Abstract: Objective To investigate the effect of acute super volume blood dilution on cardiac output and blood coagulation function in senile patients.Methods Sixty patients with large joint operation were randomly divided into experimental group and control group,30 cases in each group.The experimental group was given 6％ hydroxyethyl starch and lactated Ringer's solution 15 mL/kg for AHH,while the control group was given routine infusion.Cardiac output and blood coagulation were compared between two groups.Results In the experimental group,cardiac output (CO) increased and blood coagulation function decreased after AHH (P ＞ 0.05).There were no significant differences in hematocrit (HCT),prothrombin time (PT),activated partial prothrombin time (APTT) and plasma fibrinogen (Fib) ateach time point between two groups (P ＞ 0.05).Conclusion Acute super volume blood dilution has small influence on cardiac output andblood coagulation function in senile patients.