Electrical Injuries

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Electrical Injuries

• Robert Primavesi, MDCM, CCFP(EM)
• Montreal General Hospital
• McGill University Health Centre

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Electrical Injuries Goals

• To identify the important complications of
  electrical injuries.
• To expose the pitfalls in diagnosis.
• To explore the controversies in management.

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Electrical InjuriesObjectives

• Define the population at risk.
• Determine the factors predicting the severity of
  injury.
• Differentiate between high-voltage and
  low-voltage injuries.
• Recognize which patients require admission or
  referral.
• Decide which patients need cardiac monitoring.

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Top 10 Myths of Electrical Injury

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Top 10 Myths of Electrical InjuryMyth 1

• Electrical Injuries Are Uncommon

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Electrical InjuriesEpidemiology

• 124 deaths in Quebec 1987-1992
• 5X additional patients requiring emergency
  treatment
• 3-5 of all burn centre admissions
• Bimodal distribution
• Toddlers
• Workforce

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Top 10 Myths of Electrical InjuryMyth 2

• Voltage Is the Most Important Determinant of
  Injury

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Electrical InjuriesFactors Determining Severity

• 1. V voltage
• 2. i current
• 3. R resistance

OHMS LAW i V / R
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Electrical InjuriesFactors Determining Severity
JOULES LAW Power (watts) Energy
(Joules) time V x i i2 x R
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Electrical Injuries Factors Determining Severity

• Mucous membranes
• Vascular areas
• volar arm, inner thigh
• Wet skin
• Sweat
• Bathtub
• Other skin
• Sole of foot
• Heavily calloused palm

• Skin Resistivity - Ohms/cm2
• 100
• 300 - 10 000
• 1 200 - 1 500
• 2 500
• 10 000 - 40 000
• 100 000 - 200 000
• 1 000 000 - 2 000 000

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Top 10 Myths of Electrical InjuryMyth 3

• High Voltage Is More Likely to Kill Than Low
  Voltage

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Electrical InjuryFactors Determining Severity

• A momentary dose of high voltage electricity is
  not necessarily fatal.
• Low voltage is just as likely to kill as high
  voltage.

RK Wright, JH Davis. The investigation of
electrical deaths a report of 220 fatalities. J.
Forensic Sci. 1980 25514-521. Cunningham PA.
The need for cardiac monitoring after electrical
injury. Medical Journal of Australia. 154(11)
765-6, June 1991.
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Top 10 Myths of Electrical InjuryMyth 4

• The Extent of the Surface Burn Determines the
  Severity of Injury

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Electrical InjuriesPatterns of Injury

• Direct contact
• Direct tissue heating
• Contact burns (entry and exit)
• Thermal burns

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Top 10 Myths of Electrical InjuryMyth 5

• The Pathway the Electrical Current Takes Through
  the Victim Predicts the Pattern of Injuries

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Electrical InjuriesPatterns of Injury

• Skin Resistivity
• Least Nerves
• Blood
• Mucous membranes
• Muscle
• Intermediate Dry skin
• Tendon
• Fat
• Most Bone

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Electrical InjuriesEffects of 60 Hz Current

• 1 mAmp Threshold of perception
• 5 mA Maximum harmless current
• 6 mA Ground fault interrupter opens
• 10 mA Let-go current
• 20 mA Possible tetany of resp muscles
• 100 mA VF threshold
• 6 A Defibrillation
• 20 A Household circuit breaker opens

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Top 10 Myths of Electrical InjuryMyth 6

• Electricity Kills by Causing Myocardial Damage
• CK and/or Troponin Are Good Markers for
  Myocardial Damage in Electrical Injury

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Electrical InjuriesPatterns of Injury

• James T., Riddick L., Embry J. Cardiac
  abnormalities demonstrated post-mortem in four
  cases of accidental electrocution and their
  potential significance relative to non-fatal
  electrical injuries of the heart. American Heart
  Journal. 120 143-57, 1990
• Robinson N., Chamberlain D. Electrical injury to
  the heart may cause long-term damage to
  conducting tissue a hypothesis and review of the
  literature. Int J Cardiol. 53 273-7, 1996

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Top 10 Myths of Electrical InjuryMyth 7

• All Patients With Electrical Injury Require 24
  Hours of Cardiac Monitoring

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Electrical InjuriesCardiac Monitoring

• Alexander L. Electrical injuries of the nervous
  system. J Nerv Ment Dis 1941 94 622-632
• Jensen PJ, et. al. Electrical injury causing
  ventricular arrhythmias. Br heart J 1987 57
  279-283
• Norquist C., Rosen CL., Adler JN., Rabban JT.,
  Sheridan R. The risk of delayed dysrhythmias
  after electrical injuries. Acad Emerg Med. 6
  393, 1999

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Electrical InjuriesCardiac Monitoring
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Electrical InjuriesCardiac Monitoring

• Cardiac monitoring is not justified in
  ASYMPTOMATIC patients,
• Or, in patients with only CUTANEOUS burns,
• Who had a normal ECG after a 120 v or 240 v
  injury.

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Top 10 Myths of Electrical InjuryMyth 8

• ALL Patients Who Are Asymptomatic and Who Have a
  Normal ECG After a 120V or 240V Injury Can Be
  Safely Discharged From the ED

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Electrical InjuriesPatterns of Injury

• Pregnancy
• Fetal monitoring is mandatory for pregnant
  patients
• Oral commisure burns
• Cataracts
• Delayed neuro-psychological sequelae

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Top 10 Myths of Electrical InjuryMyth 9

• The HYDRO QUEBEC GUIDELINES Provide the Standard
  of Care for Electrical Injuries

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Electrical InjuriesSummary - The Challenges

• Electrical injuries involve multiple body
  systems.
• Entry and exit wounds fail to reflect the true
  extent of underlying tissue damage.
• Electrical current may cause injuries distant
  from its apparent pathway through the victim.
• Controversies exist regarding indications for
  admission and cardiac monitoring following low
  voltage injuries.

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Electrical InjuriesThe Future

• Surveillance electrographique des patients ayant
  subi une électrisation Étude prospective
  multicentrique. Investigateur principal Benoit
  Bailey, MD MSc FRCPC
• 21 sites across Quebec including RVH, MGH, MCH
• Primary objectives
• determine the prevalence of cardiac arrhythmias
  in patients on initial ECG
• determine the prevalence of late arrhythmias in
  patients who undergo cardiac monitoring

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• Secondary objectives
• evaluate the importance of electrical injury in
  Quebecs EDs
• given a normal initial ECG, evaluate if late
  arrhythmias develop in patients with tetany,
  current across the heart, or with gt1000V
• given a normal initial ECG, evaluate if late
  arrhythmias develop in patients with PMHx of
  cardiac disease, or decreased skin resistance
• evaluate the incidence of cardiac problems in the
  year following electrical injury

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• Secondary objectives, contd
• accumulate prospectively an experience with
  applying the Hydro Quebec protocol
• determine the utility of measuring CK, CK-MB in
  predicting ECG abnormalities and the development
  of late arrhythmias
• determine the utility of measuring Troponin in
  predicting ECG abnormalities and the development
  of late arrhythmias

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Top 10 Myths of Electrical InjuryMyth 10

• er is an Accurate Reflection of Life in the ER

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Electric Shock What Should You Do?
The victim
Felt the current pass through his/her body
The current passed through the heart
Yes
Yes
No
No
Was held by the source of the electric current
Yes
1 second or more
Yes
No
No
Lost consciousness
Cardiac Monitoring 24 hours
Yes
No
Touched a voltage source of more than 1 000 volts
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Electric Shock What Should You Do? Page 2.
Touched a voltage source of more than 1 000 volts
Cardiac Monitoring 24 hours
Yes
No
Yes
Has burn marks on his/her skin
The current passed through the heart
Evaluate and treat burns (surgical evaluation,
look for myogolbinuria, etc.)
Yes
No
No
Was thrown from the source
Evaluate trauma
Yes
No
Is pregnant
Evaluate fetal activity
Yes
No
BENIGN SHOCK Reassure and discharge
Direction Services de Sante Hydro Quebec, 1995