24364309 electrical injuries

7/28/2019 24364309 Electrical Injuries

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Stanford University Medical Center

22 April 2013

Electrical Injuries

Stephen Hunt


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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


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Physics Review

I = V/R (Ohms 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 oncurrent 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 thickskin (>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 moreheat, 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 lowerthermal 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 musclespasm 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 causingblast injuries

Even at low V, tetanic muscle contraction can resultin bone fx

Cord injury can result from severe musclecontraction, 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 vascularcoagulation 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 internalinjury & vice-versa

Muscle Necrosis 2o/2 severe contraction or thermal injury

Compartment syndrome 2o/2 edema from deepinjury & 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 Curlers 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 & spineoften warranted

Thorough serial neurological exams, as vesselcoagulation 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 requirelimb 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 (Curlingsulcers) can develop

Ileus uncommon, but should prompt evaluation forother injury

Serial evaluation of liver, pancreatic, & renal functionfor traumatic/anoxic/ischemic injury

Judicious management of fluid and electrolytes toavoid 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 withmultisystem 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 Fundamentalsof 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-ThreateningElectrical Injuries.Ann Intern Med 145:531-537.

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