Mild hypothermia prolongs the survival time during uncontrolled hemorrhagic shock in rats.
OBJECTIVE
To 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.


METHODS
Twenty-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.


RESULTS
The 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.


CONCLUSIONS
Mild hypothermia of either 36 or 34 degrees C prolongs the survival time during lethal UHS in rats.
Takasu
Akira
A
Department of Traumatology and Critical Care Medicine, National Defense Medical College, 3-2 Namiki, Saitama 359-8513, Tokorozawa, Japan. atakasu@me.ndm.ac.jp
Norio
Hirofumi
H
Sakamoto
Toshihisa
T
Okada
Yoshiaki
Y
D000818:Animals; D004195:Disease Models, Animal; D007036:Hypothermia, Induced / Q000379:methods; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012771:Shock, Hemorrhagic / Q000628:therapy*