Electrocution

Question 1

Long term sequelae of electrocution relevant to GP:

Answer 1

Types of impairments:

• 21% neurological
• 59% neuropsychological/behavioural

*Neurological impairments can be delayed by days to months post injury - up to 5 years in some cases

Question 2

What are the neurological consequences of electrocution?

Answer 2

• 50% with low voltage injuries (<1000 volts)
• 67% with high voltage injuries (>1000 volts)
• can cause spinal cord injury
• MRI spine typically normal
• epilepsy
• convulsions
• abnormal involuntary movements
• headache/migraine
• vertigo/tinnitus (may also increase lifetime risk of these)
• bilateral persistent sensorineural hearing loss
• reversible diplopia
• autonomic cardiovascular dysfunction
• bladder/sphincter dysfunction
• sensory and motor damage of peripheral nerves (often patchy and sensory deficit not correlating with motor deficits)
• motor > sensory in prominence
• traumatic brain injury

Question 3

neuropsychological/behavioural complications of electrocution?

Answer 3

• pain
• fatigue
• range of motion reduction
• joint stiffness
• depression
• PTSD
• memory disturbance

Question 4

Theories of delayed neurological effects post electrocution?

Answer 4

1) Vascular damage resulting in neuronal ischaemia
2) electrical charge results in electroporation (aberrant opening of cell membranes pores) resulting in loss of cellular functions
3) alteration of protein/lipid structure in myelin from heat or free radiacl oxidation
4) Electricity stimulates cortisol release resulting in hyperstimulation of glutamine receptors resulting in release of destructive free radicals (elevated free radicals have been demonstrated in lightning injuries)

Answer 5

Less likely to return to work 1 year post injury than survivors of fires

Question 6

Physics of electrocution injuries:

Answer 6

Types:

1) Flash = arc flash as current current only passes over the skin typically resulting in superficial burns
2) Flame = if an arc flash ignites clothing; generally current does not pass the skin
3) Lightning = short but very high voltage where current flows through entire body
4) True = body becomes part of an electrical circuit; normally an entry and exit wound is present

Voltage (V) = difference between high and low electron concentration
High voltage is >500V
Current (I) = amperes = volume of electrons
Resistance (R) = how a material reduces electrical flow
-low resistance have highest concentration of electrolytes and water = blood vessels, neurones, muscles
-high resistance tissue tends suffer the greatest tissue damage because there will be more energy dissipation = skin, fat and bone
*extent of external injury does not predict the level of internal damage
*concentration of electrons increases at joints where there is s smaller volume of low resistance tissue and more high resistance tissue = they tend to suffer injury

*Low frequency AC = tetany = unable to release contact = prolonged exposure = more tissue damage
*Electrical field strength (amount of voltage encountered relative to surface area of tissue in contact) determines injury severity also
High field strength = electrochemical/thermal damage = protein coagulation, coagulation necrosis, haemolysis, thrombosis, muscle/tendon avulsion, dehydration, tissue oedema, compartment syndrome.