Incidence and causes

Effects of cold onto human organism have been described already in the antiquity but hypothermia as a disorder was recognised only in mid- -twentieth century [1]. According to the official sources in the United States hypothermia causes 1,500 deaths yearly, in Poland 300 to 600 deaths are reported per annum. Unfortunately, the exact data concerning incidence and fatality rate are not known. Many cases of hypothermia remain undiagnosed on account of a simple fact: almost all patients have their blood pressure, heart and respiratory rates measured, in many, pain intensity is also evaluated, but temperature measurement is not a part of routine practice. Incidence of clinically important hypothermia (excluding traumatic hypothermia cases) among patients admitted to emergency wards in Poland is estimated to be 5–6 cases per 100,000 citizens per year [2].

Although hypothermia is commonly understood to be characteristic of cold climates, it is worth noting that it can develop any place on Earth any time of year. It is beyond doubt that cold environment and major heat loss are factors most predisposing to hypothermia. If the impact of low temperature is significant and properly functioning body heat retention mechanisms fail, we speak of primary hypothermia. Hypothermia however can develop as a secondary condition accompanying other disabilities and homeostasis impairments deteriorating thermal regulation [3, 4]. In both cases the underlying principle is a simple disproportion between heat generation and heat loss.

Thermoregulation

Human organism is homeothermic, i.e. it possesses the ability to maintain stable core temperature regardless of external conditions. In fact, homeothermy undergoes more profound and more precise autonomic regulation than circulatory homeostasis. In certain circumstances, when defensive mechanisms of the organism fail, heat loss becomes superior to heat generation and body temperature decreases. At this moment a cascade of organs and systems dysfunctions occurs, leading to death unless therapy is commenced.

Human organism disperses heat by means of three processes: conduction, convection, radiation, and evaporation.