| Popis: |
The pathogenesis of freezing cold injuries (FCI) is not yet entirely understood. Two possible hypothesis emerge: 1) Injury is a direct result of cryogenic insult to the cells. 2) Injury is secondary to vascular stasis which leads to anoxia. In clinical congelatio ice crystallization takes place in the EC-space. When water is transformed into ice, the osmolality in this compartment will increase leading to a passive diffusion of water from the IC-space. Cell dehydration modifies protein structure, alters membrane lipids and cellular pH leading to destructions incompatible with cell survival. Cold induces vasoconstriction of both arterioles and venules, which enhances peripheral filtration and raises plasma viscosity. The stability of red corpuscle aggregates increases and showers of emboli course microvessels. Finally progressive thrombosis will end up in anoxia. The indirect vascular effect has earlier been interpreted similar to that found in non-freezing injuries. Recent studies have, however, shown, that endothelial cells are very sensitive to freezing. The rheologic part of the pathogenesis therefore also seems to depend on a direct injury to cells. The development of FCI does not always depend on ambient temperature and duration of exposure but more to the heat loss subjected to exposed skin. Wind chill, humidity and wetness are all of significance in this matter. From a clinical point of view FCI are best subdivided into superficial and deep injuries. The superficial frostbite is limited to the skin and nearest subcutaneous tissue. A stringing, pinching pain is often the first symptom. The affected area becomes pale or waxy-white and numb.(ABSTRACT TRUNCATED AT 250 WORDS) |
