Hypothermia and minimal fluid resuscitation increase survival after uncontrolled hemorrhagic shock in rats

Objective: To test the hypothesis that protective-preservative moderate hypoth Design: Randomized outcome study in rats. Materials and Methods: UHS phase I of 90 minutes, with initial withdrawal of 3 mL/100 g of blood plus tail amputation, was followed by hemostasis and all-out resuscitation phase II from 90 to 150 minutes, and observation phase III to 72 hours, Forty male rats under light anesthesia and spontaneous breathing were randomized into four groups: Group 1 received no fluid resuscitation during UHS and normothermia (37.5 degrees C) throughout, Group 2 received no fluid resuscitation and hypothermia (30 degrees C) from 15 to 120 minutes, Group 3 received lactated Ringer's solution to maintain mean arterial pressure at 40 mm Hg during UHS and normothermia, Group 4 received lactated Ringer's solution to a mean arterial pressure of 40 mm Hg during UHS and hypothermia from 15 to 120 minutes. Results: UHS phase I was survived by 0 of 10 rats in group 1, 7 of 10 in group 2, 5 of 10 in group 3, and 10 of 10 in group 4 (p < 0.01 for group 1 vs, 2, 3, or 4; p < 0.05 for group 4 vs, 3), Survival to 72 hours was achieved by 0 of 10 rats in group 1, 3 of 10 in group 2 (p < 0.001 vs, group 1), 1 of 10 in group 3, and 7 of 10 in group 4 (p < 0.001 vs, group 1, and p < 0.01 vs, group 3), All 72-hour survivors were neurologically normal, Necropsies in rats that died early during phase III showed edema and gastrointestinal hemorrhages. Conclusions: Moderate hypothermia or limited (hypotensive) fluid resuscitation -best both combined -increases survival during and after UHS in rats.