Electrical burn

What is an electrical burn?

An electrical burn is a tissue injury caused by contact with an electric current such as live wires or lightning.

Electrical burns are divided into:

• Low-voltage injury (< 1000 V) versus high-voltage injury (> 1000 V)
• Thermal injury due to electrical flash versus a current flowing directly through the body.

A severe or fatal injury caused by an electric shock is known as electrocution.

Who gets an electrical burn?

Electrical injuries are a relatively uncommon cause of burns but result in approximately 1000 deaths each year in the US. Anyone in contact with an electric current can get an electrical burn. Typically, a low-voltage electrical injury/burn patient is a healthy young man at home or in the workplace. High-voltage injuries are less commonly occupational. One third of high-voltage electrical injuries are due to lightning. A recent art-form, fractal wood burning, is being reported to cause high-voltage electrical burns. 

What causes an electrical burn?

Electricity is defined as a flow of electrons. Electrons flow when there is a difference of electrical potential between by two points (voltage). The higher the voltage, the higher the current of electrons (the Law of Ohm).

The extent and severity of skin damage depends on:

• The strength of the current: a function of voltage and tissue resistance
• Type of electrical circuit (direct or alternating current)
• The pathway taken by the current through the body
• Duration of contact.

What are the clinical features of an electrical burn?

Electrical injury results in tissue/organ damage through three mechanisms:

• An electric current passes through the body tissues and causes direct injury
• Electrical energy is converted into thermal energy
• An indirect mechanical effect causing uncontrolled muscle contraction and falls, particularly with high-voltage injuries.

Low voltage electrical burn

Low voltage electric current results in 2 well-circumscribed deep partial-thickness or full-thickness electrothermal burns:

1. Contact burn at entry site (eg, hands, skull)
2. Exit wound (eg, heels in contact with the ground).

High voltage electrical burn

High voltage injury may be due to direct contact or flashing.

• Direct contact, high-voltage injury causes a painless, full-thickness, indented, yellowish-grey skin burn that is sometimes accompanied by central necrosis.
  
• Flashing high voltage injury can cause a superficial burn, a partial thickness burn, or devastating full-thickness injury brought about by an electric arc.
  

An electric arc or spark, including a lightning strike, is produced between a highly-charged source and the ground, reaching temperatures of up to 2500C.

• This high temperature directly burns the skin.
• The spark ignites clothing; the ensuing flames also burn the skin.
• Electrical current flowing through body tissues cause electrothermal heating.
• It results in kissing burns.

A kissing burn is an electric arc generated between two skin surfaces facing each other and sandwiching a joint, typically the elbow and knee flexures. The arc crosses the flexor crease and burns the two 'kissing' skin surfaces causing vast underlying tissue destruction.

Assessment of cutaneous involvement alone may underestimate the extent of underlying tissue damage.

How is an electrical burn diagnosed?

Preceding electrical exposure confirms the diagnosis of an electrical burn.

In an unconscious patient in an appropriate environmental setting:

• Include electrical injury in the differential diagnosis
• Activate the Advanced Trauma Life Support protocol, safely securing the airway, breathing, and circulation
• Carefully examine all organ systems (see below)
• Calculate total body surface area (TBSA) of skin burn
• Monitor neurovascular status of extremities to detect compartment syndrome.

Skin

• Cutaneous burn

Heart

• Arrhythmia
• Cardiac arrest

Respiratory system

• Respiratory arrest caused by respiratory muscle tetany or central nervous system dysfunction

Vascular system*

• Development of an aneurysm
• Tissue ischaemia

Neurological system*

• Impairment of consciousness
• Paralysis and paraesthesia (usually transient)
• Peripheral neuropathy
• Spinal cord injury

Musculoskeletal system*#

• Muscle necrosis and compartment syndrome
• Fractures/dislocation

Kidney

• Renal failure caused by myoglobinuria if extensive muscle necrosis

Other

• Cataracts
• Neuropsychological effects

Note:

• *Vessels, nerves, and muscles are good conductors and are directly destroyed as electrons pass through them.
• #Bone and tendons have the highest resistance to electrical current; electrical energy is converted into heat causing thermal injury.

Calculating total body surface area

There are several ways to determine the TBSA.

• Rule of nines: the proportion of body surface area in adults is different from that in infants and children.
• The Lund and Browder chart is more accurate than rule of nines in children and infants. 
• Use the size of the patient’s hand to represent 1% of TBSA.

Electrocardiography

Electrocardiography (ECG) should be performed in every electrical burn case. Continuous cardiac monitoring is required if there is documented arrhythmia and signs of ischaemia, history of loss of consciousness, or suspected high voltage electrical injury.

Other tests

Complete blood count, electrolytes, blood urea nitrogen, and creatinine are ordered for patients with substantial injuries or if there is a risk for conductive electrical injuries (presence of entry and exit wounds or rhythm abnormalities).

Urinalysis for the presence of blood without red blood cells may indicate myoglobinuria due to muscle destruction.

Creatinine kinase level should be measured in high voltage injuries because its peak concentration predicts extent of muscle injury, amputation risk, mortality, and length of stay.

What is the treatment for an electrical burn?

Pre-hospital setting

In the pre-hospital setting, priorities are to:

• Secure the scene: make sure the patient is no longer in contact with live wires before touching them.
• Turn off the power source suspected to be the cause of electric burn/injury
• Evaluate an unconscious patient for possible cardiac arrest and institute cardiopulmonary resuscitation (CPR)
• Provide fluid resuscitation and pain management.

Management of an electrical burn wound

Management of electric burn wounds should include:

1. Cleansing: debride loose tissue and blister remnants
2. Moisturise to promote early epithelialisation
3. Apply broad-spectrum antimicrobial agent. Options include:

• Silver sulfadiazine cream: broad spectrum, good safety profile, but unable to penetrate eschar
• Mafenide cream: broad spectrum, can penetrate eschar but may cause metabolic acidosis and application is painful
• Silver nitrate: broad spectrum, must be applied every 4 hours, stains, and has a potential osmolar diluting capacity.

Surgical management

Early decompression procedure is required for a contracted and tight compartment of extremity (eg, forearm, leg) based on a peripheral neurovascular evaluation.

• Progressive sensory and motor dysfunction
• Severe pain
• Loss of arterial signal on Doppler ultrasound
• Inadequate early resuscitation

Surgical debridement of unhealthy tissue followed with definitive wound closure is done at day 3 to 5 once the injured tissue is well demarcated.

Excision and grafting may be required for contractures a few weeks following deep partial thickness and full thickness burns.

What is the outcome of an electrical burn?

Deep partial-thickness or full-thickness wounds inevitably cause scarring. Other potential long-term complications of electrical burn injuries include:

• Neurological deficits: peripheral neuropathy and central nervous system dysfunction: these develop in several weeks to months
• Post-traumatic stress disorder and major depression
• Cataracts if the eye has been injured
• Heterotopic ossification and neuromas.

Electrical burns can be immediately fatal particularly if due to low-voltage exposure or lightening. High-voltage injuries cause more morbidity than low-voltage burns including more medical complications, require more surgical interventions, and have a greater psychological impact.