Electrical injury
●Type of current, direct (DC), or alternating (AC). AC is substantially more dangerous than DC. AC may cause tetanic muscle contraction, making the victim unable to release the electrical source. This may lead to an increased duration of current delivery. In contrast, DC usually causes a single intense muscle contraction, which often thrusts the victim away from the electrical source, resulting in a smaller duration of current flow through the body.
●Voltage: High voltage (>600 V) is generally associated with greater morbidity and mortality, although fatal injury can occasionally occur at household current ( which may induce ventricular fibrillation). High-voltage injuries may cause massive internal burns and coagulation necrosis of soft tissues (such as muscle), along with edema, which may lead to compartment syndrome.
●Duration of exposure (longer exposure is associated with more severe damage)
●Body resistance
●Pathway of current (which determines the specific tissues damaged)
Manifestations of electrical injury range from skin burns to damage to internal organs, cardiac arrhythmias, and respiratory arrest. Electrical injuries are classified into those of low voltage (≤1000 V) and high voltage (>1000 V).
Pathophysiology
The mechanisms of electricity-induced injury are the following:►Electric current causes damage to cell membranes leading to electrolyte abnormalities and cellular edema. This is eventually followed by irreversible cell damage and cell death. This process is called electroporation. Electrical injury also alters cell membrane resting potential leading to muscle tetany.
►Another mechanism of tissue damage is thermal injury to the tissues, occurring when electrical energy is converted to thermal energy causing coagulative necrosis of the tissues.
►Τhe flow of current through the tissue can cause thermal injury to the vascular endothelium and associated thrombosis.
►Mechanical injury (trauma) due to falls or violent muscle contraction.
Clinical presentation of the patient with an electric injury
The following tissues and organs can be affected by an electrical injury, depending on the severity of the incident:
The skin:
Electrical injury is often associated with partial- or full-thickness burns at entrance and exit sites. Another type of burns associated with electrical injury are arc burns, or “kissing burns” occurring when electricity jumps from a skin surface to another skin surface that is in direct contact with the first. This typically occurs across flexed areas of the body.
In some cases, clothing may catch fire resulting in thermal burns.
Important note: The size of the skin injury does not correlate well with the severity of internal injuries which can often be more extensive in cases of electrical injury.
The cardiovascular system:
An electrical injury can cause arrhythmias. The most severe arrhythmias (ventricular fibrillation ventricular tachycardia, asystole) may occur immediately and they may result in immediate cardiac arrest. In patients presenting in cardiac or respiratory arrest immediate resuscitation is needed (cardiopulmonary resuscitation) according to the ACLS protocols. Other arrhythmias such as sinus tachycardia or bradycardia, atrial fibrillation, and atrial or ventricular ectopic beats may appear immediately or in a delayed fashion following electrical injury.
Electrical injury can cause transient ECG abnormalities such as ST-segment elevations (resembling an acute myocardial infarction), or T wave flattening or inversion without true myocardial ischemia being present. Another ECG abnormality that may appear is a prolonged QT interval. Less commonly, direct injury to the myocardium with a decreased ejection fraction (EF) depicted by echocardiography, or injury to the coronary arteries causing a myocardial infarction may occur.
Vascular injury is most prominent at the intimal and medial layers of the vascular wall and it may lead to thrombosis causing tissue ischemia or aneurysmal dilation and hemorrhage (later). Decreases in tissue perfusion lead to edema and tissue death. Areas of infarction may be distributed sporadically throughout the injured region, with areas of surviving tissue adjacent to necrotic tissue.
A serious high-voltage electrical injury, because of the extensive soft tissue destruction (like an extensive burn injury), can cause massive fluid shifts, i.e. loss of fluid from the intravascular space. Thus, it is important to monitor the patient's hemodynamic status and urine output (via a Foley catheter) and adequate intravenous fluid replacement will be required.
Respiratory system:
Respiratory arrest may occur either as a result of tetanic paralysis of the respiratory muscles or of damage to the brainstem respiratory center. Apnea due to respiratory arrest may result in hypoxic cardiac arrest. Other complications from the respiratory system may include pulmonary edema, pulmonary contusion (as a result of trauma) and aspiration pneumonia.
Nervous system
Electrical injury may often involve the central and peripheral nervous systems. The most common immediate symptoms from the central nervous system (CNS) are confusion, transient loss of consciousness, agitation, coma or seizures. Seizures are common. They may appear as a transient isolated event or as a lasting seizure disorder. Immediately after electrical injury transient spastic paralysis with accompanying sensory deficits may occur. Cerebral infarction may result from arterial injury. Traumatic injury (which is common in patients with electrical injury) may cause complications, such as intracranial hemorrhage.
Late sequelae may follow, such as spinal cord dysfunction, peripheral neuropathy, cognitive impairment, insomnia and emotional lability.
Musculoskeletal system
At the time of admission of the patient with electrical injury complete neurovascular exam of each extremity should be done and documented.
Muscle necrosis may occur primarily due to electrical injury, or it may develop secondary to an impairment of blood supply. Tissue edema may result in the development of compartment syndrome, which requires fasciotomy.
Respiratory system:
Respiratory arrest may occur either as a result of tetanic paralysis of the respiratory muscles or of damage to the brainstem respiratory center. Apnea due to respiratory arrest may result in hypoxic cardiac arrest. Other complications from the respiratory system may include pulmonary edema, pulmonary contusion (as a result of trauma) and aspiration pneumonia.
Nervous system
Electrical injury may often involve the central and peripheral nervous systems. The most common immediate symptoms from the central nervous system (CNS) are confusion, transient loss of consciousness, agitation, coma or seizures. Seizures are common. They may appear as a transient isolated event or as a lasting seizure disorder. Immediately after electrical injury transient spastic paralysis with accompanying sensory deficits may occur. Cerebral infarction may result from arterial injury. Traumatic injury (which is common in patients with electrical injury) may cause complications, such as intracranial hemorrhage.
Late sequelae may follow, such as spinal cord dysfunction, peripheral neuropathy, cognitive impairment, insomnia and emotional lability.
Musculoskeletal system
At the time of admission of the patient with electrical injury complete neurovascular exam of each extremity should be done and documented.
Muscle necrosis may occur primarily due to electrical injury, or it may develop secondary to an impairment of blood supply. Tissue edema may result in the development of compartment syndrome, which requires fasciotomy.
Compartment syndrome is a common limb-threatening risk of electrical injury. The typical signs and symptoms of compartment syndrome (5 Ps: Pain Pallor, Paresthesia, Pulselessness, Paralysis) are less reliable in the setting of electrical injury. Diagnostic difficulties may arise because patients may have pain from cutaneous burns or paresthesias from nerve injury. Careful clinical evaluation is required for the diagnosis of compartment syndrome: tightness of the involved area to palpation, pain with flexion or extension, or fixed flexion. Diagnosis should be made before the development of pulselessness and paralysis, which are late signs of compartment syndrome.
Another risk of severe electrical injury is rhabdomyolysis which may cause acute renal failure. The diagnosis of rhabdomyolysis is based on the presence of elevated creatine phosphokinase (CK or CPK), myoglobinuria, and/or elevated serum potassium.
Trauma
An electrical shock can cause injury due to powerful muscle contractions or falls (eg, from a ladder). This may result in dislocations (e.g. shoulder dislocation), fractures (e.g. vertebral or long bone fractures) and blunt injuries to internal organs.
Head
Young children who bite electrical cords develop partial or full-thickness burns in their mouth and lips. Labial artery hemorrhage may occur 5 to 10 days after the electrical injury in some of these children, when the eschar separates. Such burns may also result in several late sequelae, such as cosmetic deformities and impaired growth of the teeth.
Ocular involvement is not uncommon after an electrical injury, especially cataracts and less commonly corneal or conjunctival burns, or retinal detachment.
Regarding the auditory system, vertigo commonly occurs, which may be transient or persistent, whereas the development of sensorineural deafness is rare.
Another risk of severe electrical injury is rhabdomyolysis which may cause acute renal failure. The diagnosis of rhabdomyolysis is based on the presence of elevated creatine phosphokinase (CK or CPK), myoglobinuria, and/or elevated serum potassium.
Trauma
An electrical shock can cause injury due to powerful muscle contractions or falls (eg, from a ladder). This may result in dislocations (e.g. shoulder dislocation), fractures (e.g. vertebral or long bone fractures) and blunt injuries to internal organs.
Head
Young children who bite electrical cords develop partial or full-thickness burns in their mouth and lips. Labial artery hemorrhage may occur 5 to 10 days after the electrical injury in some of these children, when the eschar separates. Such burns may also result in several late sequelae, such as cosmetic deformities and impaired growth of the teeth.
Ocular involvement is not uncommon after an electrical injury, especially cataracts and less commonly corneal or conjunctival burns, or retinal detachment.
Regarding the auditory system, vertigo commonly occurs, which may be transient or persistent, whereas the development of sensorineural deafness is rare.
Treatment of patients with electrical injury
Always turn off the power source before approaching the victim. Particularly for high-voltage injuries, involvement of authorized personnel, such as the local power company, in disconnecting the power source may be required.
After disconnecting the power source, assess the cardiopulmonary status of the patient (ABC: airway-breathing-circulation), obtain an ECG, begin cardiac monitoring, check oxygen saturation with a pulse oximeter and establish intravenous access. When head or neck trauma is possible, ensure cervical spine immobilization. Inline immobilization of the spine is one of the top priorities in a patient with trauma.
In patients with extensive burns of the face, mouth, or neck, endotracheal intubation should be provided early, as soft-tissue swelling can develop rapidly and compromise the airway.
Low-voltage electrical injuries (< 240 V) with minimal symptoms, normal physical exam, and normal ECG generally require only local wound treatment and they are not admitted to the hospital.
Patients presenting in cardiac arrest should be treated immediately according to the ACLS protocols.
Cardiac monitoring for 24 hours after the electrical injury is indicated in patients with:
● high-voltage injury
● abnormal ECG or presence of arrhythmias
● initial loss of consciousness
● chest pain
Patients without any of the above presenting features do not require cardiac monitoring.
Pain is controlled with opioid analgesics. NSAIDs should be avoided in these patients because of the risk of acute kidney injury (which may result from myoglobinuria, or from hypoperfusion of the kidneys in cases with hypotension and large intravascular volume losses).
Patients with a severe electrical injury involving possible extensive deep tissue damage will need intravenous (IV) fluid administration.
During the primary survey of the patient, IV crystalloid solution (lactated Ringer’s) should be started for adults at a rate of 500ml/hr, for children of age between 6-13 years at 250ml/hr and for children < 6 years should be started at 125ml/hr.
During the secondary survey burn size should be assessed and the starting IV fluid rate should be calculated according to the formula:
4ml x Body Weight (in kg) x %TBSA / 16 ,
where % TBSA= the estimated percentage of the total body surface area with second or third-degree burns. This initial fluid administration rate should then be adjusted on the basis of urine output, in order to achieve a urine output goal of 30ml/hr if myoglobinuria is not present. In the presence of myoglobinuria, urine output goal is 75-100 ml/hr, until myoglobinuria clears.
Injured extremities require burn wound management and they should be monitored for the possible development of compartment syndrome. In patients with an electrical injury, the visible burn wound often hides a more significant and extensive injury that lies beneath, within the deep tissue. Subsequent edema may develop leading to vascular compromise to any area distal to the injury. Thus, circulation to distal vascular beds should be repeatedly assessed because immediate escharotomy and fasciotomy may be required. The burn injury is treated with early exploration and debridement of devitalized tissues. Tissue with questionable viability is left in place, with planned repeated exploration of the wound in 48 hours. Depending on the severity of the wound, repeated explorations may be required until the wound is completely debrided because electrical damage to vessels may be delayed. Therefore, the extent of necrotic tissue may increase after the initial debridements. After the devitalized tissues are removed, closure of the wound is performed by an experienced surgeon with skin grafts or flaps.Lillard P, Markuns K . Guidance for Emergency Medical Management of Electrical Injuries
Injured extremities require burn wound management and they should be monitored for the possible development of compartment syndrome. In patients with an electrical injury, the visible burn wound often hides a more significant and extensive injury that lies beneath, within the deep tissue. Subsequent edema may develop leading to vascular compromise to any area distal to the injury. Thus, circulation to distal vascular beds should be repeatedly assessed because immediate escharotomy and fasciotomy may be required. The burn injury is treated with early exploration and debridement of devitalized tissues. Tissue with questionable viability is left in place, with planned repeated exploration of the wound in 48 hours. Depending on the severity of the wound, repeated explorations may be required until the wound is completely debrided because electrical damage to vessels may be delayed. Therefore, the extent of necrotic tissue may increase after the initial debridements. After the devitalized tissues are removed, closure of the wound is performed by an experienced surgeon with skin grafts or flaps.
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Bibliography
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Lillard P, Markuns K . Guidance for Emergency Medical Management of Electrical Injuries
LINK http://www.masscosh.org/sites/default/files/documents/Guidance%20for%20Emergency%20Medical%20Management%20of%20Electrical%20Injuries.doc
Family Practice Notebook- Electrical injury LINK https://fpnotebook.com/er/environ/ElctrclInjry.htm
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