Lightning and electrical injuries
Lightning and electrical injuries
Lightning strikes are rare accidents but carry a 10% case fatality, killing 0.1 to 0.3 per million population each year. During thunderstorms, the risk is increased by sheltering under trees or by being on open water, on tractors, or in open fields or golf courses.
Lightning causes instant asystole. It is suspected clinically if someone is found collapsed in the open with linear or feathered burns, exploded clothing, and ruptured eardrums. Victims are safe to handle, with most victims showing keraunoparalysis (cold, pulseless, mottled extremities). Immediate cardiopulmonary resuscitation (CPR) is mandatory. Survivors may develop complications including pain syndromes and psychological sequelae.
Electrocution is the fifth commonest cause of workplace death, mainly affecting utilities, mining, and construction labourers. Contact with power lines and power tools are the commonest causes, with metal ladders and antennae being particularly dangerous. Prevention is by implementing codes of safe practice.
Victims of electrocution may suffer prolonged attachment to the source of electric current and must be removed or disconnected from the source before resuscitation. Clinical presentations include (1) ventricular fibrillation, sometimes leading to persistent cardiac dysfunction; (2) neurological and muscular manifestations, both early and late, including paraesthesiae, pareses, and generalized convulsions, also tetanic spasm causing respiratory embarrassment and rhabdomyolysis; (3) burns, which may be severe and require expert surgical attention. Electroporation (cell membrane disruption) contributes to cell death; delineation using polaxamers may direct the extent of surgical debridement.
Lightning is a powerful force; it provides spectacular displays and has evoked an extensive mythology. The comparatively recent discovery and distribution of electricity have had an equally profound effect, and provide truth to the adage that ‘electricity is a good servant and a bad master’.
The latest accepted case fatality of lightning shock is around 10% and is around 0.3 per million population in the United States of America each year, but fewer than 0.1 per million in the United Kingdom.
In the early part of the 20th century, most people struck by lightning were outdoor workers (67%) and outdoor recreationalists (28%). Nowadays, the breakdown is 45% and 50%, respectively, explained by changes in social and work habits. Indoor strikes (e.g. by current conducted through communication or power apparatus) continue to account for about 5% of these accidents.
Men are more often injured than women (1.67 males to 0.33 females); the age group most at risk is 20 to 29 years. Risky situations include sheltering under trees, on open water, on tractors, in open fields, and playing golf. Regional differences correlate well with storm activity and population density in that area.
Electrocution ranks fifth in the causes of workplace death, accounting for the death of 10 000 workers each year in the United States, with a further 10 million being injured. Most of the victims work for utility companies, followed by mining and construction workers. Contact with power lines causes 53% of fatal shocks, and contact with power tools accounts for a further 22%. The most dangerous times of day seem to be between 10.00 a.m. and 3.00 p.m. on Mondays, Tuesdays, and Thursdays. Most of the victims are trade and labouring staff; sales, clerical, and professional categories are at least risk. Metal ladders and antennas are particularly dangerous and can easily be hoisted into overhead power lines. Codes of safe practice are written accordingly.
In domestic situations, contact with overhead lines is again important. Faulty, including amateur, repair of equipment and faulty apparatus, wiring, and especially power and extension cords account for large numbers of deaths and injuries. Children are at particular risk. Death from domestic electric shock has shown a marked decrease with the introduction of residual current devices (RCDs). These sense if current is diverted from the supply main to earth and interrupt it in a matter of milliseconds.
Mechanisms of injury
Lightning injury may be sustained in five separate ways:
1 A person may be struck directly.
2 A nearby object, such as a tree or a building, may be struck, and someone in direct contact with it may receive a shock.
3 Without direct contact an arc may ‘jump’ to a nearby person from the struck object, thereby generating a ‘side flash’.
4 As current disperses away from the base of a strike to ground, an individual may divert current flowing in the ground to themselves. This is termed ‘shock due to increase in earth potential’.
5 A recently documented mechanism is the transient flow of current due to corona and streamer formation.
Both cardiac and respiratory function cease instantaneously under lightning strike, the cardiac arrest being asystolic. Cardiac function restarts under local pacemaker control, but respiratory function does not recommence and secondary hypoxic cardiac arrest supervenes.
The major cranial orifices are portals of entry for lightning current, and from there pathways to the brainstem are short. Respiratory function is thought to be affected there, and thence conduction through the cerebrospinal fluid to neural tissue and bloodstream to the myocardium.
The QT prolongation resulting from lightning injury may predispose to episodic arrythmias. There is no evidence that lightning inhibits body metabolism. Resuscitation is as urgent as with any other injury. There is similarly no evidence that metal on the head, or the presence of a mobile telephone (cellphone), predisposes to being struck.
With electric shock, it is important to assess the points of entry and exit and the pathway of current through the body. Once the pathway has been determined, a locus for expected injury can be established, and the flow of current can be estimated from the applied voltage divided by the impedance of the proposed pathway. Most impedance is in the skin barriers, and is nonlinear. There is an initial (contact) impedance, which decreases as current flow continues. Impedance also varies with time since application, contact surface area, and frequency.
For currents with a frequency of 15 to 100 Hz, externally applied from hand to hand, or hand to foot, relevant variables are the threshold of perception (0.5 mA) and ‘let go’ current (10 mA). A 50% chance of fibrillation exists at 2000 mA conducted for 10 ms, or at the other extreme 100 mA conducted for 10 s. Direct internal application of less than 200 µA to the heart muscle may induce fibrillation. Dangerous current levels as well as impedance parameters are documented in standards.
Joule heating may account for tissue damage in the path of the current. It may be calculated from the power dissipation in the tissue—the square of the tissue current (often hard to estimate) times its impedance. The complex phenomenon of electroporation, where cell membranes are breached by the electrical induction of unstable pores in the membrane, may also lead to cell death. The complex nature of internal electric fields leads to internal field damage difficult to quantify and predict.
Presentation of the injured person
A witnessed strike offers the best chance of resuscitation. The victim is not dangerous to touch, and does not constitute a risk to the rescuer. Immediate cardiopulmonary resuscitation (CPR) is paramount. It has been stated that:
Any person found with linear burns and clothing exploded off should be treated as the victim of a lightning strike. Feathering burns are pathognomic of lightning injury and occur in no other type of injury. …Another complex diagnostic of lightning injury includes linear or punctate burns, tympanic membrane rupture, confusion, and outdoor location…. Cooper et al. (2000)
In assessing a lightning victim, the following features must be sought.
Cardiovascular and pulmonary consequences
Asystolic arrest is the main cardiac event in lightning injury. ECG signs may take many forms, with ischaemic and infarct forms. They almost invariably resolve completely over time. Alterations in QT interval and arrythmias of many kinds are seen. ECG changes may not occur until late in the course, and so are poor diagnostic tools. Respiratory arrest is common. A person not suffering cardiopulmonary arrest is highly unlikely to die from lightning strike (p < 0.0001).
Direct neural injury may occur both centrally and peripherally. All forms of intracranial bleeding have been reported. Direct cerebral damage particularly affects the basal ganglia, cerebellum, and brainstem. Dural tears, scalp haematomata, and fractures are also seen. Seizures occur as a result of anoxia and injury.
Peripheral nerve injury, including autonomic injury, can give prolonged and long-lasting disability, which often develops late. Other late features include spinal cord atrophic paralysis, cerebellar ataxia, incoordination, paraesthesiae, and aphasia. Continuing complex regional pain syndromes may be seen.
Keraunoparalysis and burns
More than 70% of victims demonstrate keraunoparalysis. This is a syndrome of cold, pulseless, mottled, and asensory extremities. The syndrome resembles a compartment syndrome and occurs in the line of passage of the strike current. It resolves spontaneously within 24 h with no sequelae, and requires no surgical intervention.
Burns are of minor consequence in lightning injury, and again require little intervention. Entry and exit burns may be full thickness though small. Arborescent (feathering) burns resemble fern-like patterns on the skin (Fig. 184.108.40.206). Their aetiology is unknown, but they fade within 24 h. Linear burns are due to the passage of hot plasma tongues over the skin. Eschar is simply allowed to separate without further treatment. Flash may be seen, like sunburn or welder’s flash, from the profound radiation of the strike. Sheet burns resulting from efflux of hot plasma may be a variant of linear burning, since both seem to follow moisture and sweat lines. There may be contact burns from heated metal such as buckles and coins.
Eye, ear, and explosive injuries
The explosive force of the lightning insult blasts clothing apart (Fig. 220.127.116.11), and may cause percussive injury to the lungs and abdominal viscera. Tympanic membranes are usually ruptured, perhaps from the explosive force of the strike. Percussive eye injury, particularly retinal, has been reported. Cataracts may develop much later.
In contrast to lightning injury, victims may suffer prolonged attachment to the source of electrical current, making them dangerous to touch. Before resuscitation, they must be removed from the current source, and this usually means interrupting the current flow at the supply point.
Burns are far more serious, and may merit intense surgical treatment. The likelihood of internal burning (remembering the possibility of electroporation) may require further surgical intervention. Cardiac and respiratory burns may also exist.
Fibrillation is the most common cardiac abnormality following electrical injury. Cardiopulmonary resuscitation is urgently required. Electricity suppliers have standard first aid/resuscitation procedures. Cardiac dysfunction may persist for long periods, and ECG signs may not resolve.
Neurological and muscular consequences
Neural injury may be categorized into early and late syndromes, at cerebral, cord, and peripheral levels.
Early tetanic muscular contraction locks the victim on to the electrical conductors. This tetany may compromise respiratory function. Neurological injury may be hard to distinguish from hypoxic and vasospastic injury. Similarly, neural injury is often hard to separate from ischaemic injury due to vessel spasm. Early and late generalized convulsions may occur. Pareses and paraesthesiae may develop, both early and late.
In the long term, complex regional pain syndromes and other chronic pain syndromes must be considered.
Burns are often severe in electrical injury and merit much treatment effort. Arc and flame burns and contact burns from current entry and exit are seen. For example, tetanic gripping of the electrical conductor causes grasp burns to the hand.
Severe internal thermal or electroporation damage may occur. The management is largely surgical. Joints, ligaments, and tendons may be severely damaged by the heat generated, and osteonecrosis may be seen.
Widespread muscle damage generates myoglobin that must be cleared by the kidney with a severe risk of renal damage. Other metabolic and biochemical disturbances secondary to hypoxia may develop. Massive hyperkalaemia has implications for the use of depolarizing muscle relaxants.
Eye damage includes retinal damage, with punctation and detachment, and thermal damage to other media. During follow-up the possibility of ocular pareses and cataracts must be recognized.
After shock during pregnancy, the prognosis for the fetus is poor. Nonfocal injury is more likely in survivors.
Psychological consequences of electrical and lightning injuries
Although electrical and lightning injuries are fundamentally different in nature and management, their psychological sequelae are similar. Sequelae may be profoundly disabling. They may persist for many years and may never resolve. To a large extent, psychological consequences of persisting pain and dysfunction cannot be separated from organic psychological consequences.
Emotional sequelae include depression, often with organic features. It is hard to separate this from the emotional reaction to injury and continuing disability. Aggression, anxiety, and phobic features are common. Marital disharmony commonly follows social withdrawal, disinterest, and a fatigue state. Loss of interest in sex and in relationships, together with a feeling of fault or guilt, may be associated. Sleep disturbance is common.
There is loss of short-term memory with impaired concentration, higher mental functions, and loss of identity and ability.
Treatment of the injuries
It has been documented that assessment by those unfamiliar with the injury overlooks or wrongly diagnoses over 90% of the resulting syndrome features. First, urgent and life-saving treatment must be administered. Secondly, there must be surveillance for delayed sequelae, and thirdly long-term monitoring for morbidity, including cataract formation and psychological problems.
First, the casualty is resuscitated and evacuated. Cardiopulmonary resuscitation is continued until medical emergency help is obtained. Ventilation and cardiac support may be required.
ECG monitoring must be used to detect subtle effects like QT prolongation. Associated trauma is treated.
In the long term, patients are observed for development of pain syndromes. Ocular and auditory functions are monitored. Sensitivity to the psychological sequelae is required, and preventive interviewing may be useful.
Carbemazepine, gabapentin, clonazepam, flecainide, and mexilitine are useful to control neurally derived pain and resulting weakness. An antidepressant (see following paragraphs) is a useful adjunct to this.
Urgent life support is indicated. Ventilatory and inotropic support and correction of arrhythmias may be required.
For burns, progressive debridement and/or amputation may be needed. Renal damage should be prevented.
Associated trauma is treated. Ocular and auditory functions are monitored, and psychological disturbances are reviewed. In the long term, surveillance is similar to lightning injury.
In all cases, the management of the psychological syndrome is paramount and may be the greatest determinant of long-term functional capability. Awareness of the impact of the injury on employment and relationships and social networks is fundamental. Cognitive and computer aids are being developed.
An antidepressant such as a selective serotonin reuptake inhibitor, possibly citalopram, paroxetine, venlafaxine, or a tricyclic such as clomipramine, may be useful.
Early and continuing neuropsychological assessment is desirable.
The place of polaxamers in discovering the extent of electroporation and in delineating debridement levels is of great interest.
The mechanisms of the psychological disability and remote injury remain to be elucidated. Victims are frequently written off as malingering or simply depressed, when a more extensive syndrome exists. Expert evaluation is highly desirable, especially if litigation or compensation is involved. The useful duration of monitoring of otherwise asymptomatic people has not been determined.
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