Lightning and Electrical Injury

Question 1

Discuss factors that affect the degree of injury from electrical shock

Answer 1

1) Circuit type
- uses either DC or AC
- exposure to DC most frequently causes a single strong muscular contraction THis may throw the subject back from the source
- AC is more common and more dangerous because above the so called let go current will cause muscular tetanic contractions pulling the victim closer to the source
- >16mA patient will be unable to let go

2) Amperage

3) Resistance
- Neurovascular tissue are good conductors whereas tendons, fat and bone are relatively poor conductors
- dry skin offers teh greatest resistant - current initially unable to pass through skin will create thermal energey an cause signifiacnt burns as the skin blisters the resistance lessons
- Internally current follows the path of least resistance and the degree of burns seen on the surgace typically under-estimate the damage occuring below the surface

4) Voltage
- the electrical potential or difference in electrical energy between two points
- high voltage injury >1000V
- high voltage injury are characterised by partial to full thickness burns, deep tissue desturction and frequent cardiac or respiratory arrest .

5)Current pathway

6) current duration (duration of contact)
- exposure greater than one cardiac cycle general lead to the generation of arrhythmias.

Question 2

Describe conducted electrical weapons

Answer 2

Peak voltage delivered is 1200 V but low amperage of 2.1mA

Priamry burst is followed by 100msec pulses intended to inhibit myoneurons causing the subject to fall to the ground.

Question 3

Discuss lightning injuries

Answer 3

• involve 100s of millions of volts
• drastically shorter contact average 30 microseconds
• current flow is altered with a reduction in penetration causing less destructive tissue effects overall

Question 4

Describe clinical features of electrical injury

Answer 4

1) general tissue effect
- At the cellular level current causes damage to cell membranes and alters membrane solubility leading to electrolyte abnromaltiies and cellular oedema

2) skin
- Skin burns with four patterns (entrance and exit, arc burns, thermal burns and flash burns)

3) CVS/resp
- Cardiac or resp arrest is the most common cause of death
- either DC or AC can cause VF or asystole
- resp arrest occurs due to tetanic paralysis of the thoracic respiratory muscles or as a result of damage to brainstem resp centres

4) head and neck
- occular involvement is common with cataracts being the most frequent manifestation.
- vitrous and anterior chamber haemorrhage, retinal detachment, macular laceation and corneal or conjunctival burns all occur

5) extremities
- Muscle necrosis occurs due to primary damage and secondary to damage to neurovascular bundles leading to poor blood supply
- intimal and media damage of vessels is common with intimal damage leading to immediate coagulative necrosis and thrombosis and media damage causing aneurysmal dilation and haemorrahge in a delayed fashion.
- Combination of tissue oedema and poor perfusion but limbs at high risk of compartment syndrome. - with fasciotomy and amputations not uncommon
- bony injury is also common secondary to being thrown from source or from heat generated due to bony resitance leading to periosteal burns and osteonecrosis

6) Nervous system
- CNS (altered mentations, seizures and or coma) - vascular injury may cause CVA
- delayed and chronic manigesation including ascending paralysis, transverse myelitiss and amyotrophic lateral sclerosis

7) other
- Significacnt muscle damage may result in significant myoglobinurai and subsequent renal failure and life threatenning hyperkalaemia
- stress ulcer
- Non cardiogenic pulmonary oedema

Question 5

Discuss clinical features of lightning strike

Answer 5

1) CVS and resp leading cause of death as above
- myocardial contusions are common

2) CNS as a ove

3) skin
-normally superficial bursn but common
Typically skin pattern (arborescent or fernlike pattern) - called lichtenberg figures

4) ears
- TM is typically ruptures due to the shick wave and blast effect

5) eyes
- most common is cataracts

Question 6

Discuss Ix of electrical injury

Answer 6

Evaulation only for those exposed to high voltage, those with LOC ore present with alteraed mentation or neuo deficits, other signficiant symptoms including severe entrance and exit wounds or burns more than superfical

 ECG
FBC
U&E
CK 
If intra-abdominal injury is suspected should have LFT and lipase

Question 7

Discuss management of electrical injury

Answer 7

Low voltage electrical injuries associated with minimal signs and symptoms generally require onloy local wound treatment.

Patients who present in cardiopulmonary arrest should be resuscitated regardless of rhythm because good outcomes have been documented in patients presenting in asystole.

Any patients with ECG signs of cardiac injury or dysrhythmias and patients with more than minimal ocal sings and symtpoms should be monitored in the ED or inpatient setting

Hypotension may occur due to third spacing so fluid management similar to that of crush injury may be required. Aiming for urine output of 1.5-2ml/kg
Careful monitoring of serum K