Electrical Injuries 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 • 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 InjuryMyth #1 Electrical Injuries Are Uncommon
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 1. V = voltage 2. i = current 3. R = resistance OHM’S LAW: i = V / R
Electrical InjuriesFactors Determining Severity JOULE’S LAW: Power (watts) = Energy (Joules) time = V x i = i2 x R
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 Electrical Injuries Factors Determining Severity
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.
Top 10 Myths of Electrical InjuryMyth #4 The Extent of the Surface Burn Determines the Severity of Injury
Electrical InjuriesPatterns of Injury • Direct contact • Direct tissue heating • Contact burns (entry and exit) • Thermal burns
Top 10 Myths of Electrical InjuryMyth #5 The Pathway the Electrical Current Takes Through the Victim Predicts the Pattern of Injuries
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 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
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 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 • 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 • 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 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: • determine the prevalence of cardiac arrhythmias in patients on initial ECG • 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? 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
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 Direction Services de Sante Hydro Quebec, 1995 BENIGN SHOCK Reassure and discharge