Introduction: Hypotensive (limited) fluid resuscitation (FR) improved 72h survival in our UHS 75 min outcome model. In the present study we increased UHS to 90 min. We hypothesized that hypotensive FR during UHS increases survival better with use of blood than Ringer's solution (RS) and that mild hypothermia increases survival rate further. Methods: 40 rats under light anesthesia underwent blood withdrawal of 3ml/100g over 15 min, tail amputation, start of hypotensive FR at 30 min, preventing MAP≤40mmHg during UHS 90 min (Phase I). Hemostasis and FR with shed blood was to 150 min (Phase II). Awakening and observation was to 72h (Phase III). We studied 4 groups of 10 rats each: Group 1, no FR. Group 2, RS. Group 3, shed blood. Group 4, shed blood plus mild hypothermia (34°C). Hemodynamic parameters, blood loss, blood gases, lactate, glucose, and liver and gut dysoxia (surface pCO2)were monitored. Necropsy was performed at early death or euthanasia at 72h. Results: In group 1, 9/10 rats died during untreated UHS. Survival to the end of phase II was achieved by 1 of group 1, 8 of group 2, 10 of group 3 and 10 of group 4. Survival to 72h was achieved by 0/10 rats in group 1, only 1/10 rats in groups 2 and 3, and 6/10 rats in group 4 (p<0.03 vs. groups 2 or 3, p<0.01 vs. group 1). Necropsy showed severe gut necrosis predominantly in the small intestine in rats that died early, and revealed no pathologic findings in the surviving rats. There were no differences between groups in blood loss, liver or gut surface pCO2, or arterial pH, pO2, PCO2, lactate or BE. In phases I and II, MAP was highest in Group 4. HR was lowest in Group 4. At the end of phase I, serum potassium was lower in Group 4 vs. 2 or 3. Blood glucose in phases I and II was higher in Group 4 vs. 2 or 3. Hematocrit was lowest in group 2. Conclusions: Use of blood vs. RS during UHS did not influence long-term outcome. Mild hypothermia increases survival time and rate even in a model with high mortality.