TABLE 90.8 LIGHTNING VERSUS HIGH-VOLTAGE ELECTRICAL INJURY Factor Lightning High voltage Duration Energy level Prolonged Much lower Type of current Shock wave Cardiac arrhythmia Burns Brief 100,000,000 V 200,000 A Direct Present Asystole Superficial, minor Renal failures Rare Fasciotomy and amputation Rare Usually alternating Absent Ventricular fibrillation Deep, frequently obscured Common secondary to myoglobinuria Common, early, extensive Resistance is a major factor determining the amount of current flow through tissue The intensity of the electrical shock produced by a certain voltage can vary with gender and age Tissue injury is inversely related to resistance Dry skin provides resistance of approximately 40,000 ohms, whereas thick, callused palms may provide up to × 106 ohms Thin, moist, or soiled skin lowers resistance to the 300 to 1,000 ohm range The highly vascular, moist oral mucosa has even lower resistance The type of current is another important determinant of injury Alternating current (AC) at low voltage is able to induce tetanic muscle contraction and is, therefore, more dangerous than direct current (DC) Normal household 60-Hz current changes direction 120 times per second, a frequency that induces an indefinite refractory state at neuromuscular junctions The resultant muscle contractions prevent the victim from releasing his grip (“locking-on”), thus extending the duration of contact DC is used in medical settings for cardiac defibrillation, countershock, and pacing Currents as low as mA may trigger ventricular fibrillation, and high currents may damage the heart and conducting tissues directly Lightning is another example of DC, discharged in a single, massive bolt that lasts 1/10,000 to 1/1,000 second The brevity of exposure makes deep thermal injury unlikely