Abstract: Abstract Objective: Establish severe hemorrhagic shock model On Unrestrained Conscious Rats, set up indexes and evaluate the validity of the indexes and the model to explore the severe hemorrhagic shock pathophysiology. Method: Thirty-Five Male Sprague-Dawley rats were hemorrhaged 65% of total blood volume via left Femoral artery on unrestrained consciousness, resulting in severe hemorrhagic shock model. They were randomly divided into three groups by different resuscitation fluids: NaCl (n=12), WB (whole blood) (n=12) and 6% HES (n=13). Measure the arterial pressure (Bp), respiratory rate (RR), Temperature (T), Arterial Blood Gas (ABG) and Lactic Acid (LD) at baseline, shock and 2 hours after resuscitation. Record f 24 and 48h survival after resuscitation. Results: Compared with the baseline, Bp,T,PH,PCO2,HCT and BE level of all rats decreased significantly(P<0.01); PO2, LD and SO2 level all increased significantly（P<0.01;P<0.05）. 2h after resuscitation, compared with NaCl, WB and 6%HES can improve the Bp, PH, PaCO2 and BE, decrease the LD level and improve the metabolic acidosis. Conclusion: (1) ABG, LD and survival can be as effective indexes of evaluating the severity and prognosis of severe hemorrhagic shock. (2) Severe hemorrhagic shock model On Unrestrained Conscious Rats has satisfactory reproducibility and effectiveness for the evaluation of anti-shock performance.

Key words: hemorrhagic shock, Arterial Blood Gas (ABG), Lactic Acid (LD), Base Excess (BE)