Lightning and Electrical Injuries

Gabriel PiperMay 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?

• 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 tissues2.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 amountof energy delivered may be less than withother high voltage electrical injuries becauseof the short exposure time (milliseconds)

Signs and Symptoms

Systems affected

• 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?

• 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

Oral wounds in Kids

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 electricalsource!

Case

You are at a music festival in the summer,when a lightning storm suddenly rolls in. 15people are struck by lightning and 3 have nopulse.

What do you tell the pre-hospital medics onscene 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 managementResuscitation• 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:

– 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 TaserInjuries• 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