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Lightning and Electrical Injuries

Lightning and Electrical Injuries. Gabriel Piper May 5 th , 2011. Outline. Epidemiology Physics and Pathophysiology of electrical injuries Signs and symptoms Management. Epidemiology. 17 000 Electric Injuries / Year USA 550 Electrocutions / Year in USA 300 Lightning Injuries / Year USA

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Lightning and Electrical Injuries

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  1. Lightning and Electrical Injuries Gabriel Piper May 5th, 2011

  2. Outline • Epidemiology • Physics and Pathophysiology of electrical injuries • Signs and symptoms • Management

  3. Epidemiology • 17 000 Electric Injuries / Year USA • 550 Electrocutions / Year in USA • 300 Lightning Injuries / Year USA • 100 Lightning Deaths / Year USA • Account for 3-7% of admissions to burn units

  4. Who gets electrocuted? • Trimodal distribution • Toddlers • Teens • Electrical utility and construction workers

  5. Definitions • Electricity = flow of electrons across a potential gradient from high to low concentration • Voltage (V) = force driving electrons • Current (I) = flow of electrons (Amperes) • Resistance (R) = impedance to flow

  6. What are the factors that determine electrical injury? • Current strength (voltage) • Tissue resistance • Duration of current flow • Type of current • Pathway of flow

  7. What are Ohm’s and Joule’s Law and what is their clinical significance?

  8. Physics 101 Ohm’s Law: I=V/R Joule’s Law: Energy(heat) = I2x R x T (T represents time of current flow)

  9. High energy = more damage • Current is the primary determinant of energy. • Higher voltage produces larger Currents

  10. What is considered High Voltage?

  11. High Voltage is defined as >1000 V (some sources say >600 V is enough to cause serious damage). • Typical household electricity is 110-230 V • Power lines are >100 000 V • Lightning strikes are >10 million V.

  12. Which tissues are conductors and which are insulators and why does tissue resistance matter?

  13. Tissue Resistance • Conductors: high fluid, electrolyte content • nerves and blood vessels • sweaty skin • saliva • muscle • Insulators: • Bone and tendons • Fat • dry skin

  14. What are the two types of current?

  15. Types of Current • Alternating Current (AC): the direction of electron flow changes rapidly in a cyclic fashion (ie. household  current) • Direct Current (DC) flows constantly in 1 direction across the potential (ie. batteries, power lines, lightning).

  16. Current Pathway

  17. What are the different mechanisms that electricity causes injuries?

  18. Mechanism of Injury 1.Direct effect of current on body tissues 2.Blunt mechanical injury 3.Conversion of electrical energy to thermal energy 4.Electroporation

  19. Lightning injuries

  20. Lightning Injuries • delivers a large amount of DC electricity (up to hundreds of millions of volts) • mortality rate of 25-30% • Nearly 70% will show sequelae, of which most are temporary in nature

  21. How do people survive lightning strikes if they are so high voltage?

  22. According to Joule’s law, the actual amount of energy delivered may be less than with other high voltage electrical injuries because of the short exposure time (milliseconds)

  23. Signs and Symptoms

  24. Systems affected • Cardiac • Respiratory • Nervous system • Skin • Musculoskeletal • Renal

  25. Cardiac injuries • Arrhythmias: • low-voltage AC -> V. Fib • DC and high voltage AC current -> asystole • sinus tach, PVCs most common but can get VT, A Fib and heart blocks • 10-40% will have delayed arrhythmias

  26. Myocardial damage • Often see rise in CKMB with electrical injury • Actual MI has been reported but is rare

  27. Respiratory System • Respiratory arrest is one of the common causes of acute death • result of: • direct injury to the respiratory control centre, • suffocation secondary to tetanic contraction of the respiratory muscles • combined cardiorespiratory arrest secondary to ventricular fibrillation or asystole.

  28. Cardiac Arrest • Although cardiac automaticity may spontaneously return, concomitant respiratory arrest may persist and lead to secondary hypoxic cardiac arrest • The duration of apnea, rather then the duration of cardiac arrest, appears to be the critical prognostic factor

  29. Nervous system • Effects are unpredictable and varied • loss of consciousness • generalized weakness • autonomic dysfunction • memory problems • Indirect neurological injuries may occur from trauma, anoxic brain injury

  30. Case • 35 yo M struck by lightning while hiking. He survived, but needed to be helped out because of flaccid paralysis of his lower extremities. Is he likely permanently paralyzed? What is this phenomenon called?

  31. Keraunoparalysis • specific form of reversible, transient paralysis and autonomic dysfunction that is associated with sensory disturbances, fixed/dilated pupils and peripheral vasoconstriction following lightning injuries. • Recovery is usually within 24 hours

  32. Ear and Eye injuries *Seen more commonly with Lightning injuries Eye Injuries • Cataract formation weeks to years later • Retinal detachment, corneal burns, intraocular hemorrhage, intraocular thrombosis Ear Injuries • Rupture of TM • Late complications of hemorrhage into TM, middle ear, etc. -> mastoiditis, sinus thrombosis, meningitis, brain abscess • Hearing loss immediate or late

  33. Skin injuries Types of burns: • Electrothermal Burns • Arc Burns • Flash Burns Lightning: • Burns are common (up to 89% in one series) but deep burns occur in only 5%

  34. Lichtenberg figures

  35. Case • 2 yr old boy comes in with a oral burn involving the lateral commissure of the mouth as depicted in the following slide. How does this injury differ from other electrical injuries?

  36. Oral wounds in Kids • Treat burn • Plastics f/u to prevent deformity and dysfunction • Check tetanus status • Delayed labial artery bleed • 10% risk of delayed hemorrhage • Can be 5 days or more after initially injury • some centers recommend admission until separation of the eschar occurs

  37. Musculoskeletal • Fractures 2° to tetany, falls • Shoulder dislocation (voltages >110V) • +++heat -> periosteal burns, osteonecrosis • Severe arterial spasm -> compartment syndrome • Muscle breakdown -> rhabdomyolysis -> myoglobinuria and renal failure

  38. Management

  39. Prehospital • First priority is to ensure the scene is safe: TURN OFF electrical source!

  40. Case You are at a music festival in the summer, when a lightning storm suddenly rolls in. 15 people are struck by lightning and 3 have no pulse. What do you tell the pre-hospital medics on scene in regards to who to treat first?

  41. Mass casualty lightning incidents • Normally -> arrests are triaged to blacks/morgue • However, arrested lightning strike victims can have excellent outcomes with respiratory support • In the absence of arrest lightning strike victims can generally wait for treatment • Support your arrests first, even if fixed and dilated pupils

  42. ED management Resuscitation • ACLS/ATLS protocols • Spinal immobilization • Careful physical exam! Investigations • ECG • Labs: High-voltage, extensive burns, evidence of systemic injury • CBC, lytes, Cr, BUN, CK, serum / urine myoglobin • Imaging as indicated, clear spines

  43. Who needs cardiac monitoring? Cardiac Monitoring for: • high voltage patients • patients with neuromuscular or cardiac symptoms (LOC, amnesia, altered mental status, episode of tetany, chest pain, palpitations) • Those with transthoracic current paths • Some suggest to monitor all those with underlying heart problems and children, but no evidence for this

  44. Treatment of burns • See burn lecture for details • Tetanus • Observe for neurovascular compromise, compartment syndrome • Get plastics involved

  45. Fluids? • “Rule of nines” will underestimate fluid needs • Treat as a crush injury – avoid myoglobinuric renal failure • Foley output: 1-2 cc/hr/kg • Fluid resuscitation: NS

  46. Pregnant patients • 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

  47. Disposition • Discharge if: • low voltage electrical injury or lightning injury • no cardiac arrest • no loss of consciousness • no burns • Normal neurologic examination and ECG • Others should be admitted (ICU, plastics, medicine depending on extent of injuries) • RTED if any delayed neuro symptoms • Neurologic and ophthalmic referral recommended for lightning injuries • Psychiatric assessment and support once stable

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