electrical injuries emedicine

8/12/2019 Electrical Injuries Emedicine

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Electrical injuries, although relatively uncommon, are inevitably encountered by most emergencyphysicians. Adult electrical injuries usually occur in occupational settings, whereas children areprimarily injured in the household setting. The spectrum of electrical injury is broad, ranging fromminimal injury to severe multiorgan involvement to death.

Electrical injuries are shown in the images below.

Grounded sites of low-voltage injury on the feet.

Electrical burns to the hand.

Approximately !!! deaths per year are due to electrical injuries in the "nited #tates, with amortality rate of $-%&.'( )lassifications of electrical injuries generally focus on the power source*lightning or electrical+, voltage *high or low voltage+, and type of current *alternating or direct+,each of which is associated with certain injury patterns.

This article reviews the pathophysiology, diagnosis, and treatment of electrical injuries caused bymanufactured electricity for further information on lightning injuries, please see ightning njuries.

Pathophysiology

Electricity is generated by the flow of electrons across a potential gradient from high to lowconcentration through a conductive material. The voltage */+ represents the magnitude of thispotential difference and is usually determined by the electrical source. The type and extent of anelectrical injury is determined by voltage, current strength, resistance to flow, the duration ofcontact with the source, the pathway of flow, and the type of current *ie, direct or alternating+.

Voltage

Electrical injuries are typically divided into high-voltage and low-voltage injuries, using %!!/ or!!!/ as the cutoff. 0igh morbidity and mortality has been described in 1!!/ direct current injuryassociated with railroad 2third rail2 contact.'3( n the "nited #tates and )anada, typical householdelectricity provides !/ for general use and 34!/ for high-powered appliances, while industrialelectrical and high-tension power lines can have more than !!,!!!/. '$( /oltage is directlyproportional to current and indirectly proportional to resistance, as expressed by 5hm6s aw7

/ 8 9 : where 8 current, / 8 voltage, : 8 resistance.

Current
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The volume of electrons flowing across the potential gradient is the current, which is measured inamperes *+. t is a measure of the amount of energy that flows through a body. Energy isperceptible to the touch at a current as low as mA. A narrow range exists between perceptiblecurrent and the 2let go2 current7 the maximum current at which a person can grasp and thenrelease the current before muscle tetany ma;es it impossible to let go. The 2let go2 current for theaverage child is $-% mA this is well below the %-$! A of common household circuit brea;ers.


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A histologic picture of an electrical burn is shown below.

A histologic picture of an electrical burn showing elongated py;notic;eratinocyte nuclei with vertical streaming and homogeniation of the dermal collagen *4!9+. )ourtesy of Eliabeth#atter, D@.

@irect contact7 )urrent passing directly through the body will heat the tissue causing

electrothermal burns, both to the surface of the s;in as well as deeper tissues, depending ontheir resistance. t will typically cause damage at the source contact point and the ground

contact point. )ontact burns are shown in the image below.)ontact electrical burns, 3!-/ alternating current nominal. The right ;nee was the energied side, and the leftwas ground. These are contact burns and are difficult to distinguish from thermal burns. Fote entrance and exitare not viable concepts in alternating current.

Electrical arcs7 )urrent spar;s are formed between objects of different electric potential

that are not in direct contact with each other, most often a highly charged source and a ground.The temperature of an electrical arc can reach 3%!!-%!!!o), resulting in deep thermal burns

where it contacts the s;in. These are high-voltage injuries that may cause both thermal andflame burns in addition to injury from direct current along the arc pathway.

oth electrothermal and

arcing currents can ignite clothing.


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Dorbidity and mortality are largely affected by the particular type of electrical contact involved ineach exposure. 5verall mortality is estimated to be $-%&.', I(urns are often ultimately much worse than they initially appearin the E@.

Race

Fo racial susceptibility to electrical burns exists. 5ccupational trends show more )aucasiantradespeople in high-ris; occupations, and therefore )aucasians are more li;ely than other racesin the "nited #tates to experience occupation-related electrical injuries.

Se!

:ates of childhood electrical injury are higher among boys than girls '1( rates of adult injury aresignificantly higher in men than in women, li;ely because of occupational predisposition. Dostseries show more than I!& of electrical injuries occur in men.'I, !, , 3(

"ge

A bimodal distribution of electrical injuries exists among the very young *children J 1 y+ andamong young and wor;ing-aged adults.'$( atterns of electrical injury vary by age *eg, low-voltagehousehold exposures among toddlers and high-voltage exposures among ris;-ta;ing adolescentsand via occupational exposure+. '4, $(

#istoryElectrical injuries can present with a variety of problems, including cardiac or respiratory arrest,coma, blunt trauma, and severe burns of several types. t is important to establish the type ofexposure *high or low voltage+, duration of contact, and concurrent trauma.

$o%&'oltage "C in(ury %ithout loss of consciousness andor arrest

These injuries are J !!!/ exposures usually in the home or office setting. Typically, childrenwith electrical injuries present after biting or chewing on an electrical cord and suffer oral burns.

Adults wor;ing on home appliances or electrical circuits can also experience these electricalinjuries. ow-voltage A) may result in significant injury if there is prolonged, tetanic musclecontraction.

$o%&'oltage "C in(ury %ith loss of consciousness andor arrest

n respiratory arrest or ventricular fibrillation that is not witnessed, an electrical exposure may bedifficult to diagnose. All unwitnessed arrests should include this possibility in the differentialdiagnosis. Kuery ED# personnel, family, and cowor;ers about this possibility. nBuire if a screamwas heard before the patientLs collapse this may be due to involuntary contraction of chest wallmuscles from electrical current.

#igh&'oltage "C in(ury %ithout loss of consciousness andor arrest


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"sually high-voltage injuries do not cause loss of consciousness but instead cause devastatingthermal burns. n occupational exposures, details of voltage can be obtained from the local powercompany.

#igh&'oltage "C in(ury %ith loss of consciousness andor arrest

This is an unusual presentation of high-voltage A) injuries, which do not often cause loss of

consciousness. 0istory may need to come from bystanders or ED# personnel.

)irect current *)C+ in(ury

These injuries typically cause a single muscle contraction that throws the victim away from thesource. They are rarely associated with loss of consciousness unless there is severe headtrauma, and victims can often provide their own history.

Conducted electrical de'ices

)onducted electrical weapons *)Es+ such as tasers are weapons used by law enforcement thatdeliver high-voltage current that is neither true A) or @) but is most li;e a series of low-amplitude@) shoc;s.'%( They can deliver %!,!!! / in a %-second pulse, with an average current of 3. mA.'1( Though they have been temporally associated with deaths in the law enforcement setting,conducted electrical devices *)E@s+ in healthy volunteers have been shown to be safe withoutevidence of delayed arrhythmia or cardiac damage as measured by troponin . 'H, 1(

5ne study of their use in 3! law enforcement incidents showed mostly superficial puncturewounds from the device probes, and significant injuries only from trauma subseBuent to shoc;,not from the device itself. 5f 3 deaths in custody, neither was related to )E exposure. 'I(

5verall significant injuries from )E exposure are rare, and usually occur due to trauma or inconjunction with intoxication.'=, 3!(

Physical

Electrical injuries can cause multiorgan dysfunction and a variety of burns and traumatic injuries.A thorough physical examination is reBuired to assess the full extent of injuries. 5ccupationalinjuries have a high li;elihood of future litigation, and physical examination findings should be

documented with photographs if possible, with the proper releases, and filed in the patient6smedical record.

5verall, low-voltage exposure tends to cause less overall morbidity than high-voltage, but it isimportant to ensure by accurate history that a seemingly low-voltage burn was not in fact from ahigh-voltage source *li;e a microwave, computer, or T/ monitorMany device that 2steps-up2voltage via a transformer+. ow-voltage burns can still cause cardiac arrhythmias, seiures, andlong-term complications if contact is near the chest or head.

Cardio'ascular

atients may present in asystole orventricular fibrillation*/


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Respiratory

)hest wall muscle paralysis from tetanic contraction may cause respiratory arrest if the currentpathway is over the thorax. njury to the respiratory control center of the brain can also causerespiratory arrest. The lungs are a poor conductor of electricity and generally are not assusceptible to direct injury from current as tissues with lower resistance.

S,in

A variety of burns and thermal injuries from electricity affect the s;in and soft tissues. These areoften the most severe seBuelae of electrical burns after cardiac arrhythmias and may initiallyappear minor despite significant deep tissue injury subseBuently reBuiring fasciotomy oramputation. >urns are often most severe at the source and ground contact points the source isusually the hands or the head while the ground is often in the feet. The strength and duration ofcontact with the source largely influence the severity and extent of tissue damage. All burnsshould be carefully documented and, if possible, photographed.

High-voltage electrothermal burns

Typically, these show a contact point where the person touched the circuit and a ground point.These may produce significant damage to underlying tissue while largely sparing the surface of

the s;in. These burns may appear as painless, depressed areas with central necrosis andminimal bleeding. The presence of surface burns does not accurately predict the extent ofpossible internal injuries, as s;in with high resistance will transmit energy to deeper tissues withlower resistance. A high-voltage burn is shown below.

0igh-voltage electrical burns to the chest.

Arc burns

hen an arc of current passes from an object of high to low resistance, it creates a hightemperature pathway that causes s;in lesions at the site of contact with the source and at theground contact point *not always the feet+. These areas typically have a dry parchment centerand a rim of congestion around them. There will be clues to the internal pathway ta;en by the arcbased on the location of these surface wounds. Arcs can also cause electrothermal, flash, andflame burns, so multiple burns of varying appearance may be observed. Arcs do not occur in low-voltage injuries. An arc burn is shown below.
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Arcing electrical burns through the shoe around the rubber sole. 0igh-voltage*H1!! /+ alternating current nominal. Fote cratering.

Flash burns


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Energied site of low-voltage electrical burn in a %!-year-old electrician.

Grounded sites of a low-voltage injury in a $$-year-old male suicidepatient.

Contact burns

)ontact burns usually have a pattern from the contacted item *branding+ and may appear similarto flash burns. A contact burn is shown below.

)ontact electrical burn. This was the ground of a 3!-/ alternating currentnominal circuit. Fote vesicle with surrounding erythema. Fote thermal and contact electrical burns cannot bedistinguished easily.

Pediatric oral burns

These are most commonly encountered in children younger than 1 years who bite or suc; on ahousehold electrical cord. A local arc of current crosses from one side of the mouth to the other.The orbicularis oris muscle may be involved, and cosmetic deformity of the lips may occur if theburn crosses the commissure. #ignificant edema may be noted and within 3-$ days escharformation. ife-threatening bleeding can occur at 3-$ wee;s post injury if the labial artery isexposed when the eschar falls off. nitial presentations may underestimate the extent of theultimate injury patients reBuire aggressive airway management.'=(These patients should bereferred for early follow-up to a burn specialist, plastic surgeon, and an oral surgeon.

-eurologic

Dost acute )F# or spinal deficits resulting from electrical injuries are due to secondary blunttrauma or burns. 5ften, the patient has transient confusion, amnesia, and impaired recall ofevents if not fran; loss of consciousness. @irect effects of electrical current are most severe if therespiratory control center of the brainstem is affected resulting in respiratory arrest. )urrent mayalso cause seiure or direct spinal cord injury if there is hand-to-hand flow. #pinal cord injury canalso result from direct current effects or blunt trauma. "nless a patient is completely lucid with fullrecollection of the events, initial )-spine immobiliation is indicated.
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)urrents cause acute muscle tetany at relatively low currents and freBuencies, li;e those found inmost households. Duscle tetany causes victims to grasp the source, prolonging contact time, andcan also paralye respiratory muscles resulting in asphyxiation.

ong-term neurologic complications include seiures, peripheral nerve damage, delayed spinalcord syndromes, and psychiatric problems from depression to aggressive behavior.

Musculos,eletal

Acute injuries include fractures from blunt trauma and compartment syndrome from burns. Thechest and extremities should be examined for circumferential burns. alpate the extremity andperform distal neurologic, vascular, and motor examination to determine if there is suspicion ofacompartment syndrome.f this is the case, compartment pressure can be measured and earlyfasciotomy may help prevent subseBuent amputation. '( f available, early surgical consultationshould be obtained for a patient with concerns for compartment syndrome. Dassive muscledamage can cause severe rhabdomyolysisand subseBuent renal failure.

E-Thead

The head is a common point of entry for high-voltage injuries. atients may have perforatedtympanic membranes, facial burns, and cervical spine injury. Approximately 1& of victims

develop cataracts, usually months after the initial injury, with increasing freBuency the closercontact is to the head.'34, !(

Causes

Electrical injury occurs when a person becomes part of an electrical circuit or is affected by thethermal effects of a nearby electrical arc. njuries are caused by high-voltage A), low-voltage A),or @).

#igh&'oltage "C

0igh-voltage injuries most commonly occur from a conductive object touching an overhead high-voltage power line. n the "nited #tates, most electric power is distributed and transmitted bybare aluminum or copper conductors, which are insulated by air. f the air is breached by aconductor, *eg, an aluminum pole, antenna, sailboat mast, crane+, any person touching theconductor can be injured. 5ccupational injuries may include direct contact with electricalswitching eBuipment and energied components.

$o%&'oltage "C

Generally, 3 types of low-voltage injury occur7 children biting into electrical cords producing lip,face, and tongue injuries, or the adult who becomes grounded while touching an appliance orother object that is energied. The latter type of injury is decreasing with the increasing use ofground fault circuit interrupters *G


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Electrolytes ? #odium, potassium, chloride, carbon dioxide, blood urea nitrogen, glucose

)reatinine ? 0igh ris; of rhabdomyolysisCmyoglobinuria in electrical injuries *Dortality in

one study was %=& for patients with acute renal failure. '3%( +

"rinalysis ? #pecific gravity, p0, hematuria, and urine myoglobin if urinalysis is positive

for hemoglobin

#erum myoglobin ? f urine is positive for myoglobin, a serum level should be obtained.

Arterial blood gas ? To be obtained for patients needing ventilatory support, or those withsevere rhabdomyolysis who reBuire urine al;aliniation therapy

)reatine ;inase *)N+ levels

o This level may be extremely elevated in patients with massive muscle damage

from high-voltage injuries. Formal )N values published by the laboratory may be low fortypical construction and electrical wor;ers whose vocation involves heavy exercise. #omeevidence suggests that initial )N levels may help predict which patients could benefit fromearly fasciotomy to prevent subseBuent amputations.'(

o )N-D> subfractions are also often elevated in electrical injuries, but their

significance in the setting of electrical injuries is not ;nown.'$( )N-D> fractions and troponinshould be chec;ed if the current pathway involved the chestCthorax, if the patient has anysigns of ischemia or arrhythmia on E)G, or if the patient has specific complaints of chest pain.

o 5ne retrospective review created a decision rule for clinical identification of

patients li;ely to have rhabdomyolysis.'31( Dultivariate modeling revealed that high-voltageexposure, prehospital cardiac arrest, full-thic;ness burns, and compartment syndrome wereassociated with myoglobinuria. @efining 2positive2 as O3 of these findings has a sensitivity of=1& and negative predictive value of ==&.

.maging Studies

)hoice of imaging studies is dictated by the presence of blunt trauma, altered mental status,cardiac or respiratory arrest, and type of electrical exposure. #tudies to be considered are asfollows7

)hest radiography - Any patient with cardiac or respiratory arrest, shortness of breath,

chest pain, hypoxia, ): at the scene, or fallCblunt trauma

0ead computed tomography - Any patient with altered mental status, significant traumatic

mechanism, seiure, loss of consciousness, or focal neurologic deficits )ervicalCspine imaging - atients with loss of consciousness or significant trauma should

be cervical spine immobilied and imaged accordingly. Formal mental status without significantinjuries may be clinically cleared, whereas others may reBuire plain radiography. atients withfocal neurologic deficits or evidence of spinal cord injury should undergo full spinal imaging.

)TCultrasonography - @epending on the amount of trauma sustained and the pathway of

the current exposure, patients may reBuire further imaging to evaluate for internal injuries.maging modality varies depending on suspected injury and availability.

/ther Tests

EC0cardiac monitoring

All adult patients should have an initial E)G and cardiac monitoring in the E@. The duration ofmonitoring depends on the circumstances of the exposure any patients with chest pain,

arrhythmia, abnormal initial E)G, cardiac arrest, loss of consciousness, transthoracic conduction,or history of cardiac disease should undergo monitoring. Fo definitive guideline is available onduration of monitoring for adults, but patients are unli;ely to develop significant arrhythmias after34-4I hours if they have no other significant injuries. #everal large reviews have not identified ris;of delayed arrhythmia among patients with low-voltage exposure and no arrhythmia upon initialpresentation. 5ne such review of =1 exposures concludes that admission for cardiac monitoringis not indicated among such patients.'3H(

#everal studies have shown that low-voltage *household+ exposures in patients with no cardiaccomplaints and a normal initial E)G can be safely discharged. '3I(t is unclear how this applies to


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patients with preexisting heart disease. n the pediatric population, healthy children withhousehold current exposures *3! to 4!/, no water contact+ can be safely discharged if they areasymptomatic, without a /< or cardiac arrest in the field, and have no other injuries reBuiringadmission.'3=, 3$(

Procedures

5btain intravenous access in all adult patients with electrical injuries. )onsider central access inany patient with significant trauma, large burns, cardiac or respiratory arrest, or loss ofconsciousness.


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Consultations

atients with high-voltage electrical injuries reBuire the ongoing care of a burn specialist, whichshould be instituted as early as possible, as aggressive early intervention via fasciotomy canprevent subseBuent limb amputation.

)onsider additional consultations with traumaCcritical care, orthopedics, plastic surgery, and

general surgery, depending on the type and severity of traumatic injuries.

Medication Summary

0ydration is the ;ey to reducing the morbidity of severe burns. f there is significant muscledamage with myoglobinuria, an osmotic diuretic andCor al;aliniing agent is indicated.

Fluids

Class Summary

Extravascular pooling of fluids through damaged endothelium leads to vascular hypovolemia andhypotension. atients reBuire fluid resuscitation with normal saline or lactated ringer.

$actated Ringer

Essentially isotonic and has volume restorative properties.

/smotic diuretics

Class Summary

5smotic diuretics assist the ;idneys in excreting myoglobin if present. They can help avoid acuterenal failure in patients with significant myoglobinuria.

/iew full drug information

Mannitol */smitrol+

5smotic diuretic that is not metabolied significantly and that passes through glomerulus withoutbeing reabsorbed by the ;idney.

$oop diuretics

Class Summary

These agents decrease plasma volume and edema by causing diuresis.

/iew full drug information

Furosemide *$asi!+

roposed mechanisms for furosemide in lowering intracranial pressure include *+ loweringcerebral sodium upta;e, *3+ affecting water transport into astroglial cells by inhibiting cellularmembrane cation-chloride pump, and *$+ decreasing )#< production by inhibiting carbonicanhydrase.

@ose must be individualied to patient.

Further .npatient Care

npatient care is reBuired for patients with anything other than minor low-voltage injuries. >urnand trauma care, preferably at a specialied center, should be instituted early. Any patients withcardiac arrest, loss of consciousness, abnormal E)G, hypoxia, chest pain, dysrhythmias, andsignificant burns or traumatic injuries must be admitted.

Further /utpatient Care
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atients exposed to low-voltage electrical sources who are otherwise completely asymptomaticwith a normal physical examination can often be discharged from the emergency department.

atients with minor burns or mild symptoms can be observed for several hours and discharged iftheir symptoms resolve and they do not have elevated )NCmyoglobinuria. atients should bemade aware of possible long-term neurologic or ocular effects of electrical injuries, and havefollow-up available as needed. Any patient with significant hand burns should be referred to a

hand specialist for close follow-up.

Transfer

All patients with a history of exposure to high-voltage electricity and patients with significant burnsshould be transferred to a specialied burn center for further inpatient treatment andrehabilitation.

ediatric patients with significant oral burns should be transferred to a pediatric burn center.atients with minor oral burns and close follow-up can be discharged.

)eterrencePre'ention

revention of high-voltage electrical injuries reBuires ongoing public education about potential

haards, and targeted education to individuals in construction trades, those using cranes and lifts,or those exposed to the extreme danger of overhead power lines. 5ne study found particularlyhigh rates of electrical injuries in cable splicers, electricians, line wor;ers, and substationoperators.'$!(revention strategies and occupational safety changes should be targeted to thesehigh-ris; occupations.

revention of household exposures reBuires public education about child protection, outletcovers, and appliance safety. Appliances that produce a shoc; should not be used untilprofessionally repaired. Encourage use of G


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electrical injuries emedicine

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