Electrical Burns
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Direct answer
Electrical injury kills deep while sparing the surface: a coin-sized contact point at the hand may hide coagulated muscle all the way up the forearm, because current — not voltage — determines damage and follows the low-resistance path through nerves, vessels and muscle on its way to an exit wound. Alternating current at Indian household 220-240 volts causes tetanic contraction (the let-go threshold is about 10 mA), while high-tension contact adds arc burns and deep thermal injury. Management is airway-breathing-circulation with early cardiopulmonary resuscitation — ventricular fibrillation kills at the scene — cardiac monitoring for 24-48 hours after transthoracic or high-tension injury, aggressive fluid resuscitation targeting 1.5-2 mL/kg per hour of urine to flush myoglobin, early fasciotomy for compartment syndrome, and late ophthalmology follow-up for cataract, the classic delayed complication.
What you must remember
- Physics that matters: current equals voltage divided by resistance; tissue resistance rises from nerve and vessel (lowest) through muscle, skin, tendon and fat to bone (highest) — bone heats longest, and nerves and vessels conduct the current that damages them.
- Pathway determines lethality: a hand-to-hand or hand-to-foot path crossing the heart or respiratory centre kills; a contact at the same side of the body burns ferociously but spares the rhythm.
- AC dangers: 50-60 Hz alternating current causes sustained tetanic contraction so the victim cannot release the conductor (let-go threshold about 10 mA), and a few tens of milliamps across the myocardium can precipitate ventricular fibrillation.
- Hidden injury: deep muscle necrosis with myoglobinuria (dark urine), rising creatine kinase and compartment syndrome within hours — serial compartment examination and early fasciotomy, because the skin wound size tells nothing of the volume beneath.
- Kidney protection: fluids well beyond Parkland surface estimates (deep injury is invisible to the burn formula), urine output 1.5-2 mL/kg per hour, with mannitol and urinary alkalinisation for heavy myoglobin loads; follow potassium, since lysed cells drive hyperkalaemia and arrhythmia.
- Cardiac discipline: monitor ECG for 24-48 hours after high-tension, transthoracic, loss-of-consciousness or initially arrhythmic injuries; a low-voltage household injury with a normal ECG and no transthoracic path needs no prolonged monitoring.
- Delayed complications: cataracts months later (the commonest late complication of high-tension injury), posterior shoulder dislocation and fractures from tetanic contraction, peripheral neuropathy and psychological sequelae; lightning injury leaves fern-like Lichtenberg figures and paradoxically rewards prolonged resuscitation.
Resuscitating the hidden injury
An electrician touches an 11 kV line: entry wound at the right palm, exit at the left heel, and he was briefly unconscious. Scene safety first, then cardiopulmonary resuscitation if needed — electrical arrest responds well to early defibrillation. In hospital the discipline begins: fluids started above Parkland estimates because the formula counts surface burns and his injury is volumetric, urine output targeted at 1.5-2 mL/kg per hour and watched for the tea-coloured darkness of myoglobin, creatine kinase trended, potassium corrected, ECG monitored for 24 hours.
Day one brings the surgical decisions: a forearm that is tense and tender despite resuscitation goes to theatre for fasciotomy, and necrotic muscle is debrided — often more than once, since demarcation of deep electrical injury takes days and the first look underestimates. Split-skin grafting follows once the bed stabilises; an unsalvageable limb is amputated early rather than late. Throughout admission, ophthalmology review is booked and the patient is told explicitly to report any visual blurring over the coming months, because the electrical cataract is a delayed complication whose explanation, given early, prevents later panic.
Where students slip
The physics question is asked conceptually — "does voltage or current injure?" — and the answer is current, with the resistance pathway explaining the hidden deep injury. The two numeric anchors examined are the let-go threshold (about 10 mA) and the urine output target in myoglobinuria (1.5-2 mL/kg/h, roughly double the ordinary burn target). The monitoring question separates household low-voltage (no prolonged ECG if asymptomatic) from high-tension or transthoracic (monitor 24-48 hours). And the delayed-complication one-liner is cataract — paired occasionally with posterior shoulder dislocation from tetanic contraction, a viva favourite.
Frequently asked questions
Which tissues carry electrical current most and least?
Nerves and blood vessels conduct best (lowest resistance, most injured) and bone resists most, heating longest — with muscle and skin in between.
Why is the urine output target higher in electrical burns?
Deep muscle necrosis releases myoglobin that precipitates in renal tubules, so 1.5-2 mL/kg per hour of urine with alkalinisation flushes the pigment and protects the kidneys.
Which electrical injuries need cardiac monitoring?
High-tension exposure, a transthoracic current path, loss of consciousness, or any initial arrhythmia — monitored for 24-48 hours.
What is the let-go threshold?
About 10 mA of 50-60 Hz alternating current, above which tetanic contraction prevents releasing the conductor — the reason AC is deadlier than DC at household voltages.
Name the classic delayed complication.
Cataract, developing months after high-tension injury — electrical burns also cause delayed peripheral neuropathy and neuropathic joint injuries.