5. Electrical injury

1. Definition

• Electrical injury (electric shock) → local and systemic damage from electric current passing through the body
• Sources → technical (domestic, industrial) current and lightning (atmospheric electricity)
• Children → domestic sockets, cables; adults → occupational injury

2. Mechanism of injury

Factors that decide severity

• Current strength (amperage) → main determinant of damage
• Voltage:
  • Low voltage → < 1000 V (domestic 220–240 V)
  • High voltage → > 1000 V
• Type of current:
  • Alternating current (AC) → more dangerous at 50–60 Hz; tetanic muscle contraction prevents release (no let-go)
  • Direct current (DC) → single muscle spasm, often throws the victim away
• Tissue resistance → highest in bone, then fat, tendon, skin; lowest in nerve, blood, muscle
• Skin resistance → falls sharply when skin is wet
• Path of current:
  • Hand to hand, hand to foot → crosses the heart, most dangerous
  • Head → brain, respiratory centre
• Duration of contact

Current thresholds (AC, 50–60 Hz)

• 1 mA → perception
• 10–20 mA → tetany, cannot let go
• 50–100 mA → ventricular fibrillation
• > 2 A → asystole, burns

3. Pathophysiology

• Thermal effect → heat by Joule's law (Q = I² × R × t); deep burns along the current path
• Electrolytic effect → ion shifts, cell membrane damage (electroporation)
• Mechanical effect → violent muscle contraction, falls, fractures, dislocations
• Biological effect → disturbed excitable tissue: heart, nerves, muscle
• Iceberg effect → small skin wounds over extensive deep muscle necrosis
• Deep tissue near bone heats most → periosseous muscle necrosis

4. Local changes

• Current marks (electric marks) → entry and exit wounds
  • Round, grey-white or yellow, firm, depressed centre, raised edge
  • Painless, no surrounding inflammation
• Contact burns, arc burns (up to 4000 °C), flame burns from burning clothes
• Deep muscle necrosis → oedema, compartment syndrome
• Vessel thrombosis → delayed limb gangrene
• Lightning → Lichtenberg figures (fern-like skin marks, not burns), tympanic membrane rupture

5. Systemic changes

• Heart:
  • Ventricular fibrillation → low-voltage AC
  • Asystole → high-voltage current, lightning
  • Arrhythmias, myocardial injury
• Respiration → respiratory arrest (brainstem or muscle tetany)
• Nervous system → loss of consciousness, seizures, peripheral nerve damage, spinal cord injury, keraunoparalysis (transient limb paralysis after lightning)
• Muscle → rhabdomyolysis, myoglobinuria, hyperkalaemia
• Kidney → myoglobinuric acute kidney injury
• Skeleton → fractures, posterior shoulder dislocation
• Late → cataracts, neuropathy, psychological symptoms

6. Clinical picture

• Mild → fright, pain, brief loss of consciousness, palpitations
• Moderate → loss of consciousness, arrhythmias, burns
• Severe → apparent death (clinical death): no pulse, no breathing
• Lightning victims in apparent death → resuscitate first, even with several victims (reverse triage)

7. Diagnosis

Laboratory

• Creatine kinase (CK) → marker of muscle damage
• Urine myoglobin → red-brown urine
• Urea, creatinine, potassium
• Troponin, arterial blood gas

Imaging and monitoring

• Electrocardiogram (ECG) in every patient
• Cardiac monitoring 24 h → high voltage, loss of consciousness, abnormal ECG, current across the chest
• X-ray → fractures, dislocations
• Compartment pressure measurement

8. Treatment

First aid

• Switch off the current before touching the victim; use a dry non-conducting object
• High-voltage lines → wait for the power company; keep 10 m away
• Cardiopulmonary resuscitation (CPR); defibrillate ventricular fibrillation
• Prolonged CPR → good outcomes possible
• Spinal immobilisation if a fall or throw occurred

General treatment

• Intravenous fluids:
  • Burn formula underestimates needs → start at 4 mL × kg × % TBSA (total body surface area)
  • Myoglobinuria → target urine output 1–1.5 mL/kg/h until urine clears
• Correct hyperkalaemia and acidosis
• Analgesia, tetanus prophylaxis
• Low-voltage injury, normal ECG, no symptoms → discharge

Surgical treatment

• Fasciotomy → compartment syndrome
• Early debridement of necrotic muscle, repeated every 48–72 h (second look)
• Escharotomy for circumferential burns
• Skin grafts and flaps for cover
• Amputation → non-viable limb

9. Complications

• Cardiac arrest, arrhythmias
• Acute kidney injury
• Sepsis from necrotic muscle
• Secondary haemorrhage from damaged vessels
• Limb loss
• Cataracts → months later