Objective To observe the effects of hyperoxia liquid preconditioning on myocardial enzyme in patients undergoing heart valve replacement.Methods Forty patients were randomly divided into hyperoxia liquid group(group HL) and control group(group C) with 20 cases each.The patients were given 10ml/kg Ringer's injection(group C) or 10ml/kg hyperoxia liquid(group HL) respectively.The central venous blood samples were collected in both groups before skin incision(T0),at 1h after start of CPB(T1),2h(T2)and 24h(T3) ...