Effects of desmopressin on prolonging survival in stable hypothermia in rats

The aim of the present study was to examine whether minimizing plasma volume loss due to cold-induced diuresis can increase the survival time of rats maintained in long-term stable hypothermia (~24 h at a body temperature of 19 degrees C). Infusion of desmopressin (0.5-2.0 microg), a potent antidiuretic agent, during the cooling period enhanced survival over saline controls in a dose-related manner. The enhanced survival was accompanied by a significant delay in the expected increase of hematocrit and decrease of plasma volume as compared with those seen in saline controls. In contrast, treating the rats with the same dose range of another vasopressin analog, [beta-mercapto-beta,beta-cyclopentamethyl enepropionyl]-vasopressin, which has no antidiuretic action, failed to enhance survival over saline control. Further, treating the rats with the optimal dose of desmopressin (1 microg) at the later stage of hypothermia failed to elicit any beneficial effect. Our results indicate that by using desmopressin early during the cooling phase of the hypothermia, plasma volume and rheological parameters important for sustaining microcirculation can be better maintained than those seen in saline controls. These improvements may have contributed to the observed longer survival time in hypothermia.