Free radical reaction products and antioxidant capacity in arterial plasma during coronary artery bypass grafting

Oxygen free radicals mediate the ischemia-reperfusion damage in animal hearts, but their role in human beings is still controversial because of the low xanthine oxidase level in the human heart. Besides ischemia-reperfusion, cardiac operation also includes other major interventions that might generate free radicals but have not been systematically studied. We studied the cases of nine patients throughout coronary artery operations, including general anesthesia, heparin, protamine and administration of cardioplegic solution, extracorporeal circulation, and heart reperfusion. Arterial plasma was assayed for malondialdehyde, diene conjugates, and fluorescent chromolipids, and plasma antioxidant activity was estimated from the ability to trap peroxyl radicals. Anesthesia, surgical procedures, or heparin administration did not change these parameters. Extracorporeal circulation decreased the plasma concentration of diene conjugates immediately, whereas other compounds remained unaltered. When these concentrations were corrected for hemodilution, the amount of fluorescent chromolipids actually increased after 5 minutes of extracorporeal circulation to 177% +/- 14% (mean +/- standard error of the mean), diene conjugates increased to 138% +/- 12%, and plasma antioxidant capacity increased to 144% +/- 12% of the awake value. Fluorescent chromolipid values remained at 156% to 177% throughout the perfusion and decreased to 130% +/- 13% 1 hour after perfusion. Diene conjugate levels and antioxidant capacity were 123% to 144% and 143% to 161%, respectively, from baseline during perfusion and 119% +/- 5% and 135% +/- 9%, respectively, 1 hour after perfusion. Heart reperfusion or protamine administration showed no additional increases. Malondialdehyde concentrations varied and showed no statistically significant alterations. We conclude that extracorporeal circulation devices induce generation of free radicals and plasma antioxidant activity, which are different from the damage caused by ischemia-reperfusion.