Electrical Burns
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Direct answer
Voltage above 1000 volts defines a high-tension (high-voltage) electrical injury, and its lesson is that the skin wound lies about the damage: current follows deep tissues along bones and vessels, so a small charred contact point can overlie extensive muscle necrosis, compartment syndrome and myoglobinuric renal failure. Management therefore rests on four pillars beyond standard burn care — cardiac monitoring for arrhythmias, forced alkaline diuresis for myoglobinuria, early and generous fasciotomy for compartment syndrome, and exploration or debridement guided by muscle viability rather than skin appearance. Low-voltage injuries, flash burns and arc burns are distinct entities with different depths and prognoses, and children chewing live cables sustain oral commissure burns with their classic delayed labial artery haemorrhage.
What you must remember
- Classification: low voltage (under 1000 V — household, deeper contact burns, cardiac risk mostly at the moment of contact), high voltage (over 1000 V — extensive deep injury), flash burns (superficial, no current passage), arc burns (superheated air, deep burns at flexion creases), and lightning injury (cardiorespiratory arrest, fern-like skin patterns, ear injury).
- Contact points: entry and exit wounds; exit wounds are typically explosive and depressed; internal damage follows the path of least resistance — nerve, vessels, muscle — sparing skin, so surface area rules (Parkland calculations) systematically underestimate fluid needs in high-tension injury.
- Pigment in urine means myoglobinuria: drive urine output to about 1–1.5 mL/kg/hour (higher until pigment clears), alkalinise the urine, monitor creatine kinase and potassium; renal failure is the preventable death.
- Cardiac: ventricular fibrillation at the scene and delayed conduction abnormalities — ECG on arrival for every electrical injury; monitoring continued if the ECG is abnormal, loss of consciousness occurred, or the injury is high tension.
- Compartment syndrome is common and early: deep muscle oedema under intact skin; low threshold for fasciotomy, and dead muscle is debrided — repeated second-look operations are the norm in high-tension injury.
- Delayed complications: cataracts (classically within 1–2 years after high-tension injury), neurological sequelae, and gut paralysis from current through the abdomen.
- Oral commissure burns in children: chew an electric cable; manage conservatively, feed by spoon or syringe, and warn parents about labial artery haemorrhage when the eschar separates, classically around 1–3 weeks.
- Tetanus prophylaxis and thorough documentation for medico-legal purposes apply to every electrical injury.
How to work through it
A linesman survives contact with an 11,000-volt line, arriving awake with a charred palm and a depressed burn over the heel. Surface burns total perhaps 3% — and yet his heart rate is 120, urine is cola-coloured, and the forearm compartments are tense. Step one: ECG and continuous monitoring. Step two: fluids guided by urine output rather than percentage charts — the target rises to 1–1.5 mL/kg/hour (higher until pigment clears) because the hidden muscle injury behaves like a much bigger burn; bicarbonate is added by protocol to alkalinise urine and protect tubules from myoglobin casts. Step three: the forearm — compartment pressures and clinical tension send him to theatre for fasciotomy, where pale, non-contractile muscle is excised at a planned re-look 24–48 hours later; the family is counselled that amputation remains possible if necrosis extends. Step four: the paperwork — entry and exit wounds photographed, tetanus given, ophthalmology baseline noted for future cataract surveillance. Contrast the child with an oral commissure burn from a chewed cable: no fluid drama, but the mother leaves with a written warning about bleeding from the labial artery when the eschar separates in the second week — apply pressure and return immediately.
Where students slip
Three errors recur. First, estimating fluids by body-surface-area formulae: high-tension injuries need output-guided resuscitation precisely because the burn chart lies. Second, forgetting the kidney: the urine colour is the monitor, and the target output is roughly double the usual burn target until pigment clears — candidates who quote standard Parkland volumes alone miss this. Third, the arc-versus-current confusion: a flash burn injures by heat alone, and no current traverses the body, so deep muscle injury and myoglobinuria are not expected — a stem describing "superficial burns, no contact, passing all current" points away from the electrical-injury algorithm entirely.
Frequently asked questions
Why do high-tension electrical burns need more fluid than their surface area suggests?
Because current damages deep muscle, vessel walls and bone invisible on the surface chart, producing progressive oedema, myoglobinuria and compartment syndrome — resuscitation is titrated to urine output rather than percentage totals.
What urine output is targeted in myoglobinuria?
Roughly 1–1.5 mL/kg/hour (protocols vary, some higher until pigment clears), achieved with crystalloid and alkalinisation, to flush myoglobin through the renal tubules and prevent acute kidney injury.
Which cardiac evaluation does every electrical injury need?
An immediate ECG, with continuous monitoring reserved for abnormal traces, high-tension exposure, loss of consciousness, or chest symptoms; ventricular fibrillation occurs at contact and delayed arrhythmias are possible.
What is the danger period for oral commissure burns in children?
When the eschar separates at about one to three weeks, the labial artery can bleed massively; caregivers are taught pressure control and immediate return, with elective commissure reconstruction later.
Which delayed complication is specific to high-voltage injury?
Cataract formation, classically within the first year or two, sometimes bilateral — electrical injury patients need ophthalmological follow-up, an exam favourite detail.