Mechanism of hypothermia

There are four ways on how heat loss from the body which are;

1) Radiation (55-65%)

Heat loss from infrared emissions,(in noninsulated areas of the body)

2) Conduction

Heat loss from direct contact (eg; heat loss in water immersion)

3) Convection

Removal of warmed air from around the body (eg; windy condition)

4) Evaporation

Removal of warmed water from body surface via evaporation.

Classification of hypothermia

1) Mild hypothermia is defined as a core body temperature of 90.0-95.0°F (32.2-35.0°C), and patients may initially show signs of shivering, tachycardia, vasoconstriction, and tachypnea. Later signs include apathy, ataxia, impaired judgment, and diuresis.[Lars Grimm et al]

2) Moderate hypothermia is a core body temperature of 82.4-89.9°F (28.0-32.2°C), and patients may stop shivering and shows signs of dysrhythmia, bradycardia, hypotension, J waves seen on ECG, diminished reflexes, dilated pupils, and a decreased level of consciousness[Lars Grimm et al]

3) Severe hypothermia is a core body temperature less than 82.4°F (28.0°C), at which point patients may begin to suffer from apnea, decreased activity seen on electroencephalography (EEG), nonreactive pupils, oliguria, pulmonary edema, coagulopathy, hemoconcentration, and more severe arrhythmia[Lars Grimm et al]

From Medscape CME: An Unresponsive Man Found on the Street