Transcript Electric_Lightening_Injuries

Electrical and Lightning
Injuries
Electrical and Lightning
Injuries : Lecture Outline
ƒ Physics & pathophysiology of electrical
injuries
ƒ Recognition, treatment, & prevention of :
–Household current injuries
–High voltage injuries
–Lightning injuries
Electrical Burns : History
ƒ First commercial use of electricity : 1849
ƒ First reported fatal electrocution in 1879 in
Lyon, France (250 volt AC dynamo)
ƒ First fatal electrocution in USA in 1881 : Sam
Smith in Buffalo, NY
ƒ First use of electrocution for death penalty in
1890 : William Kimmler in New York
ƒ Kouwenhoven's studies at John Hopkins for
ConEd of electrical injuries led to his
development of the defibrillator
Electrical Injuries
ƒ Three main types :
–Household current (110 to 220 Volts)
–High voltage (> 1000 Volts)
–Lightning
Electrical Line Voltages
ƒ Cross country lines : > 100,000 volts
ƒ Residential & industrial area : 7620 volts
ƒ Household heavy appliances : 220 or 240 volts
–This voltage commonly used in Europe
ƒ Interior household lines : 110 to 120 volts
alternating current : 60 cycles per second (hertz)
in U.S.A. (is direct current instead in much of
Europe)
Electricity Formulas
ƒ Energy (heat) = current times voltage
Q
=
I
X
E
ƒ Ohm's Law : Voltage = amperage X resistance
ƒ Joule's Law : Heat = amperage squared X resist.
ƒ Voltage = tension = potential = electromotive force
ƒ Amperage = intensity = current flow per unit time
ƒ Ohm = resistance
Human Tissue Electrical Resistance
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Heavily calloused hand : 1 million ohms
Average skin : 5000 ohms
Moist skin : 1000 ohms
Internal resistance of the human body :
500 ohms
Resistance of Tissues to
Electrical Current
Least
Greatest
Nerve
Blood vessel
Muscle
Skin
Tendon
Fat
Bone
Electrical Burns : Physiologic Effects
60 hz Current Level
1 milliamp
10 milliamps
100 milliamps
Physiologic Effect
Threshold of sensation
Threshold of pain
Muscle paralysis
Breathing difficulty
Ventricular fibrillation
Severe burns
Breathing stops
1 amp
Cardiac standstill
10 amps
Defibrillation current
Electrical Current Flow Effects
on Humans
ƒ Alternating current has a tetanizing effect on
muscles
–"Let-go current" (the current level at which the person
is unable to release his grasp on the conductor) is 15
milliamps for men & 10 milliamps for women
ƒ Strong sustained muscle contraction can cause
fractures
ƒ Direct current (DC) felt as heat only & can cause
a single violent muscle contraction that can
throw the victim from the power source
Household Current Injuries
ƒ In one series, caused half of all
electrical deaths
ƒ Major risk is ventricular fibrillation
(caused by the AC feature of current)
ƒ Deep tissue damage directly from the
current is very rare
ƒ Can cause fractures and dislocations
ƒ If EKG normal & no skin burn,
admission to hospital not necessary
Oral Cavity Electric Burns
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60 % in boys
Sucking extension cord socket : 54 %
Biting on electric cord : 30 %
Sucking an electric outlet : 2 %
Temperature of electric arc : 2500 degrees F
(> 1500 degrees C)
–So usually these injuries represent more a
thermal injury than an electrical current injury
Oral Cavity Electric Burns
ƒ Most involve lower lip
ƒ Can involve tongue
ƒ Complications :
–Drooling
–Adhesions
–Impaired speech
–Tooth damage
–Impaired mandible growth (rare)
Treatment of Oral Cavity Electric Burns
ƒ "Corner of mouth" burn from biting
electric cord
–Treatment by topical agent (like
Silvadene) several times daily, custommade mouth stretcher
–No surgical treatment for at least 1 year
–Warn parents about delayed bleeding if
labial eschar sloughs off
Oral Cavity Electric Burns
ƒ Labial artery bleeding :
–Occurs in 24 % of cases
–1 to 21 days delayed
–Usually stops with pressure
–Rarely requires arterial ligation with
suture
High Voltage Electrical Injuries :
Demographics
ƒ 3 to 10 % of admissions to burn units
ƒ 10 to 15 % mortality
ƒ ? > 1000 deaths / year in U.S.A.
High Voltage Electrical Injuries :
People at Risk
ƒ Electric company linemen
ƒ Roofers
ƒ Agricultural workers (carrying
irrigation pipes)
ƒ Parachutists
ƒ Reckless teenagers (climbing towers)
ƒ Car drivers (hitting power poles)
Electrocution Risk
ƒ U.S. electric company linemen
–33 per 100,000 workers per year
ƒ U.S. electricians
–8.3 per 100,000 workers per year
ƒ Not well quantified for other higher
risk groups (construction workers,
heavy equipment operators, roofers,
etc.)
Electrical Injuries
(1982 Utah Study)
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Number of high voltage injuries
Number injured from house current
Number injured from lightning
Number of electrical company linemen
Number of farm or ranch workers
Number of people injured on roofs
Number of construction workers
68
8
4
14
22
10
12
High Voltage Electrical Injuries :
Pathology
ƒ Causes coagulation necrosis of tissue along
current path
ƒ Points of maximum destruction are at skin
entrance and exit sites
ƒ May cause extensive muscle necrosis in limb
or trunk beneath unburned skin
ƒ May cause myocardial necrosis, peripheral
nerve injuries, bowel wall necrosis
ƒ Retrograde amnesia / confusion for several
days common
Location of High Voltage Skin Injuries
(1982 Utah Study)
Entrance Wounds
Hand or Forearm
Shoulder, Flank, Buttock
Scalp, Face, Neck
54 patients
11 patients
13 patients
Exit Wounds
One or Both Feet
Back, Flank, Thigh
43 patients
29 patients
Associated Injuries
(1982 Utah Study)
INJURY
Cardiac arrest requiring CPR *
Loss of consciousness > 15 minutes
Falls
Smoke inhalation
Femur fractures
Rib fractures
Skull fracture
Tibial fracture
Dislocated shoulder
Corneal abrasion
Lacerations
NUMBER
11
13
11
3
2
2
1
1
1
1
5
Total 51
* 10 of these were neurologically intact long term survivors
Resuscitation For High Voltage
(HV) Electrical Burns
ƒ Turn off current ; remove patient from source (use
nonconductive materials to push)
ƒ CPR (may need to be prolonged)
–High neurologically intact survival rate
ƒ Immobilize spine
ƒ O2 , maintain airway, respiratory support
ƒ IV LR : 4 to 12 cc / Kg / % burn / 24 hours
ƒ Assess for other injuries
ƒ NG, Foley, tetanus toxoid, Type & Cross
ƒ IV antibiotics if muscle involvement
ƒ Emergent Tc99m muscle scan
ƒ To O.R. for fasciotomy & debridement
Resuscitation Fluid and Transfusions
(1982 Utah Study)
ƒ Average amount of fluid received in first 24
hours : 9.9 liters or 12 cc / Kg / % burn
ƒ Range of amount of resuscitation fluid : 1.5 to
38 liters
ƒ Patients transfused with blood products : 41
ƒ Total units of blood used : 818
ƒ Average units of blood used per transfused
patient : 20
ƒ Units of fresh frozen plasma used : 195
Problems With Non-Visual
Assessments of Muscle Viability
ƒ Angiography : cannot evaluate small
muscle artery branches well
ƒ Fluorescein : cannot evaluate tissues
beneath surface
ƒ Muscle biopsies : take too long to
process and too many required
Tc99m (Technetium) Muscle
Scan Interpretation
ƒ Cold (nonperfused) areas = dead muscle
ƒ Hot ( increased activity) areas = damaged
muscle (20 % to 80 % fibers damaged)
ƒ Normal perfusion : areas that do not require
visual inspection for viability
ƒ So Tc99m scanning, in conjunction with direct
visual inspection, is the best way to assess
muscle viability in electrical burns
26 year old male
with high voltage
burns ;
Technetium scan
shows
nonperfused
muscle in apex of
axilla
Technetium scan of same patient on previous slide showing
nonperfusion of the thumb (so it must be amputated)
General Sequence of Surgical Care
for High Voltage Electrical Burns
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Resuscitation in ED
Tc99m muscle scan
To O.R. for fasciotomies
Wound care in burn unit
Repeat trips to O.R. every 24 to 48 hours for
debridement
ƒ Close fasciotomies with suture or skin
grafts when debridements complete
ƒ Rehabilitation
Benefits of Early Fasciotomy
ƒ Prevents decreased perfusion of limb
tissue due to increased muscle
compartment pressure
ƒ Allows visualization of muscle to assess
viability
ƒ Probably helps preserve limb length when
distal amputation is required
ƒ Not associated with significant increase in
complications or infection
HV Electrical Burns : Indications for
Emergent Surgical Decompression
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Extensive deep limb burns
"Mummified" distal extremity
Marked limb edema
Decreased distal pulses
Altered distal neurologic function
Delayed presentation
Fasciotomy : O.R. Technique
ƒ Do not use tourniquet
ƒ Check all hot and cold areas noted on
Tc99m scan
ƒ Do carpal tunnel release for wrist
involvement
Treatment Choices for Fasciotomy
Sites Prior to Closure
ƒ Silvadene dressings : reapply q8h
ƒ Cadaver or pigskin grafts
ƒ Soaked dressings (saline with
antibiotics)
Closure Techniques for
Fasciotomy Sites
ƒ Primary closure : only if edema gone
and compartment pressure not
increased
ƒ Split Thickness Skin Grafts (STSG's)
ƒ Rotated skin flaps
ƒ Free flaps
–Flaps often necessary when nerves or
tendons are exposed
Same patient as on prior slide after fasciotomy showing
extensive muscle damage under areas of unburned skin
High voltage entry wound of shoulder
Same patient as on
prior slide, showing
exit wound on right
hand and “frozen”
position of the limb
from extensive
muscle damage
Gross myoglobinuria
from the same patient
on the prior slide
High voltage contact injury to shoulder in another patient
High Voltage Electrical Injury :
Complications
ƒ Acute MI / arrhythmias
ƒ Renal failure
–This is really an iatrogenic problem &
should be preventable if sufficient
resuscitation fluid is given
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Infections / sepsis
Peripheral neuropathy
Amputations
Cataracts
Electrical Burns :
Neurologic Complications
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Mental confusion : 2 days to 3 weeks
Acute spasticity : may last 6 months to 1 year
Reflex sympathetic dystrophy
Seizures
Paralysis
uncommon
Causalgia
Electrical Burns :
Infectious Complications
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Sepsis
Pneumonia
Osteomyelitis
Amputation stump cellulitis (if this
occurs, use Tc99m scan to locate
necrotic muscle)
Electrical Injuries During Pregnancy
ƒ Only a few cases reported in the
literature
ƒ True incidence of electric shock
without any injury may be very high
ƒ Of the 15 cases reported since 1965,
the incidence of stillbirth & major fetal
anomalies was 14 / 15
ƒ No apparent increased risk to mother
due to pregnancy itself
Electrical Burns Prevention
ƒ Don't be stupid !
ƒ Turn power off at source before working on wiring or
appliance
ƒ Replace damaged electrical cords and appliances
ƒ Use non-conductive electric plug fillers when
children present
ƒ Don't handle any electrical apparatus when hands or
area are wet
ƒ Use ground fault interrupter type outlets wherever
possible
Lightning
ƒ Essentially a sudden massive Direct
Current (DC) shock (up to 1,000,000
volts and 200,000 amps)
ƒ ? Causes 300 to 600 deaths per year in
U.S.
ƒ 1/3 of victims have serious injury or
death
A picture I took of lightning in Reading, Pennsylvania
Lightning striking
the World Trade
Center
Fatal lightning strike
site at the U.S. Open
Golf Tournament
Airliner swerving to
avoid lightning
Lightning Definition
ƒ The natural atmospheric electric discharge
that occurs between regions of net positive
and net negative charge
ƒ Usually associated with cumulonimbus
clouds
ƒ May occur with :
–Nimbostatus clouds
–Snowstorms
–Volcano gas
Lightning Incidence
ƒ 50,000 thunderstorms / day in world
ƒ 8 million lightning strikes per day
ƒ Causes more deaths than any other
type of weather
ƒ Florida has much higher frequency
than other U.S. states
World map of lightning frequency
Lightning Occurence
ƒ Does strike twice in the same place
ƒ A Virginia park ranger was hit 7 times
over a 30 year period (he later
committed suicide)
ƒ Tall buildings commonly receive
multiple strikes each year
Therapeutic Effect of Lightning
ƒ The use of ECT (electroconvulsive
therapy) for treatment of depression
was suggested after a neurotic patient
improved after being struck by
lightning in 1890
Thunder
ƒ Caused by heating of air crossed by lightning
ƒ Cylindric column of air expands at supersonic
speed
ƒ Shock wave decays to sound wave
ƒ Time from sighting flash to hearing thunder
allows calculation of distance to flash site (light
: 186,000 miles per second, essentially
instantaneous ; sound : 1100 feet per second or
300 meters per second)
Forms of Lightning
ƒ Streak (branching) : most common
accounts for almost all injuries
ƒ Sheet : usually cloud to cloud
ƒ Ribbon
(rare ; current is
ƒ Bead
broken up)
ƒ Ball : rarest
Sequence of Events
Leading to Lightning Discharge
ƒ Air updrafts form ice particles
ƒ Particle collisions build up static electrical
energy
ƒ Positive charge develops in upper clouds
ƒ Negative charge develops in lower clouds
and ground
ƒ When the potential difference exceeds the
insulating properties of the air, a flash
occurs
Sequence of events leading to lightning formation
Lightning Structure
ƒ "Stepped leader" = current from cloud to
ground
ƒ Upward current = return or pilot stroke ; meets
the leader 50 meters above ground
ƒ Tip of leader releases heat and light
ƒ Secondary leader and return strikes occur (4 to
7 per stroke)
Lightning Injury : Types
ƒ Direct strike
–High morbidity (since head is hit)
ƒ Splash current
–On outside of body
–Causes flame-like burns
ƒ Ground current
–May cause mass casualities from one
strike
–Arrhythmias or asystole predominate
Lightning Injury : Skin Injuries
ƒ "Feathering"
–Very common
–Is superficial fern-like marks
–Not a true skin burn
–Disappear after a few days
ƒ 2nd or 3rd degree burns
–Usually due to clothing fire or contact
with heated metal
“Feathering” of the skin from lightning injury
Third degree skin burn (“charring”) from lightning
Second degree skin
burns from
vaporization of
moisture on the skin
by lightning
Differential Diagnosis of
Lightning Injury
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Cerebrovascular accident
Seizure disorder (postictal)
Closed head injury
Spinal cord injury
Hypertensive encephalopathy
Cardiac arrhythmia
Myocardial infarction
Toxic ingestion or intoxication
Treatment for Lightning Injury
ƒ Two different treatment regimens :
–For most victims (who have deep tissue damage
and / or flame burns on skin)
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Same scheme as for high voltage injuries (high volume
fluid resuscitation , Tc99m scan, fasciotomy, etc.)
–For victims who just have "CNS stunning" treat
same as for head trauma with increased ICP (fluid
restriction, hyperventilation, etc)
ƒ In both groups TM perforation is common
(need otic gtts & E.N.T. followup)
Lightning Injury Triage Principle
ƒ If multiple victims, ignore the ones
who are moving and awake, and
concentrate evaluation and care on the
ones who may be arrested (even
prolonged CPR often successful for
these victims)
Lightning Injury
ƒ Factors unrelated to mortality :
–Sex
–Age
–Trunk or arm burns
ƒ Factors related to mortality :
–Leg and head burns
–Immediate cardiopulmonary arrest
Lightning Injury : Neurologic Effects
ƒ Loss of consciousness : 72 % of cases
ƒ Paralysis of respiratory center ; leads to
apnea
ƒ Rarely : rapid cerebral edema and even
brainstem herniation
ƒ Transient motor paralysis : 70 %
ƒ Mechanical trauma : skull fracture,
intracranial hematomas
Lightning Injury : Cardiac Effects
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Depolarizes entire myocardium at once
Single systolic contraction ; leads to asystole
Then return of cardiac function (bradycardia)
If apnea however, leads to hypoxia, then
ventricular fibrillation
ƒ May show EKG changes c/w acute MI without
coronary artery occlusion
ƒ May have vasomotor spasm & prolonged
arterial vasoconstriction
Lightning Injury : Ocular and Otic
Effects
ƒ Cataracts : most common effect
–May appear 6 weeks to 24 months after
–Usually bilateral
–Also common after HV electrical injury
ƒ Retinal detachment : uncommon
ƒ Lid burns
ƒ Keratitis : may be severe
ƒ Direct current damage to inner ear or auditory
nerve
ƒ Tympanic memebrane rupture in up to 50 %
–Due to proximity of thunder noise generation
Lightning Injury : Other Effects
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Muscle necrosis or ruptures
Myoglobinuric renal failure
Ileus
GI bleeding
Pancreatic hemorrhage / necrosis
Thunder phobia
Risk Factors for Direct Strike by
Lightning
ƒ Outside
ƒ Carrying a metal object
ƒ Any metal object (hairpin or helmet)
even if small, on head
ƒ No taller objects in the vicinity
Lightning Injury Prevention
ƒ If outside :
–Avoid being the tallest object in the vicinity
–Avoid hilltops, poles, towers, trees
–If in a group, spread out
–Avoid wet soil
–Lie flat and curled up
–Stay away from metal equipment
–If your hair stands on end, run from the area right
away (you've been targeted !)
National Weather Service “30/30 Rule”
for Lightning
• If you can’t count to 30 between seeing
the lightning and hearing the thunder,
then you should go to a safe sheltered
location
• Don’t return outdoors until 30 minutes
after the last sound of thunder
Lightning Injury Prevention
ƒ If inside :
–Stay away from radiators, stoves,
appliances, gas and water pipes
–Avoid showering or bathing until storm over
–Do not use the phone
–Stay away from the fireplace
Electrical and Lightning
Injuries : Summary
ƒ Start cardiac monitoring & fluid resuscitation
early
ƒ Use Tc99m scan to guide early surgical therapy
for HV injuries
ƒ For lightning, determine if patient has HV-like
injuries or just "CNS stunning" since the Rx is
different for these 2 types
ƒ Prevention, mainly common sense measures,
is effective for both