【Abstract】 Objective To investigate the protective effect of intraoperative and postoperative dexmedetomidine on erythrocyte glucose metabolism and lipid peroxidation in patients undergoing heart valve replacements with cardiopulmonary bypass. Method Sixty patients undergoing elective heart valve replacements with CPB were randomly divided into control group (group C, n=30) and dexmedetomidine group(group D, n=30). The patients in group D were intravenously infused 1 μg/kg dexmedetomidine 15 minutes before operation and perioperatively followed by an infusion at a rate of 0.5 μg•kg-1•h-1 until the end of the operation. Group C was infused the same does of normal saline at the same time and route. The patient-controlled intravenous analgesia(PCIA)was used for postoperative analgesia．PCIA solution contained Sufentanil 2 μg / kg + dexmedetomidine 4 μg/kg in 100 ml of normal saline in group D, or sufentanil 2 μg / kg in 100 ml of normal saline in group C, and the infusion rate was 2 ml/h. The blood glucose, erythrocyte phosphofructokinase (PFK), glucose-6-phosphate dehydrogenase (G-6PD), aldose reductase (AR) activity，erythrocyte lipid peroxidation (ELPO) and glutathione (EGSH) were determined befor induction of anesthesia(T1), leaving operation room(T2), the first postoperative day(T3) and the second postoperative day(T4). Results Compared with these at T1, the levels of blood glucose, erythrocyte G-6PD, AR and ELPO in group C were significantly increased from T2 to T4 (P0.05), and the levels of PFK and EGSH in erythrocytes were significantly decreased from T2 to T4 (P0.05). Compared with group C, the blood glucose, erythrocyte G-6PD, AR, ELPO were significantly decreased (P0.05), and erythrocyte PFK and EGSH levels were significantly increased in group D (P0.05). Conclusion Intraoperative and postoperative dexmedetomidine therapy can significantly improve erythrocyte glucose metabolism and enhancement the antioxidant capacity of erythrocytes after cardiac valve replacement with CPB．