Objective: The effect of Radix Salviae Miltiorrhizae (RSM) on production of lung oxygen free radical products during cardiac operations was researched.Methods: Thirty cases of heart valve replacement were randomly divided into two groups: RSM treatment group (RSM group) and control group. Blood samples were taken from before (right atrium

RA) and after (left atrium

LA) pulmonary circulation before cardiopulmonary bypass operation and 10 minutes

45 minutes

2 hours

6 hours after the aortic crossclamp removal to observe the level of peroxidation product and the changes in leucocyte count.Results: The number of leucocytes in LA was smaller than that in RA and the amount of peroxidation product in LA was higher than that in RA (P < 0.01-0.05) during the early phase of lung reperfusion in the control group. There was no significant difference (P >0.05) in the amount of peroxidation product and the leucocyte count between LA and RA in the RSM group.Conclusions: RSM could markedly prevent the lung leucocyte aggregation and reduce the production of lung free radical products. It suggested that the effect of RSM of reducing the lung oxygen free radical products was related to its effect of preventing the lung leucocyte aggregation.