Air Care Series: Electrocution

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HISTORY OF PRESENT ILLNESS

The patient is a middle-aged male who presents in cardiac arrest after a suspected electrocution injury. The patient was holding an aluminum ladder when it struck a powerline, and he became unresponsive. Bystander cardiopulmonary resuscitation (CPR) was initiated and 911 was called. Upon Emergency Medical Services (EMS) arrival, the patient was pulseless, apneic, and unresponsive. Advanced Cardiac Life Support (ACLS) protocol was initiated by ground EMS providers, and the patient was determined to be in ventricular fibrillation (VF). EMS delivered five defibrillations and established an intraosseous line in the right humerus to administer four rounds of code-dose epinephrine and two doses of amiodarone per ACLS protocol. An attempt at intubation was unsuccessful due to oropharyngeal secretions obstructing visualization, and resuscitation was continued with a supraglottic device in place. Despite these interventions, the patient was in refractory VF on Air Care arrival.

PAST MEDICAL HISTORY: Unknown

PAST SURGICAL HISTORY: Unknown

MEDICATIONS: Unknown

ALLERGIES: Unknown

SOCIAL HISTORY: Unknown

FAMILY HISTORY: Unknown

VITALS

HR – Pulseless BP – N/A RR – N/A SpO2 – 100% via supraglottic airway & BVM T – N/A

PHYSICAL EXAM

The patient is an unresponsive male in cardiac arrest who was undergoing CPR via a mechanical device. The patient has a supraglottic device in place without signs of tracheal deviation. Breath sounds are clear and equal bilaterally. The head exhibits no signs of trauma. The pelvis is stable. No lesions are present on the chest or abdomen. There is a white and black circular eschar on the left lower extremity.

LABS AND IMAGING

Glucose: 331 mg/dL

HOSPITAL COURSE

At the first pulse check upon the Air Care crew’s arrival, the patient remained in VF, receiving a sixth shock. As the patient was in refractory VF, dual-sequential defibrillation at 200 Joules was attempted leading to asystole at the next pulse check. CPR was resumed and epinephrine 1 mg and calcium chloride 1 ampule were administered. The patient remained in asystole at the next pulse check, and end-tidal CO2 capnography was noted to be down-trending. At this time, further resuscitative efforts were determined to be futile and the patient was pronounced dead with family present at the patient’s side.

DISCUSSION

Background

Approximately 6,500 injuries and 1,000 deaths occur annually in the United States (US) as the result of electrocution. (1) Of these deaths, less than 30% (50 - 300) are caused by lightning strikes. (2) The extent of injury is dependent on the type, duration, and voltage. (3) Injuries sustained from a higher voltage mechanism or longer duration of exposure tend to be more severe.

Charge

Charge is the fundamental unit of electricity, measured by the unit coulomb (C). The coulomb is equal to the charge carried by 6.24 × 10^18 electrons. It should be noted that one C of charge does not specifically refer to electrons as many particles can carry a charge, with many particles having a greater capacity than an electron. For example, in a copper wire electrons are used to carry current; however, in the human body sodium, chloride, and potassium may be used to carry a charge as the body does not have free electrons.

Current, Voltage and Resistance

Electrical current is the flow of charge and is measured in ampere (A). One A is equivalent to one C (6.24 × 1018 electron if referring to a copper wire) of charge per one second (1C/second). Electrical current density, or the strength of current per unit area, is directly associated with tissue injury as demonstrated by Sances et al. Figure 1 shows the relationship between increased current density and decreased time to tissue necrosis. Paradoxically, decreased current density was associated with increased temperature achieved presumable secondary to longer exposure time. (4)

Electrocution_1.png

Figure 1: The time to epidermal necrosis varies inversely with the exponent of the current density

There are two types of current: direct current (DC) and alternating current (AC). DC flows unidirectional while AC flows cyclically. AC is typically used for household and industrial electrical power with a frequency of 50 or 60 Hz. (1) The cyclical nature of AC can lead to tetanic contractions resulting in unintentional grasping of the current and increased exposure to the electricity. (3) As a result, AC current can cause more severe injuries with a lower voltage and duration of exposure.

Voltage is the electrical potential difference between two points, or the pressure that forces a current along a path, measured by volts (V). A volt was originally defined by the volts generated by a standard battery but is now based on a solid-state circuit and defined as the difference in electric potential between two points when the electric current of one A dissipates one watt (W) of power. This is equivalent to a potential difference that generates one joule (J) of energy per C of charge passing through it. The amount of electrical current delivered can be characterized as either high-voltage (>1000 V) or low-voltage (<1000 V). Household outlets in the US carry 120 V AC whereas powerlines carry approximately 7000 V AC.

Resistance is the impedance to flow and is measured in ohms (Ω). One Ω of resistance is equivalent to the resistance present in a circuit when one V of pressure is required to generate one A of current. Under dry conditions the resistance offered by the human body is 100,000 Ω; however, moisture or skin breakdown can decrease the human body’s resistance to 1kΩ (1000 Ω). Difference tissues within the body have difference tissue resistivity (resistance of a 1 cm3 cube of the tissue, measured as Ωcm). For example, the resistivity of blood is 150 Ωcm, fat is 2,200 Ωcm, and bone is 10,000 Ωcm. (5)

Power and Energy

Power, measured in watts (W), is equal to flow rate (A) times pressure (V). Energy is the product of power (W) and time (seconds).

Mechanisms of Injury

Electrocution injuries vary in location and extent, including direct tissue damage, systemic consequences, and mechanical injury secondary to a fall, tetany, or other trauma. (1) One of the most severe injury patterns caused by electrocution is an electrical arc injury. Electricity at very high voltages arcs from one conductor to another, causing flash burns (>20,000°C), electrical damage, and physical damage from the blast force. (3) High voltage injury also results in musculoskeletal and soft tissue death, putting patients at increased risk for developing rhabdomyolysis and compartment syndrome. Soft tissue burns can range from small and painless burns to extensive electrical burns requiring admission and management from a burn specialist.

Tetanic contraction leading to musculoskeletal injury is another common injury pattern associated with high-voltage electrocution. When AC current flows through the victim’s muscles, it results in direct electrical stimulation with the potential to cause fractures and joint dislocations. (6) Atypical injury patterns, such as posterior shoulder dislocations, can occur.

Lethal ventricular arrhythmias are the electrical injury of greatest concern. Cardiac arrhythmias are a common cardiovascular manifestation, with the most common fatal arrhythmias being VF and ventricular tachycardia (VT). VF occurs through three different mechanism in electrical injury: (1) shock on T, (2) rapid cardiac capture, and (3) long term cardiac capture. (7-11)

Shock on T is caused by a single shock that occurs during the T wave, a period of ventricular relaxation where the cardiac myocytes return to their resting states. In the middle of the T wave some of the cardiac myocytes have returned to their resting state while some remain active. This is a vulnerable period of the cardiac electrical cycle as an electrical shock during this period can lead to unpredictable electrical activity within the heart and ultimately cause VF. According to the IEC (International Electrotechnical Commission) there is a 50% probability of VF with a 5,000 µC unidirectional impulse into the T-wave. (12)

Direct rapid cardiac capture is the result of strong repetitive currents which capture the cardiac myocytes at a high rate. Rapid cardiac capture (~450 BPM) leads to VF through the process of wavebreak. Wavebreak occurs when there is electrophysiologic heterogeneity of the cardiac myocytes, allowing for propagation of electrical activity in some regions while encountering refractory tissue in other regions. Direct rapid cardiac induction of VF occurs typically within in 0.1–5 s with the current required decreasing rapidly after the VF threshold has been surpassed. (9-11)

Long-term fast cardiac capture describes a phenomenon where lower (~40% of direct rapid cardiac capture) current densities lead to VF after a longer duration (~90 seconds). These rates remain significantly higher than that required of pacing (> 220) in swine models. The prolonged fast cardiac capture leads to ischemia of the cardiac myocytes, lowering the VF threshold to ~40% of the threshold of direct rapid cardiac capture. (11)

Given the low resistance of nerve tissue, the neurologic system is vulnerable to high-voltage electrical injuries. (13) Patients are at risk for seizures, spinal cord injury, peripheral paresthesias and neuropathies following electrical injury. These symptoms can be delayed, manifesting days to months after the electrocution injury. (1)

Scene & Prehospital Care

First responders must focus on maintaining their distance from sources of electricity, keeping scene safety a top priority when treating patients suffering from electrical injuries. Providers must also remain aware of potential conductors through which electricity can travel, such as water, metal, and even dry wood at high voltages. Similar to caring for other patients in the pre-hospital setting, providers must weigh the benefit of on-scene resuscitation versus early transport when caring for patients suffering electrical injury. Definitive care for patients in cardiac arrest after electrical injury includes high-quality CPR and defibrillation, with a potential role for dual-sequential defibrillation and esmolol given the refractory VF.

Emergency Department Management

Emergency care priorities remain standardized with an assessment of the patient’s airway, breathing, and circulation. In patients who progress to cardiac and/or respiratory arrest, standard ACLS protocol should be followed, with a potential role for dual-sequential defibrillation and esmolol in patients with ventricular arrhythmias. (14-17) All patients suffering an electrical injury require a thorough examination with a high suspicion for atypical injury patterns. All patients should be placed on cardiac telemetry and undergo electrocardiogram (ECG), regardless of symptoms. In the setting of low-voltage electrocutions, if the patient has minimal to no cutaneous injuries and does not have arrhythmias or ischemic changes noted on ECG, they can be discharged after initial evaluation. Continuous cardiac monitoring is not required as the risk of developing a lethal arrhythmia after an initially normal ECG is low. (18)

If significant cutaneous damage or electrocardiographic abnormalities are present, the patient needs evaluation by a burn specialist and telemetry monitoring. Patients with the injuries noted in Table 1 and those who suffer an electrical injury of >1000 V AC require transfer to a burns center according to the International Society of Burns Injuries 2018 Guidelines. (19-20)

Patients with high voltage injuries should have laboratory testing to assess for organ injury, including a renal panel, creatinine kinase, troponin, urinalysis, and urine myoglobin. The emergency provider should also evaluate for signs of compartment syndrome and rhabdomyolysis. Patients with full-thickness circumferential burns or burns extensively involving the thorax may require escharotomy. Patients with myoglobinuria, burns affecting >20% TBSA, and full-thickness burns >12% TBSA are at increased risk of requiring fasciotomy in the first 24 hours. (21)

The approach to fluid resuscitation for patients with electrical burns does not differ from patients who have suffered chemical or thermal burns. The Parkland formula, based on TBSA affected, is an appropriate starting point. However, electrical burns may disproportionately affect the deep tissues. As such, it is prudent to use urine output to guide fluid resuscitation, with a urine output goal of 1 – 2cc/kg/hr.

Disposition

In general, asymptomatic patients who have suffered a low-voltage shock can safely be discharged if there are no concerning findings on history, physical examination, and ECG. Patients who suffer a high-voltage shock should be admitted for a period of observation, even if all components of the ED evaluation are reassuring. (1)

Conclusion

The evaluation and management of patients who have suffered electrocution is challenging, as presentations range from asymptomatic to refractory cardiac arrest. Important historical features include type of current (AC or DC), voltage, and duration of exposure. Electrocuted patients are especially susceptible to cardiac arrhythmias, neurologic injury, rhabdomyolysis, and compartment syndrome. Even in the well-appearing patient, a thorough evaluation and high index of suspicion for injury is paramount, as electrocuted patients often have atypical injury patterns.

AUTHORED BY Hamza Ijaz, MD (c)

Dr. Ijaz is a second-year Emergency Medicine resident at the University of Cincinnati.

Post by Simanjit Mand, MD (@mand_sim); ADAM GOTTULA, MD (@LAERTEZZ)

Dr. Mand is a fourth-year Emergency Medicine Chief resident at the University of Cincinnati with an intersted in ultrasound.

Dr. Gottula is a fourth-year Emergency Medicine resident at the University of Cincinnati and future Anesthesia Critical Care Fellow at The University of Michigan with an interest in critical care and HEMS.

FACULTY EDITORS Annals of B Pod Editors

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