Objective To evaluation the efficacy of ketamine on the expression of adhension molecular CR3and intracellular cAMP, cGMP in neutrephils in patients associated with cardiopulmonary bypass (CPB), as well as the cardiovascular function of the CPB patients. Method Sixty patients operated on with prosthetic valve replace-rnent under CPB were randomly divided into 4 groups: placebo, ketamine 0.1 mg/kg ( ketamine Ⅰ) ,ketamine 0.5 mg/kg ( ketamine Ⅱ) ,ketamine 1 mg/kg( ketamine Ⅲ). Each group included 15 eases. Venous blood sam-pies were obtained during anesthesia induction (T1), 10 min before CPB (T2), end of CPB (T3) and 24 hoursafter operation (T4). The expression of CR3 was measured by Flow cytometry and the concentration of cAMP/cGMP by HPLC. Results Ketamine with various dosages decreased the expression of CR3 at the T3 and T4 inpatients of ketamine groups compared with patients of placebo group (P<0.05). The dosages of ketamine Ⅱgroup and ketamine Ⅲ group had more significant effect than that of ketamine Ⅰ group. The dosages of ketamineⅡ and ketamine Ⅲ group increased the intracellular cAMP at the T3 and T4 compared with ketamine Ⅰ groupand placebo (p<0.05), respectively. However,cGMP was lower in ketamine Ⅱ and ketamine Ⅲ group thanthat in ketamine Ⅰ group and placebo (P<0.05) at the T3.Morever,the mean arterial blood pressure was higherin ketamine Ⅱ and ketamine Ⅲ group at T4. Only the patients of ketamine Ⅲ group required less inotropic drugsafter operation. Conclusions Ketamine can reduce the expression of adhhension molecular CB3 and intracellularcAMP, cGMP in neutrophils from patients associated with CPB.