A.

Electrical Burn

Lichtenberg Figure

Transient phenomenon, pathognomic of a high-voltage electrical injury (classically lightning strike) that occurs due to capillary rupture and T-cell activation.

Diagnostic Approach and DDx

Investigations

Investigations are tailed towards detecting consequences of injury.

Bedside:

• ECG
  • Myocardial injury

Laboratory:

• Blood
  • FBE
  • UEC
    • AKI
  • Coag
  • CK
  • Troponin

Imaging:

Other:

Management

• Safety of rescuers
• CPR even if initial prognosis poor
• Protect spine

Resuscitation:

Specific therapy:

• Pharmacological
• Procedural
• Physical

Supportive care:

Disposition:

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

• C
  • Myocardial injury
  • Global LV dysfunction
  • Myocardial infarction
• D
  • Cataracts
• F
  • Rhabdomyolysis
  • AKI
    • Myoglobinuria

Prognosis

Key Studies

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References

1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.
2. Lindford A, Juteau S, Jaks V, Klaas M, Lagus H, Vuola J, et al. Case Report: Unravelling the Mysterious Lichtenberg Figure Skin Response in a Patient With a High-Voltage Electrical Injury. Frontiers in Medicine [Internet]. 2021 [cited 2023 Sep 27];8.