Abstract: AIM: To compare the changes of pharmacokinetics and pharmacodynamics of cis-atracurium administered in different methods of hemodilution to provide a reference for clinical anesthesia. METHODS: Ninety elective orthopedic surgery patients, ASA Ⅰ-Ⅱ, 35 to 60 years old, were randomized into three groups by the different treatment methods in preoperative transfusion (n=30 each): group A acute normovolemic hemodilution (ANH),group B acute hypervolemic hemodilution (AHH) and control group (group C). Each group was divided into three subgroups(n=10 each) with the corresponding loading dose of cis-atracurium (0.1, 0.2,0.3 mg/kg). General anesthesia was induced after intravenous doses corresponding cis-atracurium after tracheal intubation. And then, we observed in each group of patients with muscle relaxant effects and changes in plasma concentration and calculated the pharmacokinetic parameters. RESULTS: The onset time of muscle relaxation was significantly longer in group B of the same dose (P<0.05). The TOF responses of free,the duration of neuromuscular block,and the body time were increased while the onset time accelerated as the dose prolonged (P<0.05).Hemodilution group significantly decreased serum concentrations positively correlated with the dose.And the reduction of group B was more pronounced.t_1/2α and V_c increased significantly in group A and B (P<0.05). And V_c in group B doubled. CONCLUSION: The dose of cis-atracurium in AHH should be appropriately increased, which could be maintained while in ANH.

Key words: acute normovolemic hemodilution, acute hypervolemic hemodilution, cis-atracurium, pharmacokinetics, pharmacodynamics