• Akira Takasu, Hirofumi Norio, Toshihisa Sakamoto, and Yoshiaki Okada.
• Department of Traumatology and Critical Care Medicine, National Defense Medical College, 3-2 Namiki, Saitama 359-8513, Tokorozawa, Japan. atakasu@me.ndm.ac.jp
• Resuscitation. 2002 Sep 1; 54 (3): 303-9.

ObjectiveTo test our hypothesis that during lethal uncontrolled hemorrhagic shock (UHS) in rats, mild hypothermia of either 36 or 34 degrees C would prolong the survival time in comparison with normotherma of 38 degrees C.MethodsTwenty-four rats were lightly anesthetized with halothane and maintained spontaneous breathing. UHS was induced by blood withdrawal of 2.5 ml/100 g over 15 min, followed by 75% tail amputation. Immediately after the tail cut, the rats were randomly divided into three groups (eight rats for each); normothermic Group 1 (control, rectal temperature 38 degrees C), and mild hypothermic Groups 2 (36 degrees C) and 3 (34 degrees C). Hypothermia was induced and maintained by body surface cooling. The rats were then observed without fluid resuscitation until their death (apnea and no pulse) or for a period of 240 min maximum.ResultsThe rectal temperature was cooled down to 36 and 34 degrees C in 5 and 10 min, respectively. The mean survival time, which was 76+/-26 min in the control group (38 degrees C), was nearly doubled by mild hypothermia, 178+/-65 min for Group 2 (36 degrees C) (P<0.01 vs. control) and 144+/-54 min for Group 3 (34 degrees C) (P<0.05 vs. control) (no significant difference between Group 2 and 3). Additional blood losses from tail stumps were not significantly different among the three groups.ConclusionMild hypothermia of either 36 or 34 degrees C prolongs the survival time during lethal UHS in rats.

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