Electrical injury

Intro

• Classification
  • High-voltage >600
  • Low voltage <600
  • Electric arc flash burns (no passage through tissues)
• 10% complication rate
• Ohms Law
  • Current = Voltage/Resistance
  • Current proportional to voltage and inversely proportional to resistance
• Bone has the most resistance to current
• Nerves and vascular tissues have low resistance
• Dry skin has high resistance, but sweaty or wet skin much less
• Household electricity is AC vs. batteries and lightning DC
  • Low-frequency AC (50-60Hz) can be more dangerous than DC due to alternating current fluctuations and risk of VF
  • AC can also produce muscular tetany

Effects of current

• Can work out path of current as will follow path of least resistance
• What current has passed through raises suspicion for what may be injured

Electrical injury mechanisms

• Electrical burns
  • Severe when high voltage as only need fraction of a second of current flow
  • Less common with low voltage as little heat energy is produced
• Electrical arc injuries
  • Thermal burn due to current through tissues + flash burn + mechanical blast forces
  • Need thousands of volts to generate this with temperatures as high as 20 000 degrees resulting
• Tetanic contractions
  • Forceful contractions can prevent letting go of source, cause fractures/joint dislocations
  • Increased duration of contact and reduced resistance at grasp increases the heat produced and damage to deep tissues
  • Often 100x worse than if could let go immediately

Clinical features

• Possible immediate cardiac dysrhythmias, respiratory arrest (if traverses chest) or seizures (if traverses head)
• Cardiac dysrhythmias
  • Asystole or VF usually fatal prior to ED
  • Asymptomatic patients with normal ECG on arrival DO NOT develop later dysrhythmias after <1000V injuries
• CNS, spinal cord and peripheral nervous system injury
  • Neurological impairment in 50% of high-voltage injuries
  • Nerve tissue has lowest resistance in body
  • Document neurological examination prior to I&V if possible

Clinical features

• Brain injury
  • Transient LOC is common and may be followed by seizures
  • May be confused, agitated or comatose
  • May show focal neurology – need head and spine CT to rule out traumatic causes
  • MRI may be required for purely electrical damage
  • Electrical injury can cause blindness due to occipital lobe injury or direct injury to optic nerve
  • Survivors can have persistent issues with attention, memory and learning

Clinical features

• Spinal cord injury
  • 8% of high-voltage injuries
  • Can be due to fractures, direct cellular damage or vascular injury
  • Early MRI findings may be normal despite permanent spinal cord injury
  • Delayed neurological deterioration can occur days to months later
    • Often motor predominance and may be due to progressive vascular injury to spinal arteries or delayed cell membrane damage via cumulative effect of free radicals leading to progressive demyelination
    • May present as transverse myelitis, amyotrophic lateral sclerosis or GBS-like illness

Clinical features

• Peripheral nerve injury
  • Paraesthesias may be immediate and transient or delayed up to 2 years after injury
  • Extensive nerve damage can occur within minimal thermal injury
  • Palmar contact causes median or ulnar neuropathy > radial
  • Can have normal nerve conduction studies

Clinical features

• Cutaneous burns
  • Entry and exit wounds for DC and contact wounds for AC
  • Typically painless, gray-to-yellow, depressed areas
  • Mostly need admission and care by burn specialist
• Orthopaedic injury
  • Fractures due to tetany or falls

Clinical features

• Vascular and muscle injury
  • Current can pass along arteries causing spasm and persistent endothelial/smooth muscle dysfunction
  • High voltage shocks are at high risk of compartment syndrome, even if contact/arc for <1 second
  • Compartment syndrome also described for low-voltage injuries with prolonged contact
  • Often c/o ongoing mucle pain with movement
  • Significant tissue damage associated with:
    • Voltage >1000
    • Prehospital cardiac arrest
    • Crush injury
    • Full-thickness skin burns
  • Need aggressive fluid resuscitation +- fasciotomy (29%) and amputation (41%) after high voltage injuries

Clinical features

• Coagulation
  • Low-grade DIC can occur due to hypoxia, vascular stasis, rhabdomyolysis and release of procoagulants from traumatised tissue
• Blast injury
  • Electric arcs can produce strong blast pressure
  • Risk of concussion-type syndrome, ICH and arterial air emboli from blast-related alveolar disruption
• Inhalation injury
  • Ozone can be produced by arcs leading to mucous membrane irritation, reduced pulmonary function, pulmonary haemorrhage and oedema
• Ocular injury
  • Corneal erosion/keratitis, uveitis, retinal detachment, macular oedema, optic nerve damage and intraocular bleeding all seen
  • Cataract formation can occur years later after electrical injury to torso or electric arc burns

Clinical features

• Auditory injury
  • Current or haemorrhage through the TM, middle ear, cochlea and vestibular apparatus
  • Can have delayed mastoiditis, sinus thrombosis, meningitis and brain abscess
  • Hearing loss may be immediate or delayed due to complications
• GI injury
  • Suspect in all abdominal wall burns or trauma history
  • CT evaluation required with surgical consult as indicated
  • Need NG (ileus), stress ulcer prophylaxis, monitoring and surgical management as appropriate

Scene and prehospital care

• Stay 10 metres from downed power lines and support structures
• Turn off source of electricity if possible prior to rescue
• Need to prevent injury to rescuer as first priority
• Even dry wound can allow current flow at voltages >600V
• Spinal immobilisation is crucial
• Start rescue breaths while still on pole and then chest compressions once on ground
• Low-voltage AC can cause VF from direct stimulation of myocardium OR secondary to respiratory paralysis if prolonged
• High-voltage AC and DC tend to cause transient cardiac standstill and may revert to sinus rhythm once current ceases while apnoea continues (apnoea with pulses)

ED care

• Primary and secondary survey with spinal precautions
• Cardiac monitoring for high-voltage and symptomatic patients
• Admission ECG may show ventricular/atrial dysrhythmias, bradydysrhythmias and QT prolongation
• Careful vascular and neurological examination of peripheries is necessary
• Fluid resuscitation should follow Parkland formula but if extensive subcutaneous damage exists, requirements may be even higher
  • 4mL/kg/BSA over 24 hours (current thermal burn rate is 2 in adults and 3 in children)
• May have minimal cutaneous burn with significant compartment damage

Myoglobinuria

• High-voltage injuries should be monitored for compartment syndrome, rhabdo and renal failure
• If myoglobinuria is suspected, aggressive fluid resuscitation targeting UO 1-2mL/kg/hr is warranted with special attention to electrolytes
• Maintain high urine output until CK <5x ULN or urine myoglobin normalises
• Monitor serum, not urine, pH
• Prognostic factors associated with need for fasciotomy within 24 hours are:
  • Myoglobinuria
  • Burns >20% BSA
  • Full-thickness >12% BSA

Disposition

• Low-voltage injuries (<600V)
  • If <240V, asymptomatic and normal ECG on presentation – d/c
  • If symptomatic or ECG abnormality – monitor for 6 hours and reassess
• High-voltage injuries (>600V)
  • Admit for observation no matter what
  • Routine cardiac monitoring only if symptomatic or initial abnormal ECG

Special populations

• Pregnant women
  • Need CTG for at least 4 hours if >20 weeks

Special populations

• Children
  • Improved outcomes compared to adults
  • Oral and lip burns
    • Typically end of power cord put in mouth with current flow between two wires creating significant heat and tissue damage
    • Vascular injury to the labial artery may not be immediately apparent due to vascular spasm, thrombosis and overlying eschar
    • Once eschar separates (around day 5) up to 10% of cases will have severe bleeding so admit
    • Healing often results in deforming scars and contracture of oral opening
    • Saline or hydrogen peroxide rinses and gentle swabbing to debride necrotic tissue is required to ensure healthy healing
  • Hand wounds
    • If no cardiac or neurologlcal involvement, can treat hand burn and discharge

Lightning injuries

• 70-90% survival but ¾ will have permanent sequelae
• 10 million to 2 billion volts
• Current duration 10micros to 3 milliseconds
• DC
• Skin flashover usually (especially if wet); deeper pathways result in severe deep burns
• Results in asystole and apnoea
• Blunt injury can throw person and cause eardrum rupture
• Can cause burns through moisture on skin turning to steam, electric current through deeper tissues and through resistance heating of objects on skin or in pockets
• Can get retinal damage or cataracts due to intense photic stimulation

Keraunoparalysis

• Neurologic and muscular stunning after lightning strike
• Lower limb weakness > upper limb
• Sensory abnormalities, pallor, coolness and diminished peripheral pulses all thought to be due to autonomic dysfunction
• May persistent >1 hour and in such cases amnesia and neuroses often slowly clear over a week

Types of lightning strikes

• Direct strike
  • Victim struck directly
• Side flash
  • Nearby object struck and current traverses through air to the victim
  • May injure multiple victims at once
• Contact strike
  • Lightning strikes object person is holding
  • E.g. indoor telephone use during lightning storm

Types of lightning strikes

• Ground current
  • Lightning hits ground and current transmitted to nearby victims
  • Stride potential can occur with differing potential between each foot so current runs up one and down the other causing isolated neurovascular injury to the lower limbs
• Upward streamer
  • Weak upward current does not reach the completed lightning channel but courses through person

Cardiac arrest

• Get total myocardial depolarisation with asystole
• Immediate respiratory arrest occurs due to depolarisation and paralysis of the medullary respiratory centre
• Cardiac automaticity may spontaneously return, but respiratory arrest may continue leading to secondary hypoxic cardiac arrest
• The duration of apnoea vs. duration of cardiac arrest seems to be the critical prognostic factor

Care at the scene

• Reverse triage
  • Should treat those that appear dead FIRST
  • Prolonged CPR may be helpful
• Aggressive resuscitation is indicated at ED as have better prognosis than coronary artery disease arrests
• Hypotension warrants searching for haemorrhagic blood loss

Cardiac effects

• HTN and tachycardia commonly seen
• May get myocardial stunning, coronary artery spasm, pericardial effusion and arrhythmias
• ECG may show acute ST elevation and QT prolongation
• TWI often seen, especially in setting of neurological injury

Neurological injury

• Unconscious or temporary lower limb paralysis are common
• Seizures may be due to current or mechanical head injury or hypoxia
• Autonomic dysfunction may result in pupillary dilation, anisocoria and therefore these signs have no prognostic significance in comatose lightning-strike victims
• Transient amnesia, confusion, lower limb paralysis are common
• Delayed seizures, muscular atrophy, amyotrophic lateral sclerosis, parkinsonism, progressive cerebellar ataxia, myelopathy with para/quadriplegia and chronic pain syndromes are seen
• CT is indicated in comatose/ALOC/headache patients to ensure no underlying mechanical trauma has been sustained

Vascular effects

• Vasomotor spasm is common often with cycle of severe vasoconstriction and colour change from white to blue to red with hyperaemia after vasodilation resumes
• Compartment syndrome is rare in lightning strike so should check intracompartmental pressures prior to fasciotomy if suspicion exists

Ocular injury

• Lightning-induced cataracts are most common
  • May be due to radiation injury even without current flow through head
  • May occur weeks to years later
• Can cause hyphaema, vitreous haemorrhage, corneal abrasion, uveitis, retinal detachment, retinal haemorrhage, macular holes and optic nerve damage
• Any symptoms warrant careful examination and ophthalmology follow-up

Auditory injury

• Telephone injuries at highest risk
  • Persistent tinnitus
  • Sensorineural deafness
  • Ataxia
  • Vertigo
  • Nystagmus

Cutaneous injury

• Lichtenberg figures
  • Pathognomonic with superficial feathering/ferning pattern due to electron showering over skin
  • Disappear within 24 hours
• Flash burns (mild erythema)
• Punctate burns
  • Full-thickness <1cm like cigarette burns
• Contact burns due to metal close to skin
• Superficial erythema and blistering burns
• Linear burns <5cm wide in skin folds

Disposition

• Admit almost all lightning strike victims
• Definitely admit those with ongoing muscle pain, ECG changes, persistent neurological or vascular abnormalities
• Need close follow-up for delayed sequelae

Last Updated on October 9, 2020 by Andrew Crofton