Injury mechanisms and tissue resistance
The damaging effect of electric current is realized at the moment when a person becomes part of an electrical circuit. The severity of the injury directly depends on the electrical conductivity of various body structures. Tissues with a high water content have lower resistance and therefore conduct current much better.
Tissue resistance indicators (Ohm/cm²):
- Muscles: about 1,500 (excellent conductor).
- Skin: from 50,000 to 700,000. Dry and calloused skin has maximum resistance (up to 1,000,000 Ohm/cm²), which temporarily reduces current penetration.
- Bone: about 800,000.
There are three main mechanisms of electrical injury:
- Direct contact: physical touch and circuit closure.
- Action at a distance: injury by an electric arc during a powerful discharge (without direct contact with the conductor).
- Step voltage: occurs when the ground becomes the source of danger (during a lightning strike into the ground or a fall of bare wires).
First aid algorithm
The key priority is compliance with safety regulations. Touching the body of a person through whom current is currently passing is fatal to the rescuer.
Procedure:
- Release from the source: it is necessary to de-energize the circuit (turn off the circuit breaker, unscrew fuses). If this is not possible, the wire should be cut with a tool having a wooden handle (axe, shovel) or pushed away with a dry stick/board. Dragging the victim is permitted exclusively by the hem of dry clothing.
- Condition assessment and resuscitation: in the absence of breathing, mouth-to-mouth artificial ventilation is immediately initiated. If cardiac arrest is diagnosed, chest compressions are initiated.
- Local care and rest: if there are no fatal injuries, the patient is placed horizontally and provided with complete physical rest. The application of dry aseptic dressings to burn sites is performed strictly after cardiac activity is restored.
- Transportation: emergency hospitalization to a hospital is indicated for all victims without exception.
General toxic effects of burns
In addition to local necrosis, chemical and extensive electrical burns are often accompanied by systemic intoxication (resorptive action). In extensive injuries, there is always a high risk of intoxication from the breakdown products of one's own tissues, which is directly proportional to the burn area.
Specific effects of chemical agents:
- Phenol and mercury salts: cause a strong general toxic effect.
- Phosphorus: leads to severe toxic kidney damage.
- Phosphoric acid: specifically damages the liver.
Burn classification and clinical presentation
Burns are divided into superficial (1st and 2nd degree) and deep (3rd and 4th degree). The main differentiation criterion is the nature of the eschar and the preservation of sensitivity.
Superficial burns (1st–2nd degree):
- 1st degree: accompanied by pain and burning. Objectively, limited hyperemia and minor edema are detected (edema is more pronounced upon exposure to alkalis). All types of sensation are preserved, and pain sensitivity is heightened (hyperesthesia).
- 2nd degree: the main sign is the formation of a thin eschar that easily gathers into a fold. Acid burns form a dry eschar, while alkali burns form a gelatinous ("soapy") one.
Deep burns (3rd–4th degree): Characterized by the formation of a dense, thick, and immobile eschar that cannot be gathered into a fold. Sensitivity in the affected area is completely lost (anesthesia). Alkalis cause wet necrosis, and acids cause dry necrosis.
Important nuance: during the initial examination, it is impossible to differentiate between 3rd and 4th degrees. The true depth of the lesion is determined only at the 3rd–4th week during the period of eschar rejection. In 3rd-degree burns, necrotic skin is rejected, while in 4th-degree burns, deeper destroyed tissues are rejected.
Briefly: answers to topical questions
How are body tissues distributed according to their degree of electrical conductivity?
Body tissues are distributed by electrical conductivity depending on their water content: the more water, the lower the resistance and the better the conductivity. Muscles and blood vessels have the highest conductivity. Tissues with low specific electrical conductivity (high resistance) include skin and bones.
| Tissue | Resistance (Ohm/cm²) |
|---|---|
| Muscles | 1500 |
| Skin | 50 000 – 700 000 |
| Bone | 800 000 |
| Dry calloused skin | up to 1,000,000 |
The epidermis has the highest resistance — up to 2,000,000 ohms. The facial skin also has very high electrical resistance.
What do specific "current marks" (electrical marks) on the skin look like at the entry and exit points?
Specific "current marks" at the entry and exit points are burn wounds whose appearance depends on the source of injury.
- Contact marks are rounded or oval (usually 2–3 cm in diameter), dry, shiny, painless areas of whitish-gray or brown color. They are well-contoured, raised above the skin, have a central depression, and transform into a dense eschar.
- Lightning injury marks appear as red lines or dark brown tree-like stripes.
Skin sensitivity in the affected area is reduced. Pronounced tissue edema may be observed around the burn, although in some cases hyperemia and edema are completely absent.
How does the damaging effect of alternating current differ from direct current?
The main difference lies in the degree of danger to the body depending on the source voltage. Alternating current is more hazardous than direct current at voltages up to 450–500 V. In addition, different types of necrosis develop depending on the pole of the direct current: coagulation necrosis occurs at the anode, and colliquative necrosis at the cathode. A detailed comparison of other mechanisms of damaging action between alternating and direct current is not provided in the sources.
Which cardiac arrhythmias most frequently develop in the early period after an electrical injury?
Sources describe the following rhythm disorders and cardiac activity disorders in electrical injury:
- Ventricular fibrillation — complete asynchrony of contraction of individual muscle fibers, in which the pumping function of the heart ceases.
- Ventricular flutter — ventricular tachycardia with an extremely high rate of over 250 bpm; hemodynamics are ineffective.
- Tachycardia — one of the manifestations of cardiac disorders.
Cardiac arrest is possible not only at the time of injury, but also several hours or days after it. With high-voltage current, respiratory arrest and ventricular fibrillation are possible.
How to remember the type of necrosis: Acids cause coagulative (dry) eschar, whereas alkalis cause abundantly moistened (colliquative, moist, "soapy") necrosis.
Class and exam questions
In what sequence do body systems fail during an electric shock?
First, respiratory arrest occurs. Following it, cardiac arrest develops.
Is it safe to pull the victim away with bare hands?
Categorically no. This will lead to the rescuer themselves being electrocuted. Pulling is allowed only by the edges of dry clothing or using a dry stick to push the wire away.
How to quickly distinguish a deep burn from a superficial one?
The main landmark is the eschar. If it is thin and easily gathers into a fold, it is a superficial burn (2nd degree). If the eschar is dense, thick, cannot be gathered into a fold, and sensitivity in the wound is absent, it is a deep burn (3rd–4th degree).
When can a grade IV burn diagnosis be definitively established?
Only on the 3rd–4th week from the moment of injury, during the period of necrotic tissue rejection. In grade IV burns, deeper-lying tissues (fascia, muscles) begin to slough off, not just the skin.
What else to study on this topic
- Pathophysiology of electrical current effects on the myocardium
- Principles of surgical treatment for deep burns (necrectomy and skin grafting)
- Pathogenesis of intoxication by necrotic tissue breakdown products
- Methods for preventing renal failure in phosphorus burns
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