HipotermiaHypothermia is defined as a body temperature less than 95 F (35 C)This is followed by confusion, lethargy, slurred speech, loss of consciousness, and coma.Often the affected person will lie down, fall asleep, and die. In some cases, the patient will paradoxically remove their clothes just before this occurs.The decrease in brain function occurs in direct relationship to the decrease in body temperature (the colder the body, the less the brain function). Brain function stops at a core temperature of 68 F (20 C).

The heart is subject to abnormal electrical rhythms as hypothermia progresses. Ventricular fibrillation, a disorganized rhythm in which the heart is unable to pump, may occur at core temperatures below 82.4 F (28 C). This is one type of cardiac arrest.

With decreased blood supply to the skin, the far reaches of the body's circulation are at risk for damage. Fingers, toes, ears, and nose are the first parts of the body to be at risk for frostbite. Without adequate blood supply to provide internal heat, water crystals in the tissue can form small ice crystals and the first signs of frostbite begin. The skin becomes cold, numb, and hard. The hands or feet can become clumsy and after a time, the skin can blister.