Senior Report 6.14

Case Presentation by Dr. Cameron Kyle-Sidell

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Questions:

1) The injuries shown above are most consistent with which of the following clinical presentations:

a)  A furnace mechanic who suffered a flash burn

b)  A golf caddy struck by lightning

c)  A maintenance man who mishandles an overhead power line

d)  A lawyer working on a home improvement project gone wrong

2) The patient above complains of significant neck pain upon presentation.  Which of the following diagnostic modalities should be most considered:

a) CT of the neck with contrast to evaluate for underlying muscle necrosis

b)  Local surgical exploration at site of pain

c)  CT of the neck without contrast to evaluate for underlying bony injury

d)  Neck fasciotomy to relieve compartmental pressure

3)  The following patient can be safely discharged from the emergency department:

a)  A woman at 24 weeks gestation who suffers an electrical injury when plugging in a hair dryer, landing on her back, who has no loss of consciousness and a normal EKG.

b)  A 35 year old male who suffers electrical injury while plugging in the microwave, with a normal EKG and no loss of consciousness and a small cutaneous burn on his forearm.

c)  A 25-year-old male who is electrocuted by a power line at work, with an EKG demonstrating T wave inversions in the lateral leads, and no loss of consciousness.

d)  An 8-year-old male who suffers an oral burn after biting an electric extension cord with swelling of the tongue and the floor of the mouth with no active bleeding.

 

Answers:

1)  C.

The injuries pictured above are most consistent with a high voltage electrical burn.  When a patient presents with an electrical burn, it is important to establish the source of injury.  Electrical burns are typically divided into high voltage and low voltage injuries.  High voltage injury is defined as exposure to more than 1000V.  The patient pictured presented after grabbing a fallen overhead power line exceeding 10,000 V with his right hand.  High voltage injuries present as painless, depressed, yellow-gray charred craters with central necrosis. In general, high voltage injuries may largely spare the skin surface but cause extensive injury to underlying soft tissue and bone.  High voltage electrical injury can however lead to a “kissing burn” as seen running down the patient’s midline, a cutaneous burn which occurs along flexor creases when an electrical current arcs across both flexor surfaces.  These burns are important to recognize as they are often associated with significant underlying injury.  This kind of “hidden” damage is rare in low voltage injuries.

A golf caddy struck by lightning is unlikely to present with the findings in the picture. Lightning strikes act as an instantaneous current, and while its voltage can exceed 1 million volts, it rarely causes significant cutaneous burns or soft tissue damage because of its brief duration. Lightning is more likely to cause cardiac and respiratory arrest, neurologic sequelae, and autonomic instability.  There are four main types of burns that can be seen with lightning strikes: linear burns, punctate burns, feathering burns, and thermal burns. Linear burns occur where sweat or moisture has accumulated on the body, such as down a person’s chest or in the axilla.  Punctate burns resemble cigarette burns. Feathering burns show no damage to the skin itself and make a fern like pattern on the skin secondary to electron showers induced by lightning. They do not require therapy. Thermal burns occur if a person’s clothing catches on fire or if they have metal on their body that is heated by the flash.  Many people who have experienced lightening strikes will present with a combination of these types of burns.

A lawyer working on a home improvement project likely sustained a low voltage injury which creates smaller, well-demarcated contact burns at the sites of skin entry and exit than is indicated in the picture. A furnace mechanic who suffered a flash burn will normally present as a superficial partial thickness burn which more closely resembles a traditional burn as seen in victims of fires.

2)  C. 

Secondary trauma must be considered in all high-voltage exposures, especially in those involving direct current electricity.  Just as the voltage potential of electrical injuries is important to distinguish, it is important to determine if the patient was exposed to alternating current (AC) or direct current (DC).  A direct current is more often used in automobiles, batteries, and high-voltage power lines.  An alternating current is more common in homes and offices.  Exposure to each leads to muscle contractions. Direct current causes a single muscle contraction that often throws the patient away from the source while an alternating current leads to tetanic muscle contractions which can often bring the patient in closer proximity to the source.  Most electrical exposures occur to the upper extremity, and because the flexors of the upper extremity are typically stronger than the extensors, the tetanic contractions in AC exposure often cause the arm to flex and bring the source closer to the body.  While both AC and DC can lead to significant morbidity (and mortality), a direct current exposure suggests a much higher risk of secondary trauma.  Given our patient’s high voltage, direct current exposure, we should have a high degree of suspicion for secondary traumatic injury.  Our patient in fact had a loss of consciousness and sustained a contusion to the back of his head from being thrown backward during the incident.  A CT of the neck without contrast is warranted to rule out a cervical fracture from the fall.  It is not uncommon for patients to present with fractures and joint dislocations, including posterior shoulder dislocations, due to falls and forceful muscle contractions after direct current exposure.

Surgical exploration of the neck and fasciotomy are not indicated at this time.  While significant underlying muscle necrosis and edema can occur leading to increased compartmental pressures, this is far more common in the extremities.  In the absence of hard signs such as progressive neurologic dysfunction and vascular compromise, early surgical intervention is generally not indicated.  While careful monitoring for increased compartmental pressures is required, unnecessary surgical intervention including fasciotomy can lead to a prolonged hospital course including multiple ensuring surgeries and significant rehabilitation time.  A CT with contrast is not the diagnostic modality of choice to evaluate for cervical fractures or compartment pressures.

3)  B.

A 35 year old male who suffers electrical injury while plugging in the microwave with a normal EKG and no loss of consciousness and a small cutaneous burn on his forearm can be safely discharged. Current recommendations suggest that all patients who present to the emergency department after suffering an electrical injury to a low or high voltage source should have an EKG  performed to evaluate for arrhythmias and cardiac injury.  Patients who experience low-voltage injury with no EKG abnormalities, no loss of consciousness, or other significant injury can be safely discharged home with appropriate wound care.

A pregnant patient with a viable fetus requires fetal heart monitoring due to the potential for placental abruption. Ultrasound may also be indicated if the patient experiences symptoms such as vaginal bleeding, decreased fetal movement, or persistent abdominal pain to assess for fetal viability. Electric burns can increase uterine activity and affect uteroplacental circulation, which can require aggressive resuscitation in the hospital. Fetal complications as a result of electrical trauma include IUGR, spontaneous abortion, oligohydraminos, and cessation of fetal movement.

The child with an oral burn and tongue swelling has evidence of possible airway compromise.  He should be closely observed to monitor for further swelling.  If this patient had no intraoral swelling, he could be discharged home.  One of the most common injuries seen in children is an oral arc burn which occurs with biting of an electrical cord.  These patients can have delayed bleeding up to 2 weeks after the incident from the labial artery when the initial eschar separates, however observation to monitor for this delayed bleeding is unnecessary.  Parents should be properly educated on the chance for rebleeding and instructed to return should such bleeding occur.

Any patient with a high voltage injury with or without EKG abnormalities requires admission to a burn center due to the possible for significant hidden underlying injury.

References

Emergency Medicine Practice.  Electrical Injuries:  A review for the emergency clinician.  October 2009, Volume 11, Number 10. Ebmedicine.net

One Response

  1. Thanks for a good case, Cameron. My understanding was that the vast majority of high voltage transmission lines in the world are AC. (That was the whole Tesla vs Edison thing.) There has been some more recent interest in high voltage DC, especially for very long runs between different grids and for undersea transmission, but wouldn’t a maintenance man be more likely to run into an AC line?

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