AIM: To investigate the antioxidative potential of propofol (an intravenous anesthetic with a chemical structure similar to phenol-based free radical scavengers such as vitamin E) during cardiopulmonary bypass (CPB). METHODS:Thirty adult patients referred for elective cardiac procedure with CPB were included and randomly allocated to a nously for anesthesia maintenance, whereas those allocated to the control group received fentanyl 10 μg/kg intravenously and inhaled enflurane (1%-1.5 %). Blood samples were collected at 7 time points: before the start of CPB,at 30 and 60 min of CPB, at the conclusion of CPB, 10 min after the administration of protamine, and 12 and 24 h after the cessation of CPB. Plasma levels of free F2-isoprostanes (sensitive markers of free radicals production)and complement C5a were determined by mass-spectrometric assay and enzyme immunoassay, respectively. Neutrophil adhesion to endothelial cells was observed at x200 magnification under a light microscope. RESULTS:Levels of F2-isoprostanes, complement C5a and neutrophil adhesion rate increased significantly during and after CPB in both groups. There were significantly higher levels of F2-isoprostanes, C5a, and more neutrophils adhering to endothelial cells in the control group than those in the propofol group, respectively. CONCLUSION: Cardiopulmonary bypass is associated with a great production of damaging free radicals. Propofol may be beneficial both as an anesthetic and as a potent free radical scavenger in patients presenting pathologies associated with free radical reactions during CPB.