Abstract: AIM: To investigate the effect of dexmedetomidine on myocardial ischemia-reperfusion injury in patients undergoing cardiac valve replacement under cardiopulmonary bypass (CPB). METHODS: Forty ASAⅡ or Ⅲ patients of both sexes, aged 40-65 yr, scheduled for elective cardiac valve replacement under CPB, were randomly divided into 2 groups (n=20 each): contral group (group C) and dexmedetomidine group (group D). Dexmedetomidine 0.6 μg /kg was injected intravenously over 15 min before induction of anesthesia, followed by infusion at 0.2 μg·kg^-1·h^-1 until the end of operation in group D. While the equal volume of normal saline was given in group C. Blood samples were obtained from the vein before induction of anesthesia (T₀) and at 30 min, 6, 12, 24 and 48 h after aortic unclamping (T_1-5) for determination of plasma concentrations of cardiac troponin-I(cTnl) and creatine kinase isoenzyme-MB (CK-MB) and serum concentrations of TNF-α and IL-6. The duration of CPB, time of operation, time of aortic calmping, extubation time, duration of stay in ICU, and the rate of restoration of spontaneous heart beat were recorded. RESULTS: Compared with T₀, the plasma concentrations of cTnI and CK-MB and the serum concentrations of TNF-α and IL-6 were significantly increased at T_1-4 in group C and D (P<0.05). Compared with group C, the plasma concentrations of cTnI and CK-MB and the serum concentrations of TNF-α and IL-6 were significantly decreased at T_1-4 in group D, while the extubation time and duration of stay in ICU were decreased in group D (P<0.05). CONCLUSION: Dexmedetomidine can reduce the myocardial ischemia-reperfusion injury in patients undergoing cardiac valve replacement under CPB, and the mechanism may be related to inhibition of the release of proinflammatory cytokines.

Key words: dexmedetomidine, cardiopulmonary bypass, heart valve prosthesis implantation, myocardial reperfusion injury