Lightning injury

OVERVIEW

• potentially lethal electrical injury due to lightning exposure
• 24,000 deaths/ year worldwide

PHYSICS AND PATHOPHYSIOLOGY

Physics

• extremely high voltage (30 millon volts)
• high currents: 30,000 to 110,000 A
• limited energy transfer due to extremely short duration (10-100 msec)
• can be AC or DC current, but tetanic contractions are not seen
• electricity travels through path of least resistance: nerves < blood < muscle < skin < fat < bone

Types of lightning injury

• direct strike (5%)
• contact injury (15%) – victim in contact with structure that received direct strike
• side splash (30%) – current jumps to victim not in physical contact with structure that received direct strike
• ground strike (50%) – current travels through the ground to the victim (strike point)

CLINICAL FEATURES

Cardiorespiratory arrest (rare)

• immediate
• usually asystole due to electrical insult to the myocardium, typically resolves spontaneously
• respiratory arrest due to medullary paralysis
• apnea is longer duration than asystole, so untreated patients may have ROSC then suffer a second hypoxic arrest

Cardiovascular

• asystole or VF immediately
• ECG changes such as ST elevation and QT prolongation
• atrial fibrillation
• cardiomyopathy
• delayed pericarditis

Respiratory

• blast injury
• ARDS
• aspiration

Neurological

• transient, immediate
  — keraunoparalysis due to ANS-mediated vasopasm -> motor and sensory changes, cyanosis, pallor and/or pulselessness; lower limbs > upper limbs; resolves spontaneous; may mimic spinal cord injury
• permanent, immediate
  — hypoxic encephalopathy, peripheral neuropathy, intracranial hemorrhage (especially basal ganglia, brainstem), stroke, cerebral salt wasting syndrome, traumatic injuries
• delayed
  — progressive myelopathy (weeks-to-months; causative link to lightning strike is uncertain)

HEENT

• eyes — cataracts, blast injury, retinal and optic nerve injury
• ears — tympanic membrane rupture (50% – heal with conservative management), otorrhoea (suspect base of skull fracture), transient sensorineural deafness, microfractures (permanent hearing loss)

Burns

• Lichtenberg figures — transient ferning or feathering patterns pathognomonic of lightning strike (onset <1 hour, duration <24 hours)
• linear – “flashover” (sweat turns to steam)
• punctate burns – multiple circular burns due to current leaving the body e.g. tip-toe sign
• full thickness contact burns – due to fire or heated object in contact with skin (NB. deep thermal burns are rare, unlike HV electrical injuries)

Neuropsychiatric

• functional – memory and concentration impairment
• behavioural – depression, aggression, personality change

HIGH RISK FEATURES

• loss of consciousness
• focal neurological deficits
• chest pain or dyspnea
• pregnancy
• burns to head, legs or to >10% BSA
• major trauma or blast injury

INVESTIGATIONS

• ECG
• Echocardiogram (if high risk features)
• CK, troponin (not prognostically important)
• CT Head if loss of consciousness or focal deficit
• MRI if cannot exclude spinal cord injury clinically

MANAGEMENT

Prehospital

• ‘reverse triage’ applies as patients may appear dead (fixed dilated pupils with respiratory arrest) but develop ROSC and may make full recovery
• all patients with high risk features should be transported to hospital; others according to comorbidities and nature of injury

Resuscitation

• as per standard ACLS guidelines
• despite anecdotal reports there is no reason to assume nor evidence to suggest that lightning strike victims might benefit from prolonged CPR

Specific therapy

• treat injuries on merit
• seek and treat complications (e.g. rhabdomyolysis)

Supportive care and monitoring

• 24 hours cardiac monitoring if ECG changes, abnormal Echo

Disposition

• admit all patients with high risk features to hospital
• ECG changes or abnormal echocardiography require cardiology review and follow up
• burns require review by burns specialist
• visual loss or high risk features -> ophthalmology review
• hearing impairment -> ENT review
• functional or behavioural problems -> neuropsychiatric follow up

PREVENTION

• “when thunder roars, go indoors” — ideally inside a large building away from metal utilities, doors and windows, otherwise in a metal-roofed vehicle with doors and windows closed (acts as a Faraday cage)
• avoid open exposed areas, summits and ridgelines
• avoid tall structures
• if in a group space >20 feet (6 m) apart
• stay indoors until 30 minutes after the last thunderclap heard (to ensure 10 mile buffer)
• if outdoors use the ‘lightning position’ as a last resort: crouch with feet together to make one contact point, alternatively if sitting lift feet off the ground; insulate from ground if possible (e.g. sit on pack)
• exit water and stay away from the water edge
• be aware that lightning can strike despite clear skies (typically after a storm – ‘bolt from the blue’)
• remove metal objects to avoid contact burns should lightning strike
• timing thunderclaps to judge distance is unreliable (which thunderclap accounts for which lightning strike?)

References and Links

• Davis C, Engeln A, Johnson E, McIntosh SE, Zafren K, Islas AA, McStay C, Smith W’, Cushing T; Wilderness Medical Society. Wilderness medical society practice guidelines for the prevention and treatment of lightning injuries. Wilderness Environ Med. 2012 Sep;23(3):260-9. PMID 22854068.
• O’Keefe Gatewood M, Zane RD. Lightning injuries. Emerg Med Clin North Am. 2004 May;22(2):369-403. PMID: 15163573