LIGHTNING INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 443

Step, stride, or ground strike: Initial contact is with the ground or flows to ground from
another object, but ripples of current travel outward. Electrical current enters one leg
and exits though the other because the path of least resistance is through the body, not
through the ground.
Discharges that strike a human body follow two routes: Electricity can spread over the
skin,oritcanenterthebody.Usuallybothpathsarefollowed,butthevoltageofalightning
bolt is so great that most of the charge passes to ground on the outside and does not pass
through the body.
Ifasignificantamountofmoistureisontheperson'sskin—perspiration orrain—itmay
be instantly vaporized. The resulting water vapor, a gas, can explosively rip the clothing
from a person's body(flashover effect).
Many variables can affect the person's ultimate outcome. They include these:
◆ Type of strike
◆ Amperage and voltage of the lightning strike
◆ Current pathway through or over the body
◆ Resistance of tissues
◆ Duration
◆ Blunt trauma from being knocked about by the strike
◆ Environmental factors
One major difference between lightning and high-voltage electrical injuries is the very
high current, yet very short duration, of lightning.
These facts indicate that accurately predicting the consequence of being struck is chal-
lenging at best and usually nearly impossible.
EFFECTS OF LIGHTNING STRIKES
Direct lightning strikes often produce immediately lethal, global cardiac injuries. If the
electrical charge is less severe, as occurs with splash injuries or ground currents, it may
only depolarize the cardiac conduction system, causing the heart to stop beating (asystole).
(Asystole is more common than ventricular fibrillation following a lightning strike.)
However, the innate rhythmicity of the heart usually causes it to resume rhythmic contrac-
tions.
Subsequently,astheresultofhypoxiacausedbytheabsenceofbreathing,theheartmay
go into terminal ventricular fibrillation.
The nervous system is particularly vulnerable to lightning. Immediate as well as pro-
longed abnormalities occur. The most significant functional disruption is cessation of
breathing. Cardiac contractions may be resumed promptly, but resumption of respiratory
function often is delayed from thirty minutes to two hours. If resuscitation is not available,
the resulting hypoxia leads to ventricular fibrillation and death.