À PROPOS DE CET ÉPISODE
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 cardiac monitoring – however several well-designed observational studies, including 1000s of patients, have demonstrated no such evidence.
Jeff: It’s also worth noting that ST elevation MIs have also been reported, however this is usually due to coronary artery vasospasm rather than acute arterial occlusion.
Nachi: Respiratory injuries are somewhat less common. Acute respiratory failure usually occurs secondary to electrical injury-induced cardiac arrest. Thoracic tetany can cause paralysis of respiratory muscles. Late findings of respiratory injury including pulmonary effusions, pneumonitis, pneumonia, and even PE. The electrical resistance of lung tissue is relatively high, which may account for why pulmonary injury is less common.
Jeff: Vascular injuries include coagulation necrosis as well as thrombosis. In addition, those with severe burns are at increased risk of DVT, especially in those who are immobilized. In at least one study, the incidence of DVT in hospitalized burn patients was as high as 23%. That’s -- high.
Nachi: Neurologic complaints are far more common as nerve tissue is highly conductive. While the most common injury from an electric shock is loss of consciousness, other common neurologic insults include weakness, paresthesias, and difficulty concentrating.
Jeff: And if the entry and exit sites traverse the spinal cord – this also puts the patient at risk for spinal cord lesions. Specifically with respect to high voltage injuries – these victims are at risk for posterior cord syndrome. In addition, depression, pain, anxiety, mood swings, and cognitive difficulties have all been commonly described.
Nachi: Rounding out our discussion of electrical injuries, visceral injuries are rather rare, with bowel perforation being the most common. High voltage injuries have also been associated with cataracts, macular injury, retinal detachment, hearing loss, tinnitus, and vertigo.
Jeff: Perfect. I think that more or less rounds out an overview of organ specific electrical injuries. Let’s talk about prehospital care for these patients -- a broad topic in this case. As always, the first, and most important step in prehospital care is protecting oneself from the electrical exposure if the electrical source is still live.
Nachi: In cases of high voltage injuries from power lines or transformers or whatever oddity the patient has come across, it may even be necessary to wait for word from the local electrical authority prior to initiating care. Remember, the last thing you want to do is become a victim yourself.
Jeff: For those whose electrical injury resulted in cardiac arrest, follow your standard ACLS guidelines. These aren’t your standard arrest patients though, they typically have many fewer comorbidities – so CPR tends to be more successful.
Nachi: Intubation should also be considered especially early in those with facial or neck burns, as risk of airway loss is high.
Jeff: And as we mentioned previously, concurrent trauma and therefore traumatic injuries is very common, especially with high voltage injuries, so patients with electrical injuries require a complete survey and not just a brief examination of their obvious injuries.
Nachi: When determining destination, trauma takes priority over burn, so patients with significant trauma or those who are obtunded or unconscious should be transported to an appropriate trauma center rather than a burn center if those sites are different.
Jeff: Let’s move on to evaluation in the emergency department. As always, it’s ABC and IV, O2, monitor first with early airway management in those with head and neck burns being a top priority. After that, complete your primary and secondary surveys per ATLS guidelines.
Nachi: During your survey, make sure the patient is entirely undressed and all constricting items, like jewelry is removed.
Jeff: Next, make sure that all patients with high voltage injuries have an EKG and continuous cardiac monitoring. Those with low voltage injuries and a normal EKG do not require monitoring.
Nachi: Additionally, for those with severe electrical injuries, an IV should be placed and fluid resuscitation should begin. Fluid requirements will likely be higher than those predicted by the parkland formula, and you should aim for a goal of maintaining urine output of 1-1.5 ml/kg/h.
Jeff: With your initial stabilization underway, you can begin to gather a more thorough history either from bystanders or EMS if they are still present. Try to ascertain whether the current was AC or DC, and whether it was high or low voltage. Don’t forget to ask about the setting of the injury as this may point to other concurrent traumatic injuries, that may in fact take precedence during your work up.
Nachi: Moving on to the physical exam. As mentioned previously, disrobe the patient and complete a primary and secondary survey.
Jeff: If the patient has clear entry and exit wounds, the path through the body may become apparent and offer clues about what injuries to expect.
Nachi: A single exam will not suffice for electrical injury patients. All patients with serious electrical injuries will require serial exams to evaluate for vascular compromise and compartment syndrome.
Jeff: So that wraps up the physical, let’s move onto diagnostic studies.
Nachi: First off -- I know we’ve said it, but it’s definitely worth reiterating. All patients presenting with a history of an electric shock require an EKG
Jeff: In those with a low voltage injury without syncope and a normal EKG, you don’t routinely need cardiac monitoring. However, in the setting of high voltage injuries, the data is less clear. Based on current literature, the authors recommend overnight monitoring for at least 8 hours for all high voltage injuries.
Nachi: While no routine labs work is required for minor injuries, those with more serious injuries require a cbc, cmp, CK, CK-MB, and urinalysis.
Jeff: The CK is clearly for rhabdo, but interestingly, a CK-MB greater than 80 ng/mL is actually predictive of limb amputation. Oh and don’t forget that urine pregnancy test when appropriate.
Nachi: In terms of imaging, you’ll have to let your history guide your diagnostic studies. Perform a FAST exam to screen for intra-abdominal pathology for anyone with concern for concurrent trauma. Keep a low threshold to XR or CT any potentially injured body region.
Jeff: Real quick – in case you missed it – ultrasound sneaks in again. Maybe I should reconsider and do an US fellowship – seems like that’s where the money is at - well maybe not money but still. Let’s move on to treatment.
Nachi: In those with minor injuries like small burns and a low voltage exposure – if they have a normal EKG and no other symptoms, these patients require analgesia only. Give return precautions and have them follow up with their PCP or a burn center.
Jeff: In those with more severe injuries, as we mentioned before, but we’ll stress again, protect the patient’s airway early especially if you are considering transfer and have any concerns. In one study, delays in intubation was associated with a high risk of a difficult airway. Always make sure you have not only your tool of choice but also all of your backup airway devices ready as all deeper airway injuries may not be apparent externally.
Nachi: Fluid resuscitation with isotonic fluids is the standard -- again -- with a goal urine output of 1-1.5 ml/kg/h.
Jeff: Address pain with analgesia – likely in the form of opiates – and don’t be surprised if large doses are needed.
Nachi: Dress burned areas with an antibiotic dressing and update the patient’s tetanus if needed. While there is ongoing debate about the role of prophylactic antibiotics, best evidence at this point recommends against them. We talked about thermal burns in Epsiode 13 also, so go back and listen there for more...
Jeff: There is also a range of practice variation with respect to early surgical exploration of the burned limb with severe injuries. At this time, however, the best current evidence supports a conservative approach.
Nachi: Serial exams and watch and wait it is. . We have some interesting special populations to discuss this month. First up, as is often the case, the kids.
Jeff: Young children are sadly more likely to present with orofacial burns due to, well, everything ending up in their mouth. And since many of our listeners are likely in boards study mode – why don’t you fill us in on the latest evidence with respect to labial artery bleeding.
Nachi: Sure – . There is up to a 24% risk of labial artery bleeding and primary tooth damage with oral electrical injuries. Although there isn’t a clear consensus, current evidence supports early ENT consultation and a strong consideration for admission and observation for delayed bleeding.
Jeff: Keep in mind though, that labial artery bleeding is often delayed and has been reported as far as 2 weeks out from the initial insult.
Nachi: Moral of the story: don’t put electrical cords in or anywhere near your mouth. Next, we have pregnant patients. Case reports of pregnant patients suffering electrical injuries have described fetal arrhythmias, ischemic brain injury, and fetal demise. For this reason, those that are past the age of fetal viability should have fetal monitoring after experiencing an electric shock.
Jeff: If not already done, an ultrasound should be obtained as well and a two week follow up ultrasound will be needed.
Nachi: We’re switching gears a bit with this next special population – those injured by an electrical control device or taser.
Jeff: Tasers typically deliver an initial 50,000 volt shock, with a variable number of additional shocks following that.
Nachi: Most taser injuries are thankfully direct traumatic effects of the darts or indirect trauma from subsequent falls.
Jeff: While there are case reports of taser induced v fib, the validity of taser induced arrhythmias remains questionable due to confounders such as underlying disease and previously agitated states like excited delirium
Nachi: Basically, [DING SOUND} those with taser injuries should be approached as any standard trauma patient would be, with the addition of an EKG for all of these patients.
Jeff: The next special population --- the one I’m sure you’ve all been waiting patiently for -- is lightning strike victims. Lightening carries a voltage in the millions with amperage in the thousands, but with an incredibly short exposure time. Because of this, lightening causes injuries in a number of different ways.
Nachi: First, because it’s often raining when lightning strikes, wet skin may cause the energy to stay on the skin in what is known as a flashover effect.
Jeff: Similarly and not surprisingly, burns are common after a lightning strike. Lichtenberg figures are superficial skin changes that resemble bare tree branches and are pathognomonic for lightning injury. Thankfully, these usually disappear within a few weeks without intervention.
Nachi: Next, the rapid expansion of the air around the strike can lead to a concussive blast and a variety of traumatic injuries including ocular and otologic injury like TM rupture which occurs in up to two thirds of cases.
Jeff: An ophthalmologic consult should be obtained in most, if not all of these cases.
Nachi: Making matters worse, lightning can also travel through electric wiring and plumbing to cause a shock to a person indoors nearby the strike!
Jeff: And like we mentioned earlier, just as was the case with my fellow Pittsburgher or ‘Yinzer.
Nachi: Yinzer?
Jeff: Forget about it, it’s just what Pittsburghers call themselves for some reason or another - but we’re still talking lightning. Cardiac complications including death, contusion and vasospasm have all been reported secondary to lightning injury. But don’t lose hope – in fact – you should gain hope as these patients have a much higher than typical survival rates.
Nachi: From the neurologic standpoint – it’s a bit more complicated. CNS dysfunction may be immediate or delayed and can range from strokes to spinal cord injuries. Cerebral salt wasting syndrome, peripheral nerve lesions, spinal cord fracture, and cerebral hemorrhages have all been described. An MRI may be required to elucidate the true diagnosis.
Jeff: Clearly victims of lighting strikes are complex and, for that reason, among many others, the American College of Surgeons recommends that victims of lightning strikes be transferred to a burn center for a comprehensive eval.
Nachi: Let’s touch upon any other details regarding disposition.
Jeff: Those with low voltage exposures, a normal EKG and minimal injury may be discharged home with PCP follow up and strict return precautions.
Nachi: High voltage injuries on the other hand require admission to a burn center and the involvement of a burn surgeon, even if it involves transferring the patient.
Jeff: And remember, trauma takes precedence over burn and those with traumatic injuries or the possibility of traumatic injuries should be evaluated at a trauma center. Don’t forget to take the airway early if there is any concern, and consider transporting via air as the services of a critical care transport team may be required.
Nachi: That wraps up Episode 22, but let’s go over some key points and clinical pearls.
During evaluation, consider multisystem injuries due to not only the thermal injury and electrical damage to electrically sensitive tissue, but also mechanical trauma.
Thermal injury can lead to muscle breakdown, rhabdomyolysis, myonecrosis, edema, compartment syndrome, osteonecrosis, and even periosteal burns.
Mechanical injury can be a result of forceful muscular contractions, and trauma can manifest as fractures, dislocations, and significant muscular injuries.
Electrical injuries due to grasping an electric source can induce tetanic muscle contractions and therefore the inability to let go, increasing the duration of contact and extent of injury.
Current tends to follow the path of least resistance, which explains why you might have deeper injuries beyond what can be visualized in the surface.
Nerve tissue has the least resistance and can be damaged by even low voltage without cutaneous manifestations. Bone and fat, on the other hand, have the highest resistance to electrical injury.
High voltage injuries place patients at risk for spinal injuries, most notably posterior cord syndrome. High voltage injuries have also been associated with cataracts, macular injury, retinal detachment, hearing loss, tinnitus, and vertigo.
All patients with electrical injury require an EKG. Low voltage injuries with a normal presenting EKG do not always require cardiac monitoring. High voltage injuries require cardiac monitoring for at least 8 hours.
Intubation should be considered early in patients with facial or neck burns, as risk of airway loss is high. Make sure to have airway adjuncts and back up equipment at bedside, as deeper airway injuries may not be obvious upon external exam.
For severe injuries, target a urine output rate of 1-1.5 mL/kg/hr.
All patients with serious electrical injuries require serial exams to evaluate for vascular compromise and compartment syndrome.
Address pain with analgesia. Larger than expected doses may be needed.
Dress burned areas with an antibiotic dressing and update the patient’s tetanus if required.
For pediatric patients with oral electric injuries from biting on a cord, consult ENT early and consider admission for observation of delayed arterial bleeding.
Pregnant patients who are past the age of fetal viability should have fetal monitoring and ultrasound after experiencing an electric shock.
Tympanic membrane rupture is a commonly noted blast injury after a lightning strike.
Cardiac resuscitation should follow ACLS guidelines and is more likely to be successful than your tyipcal cardiac arrest patient as the patient population is typically younger and without significant comorbidities.
When determining destination, trauma centers take priority over burn centers if those sites are different.
So that wraps up episode 22 - managing electrical injury in the emergency department.
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