At 11 p.m. on Dec. 22, 1963 fire broke out aboard the Greek luxury liner Lakonia as it cruised the Atlantic near Madeira, and passengers and crew were forced into the water. The air temperature was over 60�, the sea almost 65� and rescue ships were in the area within a few hours. Nevertheless, 125 people died, 113 of these fatalities being attributed to hypothermia, the lowering of the body's inner heat, perhaps no more than 6� from the normal 98.6�.
The temperature of the hands and feet can drop 40� to 50� below normal body temperature without lasting harm. But a relatively small drop in the temperature of the body core will kill you; it makes no difference whether you're in water, the wilderness, a house out of fuel or a car out of gas.
The rule of thumb is that you can survive three weeks without food and three days or so without water, but without warmth you are lucky to last three hours. Though few people know it, the head is the most efficient portion of the body's heating system. A man who leaves his head unprotected, even in a minor wind, may lose up to one-half of the body's total heat production. There is an old mountaineer's maxim: "When your feet are cold, put on your hat."
Hypothermia is a danger even in mild temperatures, say between 30� and 50�. Indeed, the majority of cases develop in this seemingly harmless range. Being wet and in the wind at such temperatures can be fatal, for the thermal conductivity of water is 240 times that of still air.
The moment your body begins to lose heat faster than it produces it, hypothermia threatens. As heat loss continues, the temperature of the body's inner core falls below normal. Hands and arms (the extremities most needed in order to survive) are affected first. When body temperature drops to 95�, dexterity is reduced to the point where you cannot open a jackknife or light a match.
According to recent research by the Mountain Rescue Association, the body reacts in a series of predictable ways when inner-core temperature falls. At 2.5� below normal, shivering begins, an automatic body process to create heat. But it takes energy to shiver—comparable to what is expended sawing wood—and the heat loss continues. The more the core temperature drops, the less efficient the brain becomes. Although you may have a pack on your back with a sleeping bag and food in it, you may not have the sense to use them.
If the core temperature drops to 94�, you will stop shivering but every now and then will experience uncontrollable shaking. Your system, automatically getting rid of carbon dioxide and lactic acid, also releases blood sugar and a little adrenaline, giving you a surge of energy, which causes the violent shaking. This last desperate effort by the body to produce heat utilizes a tremendous amount of energy.
"Now," you think, "I must be getting warmer because I am not shivering anymore." By this time you are pretty irrational. If someone were to ask you your name and telephone number, you probably wouldn't know them, for the brain has become numb.
If nothing is done, death usually occurs within 1� hours after the shivering starts. In fact, a shivering person can go from fatigue to exhaustion to cooling beyond the recovery point so quickly he may perish before rescuers can build a shelter or get a fire started.
The speed with which hypothermia develops depends on the amount of energy available at the onset of the survival situation. If you were warm and fresh when the plane crash-landed or the car broke down, your energy reserves may be considerable. If, however, you were hiking in rugged terrain most of the day, you surely have a depleted supply of energy. The trick is to use your brain to conserve what energy remains. This is done by limiting muscular action and reducing body heat loss.