Aim To investigate the the protection effect of glutamine pretreatment on the cardiomyocyte of the patients undergoing cardiac valve replacement in cardiopulmonary bypass.Methods Sixty patients undergoing cardiac valve replacement under CPB were randomly divided into two groups:control group (n=30) and glutamine pretreatment group (n=30).The patients in glutamine pretreatment group had intravenous injection by drip with glutamine 0.5 g/kg through the peripheral vein,four days before operation,once a day.After endotracheal intubation,the same volume glutamine was injected through the centre vein at the operation day.Only the same volume of sodium chloride was injected in control group.The same anesthetic drug and plan were given in both groups.To examine serum cardiac troponin I (cTnI),the arterial blood samples were drawn at the following time point:after endotracheal intubation (T1),60 min (T2),6 h (T3),12 h (T4) and 24 h (T5) after aortic de-clamped.The right atrial tissue samples 1～2 g were taken for microscopic examination 30 min after aortic de-clamped.The amount of dopamine,sodium nitroprusside were used and the rate of spontaneous heart resuscitation in both groups were recorded.Results By light microscopy,histochemical staining showed that there were a great number of leucocyte infiltration in cardiac muscle and capillary vessel of the patients in control group,and the degree of leucocyte infiltration decreased in glutamine pretreatment group.The concentration of serum cTnI in both groups was increased significantly from T2 to T5 (P<0.05),and it reached to maximum at T4,but the value of the concentration of plasma cTnI at all time points was lower in glutamine pretreatment group except T1 than that in control group (P<0.05).Less dopamine was used in glutamine pretreatment group (P<0.05),while sodium nitroprusside used did not show significant difference in both groups.Conclusion Glutamine pretreatment has protection effects on the patients undergoing cardiac valve replacement in cardiopulmonary bypass.