Lightning is the natural electrical discharge of unequal charges between a cloud and the ground or within a cloud. These discharges are of very short duration (milliseconds) and extremely high voltage (many millions of volts). Lightning occurs nearly 50 times per second worldwide, with about 20% of those flashes becoming ground strikes.
Internationally, an estimate of 24,000 fatalities occur from lightning strikes every year. An additional quarter of a million injuries are attributed to lightning strikes, making this a common problem in the outdoors. Climbers are at particular risk for this, since their activities take place at elevated positions, often in exposed areas, and on ridgelines. However, in the United States, the incidence of lightning-related deaths has declined over the past half century. Currently, in the USA, approximately 40 deaths per year are attributed to lightning, plus approximately 400 lightning-related injuries. In the context of mountaineering, this compares to about 30 avalanche-related deaths annually. But, by definition, all avalanche-related deaths occur in mountainous terrain, whereas Florida and Texas account for fully 25% of lightning deaths, with golf courses and open fields as common locations. Therefore, epidemiologically, lightning strikes may not be among the most common sources of injury for mountaineers, and mountaineering may not be the most common activity during which a lightning strike might occur.
Regionally, thunderstorm frequency correlates with lightning strike frequency. Mountainous terrain can contribute to this pairing. For example, Central Africa has the greatest incidence of lightning strikes internationally; its mountainous terrain coupled with moist airflow from the Atlantic Ocean leads to year-round thunderstorms (Davis 2014). It is vitally important to realize that lightning can travel up to 10 to 15 miles ahead of or behind a storm cell. The familiar phrase “out of the blue” originates from lightning strikes occurring out of an apparently blue sky without storm patterns (Houghton Mifflin Harcourt 2011). Lightning is also possible in snowstorms, and graupel (snow pellets) can indicate favorable conditions for lightning formation—the pellets may generate positive and negative charges as they collide, providing an electrical gradient that promotes lightning. Cloud-to-ground lightning strikes seek the highest point to discharge, so ridgelines or high exposed points with surrounding lower ground are at high risk for lightning strikes.
When a lightning strike is imminent, many describe an “ozone smell” preceding the strike. St. Elmo’s Fire is a blue haze or glowing ball of light or sparks, well known to mariners and described in writings going back to ancient times. It is a weather phenomenon due to electrical discharge preceding lightning strikes or other electrical fields such as those around volcanic eruptions. Electrical field disturbances can also make the hair on one’s body stand on end (“goose bumps”), cause other static electricity sensations, or generate crackling sounds.
A lethal lightning strike may be hard to recognize as the source of death for someone coming upon the body later. Lightning does not always leave immediately apparent signs in the environment of its strike, so a body may be found without apparent cause of death.
But signs can sometimes be present. One effect of lightning strikes can be exploded clothing, due to the instantaneous vaporization of water/sweat particles on the body as the charge passes over it. This is particularly the case with socks and shoes, because of the high amount of moisture typical on feet. One’s entire body can be thrown through the air due to tetanic (spasming) muscle contractions or simply the force of the bolt, causing blunt trauma. Somewhat later, ferning burn-like rashes called Lichtenberg figures can appear on the body. These figures are pathognomonic for lightning strikes, meaning that no other condition causes them and their presence alone can diagnose a lightning strike. They are not true burns, but represent the capillary rupture of liquid under the skin as a lightning current superheats tissues it momentarily passes through. They are painless and, in a patient who survives a lightning strike, eventually go away. Large Lichtenberg figures can be observed in grasses or other organic materials surrounding a lightning strike, and in some cases, deaths of unknown cause in the wilderness have been identified when, a day or two later, Lichtenberg figures appear in the grass surrounding the location where the body was found.
Direct lightning strikes are relatively rare, accounting for only about 5% of human lightning strikes. Other lightning strike injury categories include contact injury (touching an object like an ice axe that transfers electricity from a remote strike), side splash (charge “jumping” from a directly struck object like a tree, accounting for about one third of lightning strike injuries), ground current (also known as step voltage, where a charge travels through the ground until it reaches a victim; this accounts for about half of lightning injuries), and upward streamers (a current passing through the ground toward a cloud, which does not involve ground strike and usually does not become part of a completed lightning channel). In all these cases, lightning follows a predictable pattern, taking the path of least resistance. That fact, coupled with environmental features and their relative resistance, helps inform the prevention techniques as discussed above. Similarly, lightning’s predictability, combined with anatomical relative resistance (nerves have least resistance and therefore better conduction, followed by blood, muscle, skin, fat, and finally bone), informs the treatment techniques discussed below.
The most important way to prevent lightning injury is to reduce exposure. If caught in a high, exposed environment, prevention becomes much more difficult. Lightning strikes are more common among those with certain outdoor occupations, such as farmers, and reductions in lightning strikes over generations reflects an increase in access to buildings and other reduced-risk sites. However, no place is absolutely safe from a lightning strike. Even within buildings, it is necessary to stay away from open windows and avoid using wired electrical tools such as wall-wired telephones. Consider open architecture when choosing huts or other structures in which climbers might seek shelter—more windows or open space equates to more risk. Fixed structures that might be used for lightning refuge can also benefit from structural features such as lightning rods. Cars can provide reasonable shelter, since their metal exoskeleton acts like a Faraday cage to transmit a strike to the ground. But the vehicle’s metal frame must be continuous (convertibles are not effective, nor are cloth-topped cars), and tires, contrary to popular myth, do not insulate from ground strikes. Although rubber is indeed a poor conductor, the contact pad of the average tire (amount of rubber in contact with the ground) is often smaller than the contact pad of your own shoe. Then there is the relatively large amount of air within the tire—air has, of course, already conducted the lightning all the way to the ground. It is the metallic shell of the car that offers protection, so it is important to stay entirely on a (non-metallic) seat inside the car without touching metal objects in it, especially if these communicate with the car exterior. If manmade structures are not available, seek shelter inside a deep cave, far into a dense forest, or in a deep ravine. Solitary trees represent a poor choice, as they are relatively tall objects that can promote side splash or ground current (discussed below). Similarly, shallow caves or open shelters (picnic shelter, canopy, open tent, lean-to) should be avoided because the quantity of free air these contain—coupled with high positioning—can attract lightning. The lightning can then jump to an individual when it reaches the non-structural (open) portion.
If access to adequate shelter is not available, there are a number of ways to reduce the risk of lightning strike.
The United States National Weather Service recommends the maxim: “When thunder roars, go indoors.” The idea is that—since lightning can travel well in advance of and behind a storm cell—if thunder is heard, one is within the potential radius of a lightning strike.
If lightning can be seen, another common maxim is to count the seconds between hearing thunder and seeing lightning to measure distance of a storm. However, this strategy depends on understanding the relative speed of light and sound. A common mistake is the notion that one second counted equates to one mile of distance. In fact, since light is faster than sound, every five seconds counted equates to one mile of distance. Therefore, the number of seconds counted must be divided by five to determine how many miles away a storm is (divide by three to determine how many kilometers away it is). Thus, people who assume seconds and mileage to be equal may think a five-second count indicates a storm five miles away, when in fact it is only 1 mile away and almost upon them!
Another numerical principle is the 30-30 rule. The first “30” in this rule (based on the calculation above) says that 30 seconds between thunder and lightning is the threshold to seek shelter. Now that you know the correct calculation, how many miles away is a storm when this threshold is reached and one should seek shelter?*
The second “30” of the 30-30 rule states that climbers should wait a minimum of 30 minutes after hearing the last thunderclap before resuming outdoor activities. Applying the calculation converting seconds to miles, the 30-30 rule predicts a ten-mile buffer between a climber and the trailing edge of a retreating storm. The Wilderness Medical Society gives these calculation-based behavioral preventions a recommendation grade of 1C (Davis 2014).
In the past, assuming the “lightning position” was the traditional standard of lightning strike prevention in wilderness activities. However, in 2014, the Wilderness Medical Society gave this technique a recommendation grade of 2C, and judged it to be only a “strategy of last resort” (Davis 2014). Other, earlier preventive measures and behaviors are far more effective. However, should climbers find themselves in the situation of an apparent impending strike (thunder, lightning strikes, or prestrike electrical phenomena described below), this position may reduce the risk of injury from lightning.
A climber taking this position squats with elbows touching knees, knees close to feet, and feet touching each other, to create a single point of contact with the ground. It is helpful to put an insulating material between the feet and ground, such as a pack (remove any metal), a rolled foam sleeping pad, or a dry coiled rope (one of the few instances in which stepping on your rope is okay in a climbing environment!). Putting palms over the ears helps prevent tympanic membrane (eardrum) rupture—a common consequence to a lightning strike—and maintains a positioning with one continuous line from the ground that discourages an attractive circuit completion for an electrical current. If there is more than one person assuming this position, it is recommended that individuals be positioned 20 feet apart to limit the possibility of several climbers injured by the same strike—note that lightning can jump up to 15 feet between objects. Climbing groups that know they will be traveling through lightning-prone areas—especially formally guided or institutional groups such as expeditions, camp trips, or outdoor education programs—should develop formal lightning safety plans and practice lightning drills with their clients. Examples of lightning safety plans are available online at the National Lightning Safety Institute† and the National Weather Service.‡
Lightning detection technology is rapidly expanding, and smartphone- or PDA-based apps represent one of the most exciting ways new electronic technologies are changing wilderness safety. Many of these technologies rely on lightning detection by the National Lightning Detection Network,§ which provides automatic notification (via email, text, or mobile phone) of lightning activity near a given location. While these technologies generally rely on mobile phone or PDA signal reception, such access is becoming increasingly common in wilderness areas. If access is not available, personal lightning detection devices can independently detect lightning as far away as 75 miles.
Finally, planning climbing, mountaineering, or trekking itineraries that acknowledge high lightning risk areas can reduce chances of lightning injury or death. Peaks and ridgelines are best avoided in the afternoon, as this is the most frequent time for thunderstorms. “Up by noon and down by two” is a common maxim among climbers that reinforces this principle of avoiding ridgelines and peaks during the afternoon. If climbers are caught in a thunderstorm, it is critically important to tie-off individually (WMS recommendation grade 1C) (Davis 2014). Wet climbing ropes make attractive electrical conductors, and strikes could pass between both belayer and climber, potentially incapacitating an entire climbing party. Also, climbers in this situation should isolate metal objects such as ski poles or ice axes to avoid contact burns or injury from lightning strike; and any direct contact with carabiners and other small metal objects should be minimized (WMS recommendation grade 1C) (Davis 2014). Additional metal objects such as watches, belt buckles, and necklaces should also be removed to avoid burn risk. If climbing involves deep-water soloing (DWS) or climbers are caught in a stream or other water while approaching or leaving a climb during a thunderstorm, they should get out of the water immediately. If the aquatic activity involves a raft or kayak, move to shore and away from the water’s edge; if a boat, seek shelter belowdecks after locking off the helm.
Lightning strikes can cause sudden death from simultaneous or sequential cardiac and respiratory arrest (sudden loss of heartbeat or breathing). The heart can stop either from a rhythm problem—a fibrillatory (irregular) rhythm that cannot sustain a pulse or blood pressure—or from loss of oxygen if breathing stops. Breathing can stop even though the pulse is normal if the lightning strike paralyzes the respiratory center in the brain, paralyzing the diaphragm and making breathing impossible, and causing cardiac arrest within minutes.
This unusual source of cardiac or respiratory arrest results in the principle of reverse triage for lightning strike deaths. In “mass casualty incidents”—for instance, coming upon three or more victims of a trauma—those who don’t have a pulse or aren’t breathing are considered definitively dead. Assuming limited resources, interventions focus on those with signs of life. In the case of lightning strikes, this is reversed, and priority is given to those without any signs of breathing or life. Unlike cases of cardiac or respiratory arrest from other causes, victims of a lightning strike often regain breathing and pulses simply from a brief period of CPR (for pulselessness) or rescue breathing (for non-breathing caused by a temporarily paralyzed respiratory center). Further discussion of CPR and rescue breathing can be found in Chapter 2. It is also important for rescuers to understand that climbers who have been struck by lightning do not carry an electrical charge, since lightning passes through the body in milliseconds, without leaving any residual electrical charge or ability to pass electricity. This is different from high-voltage injuries, which ironically have much lower voltage than lightning strikes but which continue to pass the current as long as the victim remains in contact with the source.
If an individual initially survives a lightning strike, subsequent death is very rare. Indicators for high risk of further complications or death in patients who initially survive (or are resuscitated out of cardiopulmonary arrest) include a suspected direct strike, loss of consciousness, neurological problems, chest pain or shortness of breath, major trauma, burns to the head, legs, or more than 10% of total body surface area, or pregnancy (Davis 2014). However, even if high-risk criteria are not present, all lightning strike victims deserve further medical attention and evacuation.
Neurological problems are common after lightning strikes. Nerves are by definition the best conductors of electrical current in the body and are likely to sustain the most damage from a strike. Neurological injuries can be immediate or delayed.
Immediately after a lightning strike, climbers can experience loss of consciousness, seizures, headaches, paresthesia (numbness or tingling), confusion, weakness, memory loss, brain injury from lack of oxygen, or stroke from bleeding in the brain. Keraunoparalysis is the term for temporary paralysis after a lightning strike, believed to be caused by overstimulation of the nervous system leading to the spasming of blood vessels. Legs are more often affected than arms, and symptoms may include pulselessness in the limb, discoloration, and sensation loss as well as full or partial paralysis. This condition typically resolves within hours. Needless to say, its possibility means that a central pulse (carotid artery) is more reliable than a peripheral pulse (feet or wrist) to establish pulselessness in an unconscious lightning strike patient. Keraunoparalysis can also be confused with spinal injury, with the difference being that spinal injuries rarely resolve within hours. Anyone with paralysis or weakness after a lightning strike should be presumed to have spinal injuries unless keraunoparalysis is proven by resolution of these symptoms over time, or by other testing.
Eyes are part of the nervous system and are frequently affected by lightning strikes. The lens is commonly injured: Cataracts are the most common eventual symptom. They may appear from within two days to as long as four years after a lightning strike. Retinal damage and optic nerve damage are also possible and may result in vision reduction or total loss.
Ears are also commonly affected, and eardrums rupture in as many as 60% of lightning strike victims. Such ruptures require no specific treatment, although water and ear drops should be avoided while the eardrum is healing. Any drainage from the ear may be a sign of skull fracture and warrants increased speed in evacuation and, like other head injuries, calls for close attention to level of consciousness over time (see Chapter 6). Deafness is also common and is usually temporary, but microhemorrhages and microfractures to the tiny bones and internal structures of the ear can result in permanent hearing loss.
True burns can also occur. They are typically partial thickness and involve the spontaneous vaporization of sweat and other liquids on the skin into steam. Because of this, areas of heavy sweating such as underarms, beneath the breasts, and feet tend to be most affected. Circular burns are possible where a current emerges from underlying tissue; these are generally found at the ends of the feet, where a current often exits the body. Full thickness burns are found most often in areas where skin is in contact with metal or synthetic materials that melt onto or burn the skin. True burns should not be confused with Lichtenberg figures (discussed earlier), which are painless, ferning, and disappear within hours to a day after injury. They require no treatment. Lightning burns are treated like other burns; for a more complete discussion of burns, see Chapter 9.
Psychiatric disturbances are also common after lightning strikes. These typically develop days to weeks after a strike, so they might not be part of the initial medical management of a lightning strike patient. But they can be an issue in the extended management of such patients on expeditions, long trips, or within groups that frequently climb together. These conditions include depression, sleep disturbances, emotional instability, and aggressive behavior. Lightning support networks are available (e.g., Lightning Strike and Electric Shock Survivors International, Inc.¶), and psychiatric care should be sought for any symptoms of this type.
* 6 miles away (30 divided by 5)
† www.lightningsafety.com/nlsi_pls.html
‡ www.lightningsafety.noaa.gov/outdoors.shtml
§ www.lightningsafety.com/nlsi_lhm/overview2002.html
¶ www.lightning-strike.org