1	Electrical and Lightning-related Injuries Carl W. Peters, M.D. Division of Critical Care Medicine Department of Anesthesiology University of Florida College of Medicine
2	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
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4	Electron Subatomic particle in the lepton family of subatomic particles Rest mass: 9.1 x 10^-28 grams Unit negative electrical charge: 1.6 x 10^-19 coulombs Negative electron charge is the basis of electrical and magnetic phenomena
5	Electricity Manifestation of behavior of electrons and protons Particles of opposite charge attract Particles of same charge repel “Electromagnetism” – fundamental force (1 of 4) Manifested as physical phenomena Electrical current and fields Lightning Can cause severe injuries & death
6	Four Fundamental Forces
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8	Magnetic Poles
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11	Electrical Power Generation
12	Electrical Power Generation Any suitable energy source can turn the rotor within the large magnet Electrons move, AC power generated Energy-requiring process
13	Electrical Power Generation
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16	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
17	Pioneers in Electricity: Thales of Melitus
18	Pioneers in Electricity: William Gilbert
19	Pioneers in Electricity: Gian Romagnosi Current from “voltaic pile” (i.e. a battery) deflects needle in compass Therefore: Electricity = magnetism
20	What Did Ben Franklin Do?
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22	Pioneers in Electricity: Michael Faraday Discovered “electromagnetic induction” Established Faraday’s Law Changing magnetic field produces an electrical field Constructed electrical “dynamo” Ancestor of all electrical generators
23	Pioneers in Electricity: James Maxwell “Maxwell’s Equations”— define interactions of electrical & magnetic fields Equations predict “wave” oscillations of electrical & magnetic fields Commonality of light and electromagnetism Forecast “Special Theory of Relativity”
24	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
25	Electrical Injuries: Epidemiology
26	Electrical Injuries: Epidemiology
27	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
28	Important Concepts Electromotive Force (Volts) The strength driving the flow of charge Current (Amperes) The “volume” of flow of charge Resistance (Ohms) Hinderance to flow of charge Power (Watts) Amount of work done by flow of charge
29	Important Concepts: Voltage
30	Important Concepts: Current
31	Important Concepts: Resistance
32	Important Concepts: Ohm’s Law
33	Important Concepts: Ohm’s Law Voltage = fixed (external source) Resistance = fixed for a given material May be low or high Can change during the injury process Therefore Current ~ resistance Tissue damage ~ current
34	Basic Electrical Circuit
35	Important Concepts: Power Basic concepts Power (watts – W): work performed by electric current per unit time Work = force x distance P = dE /dt = dW / dt
36	Important Concepts: Types of Current Direct Current Battery source Used in some medical equipment Defibrillators Electric scalpels Pacemakers “Safer” (no tetanic contractions) Lightning is mostly DC Alternating Current Source: the wall Single phase 120/240V Tetanic contractions = more injury potential Current flows back & forth More efficient long distance transmission Drives electric motors
37	DC Power Sources
38	Alternating Current Levels
39	Low AC-Voltage Uses
40	High AC Voltage
41	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
42	Determinants of Electrical Injury Energy imparted to tissue ~ magnitude of current Voltage is fixed Resistance (i.e. impediment to current flow) varies with type of tissue Ohm’s law Current ~ 1 / resistance Resistance varies with body part Therefore, injury varies in different body part according to varying amount of current in each body part
43	Electrical Injuries
44	Low Voltage Electrical Shock Hazard
45	Effects of Electrical Current
46	Physiologic Determinants of Injury Path through body Resistance of intervening organs (generally low) State of resistance External & internal Thick dry skin, thin moist skin Magnitude and duration of voltage Type of current AC or DC
47	Physiologic Determinants of Injury Pathway: Vertical: involves all vital organs, often lethal Horizontal: hand – hand may spare brain but involve heart à lethal Lower part of bodyà may spare vital organs
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49	Physiologic Determinants of Injury Resistance varies Construction worker hands – 100,000 ohms Current = ~1mA Wet skin à water conducts well à almost no resistance ( ~2500ohms) Underwater = <1500 ohms = maximum current à à DRT (dead right there!!) Internal resistance ~ 500 – 1,000 ohms
50	Low Resistance Situation
51	Low Resistance Areas
52	Intermediate Resistance Areas Skin generally has intermediate level of resistance Varies with skin thickness Thick skin = high resistance = less current = less injury, and v.v. Baby skin injured more easily than construction worker skin
53	High Resistance Areas
54	Physiologic Determinants of Injury Duration of contact: Longer = worse AC worse at low voltage DC tends to blow victim off source, disconnects from injury AC tetanic contractions, continued exposure High voltage — no difference, AC vs DC
55	Electrical Injuries
56	Electrical Injuries
57	Electrical Injuries: Mechanisms of Injury Direct effect of electrical current on body tissues Conversion of electrical energy to thermal energy à burns Blunt mechanical injury Muscle contraction Associated blast Associated fall
58	Electrical Injuries: the Specifics Burns Range of severity Partial thickness à extensive, with deeper injury Most often concentrated in extremities Area of greater “current density” Vascular Fluid conduit for current Coagulation necrosis and thrombosis of vessels Often compromised by surrounding tissue swelling à compartment syndrome
59	Electrical Injuries Cardiac Arrhythmias (before we see patient) DC & high-tension AC à asystole Low-tension AC à Vfib Most common: Sinus tachycardia NSSTTWave changes Many others, usually resolve
60	Electrical Injuries
61	Electrical Injuries
62	Electrical Injuries Entrance wound High resistance at entrance Heat generation Black burn spots from heat
63	Electrical Injuries Exit wound Deceptively “small” wound can hide severe injury, leading to amputation
64	Electrical Injuries
65	Electrical Injuries
66	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
67	Electrical Arcing
68	Electrical Arcing
69	Electrical Arcing Very high voltage Plasma discharge allows current flow Breaks through normally insulating substance (air) Injury potential HIGH temperature (>3000^O C) = BURNS
70	Electrical Arcing Electrical arc burn “Flash” mechanism May involve current flow also No direct contact needed Lowest fatality rate among electrical injuries Largest mean cutaneous burn size These are burn injuries
71	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
72	Penal Electrocution
73	Penal Electrocution
74	Penal Electrocution Two-point attachment: Complete circuit Electrode paste Ensures low-resistance connection Two “jolts”, minutes each: Jolt #1: 2000V = break down surface resistance, render unconscious Jolt #2, 8 Amps = destroy internal organs, fatal injuries
75	Important Topics Definition History Epidemiology Important Concepts Electrical Injuries Special issues Arcing injuries Penal electrocution Lightning
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77	Lightning Abrupt, discontinuous, natural electrical discharge in the atmosphere
78	Formation of Lightning Warm, low pressure moist air rises and condenses into a cumulonimbus cloud Typical anvil-shaped thundercloud forms
79	Formation of Lightning Water droplets accumulate and layer charges develop Weak, slow-stepped leader initiates lightning strike downward
80	Formation of Lightning Positive upward streamer rises from ground to meet the stepped leader Return stroke rushes from ground to cloud
81	Epidemiology of Lightning Injury >20,000,000 cloud- to- ground strikes / year in the U.S. Up to 50,000 flashes / afternoon during summer 1959 – 1994: 3,529 deaths 9,818 injuries 19,814 incidents of property damage
82	Lightning Casualties
83	Lightning Fatalities
84	Lightning Flashes
85	Lightning Casualties Seasonal distribution Most in summer months Diurnal variation Mostly late in the day
86	Types of Lightning
87	Types of Lightning
88	Pathophysiology of Lightning Injury Unidirectional massive current impulse Neither DC or AC, closer to DC Discharge of huge potential difference Millions (> 5 x 10⁸) of volts Discharge of enormous current Can be > 200,000 amps Lightning is phenomenon associated with current Short duration (few milliseconds)
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90	Pathophysiology of Lightning Injury External transmission Skin heats, surface moisture vaporized, external “flashover”, blow off clothing Internal transmission “Short circuit” electrical systems Heart (asystole), respiratory & ANS Heart restarts, respiratory system needs support Seldom see significant internal injuries Brief duration
91	Mechanisms of Lightning Injury Direct strike Contact – touching direct strike object Side flash (“splash”) Ground current (“step voltage”) Blunt trauma
92	Lightning: Direct Strike
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94	Lightning: Direct Strike
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96	Direct Strike: Lightning vs Tree
97	Direct Strike: Lightning vs person Instant massive heating > 30,000^oK Vaporized moisture on body surface Blows clothing off
98	Direct Strike: Lightning vs person
99	Lightning: Splash Injury Lightning hits nearby object Jumps to object(s) of less resistance (cows, people) Can occur indoors Phone, plumbing
100	“Step” Voltage Injury (“Stride Potential”)
101	Lightning: Blast Effect
102	Lightning: Blast Effect
103	Casualties from Lightning Death ~20 – 30% die from lightning strike Survivors Three quarters have long-term sequelae Peripheral neuropathy Impaired mentation Group casualties Shelter sought in groups 30% involve > 1 person
104	Injuries from Lightning Neurologic: Short term: LOC, confusion, weakness “keraunoparalysis” – brief paralytic state of lower extremities, pallor, vasoconstriction Long term: Post-hypoxic encephalopathy – delayed CPR ICH & infarctions Cerebellar syndromes Neuropsychological disorders TBI, PTSD Poor memory, irritability, depression, attention deficit
105	Injuries from Lightning Burns Superficial >5% have deep thermal burns Lung damage infrequent Abdominal trauma Result of blunt injury Orthopedic injuries Long bone & vertebral compression Muscle contraction, blunt injury Renal Rhabdomyolysis – induced renal failure
106	Injuries from Lightning Tympanic membrane perforation Blast effect
107	Injuries from Lightning
108	Lightning Phenomena “Lichtenberg figures” AKA “arborescent lightning burn” AKA “lightning flowers” Seen after lightning strikes Usually post-morten finding Capillary injury Current flow through skin Resolve with time Pathogneumonic of lightning strike
109	Lichtenberg Figures
110	Lichtenberg Figures
111	Electrical and Lightning-related Injuries: Summary These injuries are common Potentially lethal, early and late Injury ~ magnitude of current External signs may appear deceptively benign Evaluate the entire patient
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