Electrical & Lightning Injuries Carly Thompson EM-Resident April 9, 2009 Outline Electrical Injuries Lightning • Definitions • Pathophysiology of • Epidemiology and Lightning Physics • Specific Injuries: • Physiologic Effects of Lightning Electricity • ED Management • Specific Injuries • Cases • ED Management of Electrical Injuries • Cases Electric Injuries Definitions • Electric shock – response • Electrocution – death • Electrical injury – tissue damage • Electrical burn – cutaneous injury • 550 Electrocutions / Year in USA (1998) – 50% of low-voltage <1000 V AC no visible burns or marks • 100 Lightning Deaths / Year USA – Underestimate? • 17 000 Electric Injuries / Year USA • 300 Lightning Injuries / Year USA Epidemiology 3 Groups at Risk for Electrical Injuries: – Toddlers – Adolescents – Electrical Workers (1/10 000 deaths/year) Lightning Injuries Risks: - Transportation: Car, plane, water - Storms or blue sky! Mortality: - 0.5 / million in US – 8.8 / million rural SA - 70-90% survival rate - 75% of survivors will have sequelae Physics 101 • Electric flow / current = Amp • Electric potential difference = Volts • Resistance = Ohms – Conductors: high fluid, electrolyte content – nerves and blood vessels, sweaty skin, saliva, muscle – Insulators: high resistance – bone, dry skin Ohm’s Law I (Current) = V (Voltage) / R (Resistance) Current is directly proportional to potential difference, and inversely proportional to resistance. Example = Grasp 120V source, with 1000Ohms resistance = 120mAmps Types of Current • What are the two types of current? AC/DC How did the band AC/DC gain their name? They saw it on the back of their older sister’s sewing machine. • AC – alternating current Homes, usually 60Hz • DC – direct current Batteries, lightning Physiologic Effects • Related to amount duration, type, path • Current travels along multiple paths, not only path of least resistance • Nerves and blood vessels – least resistance • Muscles have most flow due to greatest area • Nerves have higher current density -> significant injury Effect of Current Effect Current Path Minimum Current 60 Hz AC mAmp Tingling sensation, Through intact skin 0.5-2 minimal perception Pain threshold Through intact skin 1-4 Inability to let go: tetany From hand, through 6-22 decreases resistance forearm into trunk Respiratory arrest: fatal Through chest 18-30 if prolonged V Fib Through chest 70-4000 Ventrical asystole, if Through chest >2000 current stops sinus rhythm may resume Physics 102 • Electrical energy -> deposited as heat • Heat causes the most tissue damage Joule’s Law Energy = I2 x R x time Energy = (V2 x time) / R Therefore the heating of tissues increases according to the square of the applied voltage, and is directly proportional to the time the voltage is applied. Electricity Power Line: 7620V Lines outside house: 220 / 240V Subway: 660V High Voltage Injury • >1000 V • Severe skin burns Low Voltage Injury • Cutaneous burns often minimal with household voltage, unless several secs contact • Electrical burns absent in 40% of low voltage deaths • 110V can cause V fib Trivia What was AC/DC’s first album? What is considered high voltage? >1000 V Cardiovascular Injuries • 1° cause of death from electrocution • Low-voltage -> v fib • High-voltage AC and DC -> transient asystole • Also: ST, PACs, PVCs, a fib, 1st / 2nd AV block • Vigorous resuscitation!!! – Victims are often young without CVD – Not possible to predict outcome based on rhythm • Vascular injury -> spasm -> delayed thrombosis or aneurysm formation, compartment syndrome CNS and Peripheral Nerve Injuries • 50% have impairment (high-voltage) – Transient LOC – Agitation, confusion, – Coma – Seizures – Quadriplegia, hemiplegia, paresthesias – Aphasia, visual disturbances Spinal Cord Injuries • Vertebral fractures – multilevel! • Delayed injury – ascending paralysis – complete or incomplete cord – transverse myelitis • MRI results not closely correlated to outcome Eye and Ear Eye Injuries • Cataract formation weeks to years later • Retinal detachment, corneal burns, intraocular hemorrhage, intraocular thrombosis Ear Injuries • Late complications of hemorrhage into TM, middle ear, etc. -> mastoiditis, sinus thrombosis, meningitis, brain abscess • Hearing loss immediate or late Cutaneous Wounds • Entry / exit wounds – painless, gray Treatment • Cleansing, Td • Silver sulfadiazine • Mafenide – Full-thickness burns – penetrates eschar – <25% BSA only – inhibits carbonic anhydrase, painful • Observe for neurovascular compromise, compartment syndrome • Splint extremities, early surgical debridement, vascular reconstruction and skin graft Flexor Crease Burns Orthopedic Injuries / MSK • Fractures 2° to tetany, falls • Shoulder dislocation (voltages >110V) • Muscle +++heat -> periosteal burns, osteonecrosis • Severe arterial spasm -> compartment syndrome • Muscle breakdown -> rhabdomyolysis -> myoglobinuria and renal failure Blast and Inhalational Injuries Blast Injuries • Strong blast pressure -> head injury, mechanical trauma, arterial air emboli Inhalational Injuries • Ozone -> mucous membrane irritation, decreased pulmonary function, pulmonary hemorrhage, edema • Carbon monoxide, etc. assoc. with fires GI Injuries • Suspect in patients with burns of abdo wall, or trauma • Lethal injuries – reported only at autopsy • Gastric ulcers – Curling’s ulcers • Fluid resuscitation -> abdominal compartment syndrome with restrictive surface burns DIC • May be due to thermal injury or tissue necrosis • Low-grade DIC from hypoxia, vascular stasis, rhabdomyolysis, release of procoagulants • Tx: eliminate precipitating factor by early surgical debridement • FFP or cryo as needed Oral Burns • Children • Unilateral – Lateral commissure, tongue, alveolar ridge • Systemic complications rare • Vascular injury to labial artery – Severe bleeding 10% cases – Occurs 5 days – 2 weeks when eschar separates Oral Burns Treatment • Admission – monitoring • Outpatient – reliable parents, who can be shown how to control bleeding, consideration? • Saline rinses, swabs to debride necrotic tissue • Petrolatum-based Abx for soothing effect • Specialty consultation – splinting / surgical procedures to prevent deformity and dysfunction Tasers • Sinusoidal electrical impulses 10-15Hz • High voltage 50 000V for Taser • Low Amps and low average energy • 2001-2007 245 deaths after Taser Injuries • R on T phenomenon -> v fib • Pacemaker or ICD malfunction • Death more likely with concomitant drug use (PCP, cocaine), trauma from struggle, preexisting CAD • Ocular injuries • Other: burns, lacs, rhabdo, testicular torsion, miscarriage Accident Scene: Rescuer Safety Downed Power Lines • Electrocution possible, recommend 9m away (3m may be enough) • Reapplication of voltage may occur -> jumping power lines Victims • Victims in contact with source may be “active” • Voltage >600V -> dry wood, rubber boots may conduct electricity • Persons inside vehicle in contact with power line, likely to be killed if they step out ED Treatment Resuscitation • ABCs as per trauma • ACLS • Spinal immobilization • Careful physical exam! Investigations • Labs: High-voltage, extensive burns, evidence of systemic injury • CBC, lytes, Cr, BUN, CK, serum / urine myoglobin • Imaging as indicated, clear spines ED Treatment Fluid Resuscitation • Fluid requirements > Parkland’s formula • Visible damage < internal damage! • Initial fluid bolus: 20-40mL/kg/ 1st hr • Considerations: – Fluid load to prevent rhabdomyolysis – Avoiding over-resuscitation in patients with restrictive burns on abdomen -> prevent compartment syndrome Disposition Admission: • In contact >600V • Symptoms (CP, palp, LOC, confusion, weakness, dyspnea, abdo pain) • Signs (weakness, burns with subcut damage, vascular compromise) • Ancillary changes (ECG, CK, myoglobinuria) • Cardiac monitoring: If ECG abnormal No Admission: • Household voltage injury 100-220V in adult + • Neglibible risk for delayed arrhythmias + • Asymptomatic, normal ECG and normal exam -> d/c Electric Injury in Pregnancy • Increased rate of fetal damage or loss after apparent harmless contact – Monitor x 4 hours in women >20-24 weeks GA – Monitor >24 hours if LOC, ECG abN, hx of CVD – Fetal ultrasonography at presentation, then at 2 weeks • No proof that monitoring or tx can influence outcome Electric Injury in Children • Children with only hand wounds from outlet, but no cardiac or neurologic involvement can be d/c home with wound care • Consider admission if equivocal home safety or reliability • Guidelines for ECG in children: – Tetany – Decreased skin resistance by water or burns – Unwitnessed event • Guidelines for cardiac monitoring x 24 hours: – Past cardiac hx – LOC – Voltage >240V – Abnormal ECG Cardiac Monitoring in Children Bailey et al. (2000). Experience with guidelines for cardiac monitoring after electrical injury in children. Am J Emerg Med; 18(6):671-5. • July 1994 – June 1998 • Tertiary pediatric teaching hospital • 224 cases – Cardiac monitoring on 13% (all normal) – No morbidity 0/172 patients – No mortality 0/224 Case 1 • 30 yo M electric worker • Found down at steel plant • Thermal burn – lateral head • Presenting in asystolic arrest What do you do? How long do you continue treatment? Case 1 Cont’d Thoughts . . . • Resuscitation as per ACLS • Spinal precautions • Vigorous resuscitation as patient is young and otherwise healthy, heart may spontaneously regain automaticity Conclusion . . . • 45 minutes in ED resuscitation – no cardiac activity • Code called Case 2 Summary: Electrical Injuries • Low-voltage <600V -> may be D/C if asymptomatic – Immediate cause of death: V Fib – Children: oral burns – consider labial artery bleed ? admission • High-voltage >1000V -> admit for observation and cardiac monitoring – Asystole, treat cardiac arrest vigorously – Deep tissue destruction with high fluid needs – Myoglobinuria and renal failureis common – Trauma: thrown – Immediate cause of death: Apnea Trivia • Name a team, a song and a runner who all have something in common with lightning. Tampa Bay Lightning Lightning Crashes – Live Usain “Lightning” Bolt http://www.youtube.com/watch?v=GIKYWl APHVQ Pathophysiology • Different injury pattern, severity, tx • Lightning = extremely high-voltage DC • Brief, intense, thermal radiation producing rapid heating and expansion of surrounding air • Flashover = less likely to cause internal cardiac injury or muscle necrosis • TM perforation, internal contusion, tear clothing, melt metal, intense photic injury Factor Lightning High-Voltage AC Low-Voltage AC Current Duration 1-3ms Often brief 1-2s, may be Prolonged prolonged Typical voltage and 10 million – 2 billion V; 600-70 000 V; <1000 A <600 V; usually < 20-30 current range 20 000 – 200 000 A A Current characteristics Unidirectional (DC) Alternating (AC) Alternating (AC) Current pathway Skin flashover Horizontal or vertical Horizontal or vertical Tissue damage Superficial, minor Deep tissue destruction Sometimes deep tissue destruction Initial rhythm in arrest Asystole Asystole > V fib V fib Renal involvement Myoglobinuria is Myoglobinuria and renal Myoglobinuria and renal uncommon, renal failure common failure occasionally failure rare Fasciotomy and Rarely necessary Relatively common Sometimes necessary amputation Blunt injury Explosive effect with Being thrown from Tetanic contraction or shock wave current source or falls falls Immediate cause of Prolonged apnea Apnea V Fib death Mechanism of Injury • Direct strike – direct contact • Side flash – hits nearby object • Contact strike – hits object being held • Ground current – through ground • Upward streamer – weak streamer Cardiac Injury • Htn, tachycardia – sympathetic activation • Depolarization -> sustained asystole • Other: – global myocardial contractility depression – coronary artery spasm – pericardial effusion – atrial and ventricular arrhythmias • ECG: acute injury – ST elevation, long QT, T wave inversion (neurologic injury) • MI is unusual • Cardiac automaticity may return spontaneously Respiratory Issues Respiratory arrest • Due to paralysis of medullary resp centre • Critical prognostic factor Neurologic Injury • Common Injuries: – ALOC – Temporary lower extremity paralysis – Seizures • Lethal injuries: heat-induced coagulation of cortex, epidural / subdural, ICH • Autonomic dysfunction: mydriasis, anisicoria • Immediate and transient effects: – LOC, confusion, amnesia, paralysis - keraunoparalysis • Delayed and progressive effects: – Seizures, spinal muscular atrophy, ALS, parkinsonian syndromes, progressive cerebellar ataxia, myelopathy with paraplegia or quadriplegia, chronic pain Neurologic Injury Indications for CT: • Coma • ALOC • Persistent headache • Confusion Neurologic Injuries Spinal Cord Injuries • Fractures may be caused by tetany, falls, secondary trauma • Maintain spinal precautions • Image entire column due to multilevel fractures Neurologic Injuries Ocular • Lightning-induced cataracts • Also: hyphema, vitreous hemorrhage, abrasions, uveitis, retinal detachment or hemorrhage, optic nerve damage Auditory • TM rupture • Strike along phone: persistent tinnitus, sensorineural deafness, ataxia, vertigo, nystagmus Cutaneous Injuries • Lictenberg Figures – Superficial ferning – Disappear in 24 hours – Pathognomonic for lightning strike Cutaneous Injuries • Flash burns: erythema • Punctate burns: cigarette burns <1cm full- thickness • Contact burns: metal close to skin • Superficial erythema and blistering burns • Linear burns: <5cm wide in skin fold • Entrance and exit wounds - rare Rescuer Safety • Beware of the “lightning strike” victim that may truly be the victim of knocked down power lines • Look for evidence of lightning: hx of electric storm, blast effect, torn clothing, melted objects, melted nylon cloths, burned vegetation • Triage: Those who are sickest – treat first! ED Management • ABCs, IV, O2, monitor • Hypotension is an unexpected finding – warrants investigation • Careful exam for secondary injuries, burns, current path • Labs: CBC, lytes, BUN, Cr, glucose, CK, urine for myoglocin • ECG • Imaging as indicated Disposition • Admission for observation recommended • No neuro injuries, normal ECG, monitoring -> may consider d/c home • Neurologic and ophthalmic referral recommended Pregnancy Considerations • Fetal injury and death more common even after little or no maternal injury (amniotic fluid) – Review: 11 women who survived lightning – 5 cases of fetal or neonatal death – Abruption can occur • Ultrasonography recommended • Maternal uterine activity and fetal HR monitor x 4 hours Case 3 You are working at Foothills one stormy afternoon, and there is a soccer game going on at McMahon Stadium . . . You get a patch . . . 32 German Soccer Players Get “Zapped” 3 Patients • Patient 1: Full cardiac and respiratory arrest. Apparently a direct strike. Has Lichtenburg figures. • Patient 2: Altered, shallow breathing, mottled, deformity to R femur. • Patient 3: Complaining of paralysis to legs, flash burns to torso. Case 3 Cont’d • How do you triage these patients? • In contrast to multiple victim events caused by mechanical trauma . . . • Persons with lightning injury who appear dead (resp +/- cardiac arrest) should be treated first!!! Summary: Lightning Injuries • Lightning is extremely high-voltage DC • CV: Causes asystole in arrest • Neuro: Apnea from medulla injury, • MSK: Explosive effect of shock wave • Cutaneous: Lichtenberg figures • Tx: ABCs, treat sickest first (even ?dead!) • Get ocular and neuro assessment • Admission for observation Thanks! Thanks also to Marc Francis and James Huffman for pictures and cases!