Episode 22 - Electrical Injuries in the Emergency Department An Evidence-Based Review

Jeff: Welcome back to Emplify, the podcast corollary to EB Medicine’s Emergency Medicine Practice. I’m Jeff Nusbaum, and I’m back with my co-host, Nachi Gupta. This month, we’re back with our old routine – no special guests. Nachi: Don’t sound so sad about it! Jeremy was great last month, and he’s definitely paved the way for more special guests in upcoming episodes. Jeff: You’re right. But this month’s episode is special in its own way - we’ll be tackling Electrical Injuries in the emergency department - from low and high voltage injuries to the more extreme and rare lightning related injuries. Nachi: And this is obviously not something we see that often, so listen up for some easy to remember high yield points to help you when you get an electrical injury in the ED. And pay particular attention to the , which, as always, signals the answer to one of our CME questions. Jeff: I hate to digress so early and drop a cliché, “let’s start with a case…” but we, just a month ago, had a lightning strike induced cardiac arrest in Pittsburgh, so this hits really close to home. Thankfully, that gentleman was successfully resuscitated despite no bystander CPR, and if you listen carefully, we hope to arm you with the tools to do so similarly. Nachi: This month’s print issue was authored by Dr. Gentges and Dr. Schieche from the Oklahoma University School of Community Medicine. It was peer reviewed by Dr. O’Keefe and Dr. Silverberg from Florida State University College of Medicine and Kings County Hospital, respectively. Jeff: And unlike past issues covering more common pathologies, like, say, sepsis, this month’s team reviewed much more literature than just the past 10 years. In total, they pulled references from 1966 until 2018. Their search yielded 477 articles, which was narrowed to 88 after initial review. Nachi: Each year, in the US, approximately 10,000 patients present with electrical burns or shocks. Thankfully, fatalities are declining, with just 565 in 2015. On average, between 25 and 50 of the yearly fatalities can be attributed to lightning strikes. Jeff: Interestingly, most of the decrease in fatalities is due to improvements in occupational protections and not due so much to changes in healthcare. Nachi: That is interesting and great to hear for workers. Also, worth noting is the trimodal distribution of patients with electrical injuries: with young children being affected by household currents, adolescent males engaging in high risk behaviors, and adult males with occupational exposures and hazards. Jeff: Electrical injuries and snake bites – leave it to us men to excel at all the wrong things… Anyway, before we get into the medicine, we unfortunately need to cover some basic physics. I know, it might seem painful, but it’s necessary. There are a couple of terms we need to define to help us understand the pathologies we’ll be discussing. Those terms are: current, amperes, voltage, and resistance. Nachi: So, the current is the total amount of electrons moving down a gradient over time, and it’s measured in amperes. Jeff: Voltage, on the other hand, is the potential difference between the top and bottom of a gradient. The current is directly proportional to the voltage. It can be alternating, AC, or direct, DC. Nachi: Resistance is the obstruction of electrical flow and it is inversely proportional to the current. Think of Ohm’s Law here. Voltage = current x resistance. Jeff: Damage to the tissues from electricity is largely due to thermal injury, which depends on the tissue resistance, voltage, amperage, type of circuit, and the duration of contact. Nachi: That brings us to an interesting concept – the let-go threshold. Since electrical injuries are often due to grasping an electric source, this can induce tetanic muscle contractions and therefore the inability to let go, thus increasing the duration of contact and extent of injury. Jeff: Definitely adding insult to injury right there. With respect to the tissue resistance, that amount varies widely depending on the type of tissue. Dry skin has high resistance, far greater than wet or lacerated skin. And the skin’s resistance breaks down as it absorbs more energy. Nerve tissue has the least resistance and can be damaged by even low voltage without cutaneous manifestations. Bone and fat have the highest resistance. In between nerve and bone or fat, we have blood and vascular tissue, which have low resistance, and muscle and the viscera which have a slightly higher resistance. Nachi: Understanding the resistances will help you anticipate the types of injuries you are treating, since current will tend to follow the path of least resistance. In high resistance tissues, most of the energy is lost as heat, causing coagulation necrosis. These concepts also explain why you may have deeper injuries beyond what can be visualized on the surface. Jeff: And not only does the resistance play a role, but so too does the amount and type of current. AC, which is often found in standard home and office settings, but can also be found in high voltage transmission lines, usually affects the electrically sensitive tissues like nerve and muscle. DC has a higher let-go threshold and does not cause as much sensation. It also requires more amperage to cause v-fib. DC is often found in batteries, car and computer electrical systems, some high voltage transmission lines, and capacitors. Nachi: Voltage has a twofold effect on tissues. The first mechanism is through electroporation, which is direct damage to cell membranes by high voltage. The second is by overcoming the resistance of body tissues and intervening objects such as clothes or water. You’re probably familiar with this concept when you see high voltages arcing through the air without direct contact with the actual electrical source, leading to diffuse burns. Jeff: As voltage increases, the resistance of dry skin is -- not surprisingly -- reduced, leading to worse injuries. Nachi: And for this reason, the US Department of Energy has set 600 Volts as the cutoff for low vs high voltage electrical exposure. Jeff: It is absolutely critical that we also mention and then re-mention throughout this episode, that those with electrical injuries often have multisystem injuries due to not only the thermal injury, electrical damage to electrically sensitive tissue, but also mechanical trauma. Injuries are not uncommon both from forceful pulling away from the source or a subsequent fall if one occurs. Nachi: That’s a great point which we’ll return to soon, as it plays an important role in destination selection. But before we get there, let’s review the common clinical manifestations of electrical injuries. Jeff: First up is – the cutaneous injuries. Most electrical injuries present with burns to the skin. Low voltage exposures typically cause superficial burns at the entry and exit sites, whereas high voltage exposures cause larger, deeper burns that may require skin grafting, debridement, and even amputation. Nachi: High voltage injuries can also travel through the sub-q tissue leading to extensive burns to deep structures despite what appears to be relatively uninjured skin. In addition, high voltage injuries can also result in superficial burns to large areas secondary to flash injury. Jeff: Electrical injuries can also lead to musculoskeletal injuries via either thermal or mechanical means. Thermal injury can lead to muscle breakdown, rhabdo, myonecrosis, edema, and in worse cases, compartment syndrome. In the bones, it can lead to osteonecrosis and periosteal burns. Nachi: In terms of mechanical injury – electrical injury often leads to forceful muscular contraction and falls. In 2 retrospective studies, 11% of patients with high voltage exposures also had traumatic injuries. Jeff: While not nearly as common, the rarer cardiovascular injuries are certainly up there as the most feared. Pay attention to the entry and exit sites, as the pathway of the shock is predictive of the potential for myocardial injury and arrhythmia. Common arrhythmias include AV block, bundle branch blocks, a fib, QT prolongation and even ventricular arrhythmias, including both v-fib and v-tach, both of which typically occur immediately after the injury. Nachi: There is a school of thought out there that victims of electrical injury can have delayed onset arrhythmias and require prolonged car