When Hypothermia Sets In
When the cold slaps your face and squeezes tears from your eyes, it could be the start of hypothermia. Nazi doctors calculated that a human can die when their body temperature drops to around 77 degrees fahrenheit. The lowest recorded core temperature in a surviving adult is 60.8 degrees fahrenheit (12). Instinctively, the web of capillaries on your hands constricts sending blood coursing away from your skin and deeper into the torso. Tibetan Buddhist Monks can raise the skin temperature on their hands and feet by 15 degrees through meditation (13). Your exercise-dilated capillaries carry the excess heat of your core to your skin and wet clothes dispel it rapidly into the night. At 97 degrees, the muscles along your neck and shoulders tighten in what is known as pre-shivering muscle tone (14).
At 95 degrees, you have entered the zone of mild hypothermia. Hypothermia is an involuntary condition in which your muscles contract rapidly to generate additional body heat. Your muscles have cooled and tightened so dramatically that they no longer contract easily, and once contracted, they won’t relax. You are locked into an ungainly, spread-armed, weak-kneed snow plow (15). With every one degree drop in body temperature below 95 degrees, your cerebral metabolic rate falls off by 3 to 5 percent. When your core temperature reaches 93 degrees, amnesia nibbles at your consciousness (16).
By the time your core temperature has fallen to 88 degrees, your body has abandoned the urge to warm itself by shivering. Your blood is thickening like crankcase oil in a cold engine. Your oxygen consumption, a measure of your metabolic rate, has fallen by more than a quarter. Your kidneys work overtime to process the fluid overload that occurred when the blood vessels in your extremities constricted and squeezed fluids toward your center. By 87 degrees, you have lost the ability to recognize a familiar face. By 86 degrees, your heart’s...
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