Electrical injuries

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Chapter 31 Electrical injuries

Gordian W.O. Fulde, Christopher J. Mobbs

In a two-year period from 2002, 1493 people in Australia were hospitalised as a result of an electrical injury, including 77 from lightning strikes. Of the 1493, 209 were aged 0–14 years, with 18 of those sustaining injury from high voltage lines.

In a four-year period (2001–2004), there were 162 deaths attributable to electrical injury (93% male), with seven from lightning strikes (all male).

Electrical injuries are more common among males, and mostly occur in the young adult and adult years. The most common locations for injury were, in order, the home and the workplace.

Despite the relative infrequency of these injuries, it is important that health providers be familiar with the types of presentation seen and aware of optimum management techniques.

The sources of electrical injury may be divided into three broad subgroups, with important differences in assessment and management of patients relevant to each. For example, cardiac arrest, as provoked by an electrical current, will more commonly be asystole from a lightning strike and ventricular fibrillation (VF) from a household AC current. The three subgroups, therefore, are:

1. lightning injury

2. high voltage (> 1000 V) electrical injury

3. low voltage (< 1000 V) electrical injury.

Low voltage electrical injury may be further subdivided into patients with or without cardiac and/or respiratory arrest.

PATHOPHYSIOLOGY

Electricity may cause injury via three broad mechanisms:

1. causing direct tissue damage, altering cell membrane resting potential and eliciting muscle tetany

2. conversion of electrical energy into thermal energy, causing tissue destruction and coagulative necrosis

3. traumatic injury resulting from falls or violent muscle contractions.

The site of either direct tissue or thermal energy damage depends on the pathway of current flow.

PHYSICS

Electricity is the flow of electrons from higher to lower potential. Direct current (DC), from sources such as car batteries or defibrillators, flows in one direction. Domestic alternating current (AC) switches to and fro at 50–60 cycles per second (hertz) as this confers advantages in terms of current generation and transmission. Ironically, human muscular tissue is sensitive to frequencies in this range, with tetany of peripheral and VF arrest of cardiac muscles a risk during contact with household electricity. Domestic voltage in Australia is 240 V.

Lightning contains around 10 × 10⁶ V and a current of 10,000–200,000 amperes. However, as a result of the incredibly brief duration (microseconds to milliseconds) of a lightning strike, the final amount of current delivered is much less than expected. It is the electrical current that is important in terms of human morbidity and mortality, and this basic electrical injury potential rests with two laws:

Ohm’s law

Joule’s law

So, while dry, thick calloused skin may be more resistant to injury by virtue of its very high resistance (up to 100,000 ohms), the resistance of moist skin is only 1000 ohms. It is therefore of vital importance to preach good electrical safety, especially in the home and workplace, and especially relating to moisture and electrical appliances and the installation of circuit breakers.

Similarly, it is the role of all health professionals to educate the public about safety during electrical storms. Those who enjoy outdoor recreation, such as golfers and hikers, are the major group of people affected by lightning strike. Solo people who are struck make up 70% of the recorded mortality. Most fatalities (about 70%) are recorded between midday and 6 pm.

Deaths occur five times more frequently in the country than in urban areas. The summer storm season is associated with the highest mortality. The annual mortality is decreasing in all recording countries.

Three major predictors of mortality are: cardiac arrest at the time of injury, cranial burns (5-fold increase) and leg burns.

In order to avoid lightning there are some simple measures which should be followed:

• Stay indoors during a storm, or seek shelter in a building or car (not a convertible).

• Avoid contact with any metal such as golf clubs, umbrellas, tent poles, gates, roofs or hair clips.

• Do not stand next to or under the tallest object in sight, such as a tree, pole or haystack.

• Avoid being in a group—split up so that someone can call for help if necessary; give CPR.

• Do not stand with your feet apart, as this increases your stride potential and can result in major burns.

• If caught alone, the correct procedure is to curl up on the ground, preferably in a ditch, well away from higher objects.

It is important to note that, contrary to popular belief, lightning does strike twice or more in the same spot.

Wide-band magnetic direction finders are increasingly used to warn of incoming lightning storms.

Lightning injuries can be markedly decreased by taking measures to avoid becoming a conductor, and by not being near an obvious conductor. Piloerection during an electrical storm can mean that a lightning strike is imminent, and immediate evasive measures along the lines of those described above should be taken.

LOW AND HIGH VOLTAGE ELECTRICAL INJURY

The type and amount of current can be inferred from the nature of the source. Electricians and other tradespeople may be able to give accurate information as to strength of power source and current type. However, within appliances conversions from the more dangerous AC to DC, and to a different voltage, are possible. Entry and exit wounds may be visible, but their absence does not rule out serious injury and they may give no indication as to severity of underlying organ damage. The current between any such wounds does not necessarily travel in straight lines.

Electrical flash burns, often seen in tradesmen, may occur where a short circuit causes an explosion, e.g. on a switch board. It is likely that the patient had very little actual current pass through him, but dermal and corneal burns and sequelae of any blunt trauma may dominate the clinical picture.

If a patient was frozen to the circuit, due to muscle tetany with AC, a life-threatening injury may have occurred, with multi-organ and limb damage.

Significant electrical injury resembles more closely a crush injury than a burn. Necrosis of deep soft tissues and organs has both immediate (e.g. cardiac arrest) and long-term (e.g. rhabdomyolysis and renal failure) adverse sequelae. Tissues and organs distant to the site of electrical injury may be affected as large and small vessel arterial and venous thrombosis occurs.

Infants and young children are prone to sustaining oral electrical injuries from electrical appliances. Mucous membranes have less resistance than skin and the current is therefore higher. These injuries may lead to eventual scarring and deformity of the face in later years. If the current travels close to the eyes, cataracts may form.

Injuries, burns and complications are frequently underdiagnosed and poorly documented. Because litigation can ensue, good clinical recording is mandatory—as with all instances of burns and trauma in the emergency department. Diagrams are essential, photography desirable.

Management

Prehospital

The most important initial consideration is the safety of the rescuer and other bystanders. No more electrocutions should be allowed to occur. All wires and appliances should be considered live, as should any patients still in contact with them. Power should be shut down and/or the victim should be removed from the current with a non-conductive substance—for example a rubber car mat. Any water or moisture should be regarded as electrically live and the potential source of more electrical injury.

When it is safe, in a witnessed arrest a praecordial thump is indicated for the patient with no signs of life—the assumption being VF cardiac arrest. An electrocuted patient must then continue to be treated according to standard life support guidelines. Nowadays, automated and semi-automated external defibrillators (AEDs/SAEDs) are available in many public areas. These devices should be utilised as rapidly as is safely possible as early defibrillation from VF gives the greatest chance of survival.

Hospital

The standard approach to an unconscious or critically ill patient must always be employed. This includes neck immobilisation where necessary and exclusion of other causes of altered conscious state such as hypoglycaemia, overdose, cerebrovascular accident or trauma. This approach is particularly important in view of the fact that the prime treatment modality for the electrically injured is support of systems while waiting for recovery, and attempting to avoid complications.

The majority of survivors presenting to the emergency department after an electrical injury are relatively well. A high level of suspicion for secondary traumatic injuries needs to be maintained, however, if there is a possibility of a fall, having been thrown or a violent muscle contraction. Emergency physicians should think of ‘worst case scenarios’, as electrical injuries can affect multiple systems and may well be covert. It is essential to keep an open mind as to causation, and to carefully explore the possibility of serious concomitant disease.

A thorough ABC reassessment, then a meticulous whole body examination (primary then secondary surveys) with aggressive early management of any injuries must occur. Fractures may be present; fasciotomies of digits and limbs may need to be done in the emergency department. An ECG should be performed.

A good urine flow (1 mL/kg/h) in the face of myoglobinuria (urine dipstick positive for blood) or shock is essential as with standard treatment of rhabdomyolysis. Urinary alkalinisation and use of mannitol and/or frusemide may be indicated, and late renal failure with acidosis must be anticipated.

A check of tetanus immunisation status is mandatory.

Cardiac monitoring and admission for observation is indicated in high voltage (> 1000 V) injury, following seizures or loss of consciousness and with ECG changes including arrhythmias. Arrhythmias will usually settle spontaneously and without sinister sequelae. Admission may also be required as dictated by traumatic injury, exacerbation of preexisting chronic illness or in the elderly.

Thus, patients with ‘low voltage’ injuries not meeting the adverse criteria detailed above may be discharged home with simple analgesia as required following a normal ECG. No blood tests are necessary. An exception to this rule is the case of the pregnant female; the fetus, situated within amniotic fluid within a hyperaemic uterus, is at great risk, even with apparently ‘minor’ exposures having no noticeable effect on the mother. An urgent obstetric ultrasound and consultation should be sought.

Adequate follow-up, both physical and psychological, must be arranged, as a high proportion of patients have some long-term effects following a significant electrical injury. Neurological damage has an especially poor prognosis.

Electrical burns should be referred to a specialist burns centre.

LIGHTNING INJURIES

Physics

Lightning occurs when particles moving up and down during a thunderstorm create static electricity. A massive negative charge builds up on the underside of a cloud until the charge difference between it and the positively-charged ground below is enough to cause electrical discharge. This lightning strike may last between 1 and 100 milliseconds. It differs from ‘high voltage’ in additional ways—the energy level is many tens of millions of volts, it is a direct current, it may cause a shock wave and may demonstrate the ‘flashover’ phenomenon, where the current passes over and around, rather than through the patient. Lightning is also associated with asystolic cardiac arrest, rather than ventricular fibrillation. Good CPR rather than early defibrillation is of paramount importance: although return to sinus rhythm may spontaneously occur, there is a risk of secondary hypoxic arrest if resuscitation is delayed.

Pathophysiology

As the injuries sustained are both multisystemic and multifactorial in aetiology (from diverse sources such as electricity, heat, blunt trauma and anoxia), the clinical possibilities are vast. Certain injuries and their sequelae are typical or may even be diagnostic (see Table 31.1):

• cardiac—asystolic arrest

• neurological—loss of consciousness, paraplegia, hemiplegia, amnesia, seizure, tinnitus, autonomic nervous system dysfunction including fixed dilated pupils

• vascular—keraunoparalysis; vascular spasm with absent pulses, mottled limbs (usually resolves over period of hours)

• skin—‘Lichtenberg flowers’—may look severe but fade within hours.

Table 31.1 Special injuries often associated with lightning

Skin	Burns—feathering or flowers (transient, not burns but electrocution showers)Superficial (often in patterns of sweat lines, or wet exploded clothing)Deep entry and exit wounds; imprints of metal buttons, belt clips, ignited clothing
Ear	Tympanic membrane rupture, barotrauma
Eye	Onset of cataracts, eye trauma and disruption of anatomy
Heart	Asystole, ventricular fibrillation, arrythmias, infarct (rare), transient hypotension or hypertension
Limbs	Trauma; keraunoparalysis, a temporary neurovascular dysfunction in the majority of serious strikes, usually resolves in hours but permanent sequelae are possible
Central nervous system	Seizures, mental state similar to that after electroconvulsive therapyAmnesia (very common), psychological sequelae

Severe burns, with their sequelae of renal failure, anaemia and tissue damage, are very uncommon.

As a generalisation, patients who survive the initial strike will usually have no major problems. Clinical expertise including a high index of suspicion must be used to rule out potential complications to the eyes, ears, heart and nervous system.

Management

Prehospital

Rescuer safety is vital. A very special aspect of lightning victims is that they require aggressive resuscitation even in the light of asystole, apparent fixed dilated pupils or pulseless limbs for the reasons detailed above.

This is also the reason why a group caught by a storm should split up, so that CPR can be administered to the victim by those not affected.

A particular pitfall to avoid is withholding CPR to the victim of a lightning strike in the mistaken assumption that they remain charged by electricity.

Contrary to usual disaster responses, if several people are struck by lightning at once, the care must go to the sickest (arrested) first, as the walking and talking wounded will survive whereas the arrested patient has only a brief opportunity to be salvaged.

The diagnosis itself may be challenging, as the strike may be unwitnessed. Again, a high index of suspicion must be maintained and clues such as multiple unconscious people, exploded clothes and Lichtenberg flowers may point to the cause.

Hospital

Patients may arrive arrested, unconscious, amnesiac, as a trauma patient or as one that has very few clinical problems.

A standard approach—e.g. advanced cardiac life support (ACLS), advanced trauma life support (ATLS)—is indicated, with simultaneous assessment and management systematically by an organised team.

The clinical picture dictates the management. It is essential that other possible causes and concomitant illness be sought and excluded as part of the patient’s management.

As always, the ABCs are secured. Lightning-strike patients rarely need fluid loading. Hypothermia due to exposure is common. If there is any loss of consciousness, arrhythmia or rise in cardiac enzymes, cardiac monitoring for 24 hours is indicated. MRI scanning is useful for subtle lesions of the brain and spinal cord.

Usually the surviving victim needs mainly supportive treatment.

Special attention should be paid to the ear and eye examinations for tympanic rupture and corneal defects, respectively. Other ocular pathology will also need to be excluded, most easily when the patient is alert and able to cooperate with full eye examination. Basal visual acuity should be recorded if possible.

Disposition is guided by the same considerations that govern other electrical injuries. A period of observation in hospital is warranted for changes in neurological or cardiological status and for other organ-specific pathology.

PEARLS AND PITFALLS

• Do not become a victim—ensure self and bystander safety before attending patient.

• Early CPR is potentially life-saving.

• The victim of lightning strike does not remain electrically charged.

• Even apparently ‘harmless’ electrical injury may have fatal consequences for the intrauterine fetus.

• Asymptomatic patients who experienced a ‘low-voltage’ electrical injury may be safely discharged from the emergency department following a normal ECG.

• Preach prevention, especially to golfers.

RECOMMENDED READING

Daley BJ. Electrical Injuries. June 2008. Online. Available: http://www.emedicine.medscape.com/article/433682-overview.

Pointer S, Harrison J. Electrical injury and death. AIHW National Injury Surveillance Unit. April 2007. Online. Available: http://www.nisu.flinders.edu.au/pubs/reports/2007/injcat99.php.

Rosen P., Barkin R.M., Braen G.R., et al, editors. Emergency medicine—concepts and clinical practice, 5th edn, St Louis: CV Mosby, 2001.

Wright RK. Electrical Injuries. eMedicine; July 2007. Online. Available: http://www.emedicine.com/EMERG/topic162.htm.

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