Transcript Electrical and Lightning injuries

Lightning and Electrical
Injuries
Gabriel Piper
May 5th, 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
• 100 Lightning Deaths / Year USA
• Account for 3-7% of admissions to burn
units
Who gets electrocuted?
• Trimodal distribution
– Toddlers
– Teens
– Electrical utility and construction workers
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
What are the factors that determine
electrical injury?
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Current strength (voltage)
Tissue resistance
Duration of current flow
Type of current
Pathway of flow
What are Ohm’s and Joule’s
Law and what is their clinical
significance?
Physics 101
Ohm’s Law: I=V/R
Joule’s Law: Energy(heat) = I2x R x T
(T represents time of current flow)
• High energy = more damage
• Current is the primary determinant of
energy.
• Higher voltage produces larger Currents
What is considered High Voltage?
• 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.
Which tissues are conductors and
which are insulators and why does
tissue resistance matter?
Tissue Resistance
• Conductors: high fluid, electrolyte content
– nerves and blood vessels
– sweaty skin
– saliva
– muscle
• Insulators:
– Bone and tendons
– Fat
– dry skin
What are the two types of current?
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).
Current Pathway
What are the different mechanisms
that electricity causes injuries?
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
Lightning injuries
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
How do people survive lightning
strikes if they are so high voltage?
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)
Signs and Symptoms
Systems affected
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Cardiac
Respiratory
Nervous system
Skin
Musculoskeletal
Renal
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
Myocardial damage
• Often see rise in CKMB with electrical
injury
• Actual MI has been reported but is rare
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.
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
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
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?
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
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
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%
Lichtenberg figures
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?
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
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
Management
Prehospital
• First priority is to ensure
the scene is safe:
TURN OFF electrical
source!
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?
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
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
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
Treatment of burns
• See burn lecture for details
• Tetanus
• Observe for neurovascular compromise,
compartment syndrome
• Get plastics involved
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
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
Disposition
• Discharge if:
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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
Key Points
• Low-voltage -> may be discharged if asymptomatic and
normal ECG
– Immediate cause of death: V Fib
– Children: oral burns – consider delayed labial artery bleed
– arrange appropriate f/u (plastics, neuro, psych, etc)
• High-voltage -> admit for observation and cardiac
monitoring
– Asystole, treat cardiac arrest vigorously, even in mass casualty
scenario
– Blunt trauma common
– Deep tissue destruction with high fluid needs; surface findings
may be misleading
– Myoglobinuria and renal failure is common
– If findings of neurovascular compromise of limb, beware of
compartment syndrome
References
• Tintinelli’s
• Primavesi, R. A shocking episode: Care of
electrical injuries. Can Fam Physician.
2009 July; 55(7): 707–709.
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