electrical injuries robert primavesi, mdcm, ccfp(em) montreal general hospital mcgill university...
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Electrical InjuriesElectrical Injuries
Robert Primavesi, MDCM, CCFP(EM)
Montreal General Hospital
McGill University Health Centre
Robert Primavesi, MDCM, CCFP(EM)
Montreal General Hospital
McGill University Health Centre
Electrical Injuries Goals
• To identify the important complications of electrical injuries.
• To expose the pitfalls in diagnosis.
• To explore the controversies in management.
Electrical InjuriesObjectives
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.
Top 10 Myths of Electrical Injury
*
Top 10 Myths of Electrical InjuryMyth #1
Electrical Injuries Are Uncommon
Electrical InjuriesEpidemiology
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
Top 10 Myths of Electrical InjuryMyth #2
Voltage Is the Most Important Determinant of Injury
Electrical InjuriesFactors Determining Severity
Electrical InjuriesFactors Determining Severity
1. V = voltage
2. i = current
3. R = resistance
OHM’S LAW: i = V / R
Electrical InjuriesFactors Determining Severity
Electrical InjuriesFactors Determining Severity
JOULE’S LAW:
Power (watts) = Energy (Joules) time= V x i= i2 x R
Electrical Injuries Factors Determining Severity
Electrical Injuries Factors Determining Severity
Mucous membranesVascular areas
• volar arm, inner thighWet skin
• Sweat• Bathtub
Other skinSole of footHeavily calloused palm
Skin Resistivity - Ohms/cm2
100300 - 10 000
1 200 - 1 5002 500
10 000 - 40 000100 000 - 200 000
1 000 000 - 2 000 000
Top 10 Myths of Electrical InjuryMyth #3
High Voltage Is More Likely to Kill Than Low Voltage
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; 25:514-521.Cunningham PA. The need for cardiac monitoring after electrical injury. Medical Journal of Australia. 154(11): 765-6, June 1991.
The Extent of the Surface Burn
Determines the Severity of Injury
Top 10 Myths of Electrical InjuryMyth #4
Electrical InjuriesPatterns of Injury
Electrical InjuriesPatterns of Injury
• Direct contact– Direct tissue heating
– Contact burns (entry and exit)
– Thermal burns
The Pathway the Electrical Current Takes Through the Victim Predicts the Pattern of
Injuries
Top 10 Myths of Electrical InjuryMyth #5
Electrical InjuriesPatterns of Injury
Electrical InjuriesPatterns of Injury
Skin Resistivity
Least Nerves
Blood
Mucous membranes
Muscle
Intermediate Dry skin
Tendon
Fat
Most Bone
Electrical InjuriesEffects of 60 Hz Current
Electrical InjuriesEffects of 60 Hz Current
1 mAmp Threshold of perception5 mA Maximum harmless current6 mA Ground fault interrupter opens10 mA “Let-go” current20 mA Possible tetany of resp muscles100 mA VF threshold6 A Defibrillation20 A Household circuit breaker
opens
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
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
Top 10 Myths of Electrical InjuryMyth #7
All Patients With Electrical Injury Require 24 Hours of Cardiac Monitoring
Electrical InjuriesCardiac MonitoringElectrical Injuries
Cardiac 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
Electrical InjuriesCardiac Monitoring
Study Voltage No. of patients
Initial ECG = Normal
Initial ECG = Abnormal
Late Arrhythmias
Purdue and Hunt
1000 48 40 8 0
Wrobel < 1000 35 31 4 0
Moran and Munster
110 – 850 42 40 2 0
Kirschmair and Denstl
220 – 900 19 15 4 0
Fatovitch and Lee
240 20 18 2 0
Cunningham 240 70 59 11 0
Kreinke and Kienst
> 220 31 29 2 0
Bailey, et. al. 120 and 240 120 119 1 0
Arrowsmith > 220 73 69 4 0
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.
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
Electrical InjuriesPatterns of Injury
Electrical InjuriesPatterns of Injury
• Pregnancy– Fetal monitoring is
mandatory for pregnant patients
• Oral commisure burns• Cataracts• Delayed neuro-
psychological sequelae
Top 10 Myths of Electrical InjuryMyth #9
The HYDRO QUEBEC GUIDELINES Provide the Standard of Care for Electrical
Injuries
Electrical InjuriesSummary - The Challenges
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.
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:1. determine the prevalence of cardiac arrhythmias in
patients on initial ECG2. determine the prevalence of late arrhythmias in patients
who undergo cardiac monitoring
• Secondary objectives:– evaluate the importance of electrical injury in Quebec’s EDs – given a normal initial ECG, evaluate if late arrhythmias
develop in patients with tetany, current across the heart, or with >1000V
– 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
• Secondary objectives, cont’d:
– 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
Top 10 Myths of Electrical InjuryMyth #10
“er” is an Accurate Reflection of Life in the ER
Electric Shock: What Should You Do?
Electric Shock: What Should You Do?
The victim:
Felt the currentpass throughhis/her body
The currentpassed through
the heart
Was held by thesource of the
electric current
Lostconsciousness
Yes
No No
No1 secondor more
Yes
No
Yes
Cardiac Monitoring24 hours
Touched a voltagesource of morethan 1 000 volts
Yes
No
Yes
Electric Shock: What Should You Do?
Page 2.
Electric Shock: What Should You Do?
Page 2.
Touched a voltagesource of morethan 1 000 volts
Cardiac Monitoring24 hours
Has burn markson his/her
skin
The currentpassed through
the heart
Yes
NoYes
YesEvaluate and treat burns
(surgical evaluation, look for myogolbinuria, etc.)
No
Was thrown fromthe source
Evaluate trauma
No
Is pregnantEvaluate fetal
activity
No
Yes
Yes
No
BENIGN SHOCKReassure and discharge
Direction Services de SanteHydro Quebec, 1995