Transcript High voltage injury

Lightning and Electrical Injuries
Phil Ukrainetz, MD, PGY5 - Nov 21, 2002
Mass Casualty Incident
• You are the G8 medical section officer and
you are prepared for all disasters. You are
notified that a G8 protest group has just
been struck by lightning. There appears to
be 30 people affected and 5 appear to be
lifeless. How does this change your normal
MCI approach?
They get easier….
Mass Casualty Incident
• Normally cardiorespiratory arrests are
“START” triaged to blacks/morgue
• In lightning strikes there is a short initial
asystole and then the heart resumes beating
• The respiratory arrest however takes longer
• Lightning strike victims then die of
secondary hypoxemic induced ventricular
fibrillation
Mass Casualty Incident
• Support your arrests first, even if fixed and
dilated pupils
• In the absence of arrest lightning strike
victims are unlikely to die
• With immediate respiratory support
lightning strike victims can have excellent
outcomes
Doc, Doc I can’t move!!
• Your 27 year old patient has flaccid
paralysis of his lower extremities. Is he for
sure paralyzed?
Doc, doc I can’t move!!
What neurologic phenomenon may account
for this patients symptoms?
Keraunoparalysis
• Lightning induced sympathetic discharge
can cause neurologic and vasomotor
instability that can render a patient
paralyzed. Recovery is usually within 24
hours
Question?
• A 22 yr old female patient has suffered
extensive hand injuries from an AC source.
Her ECG is normal but your CKMB
fraction is “diagnostic” of an MI. Has she
necessarily infarcted?
Answer
• Well described that you get inordinate rises
in CKMB with electrical injury
• May get CK rises that contain as much as
25% CKMB (JAMA 255(6):764, 1986)
• Actual MI has been reported but is rare
He bit the cord!
• 2 yr old boy comes in with a oral burn
involving the lateral commissure of the
mouth as depicted in the following slide.
What is your treatment , disposition and
follow-up advice?
He bit the cord!
He bit the cord!
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ABC’s
Tetanus
Plastics consult: do nothing for a year
Warn of delayed labial artery bleed when
the eschar drops off in 2-4 weeks
Question
• What is the order of increasing resistance of
the following tissues?
– Bone, fat, muscle, mucous membranes, nervous
tissue, blood vessels, skin
Answer
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Nervous tissue
Blood vessels
Mucous membranes
Muscle
Skin
Fat
Bone
Esoteria continues..
What arbitrary voltage is the cut-off for high
and low voltage injury?
Esoteria continues..
• 1000 v is generally recognized as the cut-off
• However amperage, voltage, resistance,
type of contact, duration of contact, current
pathway and associated injuries need to be
assessed regardless of voltage
• E=I2RT
High voltage injury
High voltage injury
High voltage injury
In the code room...
What four mechanisms of injury are you
thinking of?
Three classes of injury
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Thermal burns
Electric current
Thrown
“Internal coagulation”
Lineman touches line!
• 37 yr old male o/w healthy. Right hand has
nasty entry point and left has an identical
exit point as depicted in the following slide.
How will you fluid resuscitate this person
with approximately 5% thermal burns?
Lineman touches line!
High voltage injury
• Cannot use conventional “Rule of nines”
• Fluid needs will be grossly underestimated
• Some data says multiply “Rule of nines by
1.7” (Ann Plast Surg 12:321, 1984)
• Treat as a crush injury
Crush injury management
• Principle of treatment is to avoid
myoglobinuric renal failure
– Foley output: 1-2 cc/hr/kg
– Fluid resuscitation: NS
• If CK up/myoglobinuria:
– Alkalinization: 3 amps bicarb in D5W and aim
for urine PH of 7.5
– +/- Mannitol: 0.25 - 0.5 cc/kg
Question?
Why are electrical burns concentrated at
distal extremities?
Answer
As the cross sectional diameter of the tissue
decreases, more heat is generated and
greater damage occurs
He was gyrating for hours...
• 25 year old male mowing lawn with an
electrical mower. On pulling out the cord
he received a 10-20 second AC tetanic
contraction shock. There are no visible
marks on his hand or anywhere on his body
but his arm aches. His Mom is quite
distressed after observing her son’s dance.
What are you going to do?
He was gyrating for hours...
• AC current is three times more dangerous
than DC of the same voltage
• AC can produce v. fib at low voltage 50-100
mA
• Repetitive fibrillatory stimulus
• Tetany occurs at muscle stimulations of 40110 hz (60 Hz is standard household)
He was gyrating for hours...
• If LOC, tetany, wet skin or current flow
crosses the heart:
– Order a ECG
– Cardiac monitoring
– Renal function, CK and urine for myoglobin
Question?
• What is Ohm’s law? Why is it important?
Answer
• I = V/R
• Analogy to a river
• The quantity of current through a tissue is
often the major determinant of the damage
to that tissue
I survived!
• 35 yr old Elvis impersonator, o/w healthy
survives a witnessed lightning strike.
Besides being visibly shaken he examines
perfectly normal. Knowing this is massive
DC current how could he survive?
Lightning strikes
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Average DC voltage is massive
Extremely brief duration of current flow
Courses over body externally
Small amount of current may leak internally
Lightning strikes
• Asystole, respiratory arrest, nervous system
dysfunction, and spasm of muscles and
arteries occur with strikes
• Lightning seldom causes significant burns,
tissue destruction or rhabdo
• Remember: QT prolongation, TM rupture
and delayed cataracts
Question?
• After a lightning strike a patient is left with
a strange feathering pattern along his lateral
torso. What is it?
Answer...
• Feathering or Lichtenberg figures is not a
burn but a pathognomonic sign of lightning
strike. It is not known if it is secondary to
electron showers, or current following
superficial vasculature or lines of moisture.
They typically disappear within 24 hours
even in the post-mortem state.
Summary
• AC worse than DC because of tetany
• AC electrical injuries can cause v. fib
• DC injuries tend to be single jolt with blunt
trauma and asystole
• Lightning (DC) causes asystole, respiratory
arrest but rarely burns or muscle damage
• Electrical injury can cause internal thermal
injury that is often underestimated