Stanford University Medical CenterApril 12, 2023

Electrical Injuries

Stephen Hunt

April 12, 2023 2

Electrical Injury

• Epidemiology• Mechanisms of injury• Associated injuries• Management• Prognosis

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Epidemiology:

• Account for ~ 3% all burn-related injuries• Estimated 3,000 annual admits to burn units• ~ 1/3 fatal - about 1,000 US deaths annually• Bimodal distribution

• ~1/3 children <6 yrs (electric cords & wall outlets) • ~2/3 miners, construction, & electrical workers• Common cause occupational deaths

• Lightning responsible for ~300 injuries, 100 deaths

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Physics Review

• I = V/R (Ohm’s Law - current)• Intensity expressed in amperes (A)• DC - lightning, rails, autos, batteries• AC - most power lines, buildings

• E = IVT (Joules law - thermal energy)

• E = I2RT

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Mechanisms of Injury

• Direct effect of electrical current• Thermal burns (conversion I->E)• Mechanical Trauma• Post-trauma sequelae

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Direct effects of current• I = V/R

• In general, type & extent of injury depends on current intensity (amps)

• Type of current (DC vs AC), current pathway, and duration of current also influence severity of injury

• As current generally not known, injuries often classified into high V ( > 1,000V) vs low V

• Cardiac, neurologic and respiratory systems most susceptible to direct effects

• Skin is the resistor most effecting severity of injury• Wet skin has lower R (~1K ohm) vs. dry or thick

skin (>100K ohm), resulting in greater current flow

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Thermal (Burn) Injuries• Heat (E) = IVT = I2RT• Type & extent of injury depends on current intensity (I)• R varies significantly between tissues

• Tissues with high R (e.g., bone), generate more heat, resulting in osteonecrosis and deep tissue periosteal burns, esp surrounding long bones

• Skin also has high R, thus entry/exit wounds• Decreasing R (e.g., wet skin) results in lower thermal

injury, but higher current conductance• Coagulation of muscle, fat, vessels (i.e., the Bovie) • Duration of current exposure (T)

• DC typically shorter duration, because single muscle spasm causes victim to be thrown from the source

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Mechanical Trauma

• Trauma can result from fall or muscle contraction• Classic example is shock wave of lightning causing

blast injuries• Even at low V, tetanic muscle contraction can result

in bone fx• Cord injury can result from severe muscle

contraction, w/o any external signs of trauma• Can result in vascular compromise

• Acute hypotension should always prompt search for thoracic or intra-abdominal bleeding

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Post-trauma sequelae

• Crush injury syndrome (rhabdomyolysis, myoglobinuria)

• Multi-organ ischemic injury 2o/2 vascular coagulation or dissection

• Hypovolemic shock 2o/2 massive 3rd spacing• Iatrogenic injuries from acute resuscitation

• Abdominal compartment syndrome• ARDS

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Associated Injuries I• Respiratory System

• Suffocation 2o/2 tetanic muscle contractions• Respiratory arrest 2o/2 direct injury to RCC

• Cardiovascular System• Asystole (more likely if DC or high V)• Arrhythmias (more likely AC) (~15% pts)

• Ventricular fibrillation most common fatal arrhythmia• Myocardial necrosis (thermal effect)• Anoxic injury 2o/2 respiratory arrest

• Neurological System• Direct effects include LOC, autonomic dysfunction, amnesia,

temp paralysis (keraunoparalysis)• Cord injury 2o/2 spine fx 2o/2 muscle contractions• Peripheral motor/sensory losses (long-term sequelae)

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Associated Injuries II• Skin (~57% low V fatalities; ~96% high V fatalities)*

• Superficial, partial or full thickness thermal burns• Degree of external injury can underestimate internal

injury & vice-versa• Muscle

• Necrosis 2o/2 severe contraction or thermal injury • Compartment syndrome 2o/2 edema from deep

injury & 3rd spacing • Skeletal

• Osteonecrosis 2o/2 thermal injury• Fx 2o/2 muscle contraction or blunt trauma

*Wright, et al, J Foren Sci, 1980

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Associated Injuries III• Renal

• Pigment-induced renal failure• Hypovolemia 2o/2 3rd spacing can lead to prerenal

• GI• Injury rare, most commonly “Curler’s ulcers”

• HEENT• Cataracts can develop up to 2 years after• Hearing loss from 8th nerve injury

• Damage to any organ system 2o/2 blunt trauma• Damage to any organ system 2o/2 vascular damage

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Associated Injuries

Koumbourlis, Crit Care Med 2002

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Lichtenberg Figures

• Rare pathognomonic “flower-like” branching skin lesions in persons struck by lightning

• Caused by “flashover” effect of non-penetrating current

• Rapidly fade, not typically serious

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Management I• Standard ABCDEs of any major trauma• Pulmonary

• Low threshold for intubation, as respiratory failure common

• Cardiac • Serial monitoring if high V, abnormal ECG, LOC,

respiratory arrest, or PMH of CV dysfunction• Neuro

• C-spine and log-roll precautions; CT head & spine often warranted

• Thorough serial neurological exams, as vessel coagulation can result in late sequelae

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Management II• Musculoskeletal

• Thorough evaluation for fractures• Serial evaluations of limbs for compartment syndrome

requiring emergent decompression• Even in absence of compartment syndrome, persistent

aciduria or myoglobinuria may require limb amputation• Skin

• Early debridement and later reconstruction • Antibiotic prophylaxis (controversial)

• Renal• Fluid resuscitation key, as 3rd spacing common &

myoglobinuria 2o/2 rhabdomyolysis can cause ARF

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• GI• Ulcer prophylaxis, as gastric ulcers (Curling’s

ulcers) can develop• Ileus uncommon, but should prompt evaluation for

other injury• Serial evaluation of liver, pancreatic, & renal function

for traumatic/anoxic/ischemic injury• Judicious management of fluid and electrolytes to

avoid acidosis and compartment syndromes

Management III

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Prognosis

• Highly variable, depending on severity of both initial injury and subsequent complications

• High morbidity/mortality in patients with multisystem organ failure

• Advances in surgical interventions (early excision, fasciotomy, skin grafts, etc…) have improved

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References• DM Mozingo & BA Pruitt. 1998. Electric Injury. in Fundamentals

of Surgery, 1st ed, JE Niederhuber, pp 194-195. • DS Pinto & PF Clardy. 2007. Environmental electric injuries. Up-

to-Date, accessed 06/01/2007.• TN Pham & NS Gibran. 2007. Thermal & Electrical Injuries. Surg

Clin N Am 87:185-206.• AC Koumbourlis. 2002. Electrical Injuries. Crit Care Med

30:S424-S430.• C Spies & RG Trohman. 2006. Electrocution & Life-Threatening

Electrical Injuries. Ann Intern Med 145:531-537.