Lightning Injuries

Etiology

Lightning carries with it a tremendous amount of energy.  A bolt of lightning can carry a voltage exceeding 10 million volts with a massive current typically between 30 thousand to 110 thousand amperes. The temperature of a lightning bolt is also extremely hot, reportedly as high as 30 thousand Kelvin.  Lighting can be both negatively and positively changed, and can take the form of both direct and alternating current.  A victim’s exposure typically last from 1/1000 to 1/10 of a second. Not all lightning injuries occur during the same manner with injuries being classified as a direct strike, side splash, contact injury, or ground current.  Direct strikes are rare, accounting for 5%, and occur when a person is directly struck by lightning creating an uninterrupted connection between the person and the bolt.  Contact injuries occur by touching an object that is struck.  Side splash accounts for one-third of injuries and happens when the current jumps or "splashes" from a nearby object then following the path of least resistance to an individual. Ground current is the most common mechanism of injury, accounting for one-half, and occurs when lightning strikes an object/ground near an individual and then travels through the ground to an individual.[5][6][7][8]

Epidemiology

Lightning does not occur in a uniform pattern, globally. Areas with higher occurrences of thunderstorms will have a higher incidence of lightning strikes. Geography also plays a role in some areas with mountainous terrain will often experience more lightning strikes than surrounding lower elevation areas. Though likely underestimated, in the United States there are approximately 400 lighting injuries and 40 deaths annually. Greater than 80% of victims are males with most deaths occurring in individuals 20 to 45 years old. Most deaths occur within one hour of injury and are due to fatal arrhythmia or respiratory failure. Up to 74% of survivors may have some form of permanent disability. In the United States, most incidents occur between May through September with nearly 70% of incidents occurring in the afternoon or early evening. The greatest number of deaths due to lightning occur in Texas and Florida, but the highest incidence of lightning incidents occurs in Arizona, Arkansas, Mississippi and New Mexico. In the United States, a person has an estimated 1:10,000-lifetime risk of being struck by lightning.

Pathophysiology

Lightning can harm an individual through several mechanisms.  These include the effect of electric current on/through body tissues, burns due to conversion of electrical to thermal energy, mechanical trauma through a variety of mechanisms; including being thrown due a transmitted shockwave or direct strike from a bolt, flying debris from an object nearby due to shockwave or direct strike, fall secondary to being struck or due to muscle contraction.

Sudden death following a lightning strike is due to simultaneous cardiac and respiratory arrest and is more common with direct strikes. Typically, patients will have an asystolic arrest due to an immediate and simultaneous depolarization of all myocardial cells. Ventricular dysrhythmias are also possible, but much less common.  Spontaneous return of sinus rhythm, typically sinus bradycardia, and the return of spontaneous circulation will often precede the recovery of the respiratory system. A second cardiac arrest due to continued paralysis of the medullary respiratory center may occur if treatment is not promptly initiated.

Lightning may also cause damage to the central and peripheral nervous system. Lightning has been found to induce intracranial hemorrhage in some individuals, mostly in the basal ganglia and brainstem. It can also cause damage to other locations within the central nervous system and damage to the peripheral nervous system due to direct damage to nerve cells. Keraunoparalysis may also occur, in which a temporary paralysis due to vascular spasm and sympathetic nervous system instability occurs. This is most common in the lower extremities, is typically temporary, and resolves without treatment. 

Burns ranging from superficial to full thickness are also associated with lightning strikes, superficial burns being much more common.  Linear burns are typically partial thickness and occur when sweat is vaporized as lighting travels over the skin. Punctate burns are clustered circular burns due to current passing out from deep tissue as it exits the body.  Full thickness burns are rare, occurring in less than 5% of injuries, and most commonly occur when objects such as synthetic fabric or metal is heated to a high degree and melts to or then directly burns the skin.

Blunt injury is not uncommon and can occur either due to a person being thrown due to massive instantaneous contraction from the current passage through the body or by an explosive or implosive force as the air surrounding the bolt is superheated and then rapidly cooled resulting in a sudden and powerful shock wave.  This shock wave can cause concussive injury and has been associated with tympanic membrane rupture, organ contusions, and pneumothorax.  This can also result in multiple forms of trauma from fall or being struck by other objects creating the possibility for a myriad of injuries including a skull fracture, cervical spine injury, and internal bleeding to name a few.

Ocular injury from current, blunt or blast trauma, vasoconstriction, or heat are also common.  Cataracts, most often bilateral, are the most common but other injuries such as hyphema, vitreous hemorrhage, and optic nerve injury can also occur.  Many victims struck by lightning will also have an injury to the audio-vestibular system due to either blast trauma or electrical injury. A ruptured tympanic membrane is common and found in 50-80% of those struck by lightning. Sensorineural deafness is often both transient and common with others experiencing tinnitus, vertigo, or facial nerve paralysis/injury.

History and Physical

Patient history often will be highly suggestive of a lightning injury.  One should inquire what the patient was doing and where they were to elicit information that may be suggestive of other forms of trauma such as a fall from a height or being struck by objects that may not be obvious on physical exam. If history is questionable or unknown, other helpful signs include clothing that is singed, has punctate holes, appears in pieces and not fully intact, signs of melting to metal pieces of clothing, and damage to other nearby area/structures.

The initial exam should focus on the airway, breathing, and circulation with appropriate interventions should the patient not be found to be apneic or pulseless. One should be thorough in their evaluation for a pulse as vasospasm from the strike may make it difficult to palpate a pulse. Because of this phenomenon, CPR should not be initiated until one checks and is unable to palpate a central pulse. Neurologic status should also be assessed. Due to the peripheral nerve damage, which is common in lightning strikes, patients may have abnormal sensory and/or motor findings. Deficits may be “patchy” with sensory and/or motor deficits that may not correlate with each other. It is not uncommon for neurological deficits to be missed in the initial exam and not diagnosed for weeks to months following the event.  Care also should be taken as patients may have temporary autonomic damage resulting in dilated and non-reactive pupils, making this an unreliable indicator of death.  Keraunoparalysis, more common in the lower than the upper extremities, classically presents with blue, mottled, cold, and pulseless extremities along with paralysis of the affected extremities.

The skin should be carefully inspected for burns with great care given to skin folds, creases, and joints as burns are more common in these areas. Some patients may have Lichtenberg figures which are a transient "ferning" or "feathering" pattern. Though the cause is not fully understood, this finding is pathognomonic for a lightning strike and is transient and self-resolving. Assessment of hearing and tympanic membranes is necessary as is ophthalmic exam including visual acuity and funduscopic exam. Patients suffering from keraunoparalysis often will present with lack of pulse, pallor, cyanosis, and motor and/or sensory loss to the affected extremities, most common in lower extremities. 

Patients should also be assessed for the trauma that may have occurred as a result of a lighting strike due to direct or blunt injury.

Evaluation

There are no required labs or imaging for all patients struck by lightning, but certain tests and studies are recommended for certain subsets of patients. [9][10][11][12]

Select "high-risk" patients, those with a direct strike, chest pain, dyspnea, status post-arrest, should have an ECG and echocardiogram and be monitored on telemetry for 24 hours with other imaging and labs guided by history and physical exam.  Many would advocate for an ECG in all victims of lightning strike/injury, but the data on this is mixed as many individuals will have transient and benign ECG changes. Cardiac markers commonly are elevated but are not prognostic, and routine screening is of limited utility.

All lightning strike patients should have a thorough exam for signs of trauma with appropriate workup and imaging to be guided by history and exam. Any patient with loss of consciousness, burns to the head, or abnormal neurologic examination should have a CT of the head due to increased risk of intracranial hemorrhage.

Labs and other imaging may be ordered upon the discretion of the provider, but as mentioned, are not mandatory for all victims.

Treatment / Management

If multiple lightning victims are present, initial triage and treatment should follow a “reverse triage” system. This is of critical importance, as failure to do so may result in unnecessary and avoidable morbidity and mortality. Those who survive the initial strike rarely die prior to or after hospital arrival, and initial treatment and resuscitation should be concentrated on those who appear to be in cardiac arrest. Sudden death is most often due to a simultaneous sudden cardiac and respiratory arrest. Often there will be a return of cardiac automaticity in the form of sinus bradycardia with a concurrent return of spontaneous circulation that precedes the recovery of the respiratory system and spontaneous respiration.  Given that ROSC precedes the resolution of respiratory arrest, patient ventilation should be supported as soon as possible. This will help reduce the incidence of a secondary cardiovascular collapse. During this time, care should be taken to palpate a central pulse, and if not appreciated, CPR may be initiated.

Trauma injuries incurred due to lightning strikes should be treated appropriately as deemed fit by the provider. Those with neurological symptoms will need repeat evaluation, and if symptoms persist, they will need evaluation and treatment by a neurologist. Burns should be treated appropriately per standard guidelines.

Most lightning survivors who appear well without abnormal vital signs or injury requiring hospitalization can safely be discharged if they also do not have high-risk findings/history including suspected direct strike, loss of consciousness, focal neurological complaint, chest pain, dyspnea, major trauma, cranial or significant burns. Appropriate consultation/referral should be obtained for those with ophthalmic, audio-vestibular system, or other injuries as seemingly fit.

Lightning strikes to pregnant patients are rare. Maternal mortality is low, but fetal mortality is high, approaching 50%. It is recommended that individuals at or beyond 20 weeks’ gestation have fetal screening performed upon presentation to a medical facility.

Differential Diagnosis

• Acoustic injury

• Autonomic nervous system injury

• Barotrauma

• Blunt and explosive trauma

• Cardiorespiratory arrest

• CNS injury or stroke

• Electrical injuries

• Intracranial haemorrhage

• Musculoskeletal injury

• Stroke