Accidental Hypothermia

The “reanimations” of profoundly cold victims in prolonged cardiac arrest and the emergence of therapeutic hypothermia after cardiac arrest help explain the contemporary allure of hypothermia. A 29-year-old Norwegian physician was successfully resuscitated from accidental hypothermia at 13.7° C after a 9-hour resuscitation. This included cardiopulmonary resuscitation initiated at the scene and 179 minutes of cardiopulmonary bypass. Medical uses of cold were not scientifically evaluated until the 18th century, although it has been used for medical purposes for millennia. The hemostatic, analgesic, and therapeutic effects of cold were well known. Accidental hypothermia was also common and its treatment controversial. Biblical references cite truncal rewarming of King David by a damsel, and various remedies, including rubbing of the extremities with hot oil, were mentioned by Hippocrates, Aristotle, and Galen. Cold weather has had a major impact on military history. Hannibal lost nearly half of his army of 46,000 while traversing the Alps in 218 bce. The winter of 1777 took its toll on Washington’s troops at Valley Forge. Napoleon’s chief surgeon, Baron Larrey, reported that only 350 of the 12,000 men in the 12th division survived the cold during their retreat from Russia in 1812. Those soldiers who were rapidly rewarmed closest to the campfire died. The French subsequently suffered heavy losses in the Crimean War (1845-1855). These lessons were relearned during both world wars. Many pilots and U-boat crews perished from the cold water in the North Atlantic. Approximately 10% of the U.S. casualties in Korea were cold related. Innumerable cold-related tragedies affect both military personnel and civilians, in particular hunters, sailors, skiers, climbers, boaters, swimmers, and survivors of some natural disasters. Widespread participation in outdoor winter sports increases the number of patients who have hypothermia. Hypothermia is geographically and seasonally pervasive. Most cases occur in urban settings. “Primary” hypothermia fatalities are classified as accidental, homicidal, or suicidal. Death certificate data, however, underreport secondary hypothermia deaths, in which cold complicates many systemic diseases. The effect of cold on mortality from cardiovascular and neurologic disorders is greatly underestimated. Hypothermia is defined as a core temperature below 35° C. Many variables contribute to the development of accidental hypothermia. Exposure, age, health, nutrition, medication, and intoxicants can decrease heat production, increase heat loss, or interfere with thermostability. The healthy individual’s compensatory responses to heat loss through conduction, convection, radiation, and evaporation are often overwhelmed by exposure. Medications can also interfere with thermoregulation. Central nervous system (CNS) problems commonly decrease the efficiency of thermoregulation.