Oxygen free radical generation in healthy blood donors and cardiac patients: the protective effect of allopurinol

Cardiopulmonary bypass (CPB) activates the complement system, which leads t o granulocyte activation and free radical production. Free radical activity during CPB has been associated with myocardial dysfunction. However, the r elationship between cardiac enzymes and granulocytes to lipid peroxidation in cardiac surgery patients is unknown. Moreover, the effect of allopurinol on lipid peroxidation during mechanical trauma has to be explored. Thirty-four patients undergoing coronary bypass surgery and 26 healthy bloo d donors participated in this prospective study where granulocyte counts, c ardiac enzymes and malondialdehyde (MDA) were measured and related. Allopur inol was used ex vivo, as scavenger, to explore its effect on lipid peroxid ation. In the patient group, the mean preoperative MDA level (2.2 +/- 0.7, nmol/ml ) significantly increased after 30 min of bypass (3.3 +/- 0.9 nmol/ml; p < 0.0001), and showed a second peak at aortic declamping (4.1 <plus/minus> 0. 9 nmol/ml). There were significant correlations between MDA and granulocyte counts (r = 0.59, p < 0.0001) and cardiac enzymes (r = 0.55, p < 0.0001). In an ex vivo setting, further mechanical trauma to blood significantly inc reased the MDA levels, both in the control (p < 0.0001) and in the patient group (p < 0.0001) and this effect could be reduced by allopurinol (p < 0.0 001). CPB and mechanical trauma generate oxygen free radicals. Allopurinol was found to reduce lipid peroxidation of red cells following mechanical tr auma and this has to be further investigated regarding its ability to reduc e morbidity in patients undergoing open heart surgery.