Electrical Injuries

, , Section of Emergency Medicine and the Trauma Program, Charity Hospital of New Orleans

South Med J. 2000;93(12) 

In This Article

Discussion

Electrical injuries can be categorized as high and low voltage injuries (Table). The injuries result from direct effects of current, from conversion of electrical energy into thermal energy as the current passes through the body tissues, and from secondary effects. The severity of injury is determined by the voltage, current intensity, types of current, the current pathway, the duration of exposure, the resistance of the tissues, contact surface, the extent of multisystem involvement, and the circumstances surrounding the incident.

Initial Evaluation

The high voltage direct current (DC) electrocution tends to cause a single muscle contraction, throwing its victim from the source. These patients tend to have more blunt trauma. Direct current electrocution can also cause cardiac dysrrhythmias, depending on the phase of the cardiac cycle affected. This action is similar to the affect of a cardiac defibrillator.

Low voltage alternating current (AC) electrocution is three times more dangerous than DC current at the same voltage. The lowest frequency for electrical current in the United States is 60 Hertz (Hz) because this is the lowest frequency at which an incandescent light functions. With AC electrocution, continuous muscle contractions (tetany) may occur, since the muscle fibers are stimulated at between 40 to 110 times per second. With tetany, the victim tends to hold on to the source of current output, thereby increasing the duration of contact and worsening the injury.[2]

Generally, the longer the duration of contact with high voltage current, the greater the degree of tissue destruction. This is true until the tissue becomes carbonized and resistance develops to the current flow. Current is often concentrated at the contact and ground points of the body, where the greatest amount of tissue damage occurs. However, extensive damage may occur between the contact and ground point.

Electrical injuries occur from direct contact or as an indirect contact with a power source. Indirect contacts can be separated into arc, flash, thermal, and blunt trauma injuries. An arc injury is the most destructive of all of the indirect mechanisms. It can generate approximately 2,500°C. An electrical arc is a current spark that develops between two objects that are not in contact with each other. An arc injury occurs when the victim becomes part of the arc itself. Electrical arcs can ignite clothing and cause thermal burns. Flash burns from the electrical source usually result in superficial partial thickness burns. High voltage shocks may cause blunt trauma, usually when the electrical energy causes the victim's muscles to contract violently. This intense and diffuse muscle contraction can cause the victim to fall or fracture bones, especially in AC electrocution.[1]

Central nervous system injury is common with electrocution, as is blunt head trauma, which results from falls or from being thrown from a high voltage contact. Change in mental status is also common. Cataracts, which may occur immediately after electrocution or months later, develop in 5% of patients who have sustained electrical injury near the head or high voltage electrocution.[3] Corneal burns, intraocular hemorrhage or thrombosis, uveitis, retinal detachment, and orbital fractures may also result.

Electrical injury in pediatric patients often involves the oral cavity because children typically bite or suck on the electrical cord. Injury to the labial artery with delayed bleeding occurs in 10% of these patients.

Cardiac arrest, either from asystole or ventricular fibrillation, is common in electrocution. However, patients may present with sinus tachycardia, transient ST segment elevation, QT segment prolongation, PVCs, atrial fibrillation, or bundle branch block.[4] Acute myocardial infarction is rare but has been reported.[5] Vascular damage is greatest in the medial layer of the vessel. Intimal damage may result from immediate or delayed thrombosis as edema and thrombi form on the damaged endothelial surface. This commonly occurs in small muscle branches, where blood flow is slower. The damage to the small arterioles, along with marginal muscle viability as a direct result of the electrical energy, can lead to progressive tissue necrosis.[1] Coagulation necrosis, intravascular hemolysis, and delayed vessel rupture may also occur.

Damage to the lungs is rare because the air in the lungs is a poor conductor of electricity. More commonly, blunt pulmonary trauma occurs from falls or other associated events. Respiratory arrest may result from tetanic contraction of the diaphragm. Aspiration pneumonia and pulmonary edema are not the direct result of electrocution.

Injuries to solid abdominal organs directly from electrical current have not been reported. Solid organ damage is usually the consequence of blunt trauma. Hepatic and pancreatic necrosis, paralytic ileus, bowel perforation, esophageal hemorrhage, Curling's ulcers, and gastrointestinal bleeding have been reported. Acute renal failure usually results from rhabdomyolysis or hypovolemia.

Long bone fractures, vertebral compression fractures, and scapular fractures may result from electrical shock, either from the violent and intense muscle contraction or from secondary blunt trauma. Shoulder dislocations may result from tetanic spasm of rotator cuff muscles. Periosteal burns, bony matrix destruction, aseptic necrosis, and osteomyelitis have been reported as delayed complications. Severe muscle necrosis may require fasciotomy.

Altered mental status is usually transient unless associated with significant head injury. The victim may have confusion, agitation, emotional lability, amnesia (with loss of both short-term and long-term memory), cognitive impairment, aphasia, headache, seizures, and prolonged coma. Cerebral edema, hypoxic encephalopathy, and peripheral neuropathy have been reported. Central and peripheral nervous systems symptoms may improve, but long-term disability is common.

In high voltage electrocution, the spinal cord may be injured as a result of fractures or ligamentous injury to the spinal column caused by muscle contraction or blunt trauma. In addition, the electrical current may cause direct injury to the spinal cord. This spinal cord injury may be acute or delayed. Acute insult to the spinal cord may cause weakness and paresthesia within hours of the initial injury. Neurologic deficits are more common in lower extremities than in upper extremities. These patients have a good prognosis for partial or complete recovery. On the other hand, delayed injury may be manifested days to years after electrocution. Delayed injuries include ascending paralysis, amyotrophic lateral sclerosis, or transverse myelitis. Motor deficits are common in delayed injury, and sensory deficits are typically patchy and do not correlate well with the level of motor deficit. Although recovery has been reported, the prognosis is usually poor.[6,7]

The cutaneous system is typically involved in electrocution. Importantly, the initial size of the electrical burn site is not an accurate reflection of the amount of tissue actually involved because the subcutaneous tissue is commonly involved. Therefore, the rule of nines should not be used for calculating fluid resuscitation. Instead, adequate tissue perfusion, vital signs, and urine output should guide fluid resuscitation.

Management

Initial management of all patients with electrical injury includes evaluation of airway, breathing, and circulation. These patients should be assessed as trauma patients. Both Advanced Trauma Life Support and Advanced Cardiac Life Support protocols should be instituted when resuscitating these patients. Supplemental oxygen, cardiac monitor, pulse oximetry, and two large bore intravenous catheters are essential. Basic laboratory studies should include a complete blood count, ECG, electrolytes, liver profile, cardiac enzymes with isoenzymes, coagulation factors, arterial blood gases, blood type and screen, urinalysis, and urine myoglobin. Radiographic studies should be done as clinically indicated. Nasogastric decompression of the gastrointestinal tract should be considered. H2-blockers or sucralfate may be beneficial. Injured or fractured limbs should be splinted in a functional position. Tetanus prophylaxis should be administered.

An electrical injury should be treated more like a crush injury rather than a thermal injury. Fluid resuscitation should begin as soon as possible to maintain a urinary output of 0.5 to 1.0 mL/kg/hr in the absence of pigmented hemoglobin in the urine or 1.0 to 1.5 mL/kg/hr in its presence. A urine output of 1.0 to 1.5 mL/kg/hr should be maintained until the urine is clear of myoglobin. Additionally, the blood pH should be maintained at 7.45 or higher with sodium bicarbonate to prevent the precipitation of myoglobin into the renal tubules. Furosemide or mannitol may be used to maintain urine output. The initial recommended dose of mannitol is 25 g, followed by 50 to 200 g/day.

Cutaneous burns should be treated with silver sulfadiazine (Silvadene) or mafenide acetate (Sulfamylon). Silvadene is preferred in extensive cutaneous burns. Sulfamylon is preferred in full-thickness burns because of its superior penetration of the eschar. Sulfamylon may cause electrolyte abnormality in burns involving more than 15% to 20% of body surface.

All patients with severe electrical burns should be stabilized and considered for transfer to a burn unit. Indications for admission to an intensive care unit include cardiac arrest due to electrocution, loss of consciousness, abnormal ECG results, dysrrhythmia, history of cardiac disease or significant factors for cardiac disease, concomitant injury severe enough to warrant admission, suspicion of soft tissue injury, hypoxia, and chest pain. Outpatient management of electrical injuries may proceed if the patient has a history of low voltage exposure, has remained totally asymptomatic, and has normal findings on physical and laboratory examination. In addition, patients with small cutaneous burns or mild persistent symptoms may be discharged if their ECG is unremarkable and the urine is negative for myoglobin. These patients require follow-up evaluation.

Obstetric consultation is recommended for all pregnant patients having electrical injury, regardless of presentation. In addition, children with oral electrical burns should be admitted.

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