Lightning is the result of static charges that occur as a cold, high-pressure front moves over a warm, moist, low-pressure area. The friction of moving air particles within clouds causes ionization and other energy changes. Lightning usually occurs when a leader stroke from a cloud takes a slow, jagged, irregular path toward the earth, which is oppositely charged.
Lightning injuries are different from high-voltage electrocution injuries. The main factor differentiating the two injuries is the duration of the electrical exposure. Lightning strikes may have voltages of 100 million to 2 billion volts, but current flow is only between one-thousandth to one ten-thousandth of a second.
Lightning injuries are usually the result of five different mechanisms: direct strike, contact injury, side flash (splash), ground current (step voltage), and blunt trauma. As would be expected, direct strike injuries occur when lightning strikes a person directly. Contact injuries occur when a person touches an object that is part of the lightning current pathway. Side flash or splash injuries occur when lightning arcs from the object struck to a nearby object. Ground current or step voltage injuries occur when the lightning current spreads peripherally through the ground from the site of the strike. Blunt injuries occur in two fashions. In the first, the victim's musculature contracts diffusely, causing the victim to be thrown a distance from the lightning strike. The second mechanism is the consequence of large fluctuations in temperature associated with a lightning strike. Lightning causes instantaneous superheating and expansion of the air, which is followed immediately by an implosion as the air is rapidly cooled. The duration of heat is so brief that thermal injuries seldom occur. However, the explosion and implosion of air can lead to blunt trauma of major organ systems such as the brain, liver, and spleen.
Because the duration of a lightning strike is extremely short, little of the massive energy is transferred internally to the victim. Rather, the majority of the energy flows externally over the victim's body (a "flash over"). However, enough energy passes through the body to disrupt and short-circuit electrical systems within the body, especially the heart, vasculature, respiratory center of the brain, reticular activating system, and autonomic nervous system. The major cause of death in lightning injuries is cardiopulmonary arrest due to asystole. However, asystole can be readily converted to a coordinated cardiac rhythm with timely and aggressive cardiopulmonary resuscitation.
Often patients struck by lightning will appear free from injury. Importantly, the only sign of lightning strike may be an isolated wound that results at the site of contact of lightning with the body. Thus, all lightning victims require a detailed physical examination with pertinent laboratory tests to determine the presence of occult injuries.
Central nervous system injury, including blunt head trauma, is common. Blunt head trauma usually results from falls or the diffuse muscle contraction that causes the victim to be thrown from the site of the strike. Patients typically have a change of mental status, which may be transient or prolonged. Prolonged loss of consciousness suggests intracranial injury. Lightning victims may present with confusion, agitation, emotional lability, amnesia of both short-term and long-term memory, cognitive impairment, aphasia, headache, seizures, and prolonged coma. Hypoxic encephalopathy and peripheral neuropathy have been reported. Symptoms of central and peripheral nervous system injury may improve, but long-term disability is common. Occult injuries of the neck should always be suspected.
More than half of the victims of lightning strike suffer at least one ruptured tympanic membrane, either from the shock wave or an associated basilar skull fracture. In addition, the ossicles are often disrupted. Cataracts, which may occur immediately after injury or months later, occur in 5% of patients who have lightning strike near the head.[3,4] Corneal burns, intraocular hemorrhage or thrombosis, uveitis, retinal detachment, choroidoretinitis, iridocyclitis, hyphema, and orbital fractures may also occur. Nonreactive dilated pupils in a lightning strike victim may be a sign of direct eye involvement or autonomic dysfunction. Therefore, the presence of dilated pupils after a lightning strike may not be a reliable sign of brain death.
The spinal cord may be injured as a result of direct injury to the spinal cord or from fractures or ligamentous injury to the spinal column. Patients with spinal cord injury commonly have both acute and delayed pathologic changes. Acute insult to the spinal cord causes weakness and paresthesias within hours of the strike. The lower extremities are more commonly involved than the upper extremities. Recovery is usually complete, but a number of victims are left with residual injury. Delayed injuries include ascending paralysis, amyotrophic lateral sclerosis, and transverse myelitis. Motor deficits are common in delayed injury, while sensory deficits are typically patchy and do not correlate well with the level of motor deficit. Although recovery has been reported, prognosis for full recovery is usually poor.[5,6]
Cardiac arrest in lightning strikes is usually asystole instead of ventricular fibrillation. Furthermore, with rapid institution of cardiopulmonary resuscitation and advanced cardiac life support, asystole commonly converts to an organized cardiac rhythm. Nonetheless, victims may present with sinus tachycardia, transient ST segment elevation, QT prolongation, premature ventricular contractions, atrial fibrillation, or bundle branch block. Acute myocardial infarction is rare but has been reported. Arterial vascular spasm is a common occurrence and may lead to damage to the heart, gastrointestinal tract, and brain.
Lightning-induced lung damage is rare because of the poor conduction capacity of the air in the lungs. However, blunt pulmonary trauma is not uncommon. Respiratory arrest usually results from the transient paralysis of the medullary respiratory center. Aspiration pneumonia, pulmonary edema, pulmonary hemorrhage, and contusion have been reported but are rare.
Solid intra-abdominal organ injury is usually due to blunt trauma. Solid organ injury as a result of electrical current from lightning strike has not been reported. For example, hepatic and pancreatic necrosis, paralytic ileus, bowel perforation, esophageal hemorrhage, Curling ulcers, and gastrointestinal bleeding, which have been observed in high-voltage electrocution injuries, have not been reported with lightning injuries. Furthermore, acute renal failure from rhabdomyolysis or hypovolemia rarely occurs because little energy actually passes through the organs.
Lightning victims frequently present with keraunoparalysis in which the extremities, usually the legs, become transiently cold, cyanotic, pulseless, and mottled. Keraunoparalysis is the result of vascular spasm and autonomic nervous system instability. It usually resolves after a few hours, though some patients have long-term neurologic sequelae, including paralysis and paresis.
Long bone fractures, vertebral compression fractures, and scapular fractures may result from the electrical shock associated with lightning injury, either from the violent and intense muscle contraction or from blunt trauma. Periosteal burns, bony matrix destruction, aseptic necrosis, muscle necrosis, and osteomyelitis are not typically seen with lightning strike.
Dermal findings associated with lightning injuries are rare. Only 5% of lightning strike victims have deep thermal skin burns. Four types of superficial burns typically occur. Linear burns develop where water accumulates on the body. They are the result of steam production during the flashover of electrical current. Punctate burns are multiple small burns seen over the surface of the victim's body. They resemble cigarette burns. Feathering burns are the result of electron showers that flow over the body during the lightning strike. These burns appear as fernlike patterns on the skin and do not usually require therapy. They are considered pathognomonic of lightning injury. Finally, thermal burns may occur when clothing ignites or metal objects are superheated during the lightning flashover. Usually, lightning victims are found to have two or more types of these burns on physical examination.
All lightning strike victims should be assessed as victims of trauma, with the institution of both advanced trauma and cardiac life support. Initial management includes evaluation of the airway, breathing, and circulation. Supplemental oxygen should be given, cardiac monitoring instituted, pulse oximetry placed, and two large bore intravenous catheters inserted. Basic laboratory studies should include a complete blood count, electrocardiogram, electrolytes, liver profile, cardiac enzymes with isoenzymes, coagulation factors, arterial blood gases, blood type and screen, urinalysis, and urine myoglobin. Appropriate radiographic studies should be done. Nasogastric decompression of the gastrointestinal tract should be considered.
Care should be taken to prevent unnecessary complications. The clinician should resist the temptation to give the lightning victim massive amounts of fluid. Lightning seldom induces deep tissue or massive tissue necrosis typically seen with high-voltage injuries that cause hypovolemic shock or renal failure due to rhabdomyolysis. Instead, lightning victims often have intracranial and cardiac injuries. Thus, intravenous fluids need to be administered judiciously.
Cutaneous burns, when they do occur should be treated as thermal cutaneous burns with bacitracin, silver sulfadiazine or mafenide acetate. Bacitracin may be used on small or superficial burns. Silver sulfadiazine (Silvadene) is preferred for extensive burns. Mafenide acetate (Sulfamylon) is used for deep burns because it has better penetration of the eschar. However, it is associated with electrolyte abnormalities.
All patients with lightning injuries should be evaluated for admission. Indications for admission to an intensive care unit include respiratory or cardiac arrest, cardiac arrhythmia, or history of cardiac disease; alteration in level of consciousness; abnormal laboratory or electrocardiographic findings; and associated blunt trauma or significant soft tissue injury. Importantly, because of the potential for acute or delayed-onset cataracts, ophthalmology consultation is warranted in all lightning victims. Lightning injuries may be managed on an outpatient basis if the victim had no initial complications of the lightning strike, has normal findings on physical and laboratory examination, and remains asymptomatic.
Reprint requests to Kennan J. Buechter, MD, Louisiana State University Health Sciences Center, Department of Surgery, 1542 Tulane Ave, New Orleans, LA 70112.
South Med J. 2002;95(11) © 2002 Lippincott Williams & Wilkins
Cite this: Lightning Injuries - Medscape - Nov 01, 2002.