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Electrocution

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Electrocution

Pathophysiology

Clinical features

Microshock

High tension and lightning injuries

Investigations

Management

Late complications

Pregnancy

Further reading

Pathophysiology

Extent of injury depends on:

  • amount of current that passes through the body
  • duration of current
  • tissues traversed by the current
  • Although the extent of injury is most directly related to amount of current (amperage) often only the voltage is known. In general, low voltage causes less injury but voltages as low as 50V have caused fatalities

Clinical features

Tissue heat injury

  • currents > 1 A generate sufficient heat to cause burns to skin and internal tissues
  • blood vessels and nervous tissue particularly susceptible

Cardiac effects

  • AC of 30-200 mA may cause VF
  • currents >5 A cause asystole
  • other arrhythmias may occur
  • myocardial damage. ST and T wave changes. Global LV dysfunction may occur hours to days later, even with minimal ECG changes
  • MI has been reported. Diagnosis difficult due to raised CK levels (including CK-MB) from extensive muscle injury

Skeletal muscle

  • tetanic contractions with currents >15-20 mA. Prevent voluntary release of source of electrocution
  • may cause #s of long bones and vertebrae
  • compartment syndrome is a common manifestation of electrical injury to a limb

Vascular injuries

  • thrombosis and occlusion with resultant ischaemia and necrosis
  • affected limbs may require amputation

Neurological injuries

  • can be central or peripheral, and immediate or late in onset.
  • spinal cord damage resulting in para- or quadriplegia can result from a current traversing both arms
  • acute symptoms tend to resolve in comparison to the more ominous delayed onset symptomatology
  • monoparesis may occur in affected limbs (median nerve is very susceptible), then ulnar, radial and peroneal.
  • electrocution to the head can result in LOC, paralysis of the respiratory centre and late complications such as epilepsy, encephalopathy, and Parkinsonism.
  • autonomic dysfunction can also occur, causing acute vasospasm or a late sympathetic dystrophy.

Others

  • acute renal failure due to rhabdomyolysis
  • ruptured ear drum (high-voltage)
  • cataracts may develop later
  • associated injuries. Result of victim being thrown or falling or clothing catching fire

Microshock

  • above refers to macroshock, when current flowing through the intact skin and body passes through the heart.
  • microshock occurs when there is a direct current path to the heart muscle
  • pathway may include: a PA catheter, transvenous pacemaker wires
  • current required to produce pathological effects is in the order of 60mA.
  • can result from direct contact with faulty electrical equipment, or stray currents

High tension and lightning injuries

  • tissue damage usually due to generation of heat
  • loss of consciousness usual in initial phase
  • many survive and survival has been reported despite initial poor prognostic signs (eg fixed dilated pupils)
  • immediate death is usually due to cardiac arrest (asystole>VF)

Image

Investigations

  • ECG, echo
  • CT, EEG, nerve conduction studies
  • X-rays of spine and long bones
  • Hb, electrolytes
  • CK and urine myoglobin
  • arteriograms may help in decisions to amputate limbs

Management

  • treat burns (complete excision required) with fasciotomies ± amputation
  • consider the possibility of traumatic injuries
  • ± prophylactic treatment to prevent rhabdomyolysis induced renal failure
  • large volumes of IV fluid often required
  • supportive

Late complications

  • muscle fibrosis
  • peripheral neuropathies
  • loss of tissue from debridement
  • joint stiffness
  • reflex sympathetic dystrophy
  • cataracts
  • paraplegia
  • quadriplegia
  • subtle mental changes

Pregnancy

  • electrical pathway if often from hands to feet and therefore passes through the uterus
  • high prevalence of fetal death. Other fetal complications include oligohydramnios and intrauterine growth retardation
  • management includes cardiotocography, ultrasound and obstetric consultation

Further reading

Critchley LA, Oh TE. Electrical safety and injuries. In Oh TE, Intensive Care Manual 4th ed, Butterworth Heinemann, Oxford 1997


©Charles Gomersall and Ross Calcroft September 1999

 

©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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