Question 3

College Answer

a)

• Type of circuit – AC current worse than DC
• Duration of exposure
• Resistance of tissues : higher the resistance greater the thermal energy produced and greater the damage to the tissues
• Voltage: > 1000 V is high voltage and causes greater tissue damage. Current
• Pathway of current: affects the part of the body that is damaged

b)

• Chest compartment syndrome due to circumferential trunk burns,
• Tight burns dressing on the chest
• Pulmonary oedema due to cardiac involvement
• Pulmonary aspiration
• Lung contusions due to trauma associated with incident
• Abdominal compartment syndrome
• Undersedation/ventilator dysynchrony

c)

• Examine the patient to rule out compartment syndrome.
  • Surgical opinion and fasciotomy should be considered early
• Prevention of AKI Correction of volume depletion: if present rigorous fluid repletion until it is clear from sequential laboratory values that the plasma CK level is stable and not increasing
  • Prevention of intratubular cast formation- a forced alkaline diuresis, in which the urine pH is raised to above 6.5, may diminish the renal toxicity of haem proteins.
  • Diuresis with mannitol can be considered – currently no evidence
• Treatment of Established Renal Failure:
  • CRRT

Discussion

a)

Factors determining the severity of electrical injuries in general (Kombourlis et al, 2002)

• Size of the current: the greater the current (in amperes) the worse the injury. This is the most important determinant of electrical injury; the severity is the most directly related to amperage. Current in excess of 5A can cause sustained asystole.
• Duration of the current: the longer the duration of exposure, the worse the burn
• Magnitude of the voltage: the higher the voltage, the greater the damage
• Tissues traversed by the current: the most important examples being the brain and heart.
• Contact conduction vs. arcing: i.e. current arcing though ionised air causes surface flash burns which may be diffuse, whereas contact with an electrode causes burns at the specific site of contact.
• Presence of a surface conductor, eg. water. Wet skin has its normally high resistance reduced a hundred-fold, with a much larger
• Subcutaneous conduction: most of the resistance to current is by the dry skin. Once it is penetrated, the resistance is greatly reduced. Resistance of the blood and muscles is approximately 20-50 times less than that of the skin (500-1000 Ohm vs 100,000 Ohm). Microshock can be the consequence, which is a risk to ICU patients who have various conductive materials suspended in their bodies.

Factors determining the severity of electrical burns specifically:

• As per Kombourlis, "The severity of the burn depends on the intensity of the current, the surface area, and the duration of exposure."
• Magnitude of the current is most important factor. Current in excess of 1A is enough to cause skin burns.
• Duration of exposure is the next most important factor.
• Surface area of exposure is an important determinant of burn severity and depth: if one has a wide surface area exposed, the current is distributed across all of it, and the damage is relaitvely minor- whereas if all of the current was concentrated in a small area, the burn would be deep and severe. This is the ratonale behind making big wide electrode pads for cardioversion.
• Magnitude of the voltage does not seem to matter (Ferreriro et al, 1998)

b)

" List the potential causes of poor lung compliance", they asked. This is weird, because according to Koumbourlis, "there are no specific injuries to the lungs or the airways directly attributable to electric current." In view of this, the author was forced to concoct an imaginative list of respiratory complications for a condition which usually has none.

• Pulmonary oedema due to heart failure or enthusiastic fluid resuscitation
• Pneumothorax from CPR
• Burns causing reduced chest wall compliance
• Thoracic compartment syndrome (myonecrosis of the intercostal muscles, or circumferential burns)
• Abdominal compartment syndrome (myonecrosis of the abdominal muscles, or circumferential burns)
• Sustained tetany: especially with AC at household frequency (50-60Hz), which can induce "an indefinite refractory state at the neuromuscular junction" (Koumbourlis, 2002), causing sustained tetanic contraction.
• Fractured ribs from CPR or due to a fall
• Lung contusions from CPR, being thrown, or blast damage
• Inhalational injury from burned material (see above).
• Aspiration due to unconsciousness

c)

Something specific to high voltage electrical injury is the need to debride the necrotic muscle.  Occasionally, the whole limb is unviable and must be amputated.

As far as generic mangement of rhabdomyolysis, a recent meta-analysis of management strategies has presented the following conclusions:

• Commence IV fluids within 6 hours - as early as possible
• Aim for a urine output greater than 300ml/hr
• Use of sodium bicarbonate is only indicated to correct systemic acidosis. There is no evidence for any benefit in rhabdomyolysis-induced AKI except for some uncontrolled case series, which does not stop people from recommending it anyway. It appears in the 2010 college answer, which pre-dates the 2013 meta-analysis. The savvy trainee seeking to remain in the good books with examiners who use forced alkaline diuresis will want to mention this therapy in their answer, with the caveat that it is may not be helpful, but is also probably not harmful.
• Use of mannitol is only indicated if urine output >300ml/hr cannot be maintained

Bernstein, Theodore. "Electrical injury: electrical engineer's perspective and an historical review." Annals of the New York Academy of Sciences 720.1 (1994): 1-10.

Koumbourlis, Anastassios C. "Electrical injuries." Critical care medicine 30.11 (2002): S424-S430.

Kisner, Suzanne, and Virgil Casini. "Epidemiology of electrocution fatalities." (2002).

PITTS, WILLIAM, et al. "Electrical burns of lips and mouth in infants and children." Plastic and reconstructive surgery 44.5 (1969): 471-479.

Rosen, Carlo L., et al. "Early predictors of myoglobinuria and acute renal failure following electrical injury." The Journal of emergency medicine 17.5 (1999): 783-789.

Brumback, Roger A., Daniel L. Feeback, and Richard W. Leech. "Rhabdomyolysis following electrical injury." Seminars in neurology. Vol. 15. No. 04. © 1995 by Thieme Medical Publishers, Inc., 1995.

Price, Timothy G., and Mary Ann Cooper. "Electrical and lightning injuries." Marx et al. Rosen’s Emergency Medicine, Concepts and Clinical Practice, Mosby, 22 (2006): 67-78.