An electric shock occurs when a person becomes part of an electrical circuit, allowing current to pass through the body’s tissues. Injuries can range from minor discomfort to immediate death. The severity is determined by a specific interplay of physical and physiological variables. Understanding these factors is paramount for assessing risk and implementing safety protocols. The outcome depends on the electrical source characteristics, the body’s resistance, the current path, and the duration of exposure.
The Magnitude of Electrical Parameters
The single most significant factor determining the severity of an electrical injury is the current (amperage) that flows through the body, not the voltage of the source. Current is the direct flow of electrons, which disrupts cellular function and causes tissue damage. While voltage is the “pushing force,” high voltage may not cause significant harm if the current is limited by high resistance.
Low-frequency Alternating Current (AC), such as the 50 or 60 Hz used in household electricity, is generally more hazardous than Direct Current (DC) at the same voltage. AC is more likely to induce tetany, a sustained muscle contraction. This involuntary contraction can “freeze” the victim to the conductor, preventing them from letting go and increasing the duration of exposure.
The alternating nature of AC also increases the likelihood of ventricular fibrillation, a lethal, uncoordinated twitching of the heart muscle. DC often causes a single, violent muscle spasm that may throw the victim away from the source, potentially decreasing contact time. However, high-voltage DC can still be extremely dangerous, causing severe burns and internal damage.
Body Resistance and Environmental Factors
The amount of current entering the body is regulated by the body’s electrical resistance, primarily concentrated in the skin. Dry, intact skin offers high resistance, potentially reaching 100,000 ohms or more. This high resistance acts as a protective barrier, limiting current flow into the body’s more conductive internal tissues.
Moisture is a significant environmental factor that drastically reduces the skin’s resistance, increasing the risk of severe injury. Wet skin from sweat or water can lower resistance to approximately 1,000 ohms or less, allowing a greater and potentially lethal current to pass through. High-voltage exposure can also quickly break down the skin’s protective barrier, lowering resistance and allowing massive current flow.
Environmental conditions that promote conductivity, such as standing on a wet or grounded surface, also increase the danger. Poor insulation from the ground completes a circuit with low overall resistance, permitting a larger current to flow. Internal tissues, largely water and electrolytes, have high conductivity, meaning current flows easily once the skin barrier is breached.
The Critical Pathway and Duration of Contact
The specific route the electrical current takes through the body is a major determinant of injury severity. A path that crosses the chest, such as from hand-to-hand or hand-to-foot, is particularly dangerous. This trajectory places the heart and lungs directly in the circuit, greatly increasing the risk of cardiac arrest or respiratory paralysis.
Current passing through the head or brainstem can cause severe neurological damage and immediate loss of consciousness. Shocks localized to an extremity, such as a finger-to-wrist path, are less likely to be fatal but can still cause deep tissue damage and local burns. The body’s internal resistance is lowest in nerves, blood vessels, and muscles, so the current follows these high-conductivity pathways.
The duration of contact is intrinsically linked to the injury’s outcome. Even a relatively low current can be lethal if exposure is prolonged. Longer contact time allows more electrical energy to be converted into heat within the tissues, leading to extensive thermal injury. A longer duration also increases the chance the current will hit the heart during its vulnerable repolarization phase, triggering ventricular fibrillation.
Immediate and Delayed Physiological Consequences
The immediate physiological outcomes of an electric shock determine the immediate risk of death. The most serious immediate consequence is ventricular fibrillation, where the heart’s electrical system is disrupted, causing the muscle to quiver uselessly. Another immediate danger is respiratory paralysis, which occurs if the current causes tetanic contraction of the chest muscles or shuts down the respiratory control center in the brain.
Electrical energy passing through tissue generates heat, resulting in thermal burns that can be both external and internal. External burns are often seen at the entry and exit points. However, internal heat generation along the current’s path can cause massive, deep-seated tissue destruction not apparent on the skin’s surface.
This internal damage increases the risk of rhabdomyolysis, a condition where damaged muscle tissue breaks down and releases its contents into the bloodstream. Rhabdomyolysis poses a significant delayed risk because the released muscle proteins can overwhelm and damage the kidneys, leading to acute kidney failure. Secondary injuries, such as fractures or falls caused by the initial shock’s muscle contractions, also contribute to the overall injury risk.