Electrical Injury

Electrical Injury

Thomas R. Howdieshell, MD

UNM Burn CenterAdults & Pediatrics from tragedy… hope!

Burn Symposium

STATION 2

Electrical Injury

Thomas R. Howdieshell, MD Trauma/Surgical Critical Care University of New Mexico HSC

Albuquerque, NM

UNM Burn Center

Adult & Pediatric Injury

from tragedy… hope!

Classification of Electrical Injury

• Low voltage (< 1000 volts)

• High voltage (≥ 1000 volts)

• Electric arc (No current through tissue)

• Lightning

Principles of Electricity• Electricity is the flow of electrons through a conductor

• Alternating current (AC): Electrons flow back and forth through a conductor in a cyclic fashion

• Direct current (DC): Electrons flow only in one direction (batteries, defibrillators, pacemakers, electric scalpel)

• AC is more efficient method of generating and distributing electricity

• AC is more dangerous because it causes tetanic muscle contractions that prolong the contact

Determinants of Electrical Injury

• Ohm’s Law: Current is proportional to the voltage of the source and inversely proportional to the resistance of the conductor

I=V/R

• Joule’s Law: Amount of heat produced is directly proportional to the current, resistance, and time

J=I2RT

• Skin is the primary resistor; 40,000 – 100,000 ohms, varies with thickness, water content

Tissue Resistance (Greatest to Least)

• Bone• Tendon• Fat• Skin• Muscle• Blood Vessels• Nerves

Pathway of Current

• Determines the number of organs/tissues affected, type and severity of injury

• Vertical pathway parallel to the axis of the body is the most dangerous

• Horizontal pathway from hand to hand will spare the brain but can be fatal due to involvement of the heart, respiratory muscles, or spinal cord

• Severity of injury is inversely proportional to cross-sectional area of contact (hands, feet)

• Arc can generate extremely high temperatures (up to 5000 C)

Cardiovascular System

• Electric injury may affect heart in 2 ways: Direct necrosis of myocardium, induction of cardiac dysrhythmia

• Low current (household) may cause ventricular fibrillation, high current-voltage most likely induces asystole

• Injury to vessels due to high water content; small vessels may thrombose due to coagulative necrosis, larger vessels susceptible to medial necrosis (pseudoaneurysm, rupture)

• Clinical manifestations: sinus tachycardia, nonspecific ST and T wave changes, heartblock, BBB, prolongation QT interval, V. fib, asystole

Respiratory System

• Respiratory arrest usually result of direct injury to respiratory control center causing apnea or to suffocation secondary to tetanic contraction of the respiratory muscles (“locking-on”)

• Anoxic injury may cause irreversible injury to the heart and brain

• Thermal burn of the airway (arc) or inhalation of toxic fumes may occur

Nervous System

• Central and peripheral nervous system injury is a common clinical manifestation of electrical injury

• No specific histologic or clinical finding considered pathognomonic

• Can be injured indirectly due to trauma, anoxia

• Clinical manifestations: Loss of consciousness, confusion, impaired recall, seizures, visual disturbances, deafness, hemiplegia, quadriplegia

• Neurologic injuries can occur immediately or years later (chronic pain syndrome)

Cutaneous Burns and Muscle Injury• “Flush burn”: Thermal burn due to heat generated by arc

• “Electrothermal burn”: Passage of current through tissue

• “Flame burn”: Ignition of clothing

• Severity/surface area of the skin burn cannot be used to assess the degree of internal injury or the magnitude of resuscitation

• Techniques to assess muscle viability

Kidney

• Acute tubular necrosis (ATN) risk due to hypovolemic shock, rhabdomyolysis, vascular injury

• Development of hyperkalemia, hyperphosphatemia

• Obvious or occult muscle necrosis search (“progressive recognition”)

Others

• Traumatic injury (fall, tetanic contractions)

• Extremity, axial skeleton fractures

• Cataracts

• Perforated tympanic membrane

Diagnosis and Management• Primary and secondary survey (rule out multiple

trauma)• EKG, cardiac monitoring

Indications for 24 hour monitoring 1. Documented cardiac arrest

2. Cardiac dysrhythmia on transport or in ED3. Abnormal EKG4. Loss of consciousness5. Past medical history of cardiac disease (Crit Care Med 30:424, 2002; J Emerg Med 18:181, 2000)

Diagnosis and Management

• Fluid Resuscitation1. Remember, TBSA cutaneous burn not predictive of fluid requirements2. Use Ringers Lactate to promote urinary output of 0.5 - 1.0mL/kg/hr, 1.0-2.0 mL/kg/hr if myoglobinuria present

• Treatment of Rhabdomyolysis 1. Brisk diuresis!2. Mannitol only if resuscitated 3. Sodium bicarbonate to increase urine pH (controversial)4. Frequent electrolyte checks

Diagnosis and Treatment

• Wound Care1. Thermal burn2. Electrothermal burn

• Determination of muscle viability 1. Exam, urinalysis2. Technectium-99 pyrophosphate scan 3. MRI, 32P spectroscopy4. Exploration, fasciotomy, re-exploration

Diagnosis and Management

• Follow up – Multispecialty: PT, OT, Ophthalmology,

Neurology, Neuropsychiatry

• Neurologic exam

• Eye exam

• Cognitive evaluation

Bibliography

1. Koumbourlis, A.: Electrical injuries. Crit Care Med 30:424-430, 2002.

2. Arnoldo, B. D.: Electrical injuries: A 20 year review. J Burn Care Rehabil 25:479-484, 2004.

3. Cancio, L.C.: One hundred ninety-five cases of high-voltage electric injury. J Burn Care Rehabil 26:331-340, 2005.

4. Rai, J.: Electric injuries: A 30 year review. J Trauma 45: 933-936, 1999.

5. Fish, R. M. : Electric injury: Cardiac monitoring indications. J Emerg Med 18:181-187, 2000.

UNM Burn Center: from tragedy… hope!

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Thomas R. Howdieshell, MD

UNM Burn CenterAdults & Pediatrics

from tragedy… hope!

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Thomas R. Howdieshell, MD