The aim of this study is to provide biochemical evidence of the occurrence of cardiac preconditioning via remote organ ischaemia on the patients undergoing coronary artery surgery. Eight male patients were randomly allocated into two groups. Blood samples were collected via coronary perfusion catheter immediately before cardiopulmonary bypass (point 0), prior to declamping aorta (point 1) and 5 min after declamping the aorta (point 2) to determine creatinine phosphokinase (CPK), CPK-MB and lactate dehydrogenase (LDH) levels in the control group. A tourniquet wrapped around the right upper extremity of the patient was inflated and deflated twice to perform 3 min of ischaemia separated with 2 min of reperfusion in the preconditioning group. Blood samples were withdrawn as described for the control group. Only LDH levels at point 3 were found to be significantly higher than the control group's. These data implied that preconditioning appeared to protect myocardium by enhancing anaerobic glycolysis. (C) 2000 Academic Press.