Is there a self-preserving hypothermic mechanism in shock?

Hypoxia-induced hypothermia (HIH) is regarded as an adaptive response to hypoxia in a variety of creatures, but no details of the mechanism have yet been elucidated in the clinical setting. This study was designed to analyze alteration of core body temperature with hemorrhagic shock and to clarify HIH in the clinical setting. Patients were categorized in the hemorrhage shock (S, n = 15) or cardiopulmonary arrest (C, n = 88) group. The tympanic membrane temperature (TMT) was measured, and the length of the interval of call-to-arrival (CTA) at a hospital was set as the time-course parameter. There was a significant negative linear relationship between CTA interval and TMT (S group: TMT = -0.055 degrees C, CTA = +36.1 min, r = -0.833, P < 0.001; C group: TMT = -0.046 degrees C, CTA = +36.3 min, r = -0.548, P < 0.001). Analysis of variance revealed no significant difference in the slope of the regression lines of both groups. However, when the CTA interval was used as a covariate, there was a significant difference in the TMT (P = 0.014), which means that the regression line of the S group was significantly lower than that of the C group with time. Furthermore, in the S group, all patients were hypothermic (<35 degrees C) when their CTA interval was more than 20 min; on the other hand, in the C group, only 64 (75%) of 85 were hypothermic. Patients in S group were more likely to become hypothermic (P < 0.05). In humans with cellular hypoxia, HIH takes place, as seen in other animals. This result emphasizes the necessity for studies of analysis of the mechanisms of temperature control and determination of optimal body temperature during acute critical care.