A shocking episode

Shock value

If Edie had been taking a bath and had accidentally dropped a hair dryer into the water-filled bathtub, would the outcome have been the same?

The result of this scenario would most definitely be fatal. The most obvious difference between electrocution by a high-tension wire and electrocution by household current is the voltage itself. High or low voltage is arbitrarily defined as greater or less than 1000 V. However, voltage is only one of the factors that determine the outcome of electrical injury.

Current is the most important determinant of tissue damage. In most cases the voltage is known but the actual current cannot be determined. In general, higher voltage produces larger currents. As current moves through tissues, the electrical energy produces heat that causes tissue injury. If the voltage is high enough, current will flow through even the most resistant tissues.

Skin resistance is the most important factor in impeding current flow and protects against electrical injury; however, resistance changes with skin thickness and moisture. This explains fatal low-voltage household electrocutions or bathtub-related electrical deaths (or electrocution by stepping out of a car and into an electrically charged puddle).

Given the option, current will always flow along the path of least resistance. The most severe tissue damage occurs at the entrance and exit points where current is concentrated and reconcentrated. Entry and exit burns signify substantial current flow and represent an increased risk of deep tissue damage. The extent of deep tissue damage is not apparent from the surface appearance of the wound and must be regarded with a high degree of suspicion and trepidation. In practice, high-voltage injuries are more likely to be associated with deep tissue injury, while tissue necrosis is unlikely with household electrical currents (ie, 120 to 240 V).

Surviving electrical injury

If Edie had survived … How long would she stay in hospital? What sequelae might she suffer from? What if she were pregnant?

The notion that Edie might survive her electrocution is not unrealistic television fantasy. History shows New York’s first victim of the electric chair in 1890, convicted murderer William Kemmler, did not die the first time the switch was pulled, demonstrating that a momentary dose of high-voltage electricity is not necessarily fatal. A second attempt was initiated immediately; the current remained on until he was in flames.

While ventricular fibrillation is the most common cause of death following both high- and low-voltage electrical injuries, survivors can demonstrate many arrhythmias, from premature ventricular contraction to atrial fibrillation. Myocardial damage is uncommon. An electrocardiogram (ECG) does not show standard patterns of ischemia because injury is predominantly epicardial rather than transmural and does not follow the coronary vessels. Measurement of cardiac markers for the purpose of cardiac evaluation is not warranted for household electrical injuries. An elevated creatine kinase level is a more useful sign of extensive burns than of myocardial damage.

Several authors recommend cardiac monitoring for as long as 24 hours after electrical injuries to prevent deaths from delayed arrhythmias.1,2 However, arrhythmias in monitored patients after electric shock are uncommon and if present are documented on the first ECG. Based on the information available in the literature, cardiac monitoring is not justified in asymptomatic patients or in patients with only cutaneous thermal burns who have normal ECG results after 120- or 240-V injuries.3–7 These patients can be safely discharged.

Neurological injury is a frequent complication of high-voltage injuries. Acute central nervous system injury might manifest as respiratory arrest as a result of paralysis of the central respiratory centres, amnesia, altered mental status, seizures, coma, quadriplegia, or localized motor paresis. Delayed central nervous system effects include ascending paralysis, transverse myelitis, and amyotrophic lateral sclerosis.

High-voltage electricity causes serious vascular injury. Vein thrombosis and tissue swelling occur from capillary damage. Ongoing inflow through the artery into an extremity without sufficient outflow results in compartment syndrome. If there is substantial muscle damage, myoglobinuria might cause acute renal failure.

Cataracts are associated with electrical injuries to the head and shoulders. Signs of lens cloudiness can be seen as early as 4 to 6 months postinjury. Ophthalmology referral and long-term follow-up is necessary for all patients with high-voltage injuries to the upper chest, neck, or head.

As with extensive thermal burns, infection is a common cause of death following initial resuscitation. There is a special risk for clostridial infections (gas gangrene and tetanus). Early debridement and tetanus prophylaxis in the emergency department might minimize the risk of infection.

For pregnant patients, electrical impulses might pass through the mother and the fetus. High-voltage injuries have been associated with intrauterine growth retardation, fetal distress, and fetal death. Fetal monitoring is essential for pregnant patients.

The consequences for the survivors of electrical injuries are myriad. There is no centre of expertise in Canada for individuals who have sustained an electrical injury. It is difficult for health care providers to develop and maintain expertise owing to the relatively low incidence and prevalence of electrical injuries. To this end, Ontario’s Hydro One has funded a Chair in Electrical Injury through the Sunnybrook Foundation.

Further reading and resources