Hypothermia describes a state in which the body's mechanism for temperature regulation is overwhelmed in the face of a cold stressor. Hypothermia is classified as accidental or intentional, primary or secondary, and by the degree of hypothermia. Accidental hypothermia generally results from unanticipated exposure in an inadequately prepared person. Intentional hypothermia is an induced state generally directed at neuroprotection after an at-risk situation. Primary hypothermia is due to environmental exposure, with no underlying medical condition causing disruption of temperature regulation. Secondary hypothermia is low body temperature resulting from a medical illness lowering the temperature set-point. Many patients have recovered from severe hypothermia, so early recognition and prompt initiation of optimal treatment is paramount. Accurately estimating the incidence of hypothermia is impossible, as hospital encounters only represent the "tip of the iceberg" in that they reflect the more severe cases.
The greatest number of cases of hypothermia occur in an urban setting and are related to environmental exposure attributed to alcoholism, illicit drug use, or mental illness, often exacerbated by concurrent homelessness. This is simply due to the fact that more people are found in the urban regions rather than rural areas. A second affected group includes people in an outdoor setting for work or pleasure, including hunters, skiers, climbers, boaters/rafters, and swimmers. Prehospital management focuses on preventing further heat loss, rewarming the body core temperature, and avoiding precipitating ventricular fibrillation or another malignant cardiac rhythm.
This should be the preeminent concern. Conscious patients can develop ventricular fibrillation suddenly; prehospital workers, particularly those operating in remote search-and-rescue operations, should avoid inadvertent jerky movement of severely hypothermic patients. Patients who develop hypothermia-induced dysrhythmia in the field may be beyond resuscitation.