Contents
Introduction and Epidemiology
Lightning strike injuries are rare. It is estimated there are about 300 injuries and 100 death per year in the USA (a country with a population of about 320 million people) – which gives an incidence of about 1 per million. Worldwide lightning strikes cause 24,000 deaths per year.
- About 1/3 of lightning strikes are fatal
- 75% of survivors will have long-term disability
- Most deaths occur within 1 hour of injury and are a result of serious arrhythmia or respiratory failure
- Most victims are young men
- Most common in spring and summer, usually occur in the afternoon
- 75% are whilst doing recreational activities
- 25% whilst at work
Pathophysiology of electrical injury
Electricity can be either alternating current (AC) or direct current (DC). The current describes the flow of electrons. In alternating current, the direction of flow of electrons is ‘alternating’ approximately 50-60 times per second (50-60Hz).
In direct current, the direction of flow of electrons remains constant.
This can have implications for the injuries caused. In a DC current injury, there is usually a single massive muscle spasm and the patient is often pushed away from the source of the electricity. This means a short duration of exposure, but a higher likelihood of trauma from the mechanical force of being thrown away from the source.
Conversely, an AC current can often induce tetany in a patient causing a prolonged muscle contraction. This can lead to an increase in burns in AC injuries as the patient involuntarily cannot let go of or move away from the source.
Resistance also plays a role in the type of injury received. The greater the resistance of a substance, the lower the current that can flow through it. Normal skin has a high level of resistance. Wet skin however, has a very low level of resistance. This is an important factor during lightning storms – where a wet patient is likely to receive a greater injury than a dry patient – if they both receive the same ‘source’ of electricity.
The extent of the injury is directly related to the current that the patient received. Current can be calculated using Ohm’s Law:
I = V/R
Where:
- I = current
- V = voltage
- R = resistance
So, current (and therefore injury) is greatest when voltage is high and resistance is low. Resistance can be impacted by many factors (different body tissues have different levels of resistance), but clinically probably being wet or dry is the main thing that matters. Otherwise, the resistance of a human being is fairly constant.
So if we assume R is constant, then the current – and the degree of injury – are directly related to the voltage. Therefore, we usually class injuries as high voltage (>1000V) or low voltage (<1000V).
Normal AC electricity supply in most of the world is 220V, and 110V in America.
Lightning Strikes
- Have a very high voltage – up to 30 million volts
- Very high current – up to 110,000 amps
- Very short duration – 10-100msec
Types of Injury
There are three ways that lightning can injure a patient:
- Direct effect of electricity on body tissues and organs (more on this below)
- Burns – where the electrical energy has been converted into heat energy
- Trauma – from mechanical injury secondary to the electricity
In lightning strike there are four type of strike:
- Direct hit (5%)
- Contact Injury (15%) – injury was in contact with an object that was struck
- Side splash (30%) – main bolt hits another structure but a small side branch reaches across and hits the patient
- Ground strike (50%) – current travels up through the ground and into the patient
Avoiding lightning strikes
Basic common sense…
- Stay inside when there is a thunder storm
- When inside, stay away form large metal structure – doors, windows, garage doors
- Stay inside until 30 minutes after the last episode of thunder
- Avoid open and exposed areas. Avoid being high up – e.g. on top of hills
- Stay away from water
- Remove any metal jewellery or other metal worn objects. Don’t touch anything made of metal!
Organ Damage
The most common organ injuries are to skin, heart and brain.
Cardiac
- Approximately 15% of patients will have an arrhythmia after electrical injury. This is most common after DC (usually lightning) injury. Common arrhythmia include AF and VT. Asystole can also occur especially after lightning strike.
- There is often spontaneously resolution of arrhythmia – even asystole
- Damage to cardiac tissue, including MI is rare
- There is an associated with delayed onset pericarditis
Neurological
- Damage can occur to both the central and peripheral nervous systems
- Almost any neurological sign can occur – ranging from signs of a large CVA, loss of consciousness, confusion, to minor peripheral sensory or motor loss
- The defects are often inconsistent and do not match up to a specific pattern
- These signs often resolve spontaneously within 24 hours
- Keraunoparalysis – is a specific type of injury associated with lightning strikes. It causes blue pulses peripheries. It usually resolves spontaneously within hours but in some cases may be permanent. It is thought to be secondary to vasospasm
- Fixed and dilated pupils can also be a sign – and thus are NOT a reliably predictor of brainstem death and are NOT a reason to stop CPR
- There may also be memory impairment (usually transient) and long term there have been reports of personality change, depression and other psychiatric diagnoses
Skin
- All types of burns can occur (superficial, partial thickness, full thickness) – but full thickness burns are unusual and superficial most common
- They are the most common type of injury
- Up to 98% of high voltage injuries and 60% of low voltage injuries
- There is often an ‘entry’ and an ‘exit’ site
- Lichtenberg figures are branch like patterns causes by electricity in almost any substance. They are occasionally seen as burn patterns on electrical injury patients.
Musculoskeletal
- Breakdown of muscle is common – watch for rhabdomyolysis and compartment syndrome
Other
Almost any other organ can be damaged. Peripheral vessel clots are not uncommon (and large vessel clots can also occur), and there may also be renal problems (often AKI secondary to rhabdomyolysis). Intra-abdominal complications and lung involvement are rare but not impossible.
Eye injuries are also seen including retinal and optic nerve injury and cataracts.
Tympanic membrane rupture is seen in 50% of patients and will heal with conservative management
Presentation
See the blog post Lightning Strikes Twice for two case examples.
Management
Be careful! – Patients may appear ‘dead’ – pupils fixed and dilated and in respiratory arrest and asystole – but both of these can be transient and self-resolving signs of lightning strike
- Start with ABCDE – treat as per ALS / ACLS guidelines
- Pay specific attention to:
- C – Cardiovascular – arrhythmias
- D – Full Neurologica examination
- E – Exposure – check for burns everywhere!
- If CPR is required have a high threshold for ceasing CPR in an apparently unresponsive patient. Electrical injury patients requiring CPR may (controversial) have better outcomes that patients requiring CPR for other causes. Patents are often young.
- Also be aware that respiratory muscle paralysis can be seen and have a low threshold for intubation and ventilation indicated. Often in cases of cardiorespiratory arrest the respiratory arrest is longer than the cardiac arrest – thus a patient may have ROSC (return of spontaneous circulation) but remain in respiratory arrest.
- Be aware that surface burns often massively underestimate the extent of injury. This is clinically important in the use of fluid resuscitation – Parksland or similar formulas are not accurate in electrical injury patients and should not be used.
- There are often extensive muscle injuries causing myoglobinaemia. Be aware that this can also result in hyperkalaemia. Watch for compartment syndrome
- Skin wounds should be topically treated like any other burns
- Consider trauma team involvement early if indicated
- If there are any visual symptoms – get early ophthalmology involvement – don’t just attribute these to a neurological cause
Investigations
- ECG
- Bloods including urea and electrolytes, FBC, troponin, CK, troponin
- Imaging – as indicated – e.g. x-ray for suspected broken bones or CT brain for neurological signs
References
- Environmental and weapon-related electrical injuries – UpToDate
- Lightning Injury – Life in the Fast Lane
- Lightning Injuries – Life in the Fast Lane
- Lightning Strikes Twice – almostadoctor blog post